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Flavonoid chemistry and evolution of Dendroseris and Gunnera in the Juan Fernandez Islands (Chile)
Pacheco-Jara, Patricia, Ph.D.
The Ohio State University, 1989
UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106
FLAVONOID CHEMISTRY AND EVOLUTION OF DENDROSERT.q
AND GUNNERA IN THE JUAN FERNANDEZ ISLANDS (CHILE)
DISSERTATION
Presented in Partial Fulfillment of the Requirements for
the
Degree of Doctor of Philosophy in the Graduate
School of The Ohio State University
By
Patricia Pacheco Jara
*****
The Ohio State University
1989
Dissertation Comnittee: Approved By:
Dr. Michael L. Evans
Dr. Daniel J. Crawford
Dr. Tod F. Stuessy
Department of Botany Dedicated to
Hugo
Marcela
Cristina
Javier ACKNOWLEDGMENTS
I wish to thank all the people who have helped me during the
completion of this study. First, I thank Dr. Tod F. Stuessy and Dr.
Daniel J. Crawford for all the teaching, help, opportunities and
encouragement given throughout the course of this work. I am also grateful to Dr. Michael L. Evans for his comments and criticisms on this dissertation. This study was supported by grants from Sigma Xi,
NSF doctoral dissertation improvement grant INT-8317088, OEA PRA
Fellowship, Tinker Foundation Travel Grant and an Graduate Student
Alumnii Research Award. I am especially grateful to Dr. Jim Solomon for his invaluable help during field work in Bolivia. I also wish to thank Dr. Stephan Beck (LPB), Dr. R. Rodriguez, Dr. R. Peralta, Ms.
N. Salinas, V. Campos and many others who made the field work possible. Especial thanks to Rich Whitkus, Paul Lewis, and John
Frederick for their help during the complextion of part of this work.
Thanks also go to the curators of F, MO, NY, and UC for the loan of specimens. A very special thanks go to Hugo, my husband, for his encouragement and faith, without which this work would have been impossible. Thanks to Marcela, Christina and Javier (my children) for their understanding and help.
iii VITA
1962-1967 ...... Licenciado en Biologla, Universidad de Concepcion, Concepcion, CHILE.
1968-1971 ...... Researcher, Universidad de Concepcion, Concepcion, CHILE
1972-1973 ...... Associate Professor, Universidad de Santiago, Santiago, CHILE.
197^—1975 ...... Associate Professor, Universidad de Chile, Santiago, CHILE.
1976-1981 ...... Researcher, Universidad de Concepcion, Concepcion, CHILE.
1982-1988 ...... Graduate Teaching Associate and Graduate Research Associate, Botany Department, The Ohio State University, Columbus, Ohio.
PUBLICATIONS
Journal Articles
Pacheco, P., M.Silva, P.G. Sammes and T.W. Tyler. 1973. Triterpenoids of Colletia spinosissima. Phytochemistry, 12:893-897.
Pacheco, P., S.M.H. Albonico, and M. Silva. 1973. Alkaloids, triterpenes and other constituents of Discaria crenata. Phytochemistry, 12: 954-955.
Gopalakrishna, E.M., W.H. Watson, P. Pacheco and M. Silva. 1976. Lycorine. C^gH^NOij. Cryst. Struct. Comm. 5: 795-799.
Watson, W.H., Z. Taira, M. Silva and P. Pacheco. 1977. 1,2,3>4,4a,6 hexahydro-10 hydroxy-3, 8,9-trimethoxy-H, 10b ethanophenanthridinium picrate. (C^gH2 c0 4 NH)+ ^C6h12n3°7^~* Cryst* Struct. Comm., 0 : 797- 801.
iv
1 Gopalakrishna, E.M., W.H. Watson, M. Silva, and P. Pacheco. 1978. 17-Epihomolycorine, C^gHg^NO^. Cryst. Struct. Comm., 7 • ^1.
Pacheco, P., M.Silva, W. Steglich and W.H. Watson. 1978. Hippeastidine and Epihomolycorine, two novel alkaloids. Rev. Latinoamer. Quim., 9: 28-32.
Zabel, V., W.H. Watson, P. Pacheco and M. Silva. 1979. Maritidine. ^17^21^®3* Cryst. Struct. Comm., 8: 371.
Kimura, M . , W.H. Watson, P. Pacheco and M. Silva. 1979. Rel-(2S, 3S)- 3- hydroxy- 7- methoxy-31, 4' methylenedioxyflavan. Acta Cryst. B 35: 3124-3126.
Kimura, M . , W.H. Watson, P. Pacheco and M. Silva. 1980. 7-hydroxy-6-methoxycoumarin. Cryst. Stryct. Comm., 9 - 257.
Watson, W.H., M. Kimura, P. Pacheco and M. Silva. 1981. Proanthocyanidins of Hippeastrum ananuca I. Rev. Latinoamer. Quim., 12: 30-32.
Sepulveda, B.A., P. Pacheco, M. Silva and R. Zemelman. 1982. Alkaloids of the Chilean Amaryllidaceae III. Chemical study and biological activity in Hippeastrum bioolor (R. et P.) Baker. Bol. Soc. Chil. Quim., 27(2): 178-180.
Pacheco, P., M. Silva, P.G. Sammes and W.H. Watson. 1982. New alkaloids from Hippeastrum ananuca Phil. Bol. Soc. Chil. Quim., 27: 289-290.
Schmeda, G., P. Pacheco and M. Silva. 1983. Flavonoids of Eupatorlum laeve DC. Rev. Latinoamer. Quim., 14: 36-37.
Pacheco, P., D.J. Crawford, T.F. Stuessy and M. Silva. 1985. Flavonoid evolution in Robinsonia (Compositae) of the Juan Fernandez Islands. Amer. J. Bot., 72: 989-998.
Bittner, M., M. Silva, Z. Rozas, P. Pacheco, T. Stuessy, F. Bohlmann and J. Jakupovic. 1988. New kaurane derivatives from Robinsonia evenia. Phytochemistry 27: 487-488.
Abstracts
Pacheco, P. and M. Silva 0. 1972. Alkaloids, triterpenes and other constituents of Discaria crenata (Clos) Regel. XI Latinoamerican Congress of Chemistry. Santiago, Chile (Abstract).
v
'I Pacheco, P. and M. Silva 0. 1975. Chemotaxonomic studies in Solanaceae based on steroidal' lactones. VII Annual meeting of the Chilean Chemical Society,. Valparaiso, Chile. (Abstract).
Pacheco, P. and M. Silva 0. 1976. Alkaloids of Hippeastrum ananuca. VIII Annual meeting of the Chilean Chemical Society. Santiago, Chile (Abstract).
Pacheco, P. and M. Silva 0. 1977. Hippeastidine and Epi-homolycorine, two new alkaloids from Hippeastrum ananuca. IX Annual meeting of the Chilean Chemical Society. Jahuel, Chile (Abstract)
Silva, M . , P. Pacheco, M.T. Chiang and C. Marticorena. 1977. Quimica de plantas chilenas usadas en medicina popular. Simposio Internazionale Sulla Medicina Indigena e Popolare Dell'America Latina. Instituto Italo Latinoamericano IILA. Roma, Italia. (Abstract)
Pacheco, P. and M. Silva. 1978. Proanthocyanidins and alkaloids of Hippeastrum ananuca. XIII Latinoamerican Congress of Chemistry. Lima, Peru (Abstract).
Pacheco, P. 1978. Proanthocyanidins of Hippeastrum ananuca. X Annual meeting of the Chilean Chemical Society. Valdivia, Chile (Abstract).
Gonzalez, F. and P. Pacheco. 1981. Secondary metabolites of Antholoba achates Coutony, 1846. Meeting of Sciences of the Sea. Institute of Oceanology. Valparaiso, Chile (Abstract).
Pacheco, P. and M. Silva. 1979. New proanthocyanidins from Hippeastrum ananuca. XI Annual meeting of the Chilean Chemical Society. Concepcion, Chile (Abstract).
Pacheco, P. and M. Silva 0. 1980. Chemical studies in Chilean Amaryllldaceae. Ill National meeting of Botany. Chilean Society of Biology., Concepcion, Chile (Abstract).,
Pacheco, P., D.J. Crawford, M. Silva, and T.F. Stuessy. 1983- Flavonoid evolution in Robinsonia (Compositae) of the Juan Fernandez Islands. Amer. J. Bot. (Abstr.) 70: 124.
Pacheco, P., D.J. Crawford, M. Silva, and T.F. Stuessy. 1983. Flavonoid evolution in Robinsonia (Compositae) of the Juan Fernandez Islands. Ohio J. Sci. (Abstr.) 83: 14.
Pacheco, P., D.J. Crawford, M. Silva, and T.F. Stuessy. 1984. Evolution in Gunnera (Gunneraceae) of the Juan Fernandez Islands. Ohio J. Sci. (Abstr.) 84: 5. Pacheco, P., D.J. Crawford, M. Silva, and T.F. Stuessy. 1985. Natural hybridization in Gunnera (Gunneraceae) of the Juan Fernandez Islands. Ohio J. Sci. (Abstr.) 85: 17-
Pacheco, P., D.J. Crawford, M. Silva, and T.F. Stuessy. 1985. Flavonoid chemistry and evolution of Dendroseris (Compositae, Lactuceae) in the Juan Fernandez Islands. Amer. J. Bot. (Abstr.) 72: 965.
Pacheco, P., D.J. Crawford, and TiF. Stuessy. 1987* Flavonoid evolution in Gunnera (Gunneraceae) of the Juan Fernandez Islands, Chile. Ohio J. Sci. (Abstr.) 87: 7-
Pacheco, P., D.J. Crawford, M. Silva, and T.F. Stuessy. 1987. Natural hybridization in Gunnera (Gunneraceae) of the Juan Fernandez Islands, Chile. Amer. J. Bot. (Abstr.) 74: 748.
Book
Pacheco, P., M.T. Chiang, C. Marticorena, y M. Silva 0. 1977- Quimica de plantas Chilenas usadas en medicina popular I. Universidad de Concepcion. Concepcion, Chile, pp 1-287.
FIELD OF STUDY
Major Field: Plant Systematica
Evolution and Systematic of insular taxa. Professor Tod F. Stuessy.
Chemosystematics. Professor Daniel J. Crawford.
vii TABLE OF CONTENTS
ACKNOWLEDGEMENTS ...... iii
VITA ...... iv
LIST OF TABLES ...... x
LIST OF FIGURES ...... :...... xii
INTRODUCTION ...... 1
CHAPTER
I. FLAVONOID EVOLUTION IN DENDROSERIS (COMPOSITAE, LACTUCEAE) FROM THE JUAN FERNANDEZ ISLANDS, CHILE ... 4
Introduction ...... 4 Materials and Methods ...... 8 Results ...... 10 Discussion ...... 13 Literature Cited ...... 21
II. NATURAL INTERSPECIFIC HYBRIDIZATION IN GUNNERA (GUNNERACEAE) FROM THE JUAN FERNANDEZ ISLANDS, CHILE .. 41
Introduction ...... 41 Materials and Methods ...... 44 Results ...... 49 Discussion ...... 51 Literature Cited ...... 57
III. FLAVONOID CHEMISTRY AND EVOLUTION OF GUNNERA (GUNNERACEAE) IN THE JUAN FERNANDEZ ISLANDS, CHILE ___ 80
Introduction ...... 80 Materials and Methods ...... 83 Results ...... 85 Discussion ...... 86 Literature Cited ...... 93
viii
"I IV. FLAVONOIDS OF GUNNERA SUBGENERA MISANDRA. PANKE. AND PERPENSUM (GUNNERACEAE) ..... 114
Introduction ...... 114 Results ...... 116 Discussion ...... 117 Experimental ...... 122 References ...... 124
APPENDIX
A. Flavonoid evolution in Robinsonia (Compositae) of the Juan Fernandez Islands ...... 137
ix LIST OF TABLES
TABLE PAGE CHAPTER I
1. Collection data for specimens of Dendroseris. Hieraclum. and Hypochaeris from the Juan Fernandez Islands and continental Chile ...... 36
2. Occurrence of flavonoids in Dendroseris ...... 38
3- Distribution of flavonoids in some genera of Lactuceae . 40
CHAPTER II
4. Characters used and values assigned to character states in the morphological hybrid index ...... 77
5. Descriptive statistics for quantitative characters of populations of Gunnera onMasatierra ...... 78
6. Occurrence of flavonoids among Gunnera bracteata. G. peltata, and selected hybrid individuals ...... 79
CHAPTER III
7. New chromosome numbers of species of Gunnera subgenus Panke from the Juan Fernandez Islands and two species from mainland South America ...... 110
8. Distribution of flavonoids present in the three endemic species of Gunnera from the Juan Fernandez Islands .... 111
9. Characters and states used in the cladistic analysis of endemic species of Gunnera from the Juan Fernandez Islands and G^. tinctoria from mainland Chile ...... 113
9 A. Basic data matrix of state of characters in species of Gunnera from the Juan Fernandez Islands and G. tinctoria from mainland Chile ...... 113
x
1 CHAPTER IV
10. UV absorption of flavonoids isolated from species of Gunnera ...... 135
11. Distribution of flavonoids present in three subgenera of Gunnera ...... 136
xi LIST OF FIGURES
FIGURE PAGE CHAPTER I
1. Map showing the location of the Juan Fernandez Archipelago in southern South America ...... 29
2. Composite two-dimensional chromatographic pattern of flavonoids in leaves of Dendroseris ...... 31
3- Changes in the flavonoid system in Dendroseris. superimposed on a network of relationships based on morphological features ...... 33
4. Composite two-dimensional chromatographic pattern of flavonoids in leaves of Hieracium from continental C h i l e ...... 35
CHAPTER II
5. Map showing the location of the Juan Fernandez Islands in southern South America ...... 64
6. Map of Masatierra showing the locations of pure populations of Gunnera bracteata. G. peltata. and the intermediate zone with transects 1 and 2 ...... 66
7. Scale silhouette of the endemic species of Gunnera and intermediate individuals on Masatierra ...... 68
8. Hybrid Index. Frequency distribution of individuals of Gunnera growing in Quebrada Villagra ...... 70
9. Wells' distance diagrams of individuals of Gunnera growing in Quebrada Villagra on Masatierra ...... 72
10. Degree of correlation among eight characters in Gunnera bracteata. G. peltata. and intermediate population in Quebrada Villagra...... 74
11. Comparison of the occurrence of individuals of Gunnera in two transects in Quebrada Villagra on Masatierra .... 76
xii CHAPTER III
12. Map showing the location of the Juan Fernandez Islands in South America ...... 101
13* Cladogram showing evolutionary relationships among endemic species of Gunnera from the Juan Fernandez Islands and their presumed ancestor, tinctoria. from mainland Chile ...... 103
14. Composite two-dimensional chromatographic pattern of flavonoids in leaves of Gunnera. including the three endemic species on the Juan Fernandez Islands, G. tinctoria. and selected species from South America . 105
15. Structure of flavonoids isolated from G. bracteata. G. masafuerae, Gu. peltata. G. tinctoria. and selected species from South America ...... 107
16. Changes in the flavonoid system in species of Gunnera from the Juan Fernandez Islands, superimposed on a hypothetical evolutionary tree ...... 109
CHAPTER IV
17. Map showing distribution of the six subgenera of Gunnera 130
18. Structure of flavonoids isolated from species of three subgenera of Gunnera ...... 132
19. Composite two-dimensional chromatographic pattern of flavonoids in leaves of Gunnera subgenera Misandra. Panke. and Perpensum ...... 134
xiii
1 INTRODUCTION
Oceanic islands have been considered as natural laboratories
for the study of evolution. Analyses of insular biota have helped to
understand and unravel evolutionary processes. Several
characteristics make oceanic islands unique for evolutionary studies:
(1) oceanic islands are isolated and they possess a diversity of
ecological niches available in a restricted geographical area which promote divergence, and sometimes rapid speciation; (2) oceanic islands are young geologically, and their ages are usually known
(this makes possible hypotheses on evolutionary changes within a known time frame); and (3) oceanic islands are geologically younger than the continental areas which are often the source area for the insular biota. This provides some insight into distinguishing primitive versus derived taxa in the development of evolutionary hypotheses.
One example of oceanic islands with remarkable potentials for evolutionary studies Is the Juan Fernandez Archipelago. This set of islands is located at 33° S and 580 km west of mainland Chile. The archipelago consists of three islands of volcanic origin: Masatierra,
Kasafuera, and Santa Clara. The islands are located in an East-West position and they are very young geologically: 3-7—^-4 m.y. for Masatierra, and 1-2.4 m.y. for Masafuera. In these islands has
evolved a remarkable flora of 150 native species with a high degree
of endemism: 69? at the specific level and 19% at the generic level. «• Among the endemic taxa from the Juan Fernandez Islands, of special
interest are the genera Dendroseris (Compositae, Lactuceae) and
Gunnera (Gunneraceae).
Dendroseris is an endemic genus in the Juan Fernandez Islands.
It consists of 11 species placed in three subgenera: subgenus
Dendroseris. D. litoralls. D. macrantha. D. maorophylla. and D.
marginata: subgenus Phoenicoseris. D. berteriana. D. pinnata, and D.
regia: subgenus Rea. D. gigantea. D. micrantha, D^. neriifolia, and
D. pruinata.
Gunnera belongs to the Gunneraceae, a monotypic family.
Gunnera has been segregated into six subgenera based on its ample morphological diversity: Milligania. Misandra, Ostenigunnera. Panke,
Perpensum. and Pseudogunnera. In the Juan Fernandez Islands Gunnera
is represented by three endemic species in the subgenus Panke: G. bracteata. G. masafuerae. and G^. peltata.
The main objectives of this study are to: (1) investigate the evolution of the flavonoid chemistry in Dendroseris (Chapter 1), and
Gunnera (Chapter 3); (2) investigate the origin and evolution of the endemic species of Gunnera (Chapter 3); (3) examine the only known case of interspecific hybridization in the flora of the archipelago
(in Gunnera. Chapter 2); and (4) examine the flavonoid chemistry of other species of Gunnera in subgenera Misandra. Panke. and Perpensum
(Chapter 4). 3
In Dendroseris. the 11 species have evolved with extensive
morphological divergence in the two major islands. Study of
flavonoid chemistry, presented in chapter 1, was chosen because it
has been useful in other plant groups in elucidating phylogenetic
relationships. In Dendroseris it was hoped that trends in flavonoid
evolution could be hypothesized.
Gunnera bracteata and G^. peltata are endemic on Masatierra. In
Villagra ravine, where the two species are sympatric, a series of
intermediate morphological forms has been found. This case of
interspecific hybridization is analyzed in Chapter 2. This is the
only case of extensive interspecific hybridization in the entire
flora of the archipelago known so far. Morphological analyses and
flavonoid data were used to document the hybridization.
The origin and evolution of the endemic species of Gunnera are
analyzed in Chapter 3• Gunnera tinctoria. from the Chilean mainland
was determined by morphological and flavonoid analyses as the
hypothetical closest relative of the endemic taxa.
The flavonoid chemistry of species from subgenera Misandra.
Panke. and Perpensum is analyzed in Chapter 1* as a contribution
towards understanding the general phylogenetic relationships of the
entire family.
* Chapter I
FLAVONOID EVOLUTION IN DENDROSERIS (COMPOSITAE, LACTUCEAE)
FROM THE JUAN FERNANDEZ ISLANDS, CHILE
INTRODUCTION
The Juan Fernandez Islands are located 580 km west of mainland
Chile at latitude 33° S (Fig. 1). The archipelago consists of
three islands: Masatierra (= Robinson Crusoe), the largest island
with 78 km2; Masafuera (= Alejandro Selkirk), separated by 145 km
of ocean from Masatierra, 59 km2 ; and Santa Clara, next to the 2 coast of Masatierra, 3 km . The islands are volcanic in origin,
have never been connected to the mainland, and have resulted from
isolated intraplate volcanism, probably associated with a hot spot
(Stuessy et al., 1984). The islands are also young geologically:
3.7-4.4 m.y. for Masatierra and 1-2.4 m.y. for Masafuera (Stuessy et
al., 1984). The ages of the islands are in agreement with their
geomorphology: Masatierra has wide valleys and shows a significant
degree of erosion; Masafuera has deep and narrow ravines, is
dome-shaped, and shows only slight erosion.
