Vegetatio 110: 1-17, 1994. @ 1994 Kluwer Academicifublishers. Printed in Belgium. 1

The phytogeography of the proliferus (L. fil.) Link (: ) complex in the Canary Islands: a multivariate analysis

J. Francisco-Ortega 1, M. T. Jackson 1*, A. Santos-Guerra 2, M. Fernandez-Galvan 2 & B. V. Ford-Lloyd 1** 1School of Biological Sciences,The University of Birmingham, P.O. Box 363, Birmingham, B15 2TT, ~ UK 2Jardin de Aclimatacion de La Orotava, Calle Retama Num. 2, 38400, Puerto de La Cruz, Tenerife Canary Islands, Spain * Present address: International Rice Research Institute, P.O. Box 993, 1099 Manila, Philippines; ** Author for correspondence

7.9.1992

Keywords:Ecogeography, Fodder-legumes, In-situ-conservation, Biodiversity, Germplasm,Tagasaste

Abstract

Chamaecytisusproliferus(L.til.) Link (Fabaceae:Genisteae) represents a speciescomplex in the Canary Islands. Floristic data from 147releves from the whole complexwere collected and analysedby clas- sification (TWINSP AN) and ordination (DECORANA) methods.Results indicate that white escobon of Tenerife, escobonof El Hierro, white escobonof Gran Canaria and typical tagasastein La Palma are associatedwith those communitiesfrom the north of theseislands which are under the influ- ence of the north-easterntrade winds. Narrow-leavedescobon in Tenerifeand La Gomera, escobonof southernGran Canaria and white tagasasteof La Palma are found in those areaswhich are not under the direct influenceof thesewinds. Morphological forms from the more easterlyislands (Gran Canaria and Tenerife-La Gomera) have the broadestecological range and they have played an important role in the floristic changeswhich have taken place after the destructionof the forests in theseislands. The highestpriorities for in situ conservationshould be givento wild populations of typical tagasaste,white escobonof Tenerife and escobonof El Hierro.

Abbreviations:International Board for Plant Genetic Resources(IBPGR), Detrended Correspondence Analysis (DECORANA), Operational Taxonomic Unit (OTU), Two Way Indicator SpeciesAnalysis (TWINSP AN)

Nomenclature:Hansen, A. & Sunding,P. 1985.Flora of Macaronesia.Checklist of vascularplants. 3rd ed. Sommerfeltia 1: 1-167; Acebes-Ginoves,J.R., Del Arco, M. & Wildpret, W. 1991. Revisiontaxo- nomica del genera Chamaecytisus(t. fil.) Link en Canarias.Vieraea 20: 191-202.

