Karyotypic Relationships Among Astilboides, Bergenia, Darmera, and Mukdenia and Their Implications for Subtribal Boundaries in Saxifrageae (Saxifragaceae)

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Karyotypic relationships among Astilboides, Bergenia, Darmera, and Mukdenia and their implications for subtribal boundaries in Saxifrageae (Saxifragaceae)

Article in Canadian Journal of Botany · January 2011 DOI: 10.1139/b86-075

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Douglas E Soltis University of Florida

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Department of Botany, Washington State Universiv, Pullman, WA, U.S.A. 99164-4330 Received May 7, 1985

SOLTIS,D. E. 1986. Karyotypic relationships among Astilboides, Bergenia, Dar~nera,and Mukdenia and their implications for subtribal boundaries in Saxifrageae (Saxifragaceae). Can. J. Bot. 64: 586-588. Chromosomal studies have revealed that 2n = 34 in Astilboides, Darmera, Mukdenia, and Bergenia and that these genera have very similar karyotypes. Few taxa of Saxifrageae have x = 17, and chromosomal data therefore suggest that these four genera form a natural group. The generic affinities suggested by chromosomal data are not in agreement with the traditional interpretation of relationships in Saxifrageae. Astilboides has been placed in subtribe Astilbinae, while Bergenia, Darmera, and Mukdenia were considered members of Saxifraginae. The data presented here, in conjunction with data from earlier chromosomal studies, indicate that traditional subtribal boundaries do not accurately reflect relationships in tribe Saxifrageae.

SOLTIS,D. E. 1986. Karyotypic relationships among Astilboides, Bergenia, Darmera, and Mukdenia and their implications for subtribal boundaries in Saxifrageae (Saxifragaceae). Can. J. Bot. 64: 586-588. Des Ctudes chromosomiques ont rCvC1C que 2n = 34 chez les Astilboides, Darmera, Mukdenia et Bergenia et que ces genres ont des caryotypes trbs semblables. Ce n'est que chez quelques taxons des Saxifrageae que x = 17, et les donnCes chromosomiques suggbrent que ces quatre genres constituent un groupe naturel. Les affinitCs gCnCriques que suggbrent les donnCes chromosomiques vont i l'encontre de l'interprktation traditionnelle des affinites chez les Saxifrageae. L'Astilboides a CtC place dans la sous-tribu des Astilbinae tandis que les Bergenia, Darmera et Mukdenia Ctaient considCrCs comme membres des Saxifraginae. Les donntes ici prCsentCes, conjointement avec les donnCes d'Ctudes chromosomiques prCcCdentes, indiquent que les limites traditionnelles des sous-tribus ne rkflktent pas de manibre prkcise les affinitCs dans la tribu des Saxifrageae. [Traduit par le journal]