4
1 5
The flora of the Juan Fernandez Archipelago consists of 150
native species which have evolved from colonizers mainly from
continental South America (Skottsberg, 1956). The degree of endemism
of the flora is high, being 69? at the specific level and 19? at the
generic level (Skottsberg, 1956). The Compositae of the Juan
Fernandez Archipelago constitute the largest group of endemic taxa.
The 26 species representing eight genera make up 20? of the vascular
flora of these islands. Among these genera, Dendroseris is the
largest endemic genus with eleven species distributed on the three
islands of the archipelago.
Dendroseris (Compositae, Lactuceae) was cited by Carlquist (197-4)
as an example of adaptive radiation, which is the entrance of a group
into different habitats within a restricted geographical region. An
archipelago usually has a diversity of habitats available, primarily
during the early stages of colonization. Groups of plants reflect
adaptive radiation when their derivatives adapt to a broad variety of
situations (Carlquist, 197M). Studies by Sanders, Stuessy,
Marticorena and Silva (1987), using abiotic factors and associated
vegetation, suggested that species of Dendroseris are ecologically
separated to some degree, but that adaptive radiation in this group
has been limited or moderate. It is more likely that speciation has
occurred through geographical isolation, local selection, and drift.
The lack of ecological separation seen today might also be to some
extent a result of erosion and reduction of original island habitats.
The diversity of growth forms in Dendroseris is enormous, with
palmiform rosette trees, succulent rosette shrubs and sparsely
1 6
branched trees (Carlquist, 1967)- This diversity led Skottsberg
(1951) to recognize four genera: Dendroseris. Hesperoserls.
Phoenicoseri3 and Rea. Stebbins (1953)> however, believed that
although Dendroseris is notable by its diversity, recognizing one
genus will serve to emphasize its evolutionary unity. In the present
study we recognize one genus with the eleven species placed into
three subgenera (following Skottsberg, 1922; and Carlquist, 1967):
Dendroseris. Phoenicoseris. and Rea.
Several studies have been completed on different aspects of
Pendroseri3 including: anatomy. Carlquist (1960, 1966, 1967);
cytology. Stebbins, Jenkins and Walters (1953). Lack, Sack and
Bachmann (1978), Tomb et al. (1978), Sanders, Stuessy and Rodriguez
(1983), Spooner, Stuessy, Crawford and Silva (1987); palynology.
Erdtman (1952), Carlquist (1967), Tomb (1975); phytogeography.
Skottsberg (1956); taxonomy. Skottsberg (1922, 1951), Carlquist
(1967); evolution, phylogeny and modes of speclation, Sanders,
Stuessy, Marticorena and Silva (1987); and isozymes. Crawford,
Stuessy and Silva (1987). No previous studies of secondary
metabolites have been done on this group of endemic taxa.
Chemistry has been very useful in determining systematic
relationships in plants (Alston, 1967; Harborne, 197^; Gershenzen and
Mabry, 1983; Giannasi and Crawford, 1986). Among the secondary
metabolites, flavonoids possess many advantages which make them
useful in systematic and evolutionary studies. These include
occurrence in nearly all vascular plants, ease of isolation and
identification, chemical stability, genetic control of structure,
T 7
and considerable structural diversity (Harborne, 197^)- Many
examples have served to demonstrate how flavonoid chemistry has
provided critical data for understanding relationships and evolution
(Pacheco, Crawford, Stuessy and Silva, 1985; Bohm, Nicholls and
Ornduff, 1986; Bohm, 1988).
Dendroseris is a suitable group of endemic species in which to
examine the evolutionary implications of the flavonoid system.
Eleven species have evolved with extensive morphological divergence
in the two major islands of the archipelago. The East-West position
of the islands makes Masatierra (the closest island to mainland South
America) the probable site for the original colonization. These
factors together with the known young ages of the islands, provide
some insight into distinguishing primitive versus derived taxa.
Speciation events must have occurred within a known maximum time of
3-7 to 4.4 m.y. for Masatierra and 1 to 2.4 m.y. for Masafuera
(Stuessy et al., 1984). Flavonoid differences among species on
Masatierra, therefore, must have accumulated in fewer than four
million years. On Masafuera any flavonoid divergence has occurred in
fewer than two million years. Flavonoid chemistry also can be
compared to the closest hypothetical mainland relatives, and thus it
is possible to hypothesize trends of flavonoid evolution within the
genus.
The purposes of this study, therefore are to: (1) examine the
flavonoid compounds from the eleven species of Dendroseris of the
Juan Fernandez Islands; (2) determine flavonoid components in
selected taxa of the closest postulated mainland relatives; and (3)
1 8
compare flavonoid data to hypotheses of evolutionary relationships
based on morphology to determine whether speciation in Dendroseris
has been accompanied by diversification of flavonoid components, and
if so, to interpret these patterns of variation.
MATERIALS AND METHODS
Plant material. Plant material was collected by personnel from
laboratories of the Departments of Botany of The Ohio State
University and Universidad de Concepcion, Chile, during four
expeditions to the Juan Fernandez Islands: January-February, 1980,
November-December, 1980, January-February, 1984, and
January-February, 1986 (Table 1). Forty-five populations from all
nine species of Dendroseris were sampled from both islands. Each
sample of Dendroseris represents individual plants. Dendroseris
gjgantea and IK macrophylla were analysed, with permission, from
herbarium material only. Three samples of Hieracium and four of
Hypochaerls from southern South America were also examined. The
three samples of Hieracium were collected in continental Chile (March
1985 and January-February 1986). Each sample corresponds to several
plants pooled from one population. Three of the four species of
Hypochaerls were analyzed from herbarium material at OS.
Extraction. Isolation and identification of flavonoids.- Leaf
material was ground in a mill, and extracted twice with 85% and 50$
aqueous methanol. The combined extracts were evaporated to dryness
in a flash evaporator and cleared of chlorophylls and lipids by
■i treatment with boiling water. The water was extracted with ethyl
acetate to remove the flavonoids. The ethyl acetate was removed
under vacuum on a flash evaporator, and flavonoids were taken up in
methanol. The methanol fraction was applied to sheets of Whatman 3MM
chromatographic paper. The chromatograms were developed with
ter-butyl alcohol: acetic acid: water 3:1:1 (TBA) for 36 hr in the
first direction, and with 15? acetic acid (15? HOAc) in the second
direction for four hr. The spots were localized using ultraviolet
light (240 nm). Color, color change under NHjjOH and rate of flow
(Rf) were recorded following methods in Mabry et al. (1970).
Individual flavonoids were obtained by elution of the compounds from
the chromatograms and purified by thin layer chromatography (TLC)
using precoated polyamide DC-6 (Machery-Nagel) and precoated
cellulose (Machery-Nagel). The solvent systems used for TLC were: I.
1,2 dichloroethane: MeOH: ethylethylketone (MEK): HgO (50: 25: 21:
4); II. H20: EtOH: isopropanol: MEK (65.8: 18: 6: 10) (Wilkins and
Bohm, 1976); III. HgO: n-butanol: acetone; dioxane (70: 15: 10:
5). The structures of the flavonoids were determined by analysis of
a series of six ultraviolet spectra following the methods described
by Mabry et al. (1970). Sugars were obtained by hydrolysis of
flavonoid glycosides with 0.1N trifluoroacetic acid in a screw-cap
tube in a water bath for two hr (Wilkins and Bohm, 1976). Sugars
were identified by circular co-chromatography with standards on
cellulose precoated plates (Machery-Nagel). The solvent used was ethyl acetate: pyridine: HgO (6: 3: 2). Sugars were visualized by spraying with aniline-phthalate (1.0 g phthallc acid and 1.0 ml 10
aniline in 100 ml of 95% ethanol) (Becker, Exner and Averett, 1977).
Aglycones were extracted with ethyl acetate and identified by UV
spectral analyses and co-chromatography with standard samples.
RESULTS
A total of 16 flavonoids was isolated and identified from the
eleven species of Dendroseris (Table 2). The flavonoid system in
Dendroseris is based on mono- and diglycosides of the flavones
apigenin and luteolin, and the flavonol quercetin (Fig. 2). The
flavone glycosides are substituted only in the 7 position. Acid
hydrolysis yielded glucose as the only sugar. Therefore the
different Rf values of the glucosides in several solvents suggest
isomeric forms of glucose (pyranose or furanose), or different
position of attachment of the glucose molecule to the 7-0 position of
the aglycone. Mono- and diglucosides were identified by their Rf
values in aqueous and organic solvents (solvents I and II). Flavonol
glycosides are mono- and diglycosides at the 3-position of quercetin,
with glucose as the only sugar.
The distribution of flavonoids in Dendroseris is shown in Table
2. Where more than one population was examined, infraspecific
variation was seen, resulting in the absence of compounds or their
occurrence in smaller concentrations. In both situations it cannot
be dismissed that this variation could reflect only small amounts of
plant material used in some cases (Crawford, 1978). Although the
i 11
distribution of flavonoids in Dendroseris does not provide absolute
species-specific profiles, a well defined pattern does emerge for
each of the subgenera.
Subgenus Rea is characterized by the presence of the highest
number of flavonoid compounds. Fourteen out of the total of 16
flavonoids found in this genus are present in this subgenus. The
flavonoid profile consists of four luteolin 7-0-glucosides
(flavonoids 1, 2, 3, and 4), three luteolin 7-0-diglucosides
(flavonoids 5, 6, and 7), three apigenin 7-0-glucosides (flavonoids
8, 9, and 10), one apigenin 7-0-diglucoside (flavonoid 11), quercetin
3-0-glucoside, and the two flavone aglycones: apigenin and luteolin.
Two species-specific flavonoid were detected in Rea: luteolin
7-0-diglucoside (flavonoid 6) was present exclusively in D.
neriifolla. and luteolin 7-0-diglucoside (flavonoid 7) was detected
only in pruinata.
Subgenus Phoenlcoserls is characterized by the presence of
eight flavonoids. Three of them are luteolin 7-0-glucosides
(flavonoids 1,2, and 3)« In addition it has luteolin
7-0-diglucoside (flavonoid 5), apigenin 7-0- mono- and diglucosides
(flavonoids 10 and 12), and the aglycones apigenin and luteolin.
Flavonoid 12 (apigenin 7-0-diglucoside) is synthesized only by D.
berteriana. No flavonols are present in this subgenus.
The flavonoid profile of subgenus Dendroseris consists of
flavone and flavonol glucosides. Eleven flavonoids were detected in
species of this subgenus. The flavonoid profile consists of luteolin
7-0 monoglucosides (flavonoids 1, 2, and 3)» luteolin
i 12
7-0-diglueosides (flavonoid 5), apigenin 7-0-glucosides (flavonoids
8, 9» and 10), quercetin 3-0-mono and diglucoside (flavonoids 13 and
14), apigenin, and luteolin.
Analysis of species of Hieracium and Hypochaeris from southern
South America revealed several flavonoid glycosides (Table 3). Some of these compounds were partially identified by UV spectra and by their Rf values in TBA, 15$ HOAc and aqueous and organic solvents
(Solvents I and II). Four flavonoid glycosides were isolated from the three species of Hieracium and they correspond to luteolin and apigenin 7-0-mono- and diglycosides (Fig. 4). The flavonoid profiles were identical for the three species examined except for Hieracium sp. (7212) which lacks apigenin 7-0-glycoside (Table 3). Ho flavonol glycosides were detected in these species of Hieracium. Three species of Hypochaeris analyzed came from herbarium material with each species represented by individual plants. The fourth species,
Hypochaeris glabra, was collected in the Juan Fernandez Islands where it grows as an introduced weed. This sample represents several individuals from one population. Five flavonoids were isolated and partially identified. Luteolin 7-0-mono- and diglycosides are common for all the species. The flavonoid distribution in Hypochaeris shows a pattern of species-specific profiles and it is characterized by the common presence of luteolin 7-0-mono- and diglycosides, as well as absence of apigenin glycosides in all the species examined. In addition, a flavonol glycoside and two unidentified flavonoids were detected, but their presence varied among the species. Literature reports on the flavonoid content of some genera from the tribe 13
LaCtuceae reveal that apigenin and luteolin glycosides are common and
present in almost all the genera (Table 3). Other flavone glycosides
are also present but they are less frequent; among these, glycosides
of chrysoerlol, isoetin, and isocyanoroside are the most common.
Glycosides based on flavonols quercetin, kaempferol and isorhamnetin
were detected in mo3t of the species. The sugar complement is
diverse and the following moities have been reported: arabinose,
galactoside, glucuronic acid, glucose, rhamnose, and xylose.
DISCUSSION
Taxonomic implications.- There is some correlation between
flavonoid distribution and the subgenera proposed by Skottsberg
(1922) and Carlquist (1967) based on morphological evidence. Using morphological characters, Sanders et al. (1987) proposed a network of relationships (Fig. 3) which was constructed using Manhattan distance and the methods of Nelson and Van Horn (1975) based on Farris (1970).
This network shows taxonomic relationships and it is in agreement with the subgenera proposed by Skottsberg (1922) and Carlquist
(1967). This framework of relationships will be used to discuss taxonomic implications of flavonoid distribution.
Although few species-specific profiles exist (e.g., in D. berteriana), the distribution of flavonoids gives a clear pattern for different subgenera. Subgenus Phoenicoseris contains Dendroseris berteriana. D.plnnata, and JD;. regia. This subgenus is characterized by a simple flavonoid pattern and absence of flavonol glucosides. 14
Also the total number of flavonoids is only eight, the lowest within
the genus. Within this subgenus, Dj_ berteriana is unique among
Dendroseris by the presence of compound 12 (apigenin
7-0-diglucoside).
Subgenus Rea is the most diverse and contains the highest
number of flavonoid compounds (11of the three subgenera). This
subgenus is characterized by having quercetin monoglucoside which is
lacking from subgenus Phoenicoseris. and which in Dendroseris is
present along with quercetin diglucoside. A common problem when
working with flavonoids is discriminating between the absence of a
compound and its presence in very small amounts. This problem was
evident when analyzing Rea; flavone 9, which would have stressed the
closeness of IK pruinata and IK micrantha. was sometimes difficult to
detect. In the network of relationships shown in Fig. 3, subgenus
Rea is paraphyletic. Chemical evidence based on flavonoid compounds
supports Rea as a monophyletic group. Flavonoid 5 is common for D. gigantea. D. micrantha. and D. pruinata. Flavone 9, although difficult to detect, was present in IK. micrantha and IK pruinata.
Finally, glucoside 11 is present in IK micrantha and D^ neriifolia.
Dendroseris gigantea is not unusually distinct in its morphology from the other species in Rea (Sanders et al. 1987), however it appears to be divergent from other species in the subgenus in its flavonoid content. The reduction in number of compounds is evident, although this could be the result of the small quantity of plant material available. The flavonoid profile of IK. gigantea could be used to support Skottsberg's (1922) segregation of this taxon into a separate 15
monotypic section (Schizoglossum).
Subgenus Dendroseris (D. litoralis. D. macrantha. D.
macrophylla. and marginata) is unique by the presence of quercetin
mono- and di-glucosides. There are no species-specific compounds and
the group is very homogeneous in its flavonoid content. The similar
flavonoid data support the morphological closeness (Fig. 3) of all
the species in this subgenus except macrophylla. the species that have evolved on Masafuera, which has a simpler profile. This reduction in flavonoid profile during speciation is a common trend for the three species endemic to the younger island.
Evolution of the flavonoid system.- It is most likely that
Dendroseris represents a monophyletic group, i.e., the eleven species have originated from only one introduction to the islands from the continent. This seems a safe assumption given the uniqueness of the genus (Sanders et al., 1987)* Since Dendroseris is endemic to the
Juan Fernandez Islands, speciation and flavonoid divergence must have occurred in the archipelago.
The closest relatives of Dendroseris have been difficult to determine due to the pronounced morphological divergence of this genus from mainland taxa within the same tribe. Among the taxa proposed by different authors as relatives of Dendroseris (Stebbins et al., 1953; Stebbins, 1977; Jeffrey, 1966; Carlquist, 1967)»
Hypochaeris and Hieracium (Subgenus Stenotheca) appear to be the most probable progenitors (Sanders et al., 1987)* The similarities with
Hieracium are based on characters of the phyllaries, corollas, 16
achenes, and pappus. Also the chromosome number of n = 9 and n = 18
in Hieracium. and n. = 18 in Dendroseris add strength to Hieracium as
a possible progenitor. Since the Lactuceae have low chromosome
numbers (n. = 4 to n = 9) (Tomb et al., 1978), Dendroseris most
probably represents a polyploid on a basic chromosome number of x =
2.. Crawford et al (1987) detected extensive duplication of isozyme
loci, which would be expected if the plants are polyploids.
Polyploidy could have arisen in Dendroseris pre- or post-introduction
to the archipelago. Based on chromosome counts of several species in
two subgenera, Sanders et al. (1983) assumed that there has been no
change in chromosome number in Dendroseris after introduction to' the
archipelago, and therefore the closest relative of this group could
be from within Hieracium with n = 9* Hypochaeris. another genus from
which Dendroseris might have originated, is a large taxon in South
America (ca. 3^ spp., Cabrera, 1963; Marticorena and Quezada, 1985).
Hypochaeris resembles Dendroseris in the capitula and phyllaries.
Sanders et al. (1987) rejected this genus as a putative ancestor
because of differences in achenes, pappus and chromosomes, and also
because many species of Hypochaeris are adapted to high altitudes.
One weedy species, Hypochoeris glabra, however, does grow in
Masatierra indicating that broad ecological preferences exist in the
genus as a whole.
Comparison of the flavonoid system of Dendroseris with those of
Hypochaeris and Hieracium make it less likely that Hypochaeris is the
mainland ancestor of Dendroseris . Although Hypochaeris shows the
presence of luteolin-7-0-mono- and di-glycosides, the other
1 17
components of the flavonoid pattern are exclusive for Hypochaeris.
For example it was possible to determine by UV spectra two flavone
glycosides not related to luteolin and one flavonol glycoside based
on an aglycone different from quercetin. Apigenin glycosides are
absent in the species of Hypochaeris examined and also from those
searched in the literature (Table 3).
The analysis of the flavonoid system of Hieracium from mainland
Chile, plus literature reports (Table 3), indicate that this genus is
more likely ancestral to Dendroseris than Hypochaeris. Apigenin and
luteolin glycosides are the main components of the flavonoid profiles
of species of Hieracium (Table 3). Although quercetin was not found
in Hieracium from Chile, glycosides of quercetin are known to occur
in other species of the genus (Table 3)»
Sugar substitution in flavonoids of continental Lactuceae
(e.g., Hieracium) shows great variation (Table 3). In contrast,
Dendroseris has flavonoids yielding only glucose after hydrolysis.
As indicated earlier, variation in the flavonoid glucoside compounds
could result from one or more of several factors. The low level of
genetic variation for glycosilation could be explained by a founder
event, where the first individual or group of individuals reaching
the islands carried only a small proportion of the genetic variation
of the ancestral population in the mainland. This is concordant with
the hypothetical origin of Dendroseris by a single introduction.
In Dendroseris. it is desirable to relate the changes in the
flavonoid system to an already existing hypothetical phylogeny based
on morphology. Rea is regarded as the most primitive subgenus based
1 on morphological features and occurrence in middle elevation forests
and more open, arid habitats. Fourteen of the total of 16 flavonoids
are synthesized in this subgenus, and thus Rea is the most
genetically diverse group of Dendroseris with regard to flavonoid
chemistry. If subgenus Rea is the primitive group in Dendroseris.
then the large number of different flavone 7-0-glucosides plus the
presence of quercetin 3-0-glucoside may be considered as the
ancestral condition in Dendroseris.
Subgenus Phoenicoseris is considered to be highly derived. The
three species (D^. berteriana. D. pinnata, and D^ regia) have compound
pinnatifid leaves, are single-stemmed, and monocarpic. They are
adapted to exposed ridges (D^ pinnata) or moist tree fern forests (D.
berteriana)(Sanders et al., 1987). During the evolution of this
subgenus, expression of the gene encoding the flavanone 3-hydroxylase enzyme was lost, but the factor silencing of the gene is not known.