~Accepted Introduction truly domesticated species (Harlan 1983). No clear morphological and agronomic differences The genus Chamaecytisus Link (Fabaceae: exist between typical tagasaste from wild Genisteae) comprises approximately 28 species. and from cultivated populations. This means that The centre of highest diversity occurs in the Bal- unlike many other more domesticated crops, ta- kans where more than 15 species can be found gasastegermplasm collected in the wild is of value (Cristofolini 1991). The number of species de- as in many instances it can be used without hav- creasestowards the rest of Europe, the Near East, ing to resort to complex plant breeding proce- North Africa and the Canary Islands. Chamae- dures. The importance of germplasm from wild cytisus proliferus (L.ftl.) Link forms a taxonomic populations of this fodder speciesdetermines that species complex in the Canary Islands (Fig. 1). ecogeographical studies within its distribution are Both Acebes-Ginoves (1990) and Francisco- extremely useful in the establishment of strategies Ortega (1992) reported seven morphological for subsequent evaluation and utilisation of its forms within this complex namely, white escobon plant genetic resources. Furthermore as the cen- of Tenerife (C. proliferus ssp. proliferus sensu tre of origin and diversity of tagasaste is found stricto), narrow-leaved escobon (C. proliferus ssp. within an archipelago, it is essential to consider angustifolius (Kuntze) Kunkel), typical tagasaste the general patterns of island biogeography prior (C. proliferus ssp. proliferus var. palmensis (Christ) to any study on the phytogeography and plant Hansen & Sunding), white tagasaste (C. proliferus genetic resources of this species. ssp. proliferus var. calderaeJ .R. Acebes), escobon Studies concerning the biogeography of the Ca- of southern Gran Canaria (C. proliferus ssp. me- nary Islands have been reported extensively else- ridionalis J.R. Acebes), white escobon of Gran where (e.g. Webb & Berthelot 1836-1850; Kunkel Canaria (C. proliferus ssp. proliferus var. canariae 1976; Bramwell 1979; Santos-Guerra 1983a; (Christ) Kunkel) and escobon of El Hierro (C. Rivas- Martinez 1987). Due to the oceanic posi- proliferus ssp. proliferus var. hierrensis (Pitard) tion of the archipelago and the influence of the J.R. Acebes). cold north-eastern and the hot north-western Both kinds of tagasaste are endemic to the is- trade winds there is a stratification of different land of La Palma. Escobon ofEl Hierro, escobon climates in the archipelago both in terms of alti- of southern Gran Canaria, white escobon of Gran tude and orientation. This stratification is also Canaria and white escobon of Tenerife are only reflected by the patterns of distribution of the found in their respective islands whereas narrow- vegetation of the Canary Islands in five different leaved escobon occurs in Tenerife and La Go- life-zones namely, infra-canarian zone (semi- mera (Fig. 1). desert scrub), thermo-canarian zone (arid scrub, Although originally from La Palma, typical ta- Laurus azorica wood and heath belt), meso- gasaste is also cultivated in El Hierro, La Go- canarian zone (Pinus canariensis forest), supra- mera, Tenerife and Gran Canaria. The other six canarian zone (high altitude scrub) and oro- morphological forms are not cultivated but heavily canarian zone (only Viola cheiranthifolia). Within pruned and grazed in their wild habitats (Perez de this ecological framework the other two factors Paz et al. 1986; Francisco-Ortega et al. 1990). which determine the patterns of biogeographical White escobon of Gran Canaria has beenreported variation found in the Canary Islands are the ob- to be semi-cultivated in some areas of north- vious geographical isolation which exists between western Gran Canaria (Hernandez-Gonzalez each island and the abrupt topography. 1987; Francisco-Ortega et al. 1990) where it is Habitat stratification in life-zones has pro- used to feed livestock. duced several examples of adaptive radiation in Tagasaste appears to follow the same pattern the genera Aeonium (Lems 1960), Argyranthemum of domestication of other fodder species and al- (Humphries 1976) and Sonchus (Alridge 1980). though it is cultivated it cannot be regarded as a On the other hand geographical isolation due to 3

,J 10, 20 , km

iW

~~ ~m

EI Hierro ~; !2 ~m20

Fig. 1. The distribution of the seven morphological forms of C. proliferus (based on Acebes-Ginoves et al. (1991) and Francisco- Ortega (1992». Taxa are coded as follows: 0 C. proliferus ssp. proliferus var. proliferus; .C. proliferus ssp. angustifolius; f,. C. proliferus ssp. proliferus var. canariae; ..C. proliferus ssp. meridionalis;.C. proliferus ssp. proliferus var. palmensis; 0 C. proliferus ssp. proliferus var. calderae and .C. proliferus ssp. proliferus var. hierrensis. island topographyand/or insular isolationhas led Previousreports on the phytogeographyof C. to vicariance,examples of this evolutionarypro- proliferns (Ceballos & Ortufio 1951; Esteve- cessbeing the patterns of morphologicalvariation Chueca 1969; Sunding 1972; Rivas-Martinez and ecologyin the genera Cheirolophus,Crambe 1987)were imprecise,as firstly they did not in- and Limonium (Bramwell 1972). clude the whole distribution range of the species, 4