Introduction Results Following Engler (1930), tribe Saxifrageae (Saxifragaceae) Acetocarmine root-tip squashes showed 2n = 34 in comprises 23 genera. Most genera of Saxifrageae for which Astilboides tabularis, Bergenia cordifolia, B. crassifolia, chromosome counts have been reported are characterized B. stracheyi, Darmera peltata, and Mukdenia rosii either wholly or in part by x = 7, with 2n = 14 a very wide- (Figs. 1-4). All chromosome numbers determined in this spread number throughout the tribe (Fedorov 1969; Soltis study agree with previously reported counts (Fedorov 1969). 1980, 1984a, 19846, 1984c, 1984d; Soltis and Bohm 1984; However, in addition to an earlier count of 2n = 34, a second Spongberg 1972). Astilboides, Bergenia, Darmera, and count of ca. 36 has also been reported for A. tabularis For personal use only. Mukdenia are distinct in having 2n = 34 (Fedorov 1969). (Fedorov 1969). However, these four genera have been placed in different sub- The chromosomes of the investigated taxa are very small, tribes of Saxifrageae (Engler 1930). Earlier chromosomal stud- with the largest approaching 3.0 pm. Most of the shorter ies have provided a broad karyotypic data base for other genera pairs are less than 1.0 pm in length. The chromosomes of of Saxifrageae, including Boykinia, Elmera, Heuchera, Astilboides, Bergenia, Darmera, and Mukdenia are therefore Leptarrhena, Mitella, Sullivantia, Tanakaea, Tiarella, and smaller than the chromosomes of other genera of Saxifrageae Tolmiea (all x = 7 (Soltis 1980, 1982, 1984a, 19846, 1984c, so far examined karyotypically (Soltis 1980, 1982, 1984a, 1984d; Soltis and Bohm 1984)). In an attempt to elucidate 19846, 1984c, 1984d; Soltis and Bohm 1984). relationships among Astilboides, Bergenia, Darmera, and Because of the extremely small size and also the number of Mukdenia and also to clarify subtribal boundaries in Saxifra- chromosomes involved, it was difficult to compare many of geae, a karyotypic comparison of these genera was under- the shorter pairs among the species investigated. As a result, taken. apparent idiograms have not been provided. This study clearly demonstrates, however, a very high degree of karyotypic simi- Materials and methods larity among species of Astilboides, Bergenia, Darmera, and Can. J. Bot. Downloaded from www.nrcresearchpress.com by Marston Science Library on 09/30/14 Three of the eight species of Bergenia recognized by Engler (1930) Mukdenia (Figs. -1 -4). were investigated: B. cordifolia (Haw.) A. Br., B. crassifolia (L.) In all six species examined, the two longest pairs (pairs 1 Fritsch, and B. stracheyi (Hook. f. et Thoms.) Engl. Also analyzed and 2) are easily recognized by their slightly larger size; both was one of two described species of Mukdenia, M. rosii (Oliver) have submedian centromeres (Figs. 1-4). Pairs 3 and 4 are Koidzumi, as well as the species comprising the monotypic Darmera similar in length, but pair 3 has a submedian centromere and and Astilboides, D. peltata (Torrey) Voss and A. tabularis (Hemsl.) pair 4 is distinctive in possessing a median centromere. Engl. There is a gradual transition in chromosome length from pair Root tips for mitotic squashes were obtained from the sources given 5 to the shortest chromosome pair (pair 17) in all taxa investi- in Table 1. Plants of Bergenia species were grown from seed, while gated. Virtually all of the shorter chromosome pairs have sub- plants of Astilboides, Darmera, and Mukdenia were grown from rhi- zomes collected in the field or obtained from botanical gardens. median centromeres. These shorter pairs are numerous and Because of the great difficulty involved in obtaining living material of very small and it is therefore difficult to differentiate among species of Bergenia, Astilboides, and Mukdenia, only a single collec- them. Two of the shorter pairs typically can be recognized in tion of each was analyzed. Acetocannine root-tip squashes were all the species investigated by their median centromeres. Also, prepared and karyotypes constructed following methods discussed in all taxa, one of the shorter pairs having a submedian previously (Soltis 1980, 1984~). centromere was observed to possess satellites (Fig. 4). SOLTIS 587

TABLE1. Collection data for plants analyzed

Astilboides tabularis (Hemsl.) Engl., Botanic Garden of the Univer- sity of Copenhagen, Copenhagen, Denmark Bergenia cordifolia (Haw.) A. Br., Komarov Botanical Institute, Leningrad, U.S.S.R. Bergenia crassifolia (L.) Fritsch, Komarov Botanical Institute, Leningrad, U.S.S.R. Bergenia stracheyi (Hook. f. et Thorns.), Komarov Botanical Insti- tute, Leningrad, U.S.S.R. Darmera peltata (Torrey) Voss, CALIFORNIA: Trinity Co., river bordering Forest Glen campground, Soltis 1428; Madera Co., along stream, Rock Creek campground, Sierra National Forest, Soltis 1419; Mariposa Co., along stream, Lone Sequoia Camp, Rt. 8050, Soltis 1423; OREGON: Benton Co., near Benton Co. Boat Landing, Alsea River, Hwy . 34, 1.1 mi W of Maltby Creek cross- ing, Soltis 1364 Mukdenia rosii (Oliver) Koidzumi, University of British Columbia, Botanical Garden, Vancouver, Canada