The flavonoid profile in Phoenicoseris is the simplest among the subgenera of Dendroseris. It is characterized by the absence of flavonol glucosides (quercetin 3-0-glucoside) and a reduction in the number of flavone glucosides to eight, the fewest number of flavonoids in the three subgenera. Evolution of the flavonoid system in Phoeniooserls is characterized by a loss of classes of compounds, relative to the presumptive primitive Rea evolutionary line.
Subgenus Dendroseris is the other evolutionarily derived group within the genus. Change in the flavonoid complement during divergence of this subgenus is characterized by the synthesis of a novel flavonol diglucoslde, quercetln-3-0-dlglucoside. This 19
represents an elaboration in the flavonoid chemistry. The basis for
this evolutionary gain could be quite simple genetically, namely the
activation or synthesis of the enzyme UDP-glucose:flavonol
3-0-glucoside glucosyl transferase which is necessary to produce this
quercetin 3-0-diglucoside. Subgenus Dendroseris synthesizes eleven
flavonoids out of a total of sixteen.
Evolution of the three species in Masafuera, the younger
island, has been accompanied by loss of flavonoids in two species but
not in Di regia. In this species, the retention of the full
flavonoid chemistry could indicate that D^ regia originated recently
from a founder population of D^. berteriana. After divergence D.
berteriana could have developed the ability to synthesize the
exclusive apigenin diglucoside (flavonoid 12). Dendroseris
macrophylla. considered the most derived species in subgenus
Dendroseris. is characterized by the loss of five of the eleven
flavonoids present in the ancestral group from Masatierra.
Dendroseris gigantea shows a reduced flavonoid pattern due to loss of
flavone glucosides and quercetin glucoslde.
The main trend during the evolution of the derived subgenera,
Phoenicoseris and Dendroseris. as well as the evolution of the
species in the younger island Masafuera, is reduction in number of
flavonoid glucosides. This reduction indicates that some glucosyl
transferases are no longer functioning. Dendroseris is an example of
reduction in the flavonoid chemistry, and contrasts with the reverse
situation which was found in Roblnsonia (Pacheco et al., 1984) where
evolution has been accompanied by elaboration of the flavonoid
1 profile mainly by accumulation of intermediate metabolites in flavonoid biosynthesis. 21
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•x Fig. 1. Map showing the location of the Juan Fernandez
Archipelago in southern South America. Masafuera Masatlerra
rv> F i g . 1 vo 30
Fig. 2. Composite two-dimensional chromatographic pattern of
flavonoids in leaves of Dendroseris. Flavonoid identity (spot
numbers are shown in parenthesis): luteolin-7-0-glucoslde (1, 2, 3,
4); luteolin-7-0-diglucoside (5, 6, 7); apigenin-7-0-glucoside (8,
9, 10); apigenin-7-0-diglucoside (11, 12); quercetin-3-O-glucoside
(13); quercetin-3-0-diglucoside (14); luteolin (15); apigenin
(16). 31
GD
15% HOAc
— TBA
Fig. 2 32
Fig. 3* Changes in the flavonoid system in Dendroseris. superimposed on a network of relationships based on morphological features (from Sanders et al.f 1987). Acronyms of taxa are:
BER = Dendroseris berteriana: GIG = D^_ gigantea;
LIT = D^_ litoralis;MAC = D^ macrantha:
MIC = IK. micrantha: MAP =IK. macrophylla:
MAR = IK. marginata:NER = IK.nerilfolia:
PIN = IK. pinnata: PRU = IK. pruinata: REG = IK. regia. * Species on
Masafuera. 33
CHANGES IN THE FLAVONOID SYSTEM IN DENDROSERIS
M F MT
PHOENIOOSERIS.
b e r REG *■
PIN CHILE RE
NER GIG PRU S. A.
MAC MAP MAR LIT
Loss OF FLAV0N01S O l-OSS OF FLAVONE GLUCOSIDE % Gain of flavonol digluco'side
F i g . 3
1 Fig. 4. Composite two-dimensional chromatographic pattern of flavonoids in leaves of Hieracium from continental Chile. Flavonoid identity (spot numbers in parenthesis): luteolin 7-0-diglycoside
(1); apigenin 7-0-diglycoside (2); luteolin 7-0-monoglycoside; apigenin 7-0-monoglycoside (4). 35
15% HOAc
TBA
F i g . 4
i 36
Table 1. Collection data for specimens of Dendroseris. Hieracium.
and Hypochaeris from the Juan Fernandez Islands and continental
Chile. Collection numbers are those of Stuessv et al. unless noted
otherwise. Vouchers are on deposit at OS with duplicates at CONC
unless specified otherwise. MT = Masatierra, MF = Masafuera, S =
Santa Clara.
Dendroseris
Subgenus Dendroseris: IK litoralis. MT: San Juan Bautista,
Cumberland Bay, 5150, 6305. cultivated in CONAF garden; IK
macrantha, MT: San Juan Bautista, Cumberland Bay, 5149. cultivated in
private garden; IK macrophylla, MF: Inocentes bajos, Skottsberg 2120
(US); IK marginata, MT: Quebrada Villagra, 5205. 6515. Subgenus
Phoenicoserls: D_j_ berteriana, MT: Ridge above Pangal and Corrales de
Molina, 5366, Cordon Chifladores, 5399. 5400. Valle Ingles, top of
the main ridge, 6569, Quebrada Piedra Agujereada, 5395: IK pinnata.
MT: Cordon Central, 5165B, Quebrada Villagra, 5199. S.W. of Mirador
Selkirk, Cordon Salsipuedes, Marticorena et a K 9124. 5221. 5222; D.
regia, MF: Las Torres, Skottsberg 570 (US), Loberia Vieja 9111. Cerro
Verde £1.18, Quebrada Sandalo 9316. Subgenus Reas D- nerilfolia. MT:
Quebrada Lapiz on path from San Juan Bautista to Puerto Frances,
5 m , 63P.7> Puerto Frances up right ridge, 6625. Cordon Chifladores,
down N. side of ridge La Pesca de los Viejos, 6647. Cerro Pascua,
quebrada toward Puerto Frances, 6655: D. micrantha. MT: Cerro Pascua,
top of the ridge, 5118, Quebrada Piedra Agujereada, 5169A. 5169B.
516£C, 5377, 6308, East side Cerro DamaJuana, 6324. Quebrada
1 37
Table 1. (continued)
Villagra, 6519. Puerto Frances, 6624. 6678: D. pruinata, S: Morro
Spartan, 5108. 6218. MT: La Vaqueria, 5471 .5472. 6443. 6444. San Juan
Bautista, Cumberland Bay, 6434, cultivated in CONAF garden, Valle
Ingles, 6545; D. gigantea. MF: Quebrada del Blindado, Skottsberg
426.
Hieracium
CHILE: IX Region, Provincia Malleco, Parque Nacional
Nahuelbuta, Piedra del Aguila, Pacheco et al. 1898; X Region, Prov.
Palena, SE of Puerto Ramirez, Stuessy et al. 7212.
Hypochaeris
H. glabra. MT: San Juan Bautista, path to La Hosteria, 5463;
H. scorzonerae var. scorzonerae. CHILE:.Prov. Coquimbo, Cuesta La
Vinita, Ricardi & Marticorena 4544/929: H. tenuifolia var. eurylepis.
CHILE: Prov. Nuble, Termas de Chilian, Sparre & Smith 416: H. thrlncioides. CHILE: Prov.0*Higgins, Termas de Cauquenes, A. Pfister s.n. (CONC 25092). Table 2. Occurrence of flavonolds In Dendroseris. Collection numbers of Stuessy ei -flJL. (5000s. 6000s ana 9000s) unless otherwise specified.
F 1evones Flavonols Flavone Aolvcone Taxon Col lection f T T 4 5 & 7 8 4 l6 ll T 7 13T i 4 15 16 Number
Subg. Oamircseris
D. litoral Is Skottsb. 5150 X X X XXX X X XXX 6305 X X X X XXXX XXX D. macrantha (Bert, ex Ocne.) Skottsb. 5149 X X X X X X X X 7 X X
H, macrophylla D. Don 2120 Skottsb. XX X X XXX X (US) D. marglnata (Bert. A Ocne.) Hook. & Arn. 5205 X XXXX 7 X X 7 X X 6515 X X XXXXX XX X X
Subg. fbfifinJccserLs
H. berterlana (Ocne.) Hook. & Arn. 5366 XX X X 5399 X X X X X 5400 X XX X 6569 XXXX XX 5395 X X X X X X
0. pinnate (Bert. A Ocne.) Hook. A Arn. 51658 X X X X XX 5199 X X X X XX 5210 XX X X X X 5221 X X XX X X 5222 XX X X XX 9124 Martl- X X X X X X corena
D. regia Skottsb. 570 Skottsb. X X X X X X 7 9111 XXX X X X 9118 X XXX X X CO 03 9316 X XX X X X Table 2. Continued.
Taxon Col lection 1 2 3 4 5 6 7 8 9 10 11 12 13 14 lb 16 Number
Subg. B&O
D. pi pantea Johow 436 X X Skottsb. (US)
5118 X XXXX 7 7 X 5169A X X XXX X 51698 X XXX XX 5169C XXX X XX 5377 XX X X 7 7 7 6308 X X XX X 7 X X XX 6324 X XX X X X 6519 X X X XX 7 X X X 6624 XX X XX X X 6678 X XXX 7 7
r.erIfol la (Ocne.) Hook & Arn. 5405 XXXX XXX XX X 630/ XXX XX XX XX X 6625 X X X 7 X X X 7 X 6647 XXXX X X X X 6655 XXX XXX X X X X
orulnate (Johow) Skottsb. 5108 X X 7 X X X XX X 5471 X X 7 X X X XX X 5472 X X 7 X X X XX X 6218 X XXXX X X 7 X X X X 6434 X XXX ? X X X 7 644> XX XX )< 7 X X X X 6444 X X 7 X 7 X X X 6545 . X X X 7 7 X
oj v £ > Table 3. Distribution of flavonoids in some genera of Lactuceae.
Taxon FLAVONE FIAVONOL Reference or Voucher
Ag* Agg Cg Hg Ig Lg Lgg Sg FI Kg Qg Rg Uk
CichOtiUTO sp. X X XXX Rees and Harbome (1984) Bieracium murorwn l . ssp grandidsis X XX Haag-Berrurier and Duquenois (1969) (Dahlst.) Zahn. var. minoriceps Zahn. B* aurantiacum l . X Mihele (1971) B. pilosella X Shelyuto et al. (1977) B, utrbellatum X Shelyuto et al. (1976) Bieracium sp. X XXXXX Guppy and Bohm (1976) Hieracium sp. XXXX Eacheco et al* 1898 (os, c o n c ) Bieracium sp. XXX . Stnessy et al* 2212 (os, c o n c ) Hieracium sp. X XXX Stuessy et al* 29192) (OS, CONC) Heywoodiella oligocephala X Ha rb o m e (1978) Hvpochaeris sp. X H a r b o m e (1977) fi* scorzonerae(d .c .) f . Mueii XX Bicardi and flarticorena 4544 var. scorzonerae (CONC, OS) H. tenuifolia (H. et A.) Griseb. X X X X Scarce and Snitb 418* 1954 var. eurilepis (CONC, OS) B. thrinchicioides (Remy) Reiche XX X X A* Efister* 1952 (OONC, os) Bypochaeris glabra L. X X X Stuessy et al 5463 S*. asset XX Vedantham et al. (1978) Sonchus sp. X Bramwell and Dakshini (1971) Tragopogon sp. XXX Kroschewsky et al. (1969)
* g» sugar (arabinose, galactose, glucoronic acid, glucose, rhamnose, xylose.) A ■» apigenin; Cg = C-glycosylflavone; FI = flavonol; H = chtysoeriol; I = isoetin; K = kaempferol; L = luteolin; Q m quercetin; R = isorhamnetin; S = isocyanoroside; Uk = unknown. Chapter II
NATURAL INTERSPECIFIC HYBRIDIZATION IN GUNNERA (GUNNERACEAE)
OF THE JUAN FERNANDEZ ISLANDS, CHILE.
INTRODUCTION
Natural hybridization is a frequent phenomenon among flowering
plants (Knobloch, 1972; Grant, 1981). Although hybrids and hybrid
swarms have been detected growing in nature in many plant groups
(Grant and Wilken, 1988; Doyle and Doyle, 1988; Tanowitz and Adams,
1986; Tortosa, 1988), the role of hybridization in plant evolution is
still a controversial topic in the study of evolutionary processes
(Levin, 1979). Hybridization on the one hand may be rejected as an
evolutionarily important process because of low fitness and sterility
of the hybrid derivatives. On the other hand, hybridization may be
seen as an important process in the evolution of plant groups because
it can be a source of recombination and, therefore, its importance
can be as great as mutation and recombination (Grant, 1981).
A more realistic perspective is that hybridization can have an
evolutionarily significant effect if it is followed by establishment
41
1 of advanced hybrid generations, with or without polyploidy, or by
introgression (Grant, 1981). Although the breakdown of isolating
mechanisms is often the first factor in the appearance of natural
interspecific hybrids, the environment determines if these hybrids,
advanced generation hybrids or introgressants may become established
successfully (Stebbins, 1950). In a stable environment, hybrids are
at a disadvantage with respect to parental populations because all
niches are filled and no hybrid habitats exist where the hybrids can
survive. Disturbance of the environment disrupts stable habitats
creating new open areas and new ecological niches which can be
exploited by hybrid derivatives. In these new niches, hybrid
individuals with an enriched gene pool (Crins et al., 1988) have higher fitness than the parental populations and can compete
successfully with them.
Oceanic islands, because of their recent origin, offer new habitats within a restricted geographical area. Hybridization might be favored in insular areas where segregates can exploit these new habitats and therefore contribute to th.e evolutionary success of the group. Speciation on islands apparently has been accompanied by little genetic divergence at enzyme loci (Ganders et al., 1980; Carr and Kyhos, 1981; Lowrey and Crawford, 1985), and congeneric species are usually fully interfertile (Gillet and Lim, 1970; Lowrey and
Crawford, 1985). Hence the potential for natural interspecific hybridization in floras of oceanic islands is great.
One set of oceanic islands, the Juan Fernandez Archipelago
(Fig. 5), is a small group of three islands (Masatierra, Masafuera, 43
and Santa Clara), located at 33° S latitude and 580 km west of the
coast of Chile. Although its geographical position is not as
dramatically isolated as the Hawaiian Archipelago, the angiosperm
flora does shows a 69$ endemism at the specific level (Skottsberg,
1956).
The most conspicuous example of natural interspecific
hybridization in the Juan Fernandez Archipelago occurs in Gunnera
(Gunneraceae). This genus is represented by three endemic species:
Gunnera bracteata, G. masafuerae. and G^ peltata. All three species
belong to subgenus Panke (Schindler, 1905) which is the largest group
in the genus, with approximately 45 species distributed in South
America and Hawaii (Schindler, 1905; Saint John, 1946; Biloni, 1959;
Mora-Osejo, 1978,1984; Gomez 1983). Gunnera peltata is endemic to
Masatierra, where it grows from 350-500 m. Gunnera bracteata is
endemic to the same island, but is found at slightly higher
elevations from 400 m to the highest ridges at 600 m. Gunnera
masafuerae is found on the younger island (Masafuera), where it grows
from 100 m to 1400 m along streams and on the walls of canyons.
Skottsberg (1922) commented on a highly variable population of
Gunnera growing in Quebrada Villagra on Masatierra. He hypothesized
that intermediacy was due to hybridization between bracteata and
G. peltata.
There are other reports of hybridization in Gunnera.
Beutzenberg and Hair (1962) mentioned a possible hybrid swarm between
two species growing in New Zealand. Palkovic (1978) suggested
hybridization between (Jj. insignis and G^ talamancana in a disturbed
3 44
area in Costa Rica, and Mora (1984) mentioned hybrids between three
sympatric species of Gunnera in Colombia atropurpurea. G.
brephogea, and G^. pilosa).
During an expedition to the Juan Fernandez Islands in 1984 we
critically reexamined the highly morphologically variable population
of Gunnera in Quebrada Villagra that was mentioned by Skottsberg
(1922). This variable population is of considerable importance
because if it is the result of hybridization, it would be the most
conspicuous example of interspecific hybridization in the entire
flora of the archipelago. The objectives of this paper therefore are
to: (1) use morphological and flavonoid data to clarify whether
hybridization really occurs between (L bracteata and G^ peltata; (2)
understand the nature and dynamics of this hybridization; and (3)
evaluate its evolutionary importance.
MATERIALS AND METHODS
Sampling.
Plant material and data were collected during the expedition to
the Juan Fernandez Archipelago organized by the Departments of Botany
of The Ohio State University and Universidad de Concepcion, Chile
during January and February 1984. Vouchers of the parental species
are on deposit at OS with duplicates at CONC. Specimens of the
hybrid Individual samples are on deposit at OS only.
Ninety Individual plants from the two species of Gunnera and
1 45
intermediates were analyzed from five populations. Specimens of G.
peltata are from three isolated pure populations: (1) a population in
Plazoleta del Yunque (Stuessy et al. 6481: (2) a population in
Quebrada Pangal (Stuessy et al. 6314. 6314A): and (3) a population in
a ravine from Cordon Chifladores down toward Puerto Frances (Stuessy
et al. 6671). These three populations were isolated by at least two
km. Specimens of CL_ bracteata are from an isolated population in
Valle Ingles (Stuessy et al. 6561). For the purpose of this study
individuals growing in the higher part of the transects 1 and 2 were
used as representative of G^_ bracteata and pooled with those
individuals from the pure population of G^. bracteata from Valle
Ingles. Morphologically variable individuals are from an
intermediate population in Quebrada Villagra (Fig. 6). Sampling was
non-random because an attempt was made to cover the variation seen.
The biggest leaf from each plant was chosen for morphological
analysis. Samples for flavonoid analysis were taken at the same time
from the same leaf. Four to six scales (modified leaves which cover
the apical meristem) were chosen for detailed study. Flowers were
not available but infrutescences were collected when present. These
samples were taken from the middle of the compound spike.
Intermediate zone. The intermediate zone is located in
Quebrada Villagra (Villagra ravine, Fig. 6). This ravine runs from
NE to SW on the Vest slope of the main ridge facing Villagra Bay.
Here a trail winds down from the highest point at Selkirk's Lookout
(555 m) into the valley. The small creek at the bottom of the ravine
i 46
and the fog brought by the predominant SW winds maintain a humid
habitat in Quebrada Villagra.
Two transects were set in Quebrada Villagra. Transect 1 runs
from the bottom of the ravine up through the forest from 430 m to 575
m. This habitat has remained almost unchanged and represents a
relatively undisturbed environment. Transect 2 follows the trail up
from the ravine at 145 m to Selkirk’s Lookout at 555 m.
Parental species. Gunnera peltata Phil, is the largest herb on
Masatierra. Stems are horizontal with adventitious roots, 15-30 cm
in diameter, and with a terminal rosette of leaves. In the terminal
bud the apical meristem and new leaves are protected by modified
leaves (scales). These scales are red-crimson and deeply laciniate
(Fig. 7). Leaves are peltate, the blade is soft, chartaceous,
hirsute, aerolate, with verrucate glands and measuring up to 1.6 m
across. The blade is lobed with dentate margins. Petioles are long
(up to 85 cm) and covered with prickles and hairs. Flowers are
small, subtended by linear bracts and grouped in axillary compound
spikes. Fruits are smali coral-red drupes. Gunnera peltata is
common in the forest belt in humid valleys, extending from about 500
m (where there is sufficient moisture) and descending to 350 m above
sea level.
Gunnera bracteata is smaller than G^. peltata. The stems are
rarely over 1 m long and 10 cm thick. The terminal bud is protected
by green, thin, entire and ovate scales (Fig. 3), and by a gelatinous
substance produced by cauline glands. Leaves have orbicular-reniform
1 n
blades, 50-70 cm wide, firm-coriaceous, smooth, glabrous, and
subtended by a green glabrous and smooth petiole about 50 cm long.