and secondly they were more concerned with the and in zones with low and high rainfall of 175 and ecology of the life-zones of the archipelago rather 1200 mm respectively. than with the ecological characteristics and For each locality cover values of taxonomy of C. proliferns itself. Only recently has species were estimated using the Braun-Blanquet it been proposed (Acebes-Ginoves 1990) that scale. Special emphasis was placed upon the typical tagasaste, white escobon of Gran Canaria, compilation of Canarian and Macaronesian en- white escobon of Tenerife and escobon of El demics and of those species reported in previous Hierro were linked to the laurel (Laurns azorica) works (e.g. Santos-Guerra 1983b; Rivas-Mar- wood and the heath (Erica arborea) forma- tinez 1987) as characteristic of each life-zone, tions from the north of these islands, whereas the since they are clearly related with both the ecol- other three morphological forms were in associ- ogy and historical biogeography of the Canary ation with the plant communities of P. canarien- Islands. Numerical analyses were carried out on sis. a matrix in which each quadrat was regarded as No multivariate analyseson the phytogeogra- an OTU. Data from the Braun-Blanquet scale phy of this specieshave beenreported previously, were transformed following Feoli-Chiapella & and from our study both herbarium specimens Feoli (1977). A classification of releves was ob- and germplasmwere collected from most of the tained by the polythetic divisive method of localities of C. proliferus in the Canary Islands TWINSPAN (Hill 1979a). Ordination of reIeves with the objective that an understandingof the was accomplished using DECORANA (Hill phytogeographyof this specieswould lead to a 1979b) which avoids the curvilinear distortion better interpretation of its patterns of morpho- known as "arch effect" which is produced with logical ,variation. In turn, it was anticipated that other techniques (e.g. Principal Component this would contribute to the ecogeographical Analysis, Non-Metric Multidimensional Scaling, characterizationof the plant geneticresources of Reciprocal Averaging), when species diversity this fodder legumewith a view to future conser- among sites follows environmental gradients vation strategies. (Jackson & Somers 1991). The CEP-PC package (Mohler 1987) was utilised to accomplish these multivariate analyses. In order to avoid between- and methods island floristic vicariance effects, separate analy- ses were carried out for each island except for EI Floristic data from 147 wild populations of C. Hierro where data were collected from only three proliferns sensulaID from El Hierro, La Palma, La populations. Simple descriptions of floristic com- Gomera, Tenerife and Gran Canaria were col- positions of these stands were used for interpre- lected from quadrats of approximately 40 x 40 m tation of the ecological features of escobon of EI between March and September 1989. Populations Hierro. from the whole distribution range of the species were sampled. They were separated by 3 km and were chosen following the north-south climatic Results gradient which exist within each island (Santos- Guerra 1984). Table 1 shows localities for which Tenerife floristic lists were compiled. Further ecological information concerning each of these localities The hierarchical division of plant communities was given previously (IBPGR internal report 90/ from TWINSP AN end groups, is given in Fig. 2a. 1), and indicated that the species thrives better on Eight groups were recognised at the fifth division. sandy soils with low salinity and pH values be- These groups with their TWINSP AN indicator tween 5 and 7. Furthermore populations were species are given in Table 2. Stands identified identified in areas where periodical frosts occur within each group are shown in Fig. 3.

Materials

6

0

@

0

Fig.2. TWINSPAN classificationobtained for floristic data from Tenerife (a), Gran Canaria (b) and La Palma (c). The char- acteristicindicator speciesare also given(see species code numberin AppendixA).

End group A comprisesthose scrubs situated recordedon southernslopes at a meanaltitude of on northern and southernareas of the island at 900 m. Both end groups G and H were located a mean altitude of 1850m. Groups B, C, E and in northernTenerife. The meanaltitude for group F were found both on northern and southern G was of 1350m whereasstands from group H slopesofTenerife and with an averagealtitude of were recorded at a mean altitude of 950 m. 1600 m. Stands from end group D were only An ecologicalinterpretation of standsobtained

1 transition between the plant communities from reflected by the species scores on this axis which the centre of the island, towards the Canary pine are summarised in Table 5, as those specieslinked forest zone found at low altitudes. It is notewor- to the laurel wood zone (e.g. Laurus azorica) had thy that it is likely that in the past the plant com- positive values along this axis whilst species munities of central Gran Canaria also had P. ca- mainly found on the scrubs of La Caldera de nariensisas a common species. However intensive Taburiente gorges (e.g. Bystropogon origanifolius) deforestation has meant that it has vanished from had negative scores. Stands which had typical this area (Santos-Guerra & Fernandez-Galvan tagasaste showed the highest scores on the first 1980). DECORANA axis. The separation of stands along this axis was associated with a gradient which ran from northern La Palma towards the La Palma interior of La Caldera de Taburiente. The second DECORANA axis was related The hierarchicalclassification yielded five TWIN- with changes in the floristic composition of the SPAN end groups at the third division (Fig. 2c Canary pine communities. Stand 26 had the high- and Table 2). Releveswhich fell within eachend est positive value on this axis and it was recorded group are illustrated in Fig. 5. on a cliff, in an area where the pine forest was not A scatter diagram with values along the first so dense. This was confirmed by the fact that two DECORANA axesis shownin Fig. 5. Stands species such as Festuca agustini and Gonosper- recorded within the laurel wood-heathbelt zone mum canariensis had positive values along the had high positive values on the first axis. Popu- second axis (Table 5). Stands 254 and 255 were lations sampled on the bottom of some of the found in those areas of the pine forest of La wide gorges of La Caldera de Taburiente N a- Caldera de Taburiente, which meant that species tional Park had high negativevalues along the related to the thermo-canarian zone such as Erica first DECORANA axis. This situation was also arborea had low values on this axis (Table 5).