Discussion Species of Astilboides, Bergenia, Darmera, and Mukdenia possess the same chromosome number (2n = 34) and exhibit essentially identical karyotypes. These are the only genera of Saxifrageae, for which chromosomal data are available, characterized by 2n = 34. A chromosome number of 2n = 34 has been reported elsewhere in Saxifrageae only for several species of the large and cytologically complex genus Saxifraga. Chromosomal data therefore suggest that Astilboides, Bergenia, Darmera, and Mukdenia form a natural group of genera. These relationships are not in agreement, however, with the traditional interpretation of subtribal boundaries. Astilboides was placed in subtribe Astilbinae with Astilbe and Rodgersia, whereas Bergenia, Darmera, and Mukdenia are members of Saxifraginae (Engler 1930). Chromosome counts For personal use only. for species of Astilbe are 2n = 28 (Fedorov 1969; D. E. Soltis, unpublished) and for species of Rodgersia 2n = 30, 60 FIGS. 1-4. Somatic chromosomes, all at same scale. s, satellite. (Fedorov 1969; D. E. Soltis, unpublished). In addition, pre- Numbers designate chromosome pairs referred to in text. Fig. 1. liminary data indicate that both Astilbe and Rodgersia differ Astilboides tabularis. Fig. 2. Bergenia crassifolia. Fig. 3. Darmera from Astilboides in their karyotypes. These data further sug- peltata. Fig. 4. Mukdenia rosii. gest that Astilboides is more closely allied with genera elsewhere in Saxifrageae. Furthermore, most genera of subtribe Doyle for helpful comments and Tom Elias for help in obtain- Saxifraginae with which Bergenia, Darmera, and Mukdenia ing material. have been considered to be closely allied are characterized by 2n = 14. ENGLER,A. 1930. Saxifragaceae. In Die Natiirlichen Pflanzenfami- Chemical evidence lends further support to the contention lien. 2nd ed. 18a. Edited by A. Engler and K. Prantl. Engelmann. that subtribe Astilbinae is an unnatural assemblage of taxa. Jay Leipzig. p. 117. FEDOROV, A. (Editor). 1969. Chromosome numbers of flowering (1970) tentatively concluded that is chemically dis- Astilboides plants. Academy of Science, U.S.S.R., Leningrad. tinct from other genera of Astilbinae and has greater affinities JAY,M. 1970. Quelques problbmes taxonomiques et phylogCnCtiques Can. J. Bot. Downloaded from www.nrcresearchpress.com by Marston Science Library on 09/30/14 elsewhere in tribe Saxifrageae. des SaxifragacCes vus la lurnibre de la biochimi flavonique. Bull. The findings reported herein join a growing body of data Mus. Natl. Hist. Nat. Bot. 42: 754-775. which indicates that traditional subtribal boundaries in Saxi- SOLTIS, D. E. 1980. Karyotypic relationships among species of frageae do not accurately reflect relationships. For example, Boykinia, Heuchera, Mitella, Sullivantia, Tiarella, and Tolmiea as reviewed by Soltis (1984c), evidence from cytology, mor- (Saxifragaceae). Syst. Bot. 5: 17-29. phology, chemistry, and palynology also does not support the 1982. Heterochromatin banding in Boykinia, Heuchera, recognition of subtribe Leptarrheninae. These data suggest that Mitella, Sullivantia, Tiarella, and Tolmiea (Saxifragaceae). Am. J. subtribal boundaries in Saxifrageae should be reevaluated. Bot. 70: 1007- 1010. However, any formal taxonomic realignment of subtribes in 1984a. Karyotypic relationships among Elmera, Heuchera, and Tellima (Saxifragaceae). Syst. Bot. 9: 6- 11. this group must await investigation of additional genera. 19846. Karyotypes and relationships of species of Jepsonia (Saxifragaceae). Syst. Bot. 9: 137 - 141. Acknowledgements 1984c. Karyotypes of Leptarrhena and Tanakaea (Saxifraga- ceae). Can. J. Bot. 62: 671 -673. This research was supported by National Science Founda- 1984d. Autopolyploidy in Tolmiea menziesii (Saxifraga- tion grants DEB 8109817 and BSR 8315098. I thank Jeff ceae). Am. J. Bot. 71: 1171 - 1174. 588 CAN. 1. BOT. VOL. 64, 1986

SOLTIS,D. E., and B. A. BOHM.1984. Karyology and flavonoid SPONGBERG,S. A. 1972. The genera of Saxifragaceae in the south- chemistry of the disjunct species of Tiarella (Saxifmgaceae). Syst. eastern United States. J. Arnold Arbor. Harv. Univ. 53: 409-498. Bot. 9: 441 -447. For personal use only. Can. J. Bot. Downloaded from www.nrcresearchpress.com by Marston Science Library on 09/30/14

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