Flowers are similar to CL peltata. Flowering period is the same for
both species, from early spring (September) to February. Fruits
ripen in April. Gunnera bracteata is confined to the highest ridges
in more or less open and windy situations above 400 m.
Morphological characters.
Fifteen characters that discriminated well the two parental
species were analyzed both in the field and in herbarium material
(Table 4). Descriptive statistics for characters 4, 5, 6, 7, 8, 9,
10, and 15 are given in Table 5. Only vegetative characters were utilized because no plant was in flower; only a small proportion of individuals in the population had fruits. Each datum represents the mean value of three or four Individual measurements.
Biological data such as chromosome numbers and pollen fertility which would have helped in understanding the dynamics of hybridization between Gunnera bracteata and G^ peltata are not available at this time. Both species were in fruit at the time of sampling, making it Impossible to collect floral buds and pollen.
Seed germination was tried unsuccessfully, probably because Gunnera seeds mature in a period of 12 or more months (Mora, 1984).
Data analysis.
The data were analyzed by hybrid index values (Fig. 8;
Anderson, 1949)> and distance diagrams (Fig. 9; Wells, 1980). 48
Correlation coefficients between characters were analyzed in the
intermediate population and in the two parental species separately.
The hybrid index is a method to show visually the population
structure and the possible direction of gene flow. The hybrid index
requires delimitation of the parental individuals. The characters
used were transformed by vector transformation (Brochman, 1987) into
three clases (Table 4). Zero was defined as similar to G. bracteata.
one as intermediate, and two as similar to peltata. The summed
index scores range from zero to 30.
The distance diagram, a mutivariate approach with equal weight
to all characters, also requires a priori recognition of the parental
taxa. Two reference points, one for each parental taxon, were
determined using all the characters employed in this study. Point A
is the lowest reference point (Fig. 9), and corresponds to the
minimum value of the characters for the taxon with the lowest mean.
Point B, the highest reference point, is the maximum value of the
characters for the taxon with the highest mean. The characters must
be ranged between zero and one to give equal weight to the different
scales of measurement (Gower, 1971)*
Flavonoid analysis.
Twenty-six individual plants were chosen for flavonoid studies.
These correspond to seven plants of G^. bracteata with hybrid index
scores between 0 - 1, five individuals of G^ peltata with hybrid
index score of 24 - 29, and 14 intermediates with hybrid index scores
6 - 2 1 .
*1 49
Ground leaves were extracted with 85? and 50? of aqueous
methanol. The combined extracts were evaporated to dryness and taken
up in aqueous methanol. The aqueous methanolic soluble extracts were
spotted near the bottom left hand corner of 46 x 57 cm sheet of
Whatman 3MM chromatographic papers, and then developed in two
dimensions with TBA (ter-butanol: acetic acid: water, 3:1:1) and 15?
acetic acid . . The chromatograms were examined over ultraviolet light
following standard procedures (Mabry, Markham and Thomas, 1970).
Individual flavonoids were identified by UV spectral analysis, by
hydrolysis in 0.1N TFA (Wilkins and Bohm, 1976), and circular
chromatography of sugars (Becker, Exner and Averett, 1977).
RESULTS
Morphological analysis. In the hybrid index, Individuals with scores
between 22 and 30 represent ^ peltata and scores between 0 and 3
represent individuals of (L bracteata (Fig. 8A).
Figure 8B shows the population along transect 2 in the
intermediate area. A complex pattern of morphological variation is
shown by individuals with hybrid scores between 4-21. Plants with
hybrid Indices near 15 are morphologically intermediate between the
two parental species, and most likely represent the F^ generation.
Individuals with hybrid indices 17 to 21 may be backcrosses to G.
peltata. Individuals with hybrid scores of 4 to 13 suggest that
backcrosses to G^. bracteata are also possible in the population.
Hybrid indices of plants along transect 1, (situated on the northern
1 50
slope of Quebrada Villagra) are shown in Fig. 8C. Comparison of this
transect with plants in the disturbed area along the trail of
transect two, reveals that the proportion of hybrid individuals in
the undisturbed environment is very low, although some backcrosses to both parents may possibly exist. An estimation of the population along transect 2 in Quebrada Villagra shows that hybrid individuals make up 19$ of the population, bracteata 6$, and peltata 75$.
The distance diagram in Fig. 9A shows the distribution of individuals along transect one. Individuals of 'pure' bracteata (
) and CL. peltata ( ) are also shown. These parental individuals form two distinct clusters. Most of the plants in transect one fall in the cluster with (L. peltata. There are seven individuals between the two clusters of parental taxa. Their position in the distance diagram, filling the gap between the two parental species, suggest that these are probably backcrosses. The distance diagram in Fig. 9B shows individuals growing along the path trail (Transect 2). Gunnera bracteata ( ) and CL peltata( ) form two distinct clusters. The suspected hybrids ( ) form a morphological bridge betwen the two taxa. All hybrid Individuals fall within the semicircle demarcating the parental individuals.
Analysis of character correlations (Fig. 10), shows that some character associations are maintained in the hybrid population while others are not. The most Important relationship, however, is the detection of new character combinations which are not evident in either parent. Character correlations between number of mucros-lacinia length, number of mucros-number of warts, and ligule height-vein width are character combination seen only in the hybrids.
Flavonoid analysis. A total of eight flavonoids was isolated from
the 26 samples of G^. bracteata. G. peltata, and intermediates. Five
flavonoids were fully characterized, one partially characterized as a
flavone by and UV spectral data, and two remain unknown. The
flavonoids are: quercetin 3-0-xylosylglucoside, quercetin
3-0-arabinoside, quercetin 3-0-glucogalactoside, quercetin
3-0-diglucoside, isorhamnetin, a flavone and two unknowns. Table 6 presents the distribution of flavonoids among the two parental
species and hybrid derivatives. Gunnera peltata is characterized by the presence of all eight compounds. The flavonoid pattern of G. bracteata is characterized by the absence of quercetin 3-0-glycoside
(flavonoid 1). Infraspecific variation was detected in both species but is most pronounced in G. bracteata (Flavonoids 6, 8, and 12 are variable). The hybrids show great variation in flavonoid content.
Compounds 1, 6, 8, and 12 are variable within the hybrid population.
Since the parental species differ only in the presence of only one flavonoid (flavonoid 1), it was not possible either to detect complementation of the flavonoid profile in the hybrids, or to use these data for documenting the exact status of the hybrid individuals
(i.e., whether F1's, backcrosses, etc.). 52
DISCUSSION
Based on morphological characters, the population in Quebrada
Villagra consists of a group of bracteata growing in relative
abundance towards the highest part of the ridges, a group of G.
peltata growing between 400 m and 540 m (being most abundant around
450 m), and a variable series of individuals between 250 and 555 m.
The individuals of Gunnera growing in Quebrada Villagra were
studied in two transects. In transect 1 (Fig. 11A), located on the
north slope of Quebrada Villagra, there is no clear zonation of the
two parental species, although in general G^ peltata is more abundant
in the lower portion of the transect and G^ bracteata in the higher
part. Hybrid individuals are present along with the parents, but
their percentage is relatively lower when compared with hybrids
growing along transect 2 in disturbed areas along the trail (Fig.
11B). Here G. peltata is absent both at the top of the transect (555
m) and lower than 340 m. The hybrids are found near the highest part
of transect 2, and they are equally abundant between 420 and 460 m.
Gunnera bracteata. although relatively abundant in the highest part
of transect 2, also grows intermixed with hybrids and G^ peltata in
places where disturbance of the environment has opened the habitat
and is drier and more exposed. Below 310 m hybrids are abundant.
This part of the transect is characterized by landslides due to the
construction of a wider road.
The variable population of Gunnera growing in Quebrada Villagra
1 53
meets several criteria of hybridity (Gottlieb, 1972). It is
morphologically variable, occurs in a disturbed and ecologically
intermediate habitat, and is found in a zone of sympatry of the
parental taxa. Although none of these criteria is by itself, strong
enough to confirm the hypothesis of hybridization, the data strongly
suggest that the population in Quebrada Villagra are of hybrid
origin.
Dobzhansky (1941) pointed out that morphological intermediacy
and variability, such as documented here in Gunnera, might also be
interpreted to reflect an ancestral population out of which the two
species evolved. In an island situation this is less likely, because
deep ravines promote rapid geographical isolation of peripheral
populations, and a series of different habitats within a reduced area
stimulate rapid speciation (Sanders et al., 1987). The Veils'
distance diagram (Fig. 9) shows that the two parental species (G.
bracteata and CL. peltata) are two well defined groups.
The variable hybrid population of Gunnera is known only from
Quebrada Villagra and nowhere else in Masatierra. Here the
environment has been profoundly disturbed by human intervention and by introduced animals such as goats and domestic livestock. The construction of the trail in the upper part, and a road in the lower part of Quebrada Villagra, has contributed to the erosion of the soil and to the creation of more hybrid environments and open habitats.
Hybridization of the habitat (Anderson, 1948), brought about by disturbance of the environment, has created a series of new and different ecological niches. Here the hybrid individuals probably 54
have a higher fitness than the parental species, and could compete
effectively with them. In the lower part of Quebrada Villagra
disturbance has created open habitats where the hybrids have
survived, probably due to relaxation of interspecific competition and
stabilizing selection (Grant, 1981). Gunnera is a perennial herb
with rhizomes, which no doubt contributes to the establishment of
hybrids by asexual reproduction. To this we can add that Gunnera is
a colonizing species in open habitats and poor soils because of its
symbiosis with nitrogen-fixing blue-green algae of the genus Nostoc
(Towata, 1985).
Isolation occurs over a small geographical area on islands.
This original geographical isolation probably has been reduced in
Gunnera during the geological history of Masatierra, due to the
reduction in size of the island (Sanders et al., 1987). Populations
of Gi. bracteata and G^ peltata now occur close enough together to
allow overlapping in their distribution. In Gunnera protandry and
wind-pollinated flowers promote outcrossing (Mora, 1984).
Hybridization between the two species of Gunnera has been facilitated
by the apparent lack of reproductive isolation plus the breeding
system. Lack of reproductive isolation is not unique for the endemic
species of Gunnera, since some cases of interspecific hybridization
have been reported between pairs of closely related species of
Gunnera growing in the continent (Palkovic, 1978; Mora-Osejo, 1984).
All data suggest that the variable population growing in
Quebrada Villagra is the result of introgressive hybridization with
backcrossing to both parental species but more frequently to G^
1 55
peltata. A factor that contributes to the complex pattern seen in
Quebrada Villagra is that Gunnera is a perennial herb, and therefore,
there are probably some F1 generation plants intermixed with the
introgressants.
We propose the following hypothesis for the evolution of
introgressive hybridization in Gunnera on Masatierra. Gunnera
bracteata and G_^ peltata evolved from some common ancestor which
arrived to the islands no longer than 4.5 m.y.b.p. (Stuessy et al.,
1984). The hypothetical ancestor must have been a propagule from G.
tinctoria, the closest relative in Southern South America (Pacheco,
in prep.), or perhaps a common ancestor of G. tinctoria and the
endemics on the islands. Availability of empty niches and
geographical isolation promoted speciation in Gunnera. As a result,
G. bracteata may have speciated into higher elevations (3000 m is
estimated for Masatierra during early colonization, Sanders et al.,
1987). Increased aridity and elevation were factors which may have favored smaller and leathery leaves adapted for dry conditions.
Gunnera peltata, on the other hand, speciated into middle elevations where rainfall and humidity were high. These conditions are similar to habitats in which Gunnera now grows on the mainland. As discussed by Sanders et al. (1987), Masatierra has probably been reduced in size due to erosion and submergence, a common trend during geological histories of oceanic islands. This reduction in size together with changing climates have brought the two species of
Gunnera into contact resulting in a zone of secondary intergradation.
Hybridization probably occurred occasionally due to recent divergence and lack of reproductive isolation, but the hybrids had low chance of
survival in a stable environment. Once the environment was disturbed
because of human intervention, a series of hybridized habitats was
created where the hybrids and backcrossed individuals were favored
and survived. The result is seen now in this variable population in
Quebrada Villagra.
Character coherence, the tendency of parental species character
combinations to stick together in hybrid derivatives (Grant, 1979),
was proposed by Anderson (1949) as a characteristic of hybrid
populations. As can be seen by the correlation coefficients (Fig.
10), although some character coherence prevails in the hybrid
population, new character recombinations are present as well. There
are two types of new character recombinations. The first ones are
those not present in either parents, such as correlations between
number of mucros-lacinia length and ligule height-vein width (Fig.
10, marked with asterisks). The second, are those correlations which
show a shift from positive to negative values in the hybrid population. Both innovations indicate that selection would favor
character recombination over character coherence, and this is possible due to the appropriate environmental conditions in the disturbed enviroment in Quebrada Villagra. It is possible that the hybrids growing below 310 m, where no parents were found, are the most likely to represent the new recombinants which are exploiting still newer habitats. 57
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Archipelago in southern South America. ED
Masafuera Masatlerra
1 60 km
F i g . 5 CT> 65
Fig. 6. Map of Masatierra showing the locations of pure
populations of Gunnera bracteata. G. peltata and the intermediate
zone with transects 1 and 2.
n Puerto Ingles
V i l l a g r a Bay
♦ ♦♦T ransect 1, Quebrada V illagra
• •■ T ra n sect 2 , Quebrada V illagra
o Gunnera braeteata. Quebrada Puerto Ingles 0 Gunnera peltata. Plazoleta del Yunque Gunnera p e lta ta . Quebrada El Pangal Gunnera p e lta ta . Quebrada Puerto Prances
F i g . 6 67
Fig. 7* Scale silhouettes of the endemic species of Gunnera on
Masatierra. Typical CL_ bracteata forms are shown in the upper left
corner, typical peltata in the lower right corner, and
intermediate hybrid variations in between. Numbers refers to
accessions. A gradation of forms exists from one species to the
other.
1 68
r***
tP •H
*i 69
Fig. 8. Hybrid Index. Frequency distribution of individuals
(boxes) of Gunnera growing in Quebrada Villagra on Masatierra.
Numbers refers to accessions. Hybrid scale values are derived from
the analysis of 15 morphological characters (7 qualitative and 8
quantitative). A = Individuals of G^ peltata growing in Quebrada "El
Pangal", Plazoleta del Yunque, and Quebrada Puerto Frances.
Individuals of CL, bracteata from Valle Ingles, and selected
individuals growing in the upper part of Quebrada Villagra. B =
Population growing along the disturbed trail in Quebrada Villagra
(Transect 2). C = Population growing along the undisturbed north
slope of Quebrada Villagra (Transect 1).
l 70
HYBRID INDEX
31 37 75 41 17 37 33 (4 73 71 71 (311 IS (31 ( i s II IS 71 7S 31 G. bracteata G. p e lta ta
B U 73 17 11 4S 57 71 74 34 77 SI u 11 41 SI 47 S3 47 11 14 41 74 35 71 37 31 11 71 11 1 71 73171 j 71144 S4 17 » l » l 31 IS 41 { 77 31 13 E s is
T ransect 2 Disturbed area
[« m d run m lal'il f»l 17 a i u is 71 7S
Transect 1 Undisturbed area
Fig. 8. 71
Fig. 9. Wells' (1980) distance diagrams of individuals of
Gunnera growing in Quebrada Villagra on Masatierra. A = Transect 1, north slope of the ravine; B = Transect 2, disturbed area along the trail. Symbols: squares = G. bracteata: dots = G. peltata; asterisks
= hybrids in the transects. 72
DlSTANCf DIAGRAM
He Individual* In TH and T-2 TRANSECT i Undisturbed area ° O.bracteofa • O.pelfofq .
** **■
TRANSECT 2 Disturbed area
F i g . 9 73
Fig. 10. Degree of correlation among eight characters in G. bracteata, G. peltata. and with the intermediate population in
Quebrada Villagra. Asterisks indicate new character recombinations no present in the parental taxa. Liang 7 4
Vawld Nmucr
t-«l«aa
Lwldt Nwart
Vawld Q. bractaata Nmucr
Htaat
Liang Nwart
Vawld Nmucr
Hybrids
Laltn Htaat
Lwldt Nwart Lhalg — >|0.50| — < |0.49|
F i g . 1 0 75
Fig. 11. Comparison of occurrence of individuals of Gunnera in
two transects in Quebrada Villagra on Masatlerra. b = .G^ bracteata:
p = G. peltata: h = hybrid individuals (shaded). Bars represent
number of individual plants growing approximately at that elevation.
A = Transect 1, undisturbed. B = Transect 2, disturbed.
1
77
Table 4. Characters used and values assigned to character states
In the morphological hybrid Index In the analysis of hybrfdfzatlon
within Gunnera of Masafuera.
Hybrid Index Value
Character 0 1 2
1. Leaf vestlture glabrous Intermediate hirsute
2. Leaf texture smooth Intermediate rugose
3. Mur IcatIons absent scarce many
4. Leaf length (cm) 16-37 38-59 60-81
5. Number of mucros In leaf margln/3cm 0-8 9-17 18-26
6. Height of tertiary teeth (cm) 0-0.6 0.7-1.3 1.4-2
7. Warts on primary velns/3cm 0-8 9-17 18-26
8. Scale height (cm) 1.5-10 11-20 21-30
9. Scale width (cm) 2.3-1.7 1.8-1.2 1.1-0.5
10. Laclnla length (cm) 0-0.9 1-7 8-15
11. Number of 1ascIn1 a absent scarce many
12. Petiole murI cations absent scarce many
13. Slime on apical merlstem present little absent
14. Scale color green green/redd Ish red
15. Vein width (mm) 5-10 11-16 17-22
1 78
Table 5. Descriptive statistics for quantitative characters of
populations of Gunnera on Masatierra. Characters are numbered as In
Table 4.
Character Taxon Mean St. Dev. Range N
4. Leaf peltata 60.8 10.4 48.0 - 80.0 7 length bracteata 29.5 5.8 16.0 - 37.0 11 hybrid 41.7 13.4 19.5 - 80.0 72
5. Number of peltata 16.9 4.0 11.0 _ 24.5 7 mucros bracteata 4.0 1.7 0.0 - 7.0 11 hybrid 11.2 6.7 3.0 - 27.5 72
6. Height of peltata 1.2 0.4 0.8 - 2.0 7 terclary bracteata 0.1 0.1 0.0 - 0.3 11 teeth hybrId 1.1 0.9 0.0 - 4.3 72
7. Number of peltata 20.7 4.6 14.0 _ 26.0 7 warts on bracteata 0.0 0.0 0.0 - 0.0 11 veins hybrid 11.3 11 .7 0.0 - 41 .0 72
8. Scale peltata 19.6 5.9 11 .5 — 30.0 7 height bracteata 5.1 3.6 2.6 - 15.6 11 hybrid 9.0 4.9 2.8 - 24.2 72
9. Scale peltata 0.9 0.3 0.4 _ 1.3 7 width bracteata 1.1 0.9 0.1 - 2.4 11 hybrid 1.1 0.5 0.1 - 2.4 72
10. LacInla peltata 7.7 3.9 3.6 15.0 7 1ength bracteata 0.0 0.0 0.0 - 0.0 11 hybrid 1.5 1.8 0.0 - 6.2 72
15 . Vein peltata 18.1 5.3 10.0 _ 24.0 7 width bracteata 7.4 1.6 5.0 - 11.0 11 hybrid 10.8 4.3 5.0 - 23.0 72
1 79
Table 6. Occurrence of flavonoids among Gunnera bracteata, G. peltata, and selected hybrid individuals. Collection numbers from Stuessy et al.
Flavonols F UK Taxon Collection HIV 1 9 10 12 8 6 3 11 Number Q-xg Q-a Q-gga Q-gg I Fl
G. bracteata 6481-28 0 XXXXX X X 6481-32 0 X X X XX X X 6 481-21A 1 X X X X 6481-22A 1 X X X X X 6481-24 1 XXX 7 7 X X 6481-33 1 X XX X X X 6494-25 1 X X X X X
G. peltata 6671-69 23 XXXX 7 X 6481-65 25 X X XX X X X X 6671-73 28 XX XX X X X X 6671-68 29 XXXXX X X X 6671-71 29 X X X X X X X
G. bracteata 6481-56 6 X X XX XXXX X 6494-5 7 X X XX XX 6481-35 10 X XX X X XX G. peltata 6481-61 10 X X XX XXXX 6481-12 11 XX X 7 XX 6481-51 12 X . X XXXXX 6481-30 15 X X X 7 X 6481-41 15 X X XXX XX 6481-21B 16 XX XX XX 6481-15 17 XX X X XX X 6481-47 17 X XX XX 6481-46 18 X XX X 7 XX 6481-36 22 XX XXX 7 XX 6481-14 26 XX X 7 XX
Q-xg = Quercetin 3-0-xylosilglucoside; Q-a = Quercetin 3-0- arabinoside; Q-gga = Quercetin 3-0-glucogalactoside; Q -gg = Quercetin 3-0-diglucoside; I = Isorhamnetin; Fl = Flavone; UK = unknown; HIV = Hybrid Index Value. CHAPTER III
FLAVONOID CHEMISTRY AND EVOLUTION OF OUNNERA (GUNNERACEAE)
IN THE JUAN FERNANDEZ ISLANDS, CHILE.
INTRODUCTION
Evolutionary phenomena in flowering plants are sometimes more easily Investigated on oceanic islands than in continental areas.
These small isolated areas have been the sites of dramatic evolutionary differentiation and adaptation. Oceanic islands contain unique plants, often quite different from closely related mainland relatives, which have diverged into different ecological niches in a restricted geographical area. Many evolutionary investigations have been made on island taxa (e.g. Carlqulst 1965, 1974; Carr and Kyhos,
1981; Crawford et al., 1987; Crins, Bohm and Carr, 1988; Gardner,
1976; Pacheco, Crawford, Stuessy and Silva, 1985; Patterson, 1984;
Sanders et al., 1987; Witter and Carr, 1988). These numerous studies have established the potential of understanding phylogeny and
8 0 evolutionary processes in island biotas.
The Juan Fernandez Archipelago is an example of oceanic islands
with a high degree of endemism in the native flora. The archipelago
(Fig. 12) is located in the Pacific Ocean about 660 km west of
mainland Chile at 33° S latitude. There are three major islands:
Masatierra (= Isla Robinson Crusoe), Masafuera (= Isla Alejandro
Selkirk), and Santa Clara just, off the coast of Masatierra.
Masatierra and Masafuera are separated by 150 km of ocean in an
East-West orientation. The ages of these islands are known to be
3.7-4.2 my for Masatierra and 1-2 my for Masafuera (Stuessy et al.,
1984). In these geographically isolated islands there has evolved a
unique flora characterized by a high degree of endemism. Of a total of 147 native species, 6 95t are endemic (Skottsberg, 1922).
The flora of the Juan Fernandez Islands has been the object of several studies. Florlstic investigations have been published by
Philippi (1856), Johow (1896), and Skottsberg (1951, 1953, 1956).
More recently the emphasis has changed to evolutionary studies and the endemic taxa have been analyzed in terms of flavonoid evolution.
(Pacheco et al., 1985; Crawford et al., 1986; Pacheco, 1988, Chapter
I), allozvme variation (Crawford, Stuessy and Silva, 1987, 1988), chromosome numbers (Sanders, Stuessy and Rodriguez, 1985; Spooner et al., 1987), and phylogeny and patterns of speclation (Lammers.
Stuessy, and Silva, 1986; Sanders et al., 1987; Crawford, Whitkus and
Stuessy, 1987; Stuessy, Crawford and Marticorena, submitted).
Among the taxa of the Juan Fernandez Islands, the endemic species of Gunnera (Gunneraceae) are particularly interesting because 82
they are the largest herbs in the archipelago, they have speciated
within the islands, they belong to a genus with ample distribution on
mainland South America, and they present the only known case of
natural interspecific hybridization between two species growing on
Masatierra (Skottsberg, 1922; Pacheco, Chapter II).
On a worldwide basis Gunnera has been segregated
morphologically into six subgenera (Schindler, 1905; Bader, 1961) :
Milligania. Misandra, Ostenigunnera. Panke, Perpensum and
Pseudogunnera. The endemic species of Gunnera from the Juan
Fernandez Archipelago belong to subgenus Panke. which is the largest
group in Gunnera with approximately 50 species distributed in South
America and Hawaii (Mora-Osejo, 1984; St John, 1946, 1957). The
species in subgenus Panke are gigantic perennial herbs with creeping
or suberect rhizomes. The leaves, enormous and long-petiolated, are
in a rosette at the end of the rhizome. In the terminal bud the leaf
primordium is protected by scales (modified leaves or 'lepidofilos';
Mora-Osejo, 1984). The inflorescence, a large compound spike, bears numerous small red to brownish drupes. The habitats in which species of subgenus Panke are found are characterized by moderate to heavy rainfall and moderate to high elevation (Bader, 1961). In the Juan
Fernandez Archipelago, subgenus Panke is represented by three endemic species: Gunnera bracteata Steud., .G^ masafuerae Skottsb., and G. peltata Phil.
The purposes of the present study are to: (1) determine relationships of the endemic Juan Fernandez species of Gunnera with their closest mainland relatives; (2) determine phylogenetic affinities among the endemic species in the Juan Fernandez islands;
(3) examine the flavonoid components of the endemic species of
Gunnera and their continental relatives; and (4) interpret all data
for evolutionary implications, with particular reference to changes in the flavonoid system during evolution of Gunnera in the archipelago.
MATERIALS AND METHODS
Morphological analysis. The three endemic species of Gunnera were collected during expeditions to the Juan Fernandez Islands organized by the Departments of Botany of The Ohio State University and Universidad de Concepcion in 1980, 1981, 1984 and 1986. Voucher specimens are at CONC and OS.
The study of the relationships of the island species with continental species in Gunnera subgenus Panke was based on the material collected during the expeditions to mainland Chile (1986),
Bolivia (1987) and Peru (1987), and on material borrowed from the following herbaria: F, MO, NY, and UC. For phylogenetic reconstruction, (L tinctoria was selected as out-group. The computer program developed by Swofford (1985) was used to construct the most parsimonious cladogram. Morphological plus chemical characters were polarized by the out group criterion (Crisci and Stuessy, 1980).
Flavonoid analysis. For flavonoid analysis, ground leaf material was extracted with 85? and 50% methanol. The extracts were 84
taken to dryness, suspended in water, filter, and then applied to 55
x 35 cm 3MM chromatographic paper. The two-dimensional chromatograms
(2-D) were developed in ter-butyl alcohol: acetic acid: water (3:1:1;
TBA) in the first dimension and in 15$ acetic acid (15$ HOAc) in the
second dimension. Spots on the chromatograms containing individual
compounds were eluted with spectral methanol. When purification of
individual fla.onoids was necessary, this was accomplished by
thin-layer chromatography (TLC) on precoated polyamide DC-6 plates
(Macherey-Nagel). The solvent system used was 1,2 dichloroethane:
methanol: methyl ethyl ketone: water: formic acid (50: 25: 20.5: 4:
0.5). Identifications of the flavonoids were done by the study of a
set of six ultraviolet spectra obtained following standard procedures
(Mabry et al., 1970). Flavonoid glycosides were hydrolyzed with 0.1N
trifluoroacetic acid in screw-cap test tubes in water bath for one
hour (Wilkins and Bohm, 1976). Sugars were identified by circular
co-chromatography with standards on precoated cellulose thin-layer
plates (Macherey-Nagel) using as solvent system pyridine: ethyl
acetate: water (6:3:2:) (Becker et al.,1977). The chromatograms
were sprayed with p-anisidine phthalate (1.0 g phthalic acid and 1.0
ml anisidine in 100 ml of 96$ ethanol) to visualize the sugar
compounds.
Chromosome counts. Living material of (K bracteata, G.
masafuerae. and peltata, was collected during the expedition to
Juan Fernandez Islands in January and February of 1984. Gunnera
tinctoria was collected in Concepcion, Chile in February of 1984.
These specimens were grown in the greenhouse at Ohio State. For
1 85 mitotic studies, root tips of the four species were treated with 0.2? colchicine, fixed in 95? ethanol: 99? propionic acid (4:1) for two days, stained with acetocaraine, macerated with 45? acetic acid at
60°, and then squashed. Material for meiotic counts was obtained from G boliviana in 1987. Buds were fixed in Carnoy's solution and chromosomes were counted following the conventional squash technique using acetocarmine as stain (Snow, 1963)•
RESULTS
Chromosome counts. Our chromosome counts for boliviana, G. bracteata. G. masafuerae. and G^. peltata represent the first reports for these taxa. The number 2n = 34 for all five species reported here (Table 7) is consistent with the counts reported for other species in subgenus Panke.
Flavonoid analysis. Fifteen flavonoids were isolated from the species of Gunnera studied. The flavonoid pattern is charaterized by the presence of glycosides of quercetin, kaempferol and isorhamnetin, a partially Identified flavone and two unknown phenolic compounds. A two-dimensional chromatographic pattern of the flavonoids isolated is shown in Fig. 14. The structure of these compounds is shown in Fig.
15. The distribution of flavonoid compounds is presented in Table 8.
The endemic species of Gunnera and G^ tinctoria are characterized by the absence of glycosides of kaempferol. Kaempferol glycosides are common in the species of Gunnera from Bolivia, Peru and Mexico. 86
Flavone A is restricted mainly to the endemic species of Gunnera and
G. tinctoria, however, it might also be present in G^ bolivari.
A cladogram showing hypothetical evolutionary relationships
among the endemic species of Gunnera in the Juan Fernandez islands
and Gk. tinctoria from mainland Chile is shown in Fig. 13. Changes in-
the flavonoid system in the endemic species of Gunnera superimposed
on the hypothetical evolutionary tree for these species is shown in
Fig. 16. Table 9 shows the basic data matrix with the characters and
character states used.
DISCUSSION
Phylogeny. It seems likely that Gunnera in the Juan Fernandez
Archipelago originated from a single introduction, and is therefore
monophyletic. The geographical isolation of the archipelago, the
probabilities of the colonization process, the chemical homogeneity
of the group, and the natural hybridization of the two endemic
species on Masatierra (Pacheco, Chapter II) all support the idea of a
single introduction. Analysis of morphological characters in species
from South America plus study of species elsewhere in the genus
reveal that Gjs. tinctoria. a widely distributed species in continental
Chile, is clearly the closest relative of the endemic species of
Gunnera on the islands. Further support for this conclusion comes
from the flavonoid contents of selected species of Gunnera in
subgenus Panke from South America (Table 8). All the species of
Gunnera from Bolivia, Peru and Mexico are characterized by the
1 presence of kaempferol and glycosides of kaempferol, compounds which
are absent in the endemic species of Gunnera as well as in G.
tinctoria. Gunnera tinctoria and the endemic species on the islands
form one group characterized by the presence of a unique flavone
(flavonoid 12) which is absent from the group of Gunnera from
Bolivia, Peru and Mexico. The morphological and flavonoid data
suggest that Gunnera tinctoria is the closest relative of the endemic species in the Juan Fernandez Archipelago, and it was, therefore, chosen as the out-group for cladistic analysis. Since the continental area is older than the islands, it is highly probable that the most closely related taxon on the mainland would represent the ancestor of the insular taxa, rather than the reverse.
A cladogram of phylogenetic relationships is shown in Fig. 13.
Gunnera peltata is the most primitive species of this group in the archipielago. It is endemic on Masatierra and it grows throughout the forests in humid valleys from 350 to 500 m. The leaves are peltate, soft-chartaceous, and the fruits are small drupes. The habitat of G. peltata is very similar to that of G^ tinctoria on mainland Chile.
Gunnera masafuerae is closely related to G^ peltata. It evolved on the younger island, Masafuera, where it grows along the water courses and on walls of the canyons, similar to the habitat of G^ peltata. It is also abundant in the fog-swept highlands especially along water courses and depressions in the fern beds. Gunnera masafuerae differs from Gi_ peltata in having reniform leaves and growing to 1,100 m of elevation. Gunnera bracteata is the most divergent species in the group. This species, endemic to Masatierra, is confined to the 88
highest ridges above 400 m. The leaves are completely glabrous and
smaller than those of peltata and masafuerae. Gunnera
bracteata is adapted to more open habitats outside the range of the
forest vegetation on ridges exposed to continuous winds.
The considerable divergence in morphological characters of G.
bracteata led us to test the hypothesis of a double introduction of
this group to the islands. Two species have been proposed as
possible close relatives of bracteata: G. bolivari and G.
magnifica. St John (1957) described G. magnifies from Colombia and
suggested that its closest relative was G^. bracteata. We dismiss
this idea based on the shape and the size of the scales and leaf
vestiture. In G. magnifica the scales are 10-39 cm long and
lance-linear with the margins laciniate. In G^ bracteata the scales
are entire, broad-ovate and 2.5-4 cm long. The petioles and blades
are muricated and covered with unicellular hairs in magnifica
whereas in G^ bracteata leaves are completely glabrous. According to
MacBride (1959), G. bolivari from Peru could be another close
relative of bracteata. He based this statement on the size of the
leaves, which in these two species are smaller than in many other
species of Gunnera. and also on their smooth and glabrous nature. We
agree that these three features are also present in G^ bracteata. but
whereas G. bolivari is almost ebracteate, G. bracteata has
conspicuous spathulate bracts in the inflorescence. Additional
support to help dismiss a close relationship between G^ bracteata and
G. bolivari comes from the analysis of the flavonoid components of
these two species. In Gu. bolivari the flavonoid profile is
1 characterized by the presence of kaempferol glycosides and absence of
a flavone compound (flavonoid 12). This flavonoid pattern is also
shown by species from Peru, Bolivia and Mexico (Table 8), but not in
G. bracteata. The profile of the later species is clearly most
similar to those of the other two endemic species and to that of G.
tinctoria.
Origin of Gunnera in the Juan Fernandez Islands.
The founder population of Gunnera must have arrived to
Masafuera within the last four million years, the age calculated for
Masatierra (Stuessy et al., 1984). Gunnera is a small group in the
islands which suggests that arrival could have possibly occurred
somewhat late during the colonization process of the archipelago,
when the ecological opportunities were not as numerous as in earlier
phases. Colonization of Masafuera must have occurred within the last
1 to 2 million years from propagules from Masatierra.
Propagules of G^ tinctoria or perhaps a common ancestor of G.
tinctoria and the endemic island species, probably come from southern
South America. The fruits of Gunnera are small fleshy drupes (1.5
mm) that might well be adapted for dispersal by frugivorous birds
(Carlquist, 1974). Seeds of Gunnera from mainland Chile could have arrived inside the digestive system of birds on erratic courses brought by cyclonic winds. There are no known usual migration routes between Southern South America and the Juan Fernandez Archipelago
(Dorst, 1961), but bird3 from mainland Chile, especially waterfowl, have been recorded occasionally on the Juan Fernandez Islands 90
(Weller, 1980). Dispersal from Masatierra to Masafuera was probably
effected by internal transport by endemic birds. The Juan Fernandez
Petrel and Masafuera Petrel are the two possible vectors for
dispersal of Gunnera fruits. Although they nest only in Masafuera,
they make long flights out into the ocean and it is likely that they
make occasional trips to Masatierra (Johnson, 1965).
Speciation in the endemic species of Gunnera.
The mode of speciation of G^ masafuerae can be postulated with
confidence as geographical speciation. Gunnera masafuerae evolved on
Masafuera in isolation from populations on Masatierra within the
lapsus of 1-2 my, the age calculated for this island (Stuessy et al.,
1984). On Masatierra G. bracteata evolved on the highest parts of
the ridges perhaps through quantum speciation. This mode refers to
the origin of a new and divergent species from a geographically
isolated peripheral population in an outcrossing organism (Grant,
1981). It is known that geographical isolation can occur over short
distances in an insular environment. Gunnera bracteata is so
divergent morphologically from G^. peltata that a rapid and radical
process can be postulated as the mode of origin for this species.
Gunnera peltata probably has originated from the ancestral mainland population by more gradual and conservative processes.
Speciation in Gunnera in Masatierra has not been accompanied by reproductive Isolation. Lack of reproductive isolation and few genetic differences are characteristics that have been reported for insular taxa (Gillet and Lim, 1970; Carlquist, 1980; Carr and Kyhos, 1981; Crawford et al.f 1987). In Gunnera, speciation on Masatierra
has involved conspicuous morphological changes but little genetic
isolation. Because of lack of reproductive isolation, bracteata
and peltata hybridize in zones of contact. These two species have
come together probably due to the*reduction in total surface area of
the island postulated by Sanders et al. (1987). Hybridization in the disturbed area.in Quebrada Villagra is one of the few examples of
extensive hybridization in an island environment (Pacheco, Chapter
II) and the only example of natural hybridization in the flora of the
Juan Fernandez Islands.
Chromosome numbers for species of Gunnera subgenus Panke have been reported to be 2n = 3^ (Dawson, 1983; Mora-Osejo, 1984). Our counts for the three endemic species of Gunnera of 2n = 31* suggest that the endemic species are polyploids at the tetraploid level- and that speciation within the archipelago has occurred without change in ploidy level. The same chromosome number of 2n = 31* in G^ tinctoria. the presumed ancestor for the endemic group, indicates that there have not been changes in ploidy level with respect to the ancestor from the mainland. The endemic Gunnera. therefore, can be regarded as ancient polyploids (Sanders et, al. 1983).
Flavonoid evolution. To investigate flavonoid changes during the evolution of the endemic species of Gunnera in the Juan Fernandez
Islands, we assume that the relationships based on morphological data, and depicted as a cladogram (Fig 13)» reflect the actual evolutionary relationships among the three endemic taxa and their 92
presumed ancestor, (L. tinctoria. Evolution of the flavonoid system
can be seen by superimposing the distribution of flavonoid data
(Table 8) upon the hypothetical evolutionary relationships (Fig. 16).
The evolution of the group on the islands is characterized mainly by
loss of compounds even though gain of compounds is also seen. The
evolution of the flavonoid system during speciation of the group on the islands is characterized by two main features. First, little flavonoid divergence has accumulated between the island species and their presumed progenitor on the mainland. Changes in the flavonoid system in the endemic species are characterized by the loss of isorhamnetin 3-0-glucoside and the gain of the flavonol quercetin
3-0-xyloxylglucoside. Second, minimal changes in flavonoid chemistry have occurred during speciation among the endemic species on the archipelago, and these are largely losses of compounds. Quercetin
3-0-digalactoside (flavonoid 3) is lost in the lines going to G. peltata and G^. bracteata. An additional loss occurred in G. bracteata with the disappearance of quercetin 3-0-xyloxylglucoside.
One innovation occurred during speciation of G^. masafuerae in the younger island: a unique flavonol, quercetin 3»7-0 diglucoside. This gain mutation must have occurred within 1-1.2 my as this is the age of Masafuera. Simple flavonoid profiles in island endemics have been documented previously (Gardner, 1976; Patterson, 1984). Explanation for reduction in number of flavonoids is based largely on the suspected role of these compounds as defensive mechanisms against predators or pathogens (Levin, 1971; Gardner, 1976), which are often not present in at least the same degree in Islands. 9 3
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Chromosome numbers from the flora of the Juan Fernandez Islands.
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of the Hawaiian species of Gunnera (Haloragidaceae). Hawaiian
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______. 1957. Gunnera magnifica. a new species from the Andes
of Colombia. Sv. Bot. Tidskr. 51: 521-528.
STUESSY, T. F., K. FOLAND, J. F. SUTTER, R. W. SANDERS and M. SILVA.
1984. Botanical and geological significance of Potassium-Argon
dates from the Juan Fernandez Islands. Science 225: 49-51.
______, D. J. CRAWFORD and C. MARTICORENA. In press. Patterns 99
of phylogeny in the endemic vascular flora of the Juan Fernandez
Islands, Chile.
SWOFFORD, D. L. 1985. Phylogenetic analysis using parsimony. Typed
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VIRKKI, N. 1962. Heiosis and development of the embryo sac in G.
insignia (Oersted) D.C. (Halorrhagaceae). J. Agric. Univ.
Puerto Rico 46: 254-268.
HELLER, M. W. 1980. The island waterfowl. Iowa Sstate University
Press. Ames, Iowa.
WILKINS, C.K. and B. A. BOHM. 1976. Chemotaxanomic studies in the
Saxifragaceae sensu lato 4. Flavonoids of Heuchera mlcrantha
var. diver3lfolla. Canad. J. Bot. 54: 2133-2140.
WITTER, M. S., and G. 0. CARR. 1988. Adaptive radiation and genetic
differentiation in the Hawaiian Sllversword alliance
(Compositae: Madiinae). Evolution 42: 1278-1287.
1 Fig. 12. Map showing the location of the Juan Fernandez
Islands in South America. Masafuera Masatierra
1.50 km
Fig. 12 102
Fig. 13. Cladogram showing evolutionary relationships among endemic
species of Gunnera from the Juan Fernandez Islands and th eir presumed ancestor, G. tinctoria. from mainland Chile. Characters and states are given in Table 9. MF= Masafuera; MT = Masatierra; b = G. bracteata;
® = G» masafuerae; p = G. peltata: t = G. tinctoria. MF
Fig. 13
u>o 104
Fig. 14. Composite two-dimensional chromatographic pattern of flavonoids in leaves of Gunnera. including the three endemic 3pecies on the Juan Fernandez Islands, G^. tinctoria. and selected species from South America. Spot numbers correspond to flavonoids listed in
Fig. 16. 0 9 >
15% HO Ac 105 106
Fig. 15. Structure of flavonoids isolated from G. bracteata.
G. masafuerae. G. peltata, G. tinctoria. and selected species of
Gunnera from South America. 1 0 7
OH
OB
1. Quercetin 3-0 arabinoside Rj=Ara; R2=H; R 3=0H; r 4-o b
2. Quercetin 3-0 glucogalactoside R^=Glu-galj R2*H j R3=OR j r 4«o b
3. Quercetin 3-0 digalactoside Rj=Gal-galf r2*=b t R 3-OBj r 4*o h
4. Quercetin 3-0 diglucoaide Rj-Glu-gluj R2-B j r 3«o b > r 4-o b
5. Quercetin 3-0 xyloxylgluco«ide R^Xyl-gluj Rj-B; R 3«0B| r 4-o b
5A.Quercetin 3»7-0 diglucoside • Rj<»Gluj R3*G1u )R^"OB
6. Kaempferol 3-0 glycoside Rj-Glyi *2-H; R 3«0H; r 4-h
. > 7. Kaempferol 3-0 glycoside Rj»Cly» Rj-B; R 3-OB; r 4-h
8. Kaempferol 3-0 glycoside R 1«=Gly; R2-B; R 3=0H; r 4=h
9. Kaempferol Rj=OH; R2-H; R 3=0H; r 4»b
10. Isorhamnetin 3-0 glucoside R^=Glu; R2-B; R 3=OHj r 4-o c h
11. Isorhamnetin R^OH ; R2-H; R 3=0H; r 4=o c h
12. Flavone A R ^ H ; R2=OBj R 3=0Hj r 4*=o h
Fig. 15
i 1 0 8
Fig. 16. Changes in the flavonoid system in species of Gunnera from the Juan Fernandez Islands, superimposed on a hypothetical evolutionary tree. MF = Masafuera, MT = Masatierra, b = G. bracteata, m = G. masafuerae. p = G. peltata, t = G. tinctoria. Numbers refer to flavonoid compounds : 3 = quercetin 3-0- digalactoside, 5 = quercetin 3-0-xyloxylglucoside, 5A = quercetin 3,7- O-diglucoside, 10 = isorhamnetin 3-0-glucoside. *Gain of compounds; • Loss of compounds. u
Mainland MF MT chile
Fig. 16 110
Table 7. New chromosome numbers of species of Gunnera subgenus Panke from the Juan Fernandez Islands and two species from mainland South America. Vouchers deposited at O S .
Chromosome Taxon number Voucher
G. boliviana Morong XL = 17* BOLIVIA:COCHABAMBA: Villa Tunari, Pacheco et al. 1563.
G. bracteata Steud. ex Benn . 2n = 34* MASATIERRA:Quebrada Villagra, Stuessy et al 6 4 81-A.
G. masafuerae Skottsb. 2n = 34* MASAFUERA:Quebrada Las Casas, Pacheco and Ruiz 6398.
G. peltata Phil. 2n = 34* MASATIERRA:Puerto Frances, Pacheco and Ruiz 6670.
G. tinctoria (Mol.) Mirb. 2n = 34 CHILE:CONCEPCION:San Pedro, near Concepcion, Stuessy et al. 6692.
* First report for the taxon
1 Table 8. Distribution of flavonoids present in the three endemic species of Gunnera in the Juan Fernandez Islands, G. tinctoria, and selected other species of Gunnera from South America.
Flavonol Fla. Que-gly K-gly K I-glu I F-gly U n k . Species Collection Locality 1 2 3 4 5 5A 6 7 8 9 10 11 number 12 14 15 Endemic species G. bracteata 6481-21A MT:Q. Villagra XX X X M ft 6481-22A XXX X X 6481-24 ft M X XX X X X X n it 6481-28 X X X X X X X it it 6481-32 XXX XX X X It N 6481-33 X X X X X X ii n 6494-25 XXX X X
G. masafuerae 5050 MF:Q. Las Casas XXX XX X X X X 6362 MF:Q. Mono XXXX XX XX X X 6396 MF:Q. Las Casas XX XXX XX ? X 8017 MF:” XXXX XX X X X X 8081 MF:” X XXX XX X X X X
G. peltata 6481-65 MT:Q. Villagra X X XX X X X X 6671-68 MT:Pto. Frances X X XX X X X X 6671-69 MT: " X XX X XX 6671-71 MT: " XXX X X X X 6671-75 MT: ” X XXX X X X X
Mainland species •
G. tinctoria 1090 CHILE:Malleco X XXXX X X X 1101 CHILE:Malleco X XX X X X X X X 1178 CHILE:Chiloe XXXX X X X X X 1207 CHILE:Chiloe X XXXX X X X X 1247 CHILE:Nuble X X XX 9 X X X 1304 CHILE:Concepcion X XX X X X X 1917 CHILE:Arauco XXXXX X X X X 6692 CHILE:Concepcion XXX XX ? X X X 6786 ARGENTINA:R i o N e g r o X X XXX X X X TABLE 8. Continued.
Flavonol Fla Species Collection Locality Que-gly K-gly K i-glu I F-gly link. number 1 2 3 4 5 5A 6 7 8 9 10 11 12 14 15
G. bolivari 1421 PERU:Pillahuata X X XXX X XX G. boliviana 1563 BOLIVIA;Cochab. XXX XX G. margaretae 1547 BOLIVIAjCochab. XXXXX X X G. peruviana 1411 PERU:Paucartambo XXX XX X XX G. mexicana 2793 MEXICO: Chiapas X X X X X X X XX
Fla= Flavone; glu= glucose; gly= arabinose, galactose, glucose, xylose; 1= isorhamnetin; K= kaempferol; Q= quercetin; Unk= unknown. Collection numbers: 1000s are Pacheco et al.; G. mexicana Is Spooner 2793; 5000s, 6000s and 8000s are Stuessy et al. For flavonoid identification see Fig. 15. Table 9. Characters and states used in the cladistic analysis of endemic sp ecies of Gunnera from the Juan Fernandez Islands and G. tinctG ria from mainland C hile.
Character Primitive (0) Derived (1)
1. Blade surface p ilo se glabrous 2. Scale shape lancelinear ovate 3. Scale margin lacerate entire L- Leaf lobe apex acute obtuse 5. Blade lobes deeply lobed shallowly lobed 6. Verrucate glands present absent 7. Leaf base cordata peltata 8. Bract shape lin e a l spathulate 9. Isorhamnetin 3-0-glucoside present absent 10. Quercetin 3,7-0-diglucoside absent present
Table 9 A. Basic data matrix of state of characters in species of Gunnera from the Juan Fernandez Islands and G. tin c to r ia from mainland C hile. See Table 9 for descriptors and numerical assignments of characters and sta te s.
Taxa Characters 1 2 3 4 5 6 7 8 9 10
G. tricteata 1 1 1 1 c 1 C 1 1 0
G. masafuerae 0 0 c 1 1 0 0 0 1 1
G. peltata 0 0 0 0 1 0 I 0 1 0
G. tinctoria 0 0 0 0 0 0 c 0 0 0 Chapter IV
FLAVONOIDS OF GUNNERA SUBGENERA MISANDRA.
PANKE. AND PERPENSUM (GUNNERACEAE)
INTRODUCTION
The Gunneraceae are a monotypic family consisting of only one genus, Gunnera, with more than 60 species of rhizomatou3 or stoloniferous perennial herbs. Gunnera is essentially restricted to the Southern Hemisphere (Bader, 1961; Biloni, 1959; Mora-Osejo,
1984), where it occurs in temperate and subtropical humid habitats.
The family appears to be a natural one and its monophyletic nature is supported by the presence of symbiosis with blue-green algae (Nostoc) in the rhizome (Fernandez, 1984; Silvester, 1976;
Silvester and McNamara, 1976; Towata, 1985), and its pollen morphology (Praglowski, 1970).
Gunnera is very diverse morphologically. Leaves range from very small (5x7 mm) to exceptionally large (1x2 m). Flowers are small, anemophyllous, epigynous, perfect or unisexual and aggregated into spikes, racemes or panicles. The minute perianth, absent in
114 115
some species, consists of two sepals and two petals. Species can be
dioecious or monoecious, and in the latter case inflorescences
contain pistillate flowers in the lower part and staminate flowers in
the upper part, or unisexual inflorescences are present on different
parts of the same plant (Schindler, 1905; Cronquist, 1981). Fruits
are small, yellow to red drupes. Based on this ample morphological diversity, Gunnera has been segregated into six subgenera:
Milligania. Misandra. Ostenlgunnera. Panke, Perpensum. .and
Pseudogunnera (Schindler, 1905; Biloni, 1959).
Subgenera Milligania. Misandra. and Ostenlgunnera consists to small-leaved subantarctlc species concentrated in New Zealand,
Tasmania, and Southern South America (Argentina, Chile, Uruguay)
(Fig. 17), with an interesting disjunct distribution of G. magellanica which also occurs in the Eastern slopes of the Andes
Mountains from Bolivia to Colombia.
Subgenera Panke. Perpensum. and Pseudogunnera (Fig. 17) are large-leaved palaeo- or neotropical species distributed in Southwest
Africa, Madagascar, Southeast Asia, and South and Central America.
Subgenus Panke is the largest group in Gunnera. It comprises about
55 species which occur mainly in the western part of South America from 1000 m up to 3500 m. A few species are found north of the equator (Southern Mexico). Subgenus Panke also has representatives in the archipelagoes of Hawaii (St. John, 19*16) and Juan Fernandez,
Chile (Skottsberg, 1922). Previous studies in Gunnera have focused on taxonomy (Mora-Osejo, 1978, 1984; St. John, 1946, 1957), ultrastructure (Behnke, 1986), and symbiotic aspects (Silvester and 116
McNamara, 1976).
Flavonoid chemistry has been useful in determining systematic
relationships and evolutionary affinities within and among taxa
(Alston, 1967; Crins et al., 1988; Bohm, 1988; Schilling, 1988). To
date the information on chemistry of Gunnera is scarce (Doyle and
Scogin, 1988). Therefore, we wish to report the flavonoid chemistry
of twelve species of Gunnera in three subgenera as a contribution
towards understanding the phylogenetic relationships of the family.
RESULTS
Fifteen flavonoids were isolated from twelve species of Gunnera
(Fig. 18). The foliar flavonoid profile of these species consists of
glycosides of the flavonols kaempferol, quercetin and isorhamnetin,
two partially identified flavone glycosides, the aglycones kaempferol
and isorhamnetin, and two unknown phenolic compounds. The structures
of the flavonoids isolated are given in Fig. 18, and a composite
two-dimensional chromatographic pattern of these compounds is shown
in Fig. 19* The UV absorption values are provided for all the
flavonoids isolated (Table 10). Table 11 shows the distribution of
the flavonoids among the twelve species.
Some infraspecific flavonoid variation is seen. In Gunnera
magellanica. populations are variable with respect to quercetin 3-0
diglucoside. In G^ tinctoria variation between populations was
detected for quercetin 3-0 digalactoside, quercetin 3-0 diglucoside
and isorhamnetin.
1 117
In subgenus Misandra. G. lobata and magellanica have
identical profiles. There are no species-specific flavonoids in this
subgenus. Subgenus Panke is the most diverse of the three subgenera
studied. Within Panke. G. kaalensis and G^. tinctoria present very
distinctive flavonoid profiles. Gunnera tinctoria is characterized
by the absence of the glycosides of kaempferol and G^ kaalensis by
its very simple flavonoid profile where the absence of glycosides of kaempferol is also noticeable. In G^ kaalensis only five compounds were detected (Table 11). In subgenus Perpensum. G. perpensa is characterized by a simple flavonoid profile consisting of five compounds. Quercetin 3-0-arabinoside and quercetin
3-0-glucogalactoside occur in all the species examined except for G. kaalensis and G^ perpensa. Kaempferol glycosides are of limited distribution being present only in some species of Panke.
Isorhamnetin and isorhamnetin glucoside are also of restricted distribution. The glycoside part of the flavonoid glycosides is varied. The following sugars were found: arabinose, galactose, and glucose. Flavone A and flavone B, partially identified are likely to be 8-OH flavones, deduction based on their R^»a and comparison with
UV spectra from the literature (Whalen, 1977, 1978).
DISCUSSION
The flavonoid data from Gunnera presented in this paper have taxonomic significance. The distribution of flavonoids among the three subgenera (Table 11) supports the subgenera as delimited by 118
morphological characters (Schlinder, 1904; Biloni, 1959)•
Intraspecific flavonoid variation, a phenomenon widely present
among plant species (Bohm, 1987), is evident in magellanica and G.
tinctoria. The distribution of quercetin 3-0-diglucoside in G.
magellanlca (Table 11) suggests that there could be a relationship
between the absence of this compound and geographic distribution in
cooler climates, like the ones that are present in the higher Andean
regions of Bolivia and Peru and Southern Chile. It would be
necessary to study more populations in order to test this hypothesis.
In Gi. tinctoria. variation between populations with respect to
quercetin 3-0-digalactoside, quercetin 3-0-diglucoside, and
isorhamnetin is seen. Variation in isorhamnetin is difficult to
explain since individuals which lack isorhamnetin, accumulate
isorhamnetin glucoside. A plausible explanation could be the
presence of an inefficient system of glycosylation in those
individuals which accumulate both the aglycone and the glucoside. No
attempt was made to relate variation of these compounds with the
distribution of G^ tinctoria populations.
Subgenus Perpensum is unique because of its simple flavonoid profile composed of only five compounds. It shares
quercetin-3-0-diglucoside plus the two unknown compounds with subgenera Misandra and Panke. Perpensum differs from the other two subgenera in that it contains two subgeneric markers. One is a quercetin 3-0 diglycoside, and the other is a flavone glycoside
(flavone B, compound 13)• Although there are two unique flavonoids in Perpensum. from the biosynthetic standpoint, they may not 119
represent a large difference from Panke and Milligania. In quercetin
3-0 diglycoside, subgenus Perpensum may simply contain a different
sugar or a different sugar attachment (Hosel, 1981). Flavone B has a
UV spectrum very similar to flavone A, and hence this flavonoid could
represent a different glycoside of the same flavone nucleus.
In spite of the tremendous morphological divergence, the
flavonoid profiles of subgenera Misandra and Panke are very similar
to each other. Seven flavonoids are shared by these two subgenera.
Chemically, Misandra is most similar to one species in subgenus
Panke: G. tinctoria. It is interesting that G^ tinctoria and
subgenus Misandra are restricted to southern South America (Chile,
Argentina). Gunnera lobata and G^ magellanioa are both dioecious
species, and based on morphological data (Pacheco, unpubl.), they
seem more related to species in subgenus Milligania from New Zealand,
than to those of subgenus Panke. Nothing is yet known about the
flavonoids of subgenus Milligania. and this information might help
clarify the relationships with subgenus Misandra.
Subgenus Panke has the most diverse array of compounds; it
accumulates both flavones and flavonols. The diversity within the
flavonol compounds is based on different patterns of oxygenation in
the B ring. Both mono- and di-hydroxylation as well as
methoxylation, all are known for for flavonoids in this subgenus. In
Panke three main groups can be discerned based on flavonoid
chemistry. One is composed solely of G^ tinctoria which is
characterized by flavones and flavonols. Flavonols with
dihydroxylation (quercetin) and methoxylation (isorhamnetin) in the B
1 120
ring are present in this group, but no flavonols with simple
hydroxylation in the B ring (kaempferol) were detected. The second
group comprises the species from Peru, Bolivia and Mexico. These
species grow on the upper region of the east-facing slope of the
Andes mountains from 2100 m to 3400 m in the belt called "ceja de la
montana" ("brow of the forest"; MacBride, 1936). This group is
characterized mainly by the presence of flavonols with mono- and
dihydroxylation in the B ring. As discussed before, Misandra is more
closely related chemically to tinctoria of subgenus Panke than to
subgenus Perpensum. The third group comprises Gunnera kaalensis from
Hawaii. This species has a very reduced flavonoid profile. Similar
to G^. tinctoria in that both accumulate quercetin 3-0 arablnoslde,
quercetin 3-0 digalactoside, and isorhamnetin 3-0 glucoside. These
two last flavonoids are rare in subgenus Panke. Reduced flavonoid
profiles also have been documented in other island taxa (Gardner,
1976; Pacheco et al., 1983; Patterson, 1984) and it seems to be one
of the common (but not universal) trends in island biotas. This
reduced flavonoid content may be explained as a result of the release
of predator or pathogen pressure. As suggested by Levin (1971),
phenolic constituents have at least some defensive role, and in an
environment such as in islands where predators and pathogens are
reduced (Carlquist, 1974), continuing selection for synthesis of
complex arrays of phenolic constituents might be absent.
Within subgenus Misandra, G. lobata and G^. magellanica have
identical flavonoid profiles. This suggests a very close
phylogenetic relatioship between these two species which is in
■J 121
accordance with the morphological data (Pacheco, in prep.).
Gunnera perpensa, the only species in subgenus Perpensum. is
undoubtedly not closely related either to subgenus Misandra or Panke.
Based on leaf shape and size and inflorescence type, ^ perpensa is
more likely closely related to G_j_ macrophylla (subgenus
Pseudogunnera) from Borneo, Malaysia and The Philippine islands.
Flavonoid studies of G^ macrophylla would be very helpful to
understand the relationship with G^. perpensa.
No phylogenetic hypotheses exist for Panke or for any other
part of Gunnera against which we can compare the flavonoid
distribution for insights on the evolution of the flavonoid system in
this genus. Chromosome numbers do not offer any help in
distinguishing a primitive group from among the three subgenera
studied. Chromosome numbers are known for Gunnera subgenus
Milligania from New Zealand (Beutzenberg and Hair, 1962)., for
subgenus Panke. G. manicata. G. tinctoria (Dawson, 1983), G.
bogotana. G. colombiana (Mora-Osejo, 1984), and for subgenus
Misandra. G. magellanica (Dawson, 1983), All species have a
chromosome number of 2n = 34 which undoubtedly represent the
tetraploid level, but these data do not help in selecting a primitive
group within Gunnera.
1 122
EXPERIMENTAL
The plant material was collected during expeditions to mainland
Chile (1986), Bolivia (1987) and Peru (1987). Voucher specimens are
deposited at OS with duplicates at CONC, CUZ, and LPB. For flavonoid
analysis, ground leaf material was extracted with 85? and 50?
methanol. The extracts were taken to dryness, suspended in water,
filtered, and then applied to 55 x 35 cm 3MM chromatographic paper.
The two dimensional chromatograms were developed in Ter-butanol:
acetic acid: water, 3:1:1 (TBA) in the first direction and 15? acetic
acid (15? HOAc) in the second. Spots in the chromatograms containing
individual compounds were eluted with spectral methanol. In cases
where purification of Individual flavonoids was necessary, this was
accomplished by thin-layer chromatography on precoated polyamide DC-6
plates (Macherey-Nagel). Flavonoids were detected on TLC plates with
0.1? aminoethyl dlphenylborinate in MeOH (= 'Naturstoffeagenz A')
(Aldrich Chem. Co.) (Wollenweber, 1975). The solvent systems used
were: I. 1,2 dichloroethane: methanol: methyl ethyl ketone: water:
formic acid (50:25:20.5:H:0.5) and II. water: ethanol: isopropanol:
methyl ethyl ketone (65.8:18:6:10) (Wilkins and Bohm, 1976). A set
of six ultraviolet spectra were run for each compound following
standard procedures (Mabry et al., 1970). Flavonoid glycosides were
hydrolyzed with 0.1N trifluoroacetic acid in a screw-cap test tube in
water bath for one hour (Wilkins and Bohm, 1976). Sugars were
identified by circular co-chromatography with standards on precoated
i 123
cellulose thin layer plates (Macherey-Nagel). The solvent system
used was ethyl acetate: pyridine: water (6:3:2) (Becker et al. 1977).
The chromatograms were sprayed with p-anisidine phthalate (1.0g
phthalic acid and 1.0ml anisidine in 100ml of 96> ethanol) (Becker et
al., 1977) to visualize the sugar compounds.
1 124
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Flavonoid evolution in Robinsonia (Compositae) of the Juan
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WHALEN, M. D. 1977. A systematic and evolutioary investigation of
Solanum section Androceras. Ph. D. Dissertation. Univ. Texas,
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______. 1978. Foliar flavonoids of Solanum section Androceras:
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WILKINS, C. K. and B. A. BOHM. 1976. Chemotaxonomic studies in the
Saxifragaceae sensu lato 4. Flavonoids of Heuchera micrantha
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* 129
Fig. 17. Map showing distribution of the six subgenera of
Gunnera. JL I
&
fy-V* MILLIGANIA 0 - 0 p" ™ 4 H MISANDRA j f e pgRFBlSUH O OSTBIIGUNNm # m + PSHUXGUNNERA 130 Fig.17 131
Fig. 18. Structures of flavonoids isolated from Gunnera.
>1 1 3 2
OH OH
OH 0
R1 R2 R3 1. Quercetin 3-0 arablnoslde Ara H OH
2. Quercetin 3-0 glucogalactoslde Glu-gal H OH
3. Quercetin 3-0 dlgalactoslde Gal-gal H OH
4. Quercetin 3-0 diglucoside Glu-glu H OH
5. Quercetin 3-0 dlglycoslde Gly-gly H OH
6. Kaempferol 3-0 glycoside Gly H H
7. Kaempferol 3-0 dlglycoslde Gly-gly H H
8. Kaempferol 3-0 dlglycoslde Gly-gly HH
9. Kaempferol OH H H
10. Isorhamnetin 3-0 glucoside GI u H 0CH.
11. Isorhamnetin OH H OCH.
12. Flavone A H OH OH
13. Flavone B H OH OH
F i g . 1 8
•J 133
Fig. 19- Composite two-dimensional chromatographic pattern of flavonoids in leaves of Gunnera subgenera Misandra. Panke. and
Perpensum. Spot numbers correspond to flavonoids listed in Fig. 2. f y 0 QD © © ©Q
15% HO Ac 135
Table 10. UV absorption of flavonoids isolated from species of
Gunnera.
Flavonoid MeCH NaOMe A! Cl A1C1 NaOAc NaOAc
HC1 H 3 BO 3
1 352, 250 I-* O 275 428, 355 393, 300 375, 265 370, 255 268 263 2 350, 252 404, 314, 423, 268 393, 260 375, 265 370, 258 265 3 353, 255 400, 315, 423, 263 395 380, 268 368, 258 268 4 355, 268, 420, 274 430, 270 395, 355, 390, 320, 375, 259 255 265 268 5 353, 265, 407, 325, 428, 273 395, 365, 375, 264 375, 260 255 273 268 6 343, 263 395, 320, 393, 345, 393, 345, 368, 271 345 273 273 272 7 343, 263 395, 328 390, 343, 390, 343, 363, 270 343 273 273 273 8 344, 263 393, 318, 391, 345, 391, 345, 370, 274 345 273 273 273 10 365, 250 425, 320 420, 355, 415, 355, 385, 325, 367, 255 263 255 265 11 368, 253 440, 320 430, 265 420, 260 375, 253 380, 258 12 333, 250 398, 275 425, 353, 390, 325 325, 268 355, 255 265 265 13 335, 267, 395, 273 435, 343, 395, 328, 375, 335 360, 258 253 275 260 270 14 355, 250 390, 355, 373, 265 358, 250 350, 273 370 283 15 350, 280 400, 323 370, 293 353, 475 386, 305 365, 288 Table 11. Distribution of fluvonoids present in species of three subgenera of Gunnera.
Flavonol Flavone Subgenus Species Collection Location Q-giy K-gly K I-g ly I F-gly Uk number 1 2 3 4 5 6 7 8 9 10 11 12 13 U 15
M isandra G. lobata 7179 Chile X XXX XX X G. magellanicaII 1089 Chile X X XXX XX If 1120 Chi le XXXX X XX II 1192 Chile XX X X X X X II 1200 Chile X X X X XX X II 1404 Peru XXX XX X It U30 B olivia XXX X XX ft 1520 B olivia X XX XX X II 1882 Chile XX XX XXX 7073 Chile XXXX X XX II 7298 Chile X XXX XX X II 7587 Chile XXX XX X Panke G. annae U37 B olivia X XX X XXX X XX G. apiculata 1550 B olivia XXX XX 11 II 1552 B olivia XXX XX G. bolivari 1421 Peru X X X X X X ? XX G. boliviana 1563 B olivia XXX XX G. kaalensis 4160 Hawai i XX XXX G. margaretae 1547 B olivia XXXXX XX G. mexicana 2793 Mexico XXX XXXXXX G. peruviana 1411 Peru XXXXXXXX G. tin cto ria 1090 Chile X XXXX X XX " 1101 Chile X X XXXX XX X ft 1178 Chile XXXXX X XXX II 1207 Chile XXXX XX X XX II 0 II 1247 Chile XXXX XXX II 1307 Chile X XXXXX X It 1917 Chile XXXXXXXXX 6692 Chile X XX XX 9 XX X 11 6786 Argentina XXXX X XX X Perpensum G. perpenca sn S. Africa X X X X X
Q - quercetin, K = kaempferol, I = isorhamnetin, F = flavone, gly = arabinose, galactose, glucose. For specific flavonoid identification see Fig. 18. APPENDIX A
Amer J. Bot. 7J(7) 989-998. I98J.
FLAVONOID EVOLUTION IN ROBINSONIA (COMPOSITAE) OF THE JUAN FERNANDEZ ISLANDS'
Patricia Pacheco, D aniel J. C r a w f o r d . T o d F. Stuessy, and M ario Silva O. Department of Bourn. The Ohio Sute 1‘mvmity, Columbui. Ohio 43210. and Depanamemo dc Botimca. L'nivmidid de Concepcidn. Concepcidn. Chile
ABSTRACT Leaf flavonoidi ^erc nolaud and identified from S4 populations representing all seven species o f Robinjcnio a genu* o f dioecious rosette trees endemic to the Juan Fernandez Islands Fourteen compounds »ere detected consisting of Aavonols. flavones, flavanones and dihydroflavonolt The distribution o f these compounds in Robinsoma largely corresponds to specific and sectional lim its based on morpholo|ica) dau The morphological!) similar species. A gayana and R thun/fra, have identical flavonol profiles (derivatives ofquercetin). Likewise, the closely related R. f\tn io and ft ma*ofucrac are unique in the genus by possessing flavones. The inclusion o f Rbetinodtndron (i.e.. R bcrteroi) in R o b iw m o is supported by its strong flavonoid similarity ^ith species in two other sections of the genus The morphological!) diverse section Eleuih‘ erolepts exhibits the greatest flavonoid variation of any section, and only here are found flavones, flavanones and dihydroflavonols. The direction of flavonoid evolution in Robinsoma is by* pothesiied to be from fewer to more classes of compounds Biosynthetic considerations suggest that this p m in compounds is due both to a p in o f an additional enzymatic step and to the sequesicringofprecursorvThisinterprcuiionofdircciion of flavonoid evolution is in agreement with several lines o f evidence including the flavonoid chemistry of the hypothesized outgroup (i e., species o f S tn tcio on mainland Chile), the ages o f the two islands, and morphological trends.
The Juan Fernande z I s l a n d s , located 6 0 0 native species of which 69% are endemic lun ofT the coast of Chile at latitude 33*S. con (Skottsberg, 1956). Nineteen percent of the sist of two major islands. Masatierra (* Is!a genera are also endemic, and there is one en Robinson Crusoe) and Masafuera (s Ista Ale demic famil} (Lactoridaceae), Among these jandro Selkirk), separated in an east-west line endemic taxa. the Compositae contain more by 150 km of ocean (Fig. 1). These islands species (26) than an> other Tamils in thr ar- contain an unusual angiosperm flora of 147 chipelago(four o f the genera are also endemic). Studies attempting to understand patterns and processes of esolution in the endemic species 1 Received for publication 28 July 1984. accepted with out revision 4 December 1984. o f the Juan Fernande; Islands, therefore, must Appreciation is expressed to many people and institu focus attention at some point on the Compos tions for having made this work possible our colleagues itae. on the two expeditions to the islands in 1980. J Amagada. R o b in so m a DC. of the tribe Senecioneae is C Manicorena. O Matthet. O Parra. R Rodnguez. R. the second largest genus of the Compositae Sandrrs. E U prte. and H Valdebcnitd R DotVoich for NMR spectra of nanngenin 7-O-gljfoside and taxifolin endemic to the Juan Femande; Islands (D en- ■*•0 glucoside. P G Sammrs for MS and NMR dan for d ro seris is the largest). Seven species are rec enodictyol 7-O-glucoside and quercenn ?-0*glucot>dc. B ognized. including the monotjpic genus R hc- A Bohm for MS of kaempferol ?-0-glucoside. to thr Na n n o d en d ro n (Sanders. Stuessy. Marticorena and tional Science Foundation for Grants IN T * n 2 l6 3 1 to T.F.S and BSR-8306436 to T.F S. and D J.C.. C O M O T S ilv a , in prep.)-* T h ese rosette d io e c io u s trees of Chile for support to M.S.O.; Vicerectona de Investi- grow in various habitats but are confined to gaciones of the Universidadde Concepcidn for additional the upper forest zone and rocky ridges from support for the field work; CONAF ofChile for permission 450-700 m. Pre'ious work on the genus has to collect in the Islands National Park; Dieier Wasihauseo focused on the taxonomy (Skottsberg, 1922. o f the U.S. National Herbarium for permission to analyze flavonoids from leaf fragments of a collection of Robm• 19 5 1). wood and leaf anatomy (Carlquist, 1962. soma macrocepholo\ and especially Bernardo Ackermann 1974), phytogeography (Skottsberg. 19 56), and and Gaston Gontilez. former and present Chief of the Juan Fernandez National Park, whose help and dedication to our research iotcreiu have been a major factor in their 1 Robimonia btrttroi (Hems).) Sanders. Stuessy and success; and to the CONAF guides, including Oscar Cha Marticorena. comb. nov. Rhrtinodendron txntroi Hemsl. morro, A) vis ConzDez, Eduardo and Manuel Paredes, Do Bot. Voy. Challenier 1:3 9 .1884. Rationale for this transfer mingo Retamal, and Ramdn Schiller. is more fully detailed in Sanders et at. (in prep.).
137
1 AMERICAN JOl'RNAL OF BOT ANV 138
UJ
Masatierra 0 100 2 0 0
1 JO k
Fig. I. Location of the Juan Femandez Islands in South America. more recently cytology (Sanders. Stuessy and most of the flora is mainland South America, Rodriguez. 1983) and phylogeny (Sanders et which makes the closest island. Masatierra. the al.. in prep.). Flavonoid chemistry has not yet likely initial site for colonization by new im been examined. migrants. Flavonoids are known to be extremely help The purposes of this paper, therefore, are to: ful in some instances in determining systematic 1) examine the flavonoids from all seven species and evolutionary relationships in flowering of R o b in s o m a of the Juan Femandez Islands; plants (Harbome. 1977; Swain. 1977; Craw 2) determine flavonoid components in selected ford. 1978; Giannasi. 1978; Crawford and taxa of the closest mainland relative ( S e n e c to); Giannasi, 1982; Stuessy and Crawford. 1983). and 3) interpret these data in consort with other They have been useful particularly in helping available information for taxonomic and evo to resolve systematic problems in the Com lutionary implications, with particular refer positae as evidenced by numerous studies over ence to changes in the flavonoid system during the past two decades (e.g.. Crawford. 1970; ev olution o f the species in the archipelago. Giannasi. 1975; Crawford and Stuessy. 1981; Craw ford and Smith, 1983a. b). Flavonoids are M aterials and methods — Acquisition of especially well-suited for studies in isolated plant material — All but one of the plant sam oceanic archipelagoes because the compounds ples were collected during two expeditions to are relatively stable and no special equipment the Juan Fernandez Islands in January-Feb- or precautions are needed in the collection of ruary and Novcmber-December 1980 by per samples. The Juan Femandez Islands are a sonnel from laboratories of the Departments good archipelago in which to examine the taxo of Botany of The Ohio State University and nomic and, more importantly, the evolution the Universidad de Concepcion. Fifty-four ary implications of the flavonoid system be populations from all seven species of R o b in - cause there are only two major islands of small s o n ia were sampled from both islands, but size (ca. 20 kmJ each), the approximate geo principally from Masatierra (Table 1; Fig. 2). logical ages o f the islands are known (3.7-4.4 Specimens were air-dried in the field. Vouchers m .y. for Masatierra and 1-2.4 m .y. for Masa- are on deposit at OS with duplicates at CONC. fuera; Stuessy et al., 1984), and the source for Available species of S e n e c io from southern July. 1985) PACHECO ET AL. — FLAVONOID EVOLUTION IN ROHINSONIA 139
South America were analyzed from material in The Ohio State L niversitv Herbarium (Ta ble 2).
Extraction, isolation, and identification of flavonoids Ground — leaves were extracted with 85% and then 50% aqueous methanol. The combined extracts were evaporated to dryness under vacuum, taken up in methanol and then applied to sheets (46 x 50 cm) of Whatman 3MM chromatographic paper. The 2D chro • - 3 r matograms were developed with TBA and 15% HOAc and examined over ultraviolet light fol lowing standard procedures (Mabry , Markham and Thomas, 1970). Individual flavonoids were obtained by elution of compounds from paper with methanol and further purified by TLC Fig 2. Map of the easiem pan of Masatierra showing using precoated polyamide DC-6 (Macherey- locations of collections of R obinsom a Numbers refer to collections of taxa listed in Table I. Dashed line shows Nagel) and precoated cellulose (Macherey- approximate extent of the R obinsonia zone (from Skotts- Nagel). The solvent svstems were: 1,2 dichloro- bcrg. 1922, and pers. field obs.). ethane : MeOH : MEK : H:0 (50:25:21:4) (Wilkins and Bohm. 1976); MEK:n-butyl ace tate : acetic acid : H:0 (60:25:12:3) (Wilkins sented by the 14 compounds: the first eight are and Bohm, 1976); MeOH : MEK : acetone(10: flavonols, the next three are flavones, the next 5:10); t-butanol: acetic acid : H20(3:1.T); 15% two are flavanones, and the last is a dihydro- HOAc; and 40% HOAc. Hydrolysis of flavo flavonol. noid glycosides was carried out with 0.1 n TFA In two instances flavonoids were examined in a screw-cap test tube on a steam bath for 2 - from the same plants at two different times. 2.5 hr (modified from Wilkins and Bohm, The same plant of Robinsonia evenia was sam 1976). The identification o f sugars was done pled in February (5 0 0 5 , Table 1) and N ovem by circular chromatography against standards ber (5 5 1 7 ), and the same plant o f R. thurifera in pyridine: ethyl acetate: H:0 (6:3:2) (Becker, was likewise sampled in February and Novem Exner and Averett. 1977). and the sugars were ber (5 0 0 4 and 5 5 1 8 , respectively. Table 1). No visualized by spraying with aniline phlhalate variation was detected in the latter species, but. (1.0 g phthalic acid and 1.0 ml aniline in 100 in the former, apigenin 7-O-diglycoside was ml 95% ethanol). Identifications of the flavo detected in the second sample but not the first, noids were performed by l v spectral analysis and quercetin was detected in 5 0 0 5 but not in (Mabry et al., 1970). In addition, mass- and/ 5 5 1 7 . or NMR-spectra were obtained for the follow Analyses of selected species of S e n e c io from ing compounds: naringenin 7-O-glucoside South America yielded a series of flavonoids (NMR): taxifolin 7-O-glucoside (NMR); quer- that, because of scanty material, have been only cetin 7-O-glucoside (MS. NMR): kaempferol partially identified (Table 2). In most instances, 7-O-glucoside (MS): and eriodictyol 7-O-glu the compounds have been characterized as fla- coside (MS. NMR). All spectral data arc avail vone or flavonol glycosides by RF and uv spec able from the senior author upon request. tral data: Table 2 indicates those instances when only RF values were available. Most flavonoids R e s u l t s — Identities o f the flavonoids from appear to be common flavonc and flavonol all collections of the seven species of R o b - glycosides, but for present purposes of com in so n ia (Table 1) are: quercetin. quercetin parison we are concerned only with whether 3-O-galactoside, quercetin 3-O-digalactoside, they are flavones or flavonols. No flavanones quercetin 7-O-glucoside. quercetin 3.7-0- ordihydroflavonols were detected in the species diglucoside. kaempferol 7-O-glucoside, iso- o f S e n e c io examined. rhamnetin 3-O-glucoside; isorhamnetin 7-O- The distribution of flavonoids in R o b in s o n ia glucoside, luteolin 7-O-glucoside, luteolin shows a general pattern o f species-specific pro 7-O-diglycoside (glucose and galactose), api- files (Table 1). The only exceptions are R . g a y - genin 7-O-diglycoside, eriodictyol 7-O-gluco a n a and R. thurifera, which have identical ar side; naringenin 7-O-glucosidc, and taxifolin rays of compounds. In addition, R. berteroi and 7-O-glucoside (dihydroquercetin 7-O-gluco- R. macrocephala differ only by the presence o f sidej. Four classes of compounds are repre- quercetin in the latter (Table 1). Because the T able I. Occurence of flavonoids in Robinsonia (\dlcctum numbers those of Stuessy el al. and Marticorena et at (9.000's) except as noted otherwise. A =* apigrm n. /:' = eriodictyol; / * tsorhanincdn; K ~ kaempferol; /. 3 luteolin; N » naringenin; Q ~ quercetin; T m taxifolin
Flavones I 7 .0- d ifJy Oihiilm- coside Antinol (glucose Q 3 0 - Q 3-0. Q 7-0* Q 3.7- K 7*0* I 1-0. I 7 -0. L 7-0- and A 7-0- E 7 .0 . N t o - 1 7 t). l> pr »rf Mip galac- digalac- gJu- O-diglu- glu- glu- glu- glu- ga digly- flu- glu- g>U- nllet linn nuinKrr umitlr* numhri tmide icmde costdc coside coside coside cnsidc lactose) coside coside Cusidc
R. bertcroi (H cm sl.) 520 3 P 1 X X Sanders, Stuessy and Mar ticorena R. evenia Phil. 5005 F 2 X XXX 5171 P 3 XXX M A BUT Or RNAL JOI AMERICAN 5IH7 P. 4 XX 5192 M 5 X X X 5 /9 5 P 6 XXX X X 5197 P 7 XX 7 1 520H F K X X 5225 M 9 XX 7 7 5355 P 10 X X ? 53 93 M 1 1 X X X 539 3 F 1 1 X XX 539ft F 12 XX XX X 5 5 1 7* F 2 X XXX R. g a ya n a D ene. 50 0 3 F 13 XX X X 5020 P 14 XX X X 5 0 9 9 P IS X X X 5115 P lb X X X 5 1 2 / P 17 X X X 5152 M IN X X X 5 1 1>3 P IV X X X X 5104 P 30 X X X 5190 P 21 XX X X 5193 P 22 X X X 5210 M 23 XX X X 52 2 0 P 24 X X X X 52 2 3 F 25 X X X 5241 P 2A X X X X 5322 P 27 X X X 5 3 5 7 F 2K X X X X 5 3 7 4 M 29 X X X X
O uy 1985] July.
Table I. Continued
FUvonci L 7 0 - <*»gl>- H,hydro. FlavonoU inside Flavanones Hjmnul (glucose <> \ () Q VO. Q Tib Q 1.7- 1 1-0. 1 7-0. K 7 0 - a m o s n i b o r L in7-0- n o i and t u l o v A e 7 .0 . d i o F n 7 o .0 v a l f N M — . l l a ET 1 »I > O C E H C A P 1 vpr of Map p la t • dig* lac- glu* O-dtgJu- glu- flu- flu- gJu- ga- dtgly- glu glu- glu C olkvlnm numhrr vantpk-* number *) lustdc lUIMk coside costdc cottdc costdc costdc costdc lactose) costdc costdc rnstilc ii'Stdc
5J 7 4 F 29 XXXX 5404 M 30 XXX 9115 F 31 XX XX 9139 F 32 XXX R. gracilis D ene. 5227 P 33 X X X X XX •) X 522S I’ 34 X X X X X X 7 X 52 3 4 P 35 X X X X X X 7 X 5 2 3 9 P 36 X X X XXX X X 53 5 3 M 37 X X X X X X XX 5354 F 38 X X X XXX 536 0 M 39 X X X XXX S ift’ M 40 X X X X XXX S.*7J M 41 X X X X X XX 537 3 F 41 X X X X X X 5397 P 42 X X X X XXX 5416 M 43 X X X X X XXX 542 2 M 44 X X X X XX X 54 2 7 M 45 X X X X X X X 90S 7 F 46 X X X X X o X R. macrocephala Dene. Skottsh 131 (U S) 1 47 XX R. masafuerac Skottsb. 5071 M 48 XX X R. thurifera D ene. 500 4 F 49 X X X 5006 P M> X X 5196 P M XX 5201 P 52 X XX 5 2 0 9 P 55 XXX 5424 F 54 X X X j J / # “ F 49 X XX • F ** female plant: M - male plant: P “ population sample including mat and/or female plants or immature plant with sex uncertain * Collection 55 1 7 from the same plant as 5005. and 55 IS same plant as 5004. the former in each case collected Nov. 1980. the latter Feb. 1980. AMERICAN JOURNAL OF BOTANY J 4 2
T M il F 2. Occurrence ofllavonnids in South American Senecio Flj'.iridll Fljtorto Refer- FllNv'- encr or pjtonol Pjtnnul nol ) * FUwne FUtone voucher CMijjv. HI*. Spectfs (OS) coside cotide costdr ct'tide cone Localtiv
S adcnophyilotdes Sch. Bip. Richardson 2079 + • Peru S argyreus Phil. Caniino 103 ■ Argentina S. cym osus Rem y Reyes et al. (1977) + + C hile 5. hstulosus Less. Reyes et al. (1977) + C hile S. glaber Less. Stuessy 4617 + C hile S. mageiianicus H. & A. Canltno 106 + + Argentina S. orues Kunze ex DC. R eyes et al. (1 9 7 7 ) + + + C hile S. polyphyllus Kunze ex DC. Cabrera 19679 + ■ C hile 5. subdiscoideus Reyes, Oyarzun and + C hile Sch. Bip. ex Weddel Romero (in press) S. irifurcalus (Forst). Less. Reyes. Oyarzun and C hile Romero (in press) S. yegua (Colla) Cabr. R cvcs etal. (1 9 7 7 ) + + + C hile S. sp. H a n 16 0 9 + Ecuador • Tentative identification based only on chromatographic properties.
source of flavonoids of R. macrocephala was somewhat closely to section Robinsonia, with herbarium material collected several decades the close relatives R . g a y a n and a R. thurifera. ago, there is the possibility that the presence The remaining three species, R. evenia, R. grac of quercetin is an artifact resulting from loss ilis, and R. masafuerae, form section E le u th - of sugars from the naturally occurring glyco erolepis. Robinsonia evenia and R. masafuerae sides. There is some infraspecific (interpopu- are very closely related morphologically, al lational) variation in all taxa, but it is most though the former is confined to Masatierra pronounced in R . e v e n ia and R. gracilis, in and the latter to Masafuera. The flavonoid data cluding the aforementioned seasonal variation correlate well with these taxonomic perspec in the same plant of R . e v e n ia (Table 1). No tives based on morphology. The closeness of correlations of flavonoid variation with gender R . g a y a n and a R. thurifera in sect. R o b in s o n ia are seen. is substantiated by their identical flavonol de Only flavonols were found in species of S e rivatives of quercetin (Table 1). At the other n e cio examined from Chile; the s*>me is true end of the network the morphologically closely for the one species from Ecuador (Table 2). related R . e ve n ia and R. masafuerae both have One species from Argentina and one from Peru flavones. and these are the only two species in contained only flavones. and S. argyreus from the genus with this class of flavonoid (Table 1; Argentina has both flavones and flavonols. Fig. 3). Robinsonia gracilis of the same taxo nomic section does not have flavones. The de D i s c u s s i o n — Taxonomic implications—The cision to include Rhetinodendron (R. berteroi) taxonomic significance of the flaxonoid data in Robinsonia. based on morphological data, in R o b in s o m a lies in their correlation with is supported b> its strong flavonoid similarity morphological evidence gathered and synthe (only quercetin) to three other species (R . g a y sized previously (Fig. 3; from Sanders et al.. ana. R. thurifera. and R. macrocephala) in two in prep.) as a network of relationships based of the three sections of R o b in s o n iaproper. Sec on Manhattan distance (Farris. 1970; Nelson tion Eleuthcrolepisoniains c more morpholog and Van Horn. 1975). Robinsonia bertcroi, ical diversity than any other section of the ge previously regarded by Skottsberg (1956) as a nus. and this is paralleled by the presence of monotypic genus, is here treated as belonging considerable flavonoid variation (Table 1; Fig. within R o b in s o n ia as a monotypic subgenus 3>. In fact, all of the classes of flavonoids are (subg. Rhetinodendron).3 The other species of found here w ith the only flavones, flavanones. R o b in s o n ia are divided into three sections. and dihydroflavonols known in the genus. Robinsonia macrocephala is in a section by itself (sect. Symphyochaeta), and this connects Evolution of the flavonoid systemTo — in vestigate evolutionary changes of flavonoids in R o b in s o n ia requires making several assump ’ R obinsonia DC. subg. (Meisner)Sand ers , Stuessy and Marticorena. comb. nov. Rhetinodendron tions. First, it is assumed that all seven species M eisner. PI. Vase. G en. I. 216, comm. 136. 1839. of R o b in s o n iahave developed from only one July. 1985] PACHECO ET AL. — FLAVONOID EVOLUTION IN ROBINSONIA 143
consequence, but its phy letic significance is not apparent to us in the context of this study. The distribution of flavonoid compounds in R o b in s o n can ia be superimposed upon the net work based on morphology (Fig. 3). All species and sections have the flavonol quercetin with its various glycosides. These compounds are common in the closely related S e n e c io of con tinental South America (Reyes et al., 1977; Reyes, Oyarzun and Romero, in press), and twms they are also widespread in the entire tribe Senecioneae (Robins, 1977). Robinsonia graci lis is the most diverse chemically with glyco sides based on two additional flavonols, Fig. 3, Changes in ihe flavonoid system in Robinsom a kaempferol and isorhamnetin. plus two fla superimposed on a network of relationships based on vanones and one dihydroflavonol (Table 1). morphological features (from Sanders et al.. in prep.). All Robinsonia evenia and R. masafuerae are the species have flavonols based on quercetin. Occurrence of only flavone-containing species in the genus, additional flavonols and other classes o f flavon.rids is shown the former with two and the latter with one b> bars leading to the taxon (or taxa) possessing them. (Table 1). Numbers and dots refer to different alternative positions for rooting the network. The network of changes in the flavonoid sys tem (Fig. 3) does not reveal evolutionary di rectionality. To indicate directionality requires rooting the network at some point, thus making introduction from the continent, and therefore, an evolutionary tree. Four possible positions that the group is monophvletic. Evidence for exist for rooting the network with reference to this point of view is that the species of R o b in changes in the flavonoid system (Fig. 3; Root so n ia are more similar to each other morpho 1 could be placed at any point along the net logically than to any known species of S e n e c io work outside o f sect. Eleutherolepis\ rationale on the continent (Sanders et al., in prep.). Sec for its specific placement is explained in detail ond, it is assumed that evolution in R o b in s o n ia below). Roots 3 and 4 seem less likely as prob has proceded more or less parsimoniously and able ancestral connections than 1 and 2 because that postulating complex scenarios, such as the former two occur in the subgroup of sect. those involving numerous extinctions, is not Eleuiherolepis, which is probably the most re necessary. Evidence to date suggests that evo cently evolved o f the entire genus. Certainly lution in most groups o f plants and animals is Robinsonia masafuerae is the only species on largely parsimonious, with occasional excep the y oungest island. Masafuera. being only 1- tions (Sober. 1983; KJuge. 1984). Two factors 2 million years old (Stuessy et al.. 1984). Pos frequently complicating phylogenetic recon tulating this line o f evolution as the basal one struction in angiosperms. hybridization and for the entire genus seems unreasonable. Roots polyploidy, are unknown in R o b in s o n ia(three 1 and 2 seem more probable, but discrimi species have been counted chromosomally as nating between them is difficult. Root 1 is se n = 20; Sanders et al.. 1983). Third, it is as lected as the more likely possibility for two sumed that the network o f morphological re reasons. First, all the taxa of the genus have lationships generated previously (Sanders et flavonols, which makes it likely that this class al., in prep.; Fig. 3) does reflect the actual evo o f compounds occurred in the ancestor of the lutionary affinities o f the taxa. Evidence is that group. Second, additional clues to the ancestral this method has been used successfully to il chemical condition come from examining the lustrate patterns of phylogeny in other groups presumptive outgroup, S e n ec io . Despite the (e.g.. in Pentachaeta in the Compositae; Nelson large size o f S e n e c io (over 1.000 species world- and Van Hom, 1975). Fourth, it is assumed w ide with more than 200 in Chile alone; Ca that different sugar substitutions (glucose and brera, 1949), the genus has relati vely few known galactose at the 3- and 7-positions) have little classes of flavonoid compounds. In a survey phyletic value. Evidence for this assumption of 25 African species of the 5. ra d ic a n com s is that the patterns o f sugar substitutions do plex, only flavonols and flavones were en not correlate with the morphological data o f countered (Glennie, Harbome and Rowley, presumptive phyletic import. This does not 1971). South American species of S e n ec io from , mean that the type or position of sugar sub which R o b in s o n presumably ia originated, have stitution is of no taxonomic or evolutionary not been surveyed extensively for flavonoids, 144 AMERICAN JOURNAL OF BOTANY
M ASAFUERA m a s a t ie r r a as the ev olution of R. gracilis occurred. In a U-J my) (4 rollon yea’s) similar fashion, there was gain of a flavone. luteolin, in the evolutionary line leading to R. M A S EVE GRA MAC THU GAV BER e v e n ia and R. masafuerae. An additional gain of another flavone. apigcnin. occurred in the evolution ofR . e ven ia . The general pattern of flavonoid evolution inRobinsonia. therefore, is for three successive gains of compounds in the genus; these changes occurred within the past four million years. Mabry (1974) suggested that within genera the more advanced taxa have fewer and struc turally simpler compounds compared to those found in the more primitive members of the same genus. While admitting that numerous FLAVONOLS exceptions will be found, Mabry hypothesized Fig. 4. Hypothetical evolutionary relationships among that loss mutations occur more frequently than species of R obinsonia based on rooting the network at gain mutations during the course of speciation Position I in Fig. 3. in a genus. With regard to complexity of fla vonoid chemistry and phyletic advancement in a genus, it appears that different patterns but some insights can be gained at this time. may emerge depending upon the plants. How Only flavonols have been reported previously ever, several points must first be made with from six species o f S e n e c io from Chile (Reyes regard to the concepts of loss or gain of com et al., 1977; Reyes et al., in press; Table 2), pounds. Differences in numbers and kinds of which suggests that this class of compound compounds present in species ofa genus should might be ancestral in Robinsonia. Six addi be viewed from a biosynthetic perspective. For tional species from Argentina, Chile, Ecuador, example, differences in number of compounds and Peru also have been examined (Table 2). among species could be due to various bio All the species have only flavonols except S'. synthetic factors such as changes in capacity adenophylloides, S. argyreus, and S . m a g e l- to glycosylate the same flavonoid aglycones la n ic u s.The latter two occur in extreme south (adding different sugars, sugars in various com ern Chile and Argentina (Cabrera, 1949) and binations. or sugars at different positions), climatically as well as geographically would be changes in capacity to effect substitutions at unlikely sources as ancestral slocks with dis various positions on a molecule (i.e.. gain or persal to the Juan Femandez Islands. The Pe loss of methylation. hydroxylation. etc.) or ruvian occurrence o f S. adenophylloides on the changes in ability to produce different classes western side of the Andes offers more possi of compounds (that is. flavones, flavonols. etc.). bilities as an ancestral stock, but geographically Examples exist where there appears to be it is still a considerable distance north of the decrease in flavonoid complexity with increas Islands. It is much more likely that R o b in s o n ia ing specialization in a genus or parts of a genus developed from ancestors from Chile, which is (sec examples cited by Mabry, 1974; also Wells the closest source area and in which many ties and Bohm, 1980). by contrast, other studies from the endemic taxa of the Islands to those report a genera! increase in numbers of com on the mainland can be seen (Skottsberg. 1956; pounds with phyletic advancement in a genus C. Marticorena. pers. comm ). It is likely, (see Whalen. 1978; Crawford and Smith. 1983a; therefore, that the ancestral taxon of R o b in Stuessy and Crawford, 1983). Other studies so n ia contained only flavonols. Morphological have demonstrated the utility of flavonoids for studies (Sanders et al., in prep.) support this suggesting phyletic lines within a genus with conclusion and suggest a specific placement of different classes of compounds characterizing Root 1 as shown in Fig. 3. different groups of species, but with no trend If Position 1 is selected as the root for the toward reduction or elaboration of flavonoids netw ork o f relationships among species o f R o b (see Giannasi, 1975, as an example). Still other in so n ia then , the following trends in flavonoid results reveal no clear-cut trends and less-than- evolution can be suggested (Fig. 4). The ances perfect correlations between flavonoid chem tor of the group had only flavonols, and these istry and phyletic lines (Crawford and Smith, would be quercetin derivatives. Two new fla 1983b). vonols (kaempferol and isorhamnetin), two fla The foregoing discussion demonstrates the vanones, and one dihydroflavonol were gained importance of hypothesizing trends of flavo- July. 1985] PACHECO ET AL. — FLAVONOID EVOLUTION IN ROBINSONIA 145
noid evolution for each group of species with R beMeroi R evenia out regard to results obtained for other taxa. A/' Clearly, it appears that different patterns may R. masafuerae emerge depending on the plants. In R o b in s o n ia R. gayana the trend appears to be toward increased com R. thurifera plexity with phylogenetic derivation. The in — R gracilis crease in number of compounds in certain taxa — R. macrocephala is due primarily to increase in classes o f com pounds and biosynthetic aspects of this in crease are o f interest (Fig. 5). The two flava nones and the dihydroflavonol are direct precursors to flavones and flavonols, respec tively (cf. Wong, 1976; Ebc! and Hahlbrock, 1982). Thus, the occurrence o f these two classes (flavanones and dihydroflavonols) in R . g ra c i Fig. 5. Biosynthetic relationships and sectional occur rences of compounds in Robinsonia. lis suggests that they are not being completely converted to flavones and flavonols, i.e., a cer tain proportion of the precursors are being se questered (Fig. 5). Examples are known o f mu it is interesting to note that during phyletic tants that prevent the conversion offlavanones evolution of the latter from the former in iso and dihydroflavonols to other classes of fla lation on Masafuera during the past 1-2 mil vonoids (KJho, Bennink and Wiering, 1975; lion years, there have been no major flavonoid Forkmann, 1979). Thus, while we cannot say changes except sugar substitutions. The unique with certainty why Robinsonia gracilis has flavone (apigenin) found in R . even ia from “gained” (i.e., sequesters) flavanones and dihy Masatierra may have occurred after the split droflavonols, the most likely explanation is that in the line leading to it and R. masafuerae. a genetic change has occurred, in effect making However, since certain populations of R . e v this species less efficient at carrying out the e n ia appear to lack apigenin (Table 1), it is also flavonoid biosynthesis steps that convert these possible that R. masafuerae may have origi intermediates. There is little question that all nated from a founder population lacking this other species of R o b in s o n iasynthesize (but do compound. not sequester in detectable quantities) these two flavonoid classes because they represent LITERATURE CITED intermediates in flavonoid biosynthesis in all B e c r e r , H ..J. E x n e r , a n d J. E. A v er e t t. 1977. Circular plants that have been studied (Wong, 1976; chromatography, a convenient method for phyto Hahlbrook and Grisebach. 1979; Ebel and chemical analyses. Phytochem. Bull. 10. 36-41. Hahlbrook, 1982). Thus, we do not view the C a brera , A. L. 1949. El genero "Senecio" en Chile. presence o f flavanones and dihydroflavonols Lilloa 15: 2 7 -5 0 1 . C a rlq u ist . S. 1962. Wood anatomy of Sencctoneae in R. gracilis as "gain" mutations even though (Compositae). Trop. Woods 5: 123-146. the species sequesters additional compounds. . 1974. Island biology. Columbia Unnersity Press, However, the presence of flavones inR . even ia N ew York. and R. masafuerae probably docs represent a C r a w f o r d . D . J. 1970. Systematic studies in Mexican "gain" mutation, because these plants can ox Coreopsis (Compositae). Coreopsis munca: flavonoid idize the flavanone and carry out a biosynthetic chemistry, chromosome numbers, morphology, and hybridization. Brittonia 22: 93-111. step unknown in other species of Robinsonia. . 1978. Flavonoid chemistry and angiosperm evo Evidence for such enzymatic regulation comes lution. Bot. Rev. 44: 431-456. from Stotz and Forkmann (1981). who dem , a n d D. E. G ia n n a si . 1982. Plant chemosyste- onstrated that microsomal fractions from fla- malics. BioScience 32: 1 14-124. vone-producing plants o f A n tir r h in u m m a ju s , a n d E. B. S m it h . 1983a. The distribution of contained an enzyme capable of oxidizing na anthochlor floral pigments in North Amencan C ore opsis (Compositae): taxonomic and phyletic interpre ringenin and eriodictyol (flavanones) to api- tations. Amer. J. Bot. 70: 355-362. genin and luteolin (flavones), respectively. By . a n d . 1983b. Leaf flavonoid chemistry of contrast, plants of A . m a ju slacking flavones North American C oreopsis (Compositae): intra- and also failed to exhibit the enzyme activity. Stotz intersectional variation. Bot. Gaz. 144: 577-583. and Forkmann (1981) also showed the same , a n d T . F. S t u e s s y. 1981. The taxonomic sig correlation between microsomal activity and nificance ofanthochlors in the subtribe Corcopsidinae (Helianthcae: Compositae). Amer. J. Bot. 6 8 : 107— presence of flavones in several other genera of 117. plants. E bel, J., a n d K. H a h l b r o c k . 1982. Biosynthesis. In J. With regard to R . e v e n ia and R. masafuerae, B. Harbome and T. J. Mabry [eds.], The flavonoids: AMERICAN JOURNAL OI BOT \NV 146
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