300l D '026 -', ,

A ,--- E /-', :/ 014' 8218! .23 ,O16 O17 ~- :13 ~OIB 0222; ---'

1001 c ', 8217) ~/

0255 - 0254 at ;; < A"IS I 100 200 300 400 ..10 800 Fig.5. DECORANA ordination for La Palma.The five TWINSPAN end groupsare also given. Stands with typical tagasaste are representedby closedcircles; stands with white tagasasteare representedby opencircles. Stands with intermediateplants are representedby opencircle plus dot. 12

Table5. Ten specieswhich had the highestpositive and negativevalues along the first two DECORANA axesin relevesfrom La Palma.

DECORANAI DECORANA2

Laurus azorica 673 Tinguarra montana 383 Teline stenopetala 673 Festuca agustini 383 Hypericum grandifolium 67390 Silene pogonocalyx 366 Myrica faya 5 Gonospermumcanariense 358 Erica arborea 585 Helianthemum broussonetii 335 Paronychia canariensis 82 Lotus hillebrandii 39 Lobularia palmensis 82 Andryala webbii 39 Spartocytisusfilipes '-r"8991 Erica arborea "'! 85 Bystropogonoriganifolius Rubus ulmifolius J- 90 Seneciopalmensis -.1 11 Sideritis bolleana -1 04

Eigenvalue 0.821 0.401

Four stands froqI La Caldera de Taburiente tude zones of southern Tenerife. The hierarchical had plants of white tagasasteand typical taga- classification yielded two end groups at the first sastegrowing together(Francisco-Ortega 1992). division. However in these localities white tagasastewas The first end group (TWINSP AN end group alwaysdominant. Furthermore,this morphologi- A) had Erica arborea as characteristic species cal form was never detected within the laurel whereas the second (TWINSPAN end group B) wood life-zone. had Artemisia thusculaand Micromeria lepida. The two releves from end group A had also other characteristic species from the heath-belt and lau- La Gomera rel wood plant communities (e.g. Myricafaya and flex canariensis)however these two sites were not All the stands of narrow-leaved escobon from La within the limits of the actual laurel wood or heath Gomera were associated with Cistus monspelien- belt. sis, and were similar to the scrubs from low alti- A scatter diagram for the first two DECO-

Table6. Ten species which had the highest positive and negative values along the first two DECORANA axes in releves CrOff La Gomera.

DECORANA DECORANA2

Micromeria lepida 258 Sonchusortunoi 348 Euphorbia obtusifolia 238 Phagnalon saxatile 220 Kleinia neriifolia 201 Adenocarpusfoliolosus 188 Artemisia thuscula 194 Phagnalon saxatile 125 Polycarpaea divaricata 169 Hypericum grandifolium 99 Bystropogon origanifolius -165 Hyparrhenia hirta -35 Bituminaria bituminosa -221 Carlina salicifolia -98 /lex canariensis -234 Andryala pinnatifida -159 Myrica Jaya -234 Dittrichia viscosa -178 Erica arborea -250 Micromeria varia -317

Eigenvalue 0.233 0.101 13

RAN A. axes (Fig. 6) showed that populations It was difficult from the data set to obtain an from TWINSP AN end group A had low values ecological interpretation for the second DECO- along the second axis and were regarded as being RANA axis, which separated stands 139 and 142 more influenced by the northern trade winds. All at one end and stands 138 and 140 at the other the localities, with the exception of one (popula- (Fig. 6). However floristic species scores tion 165), were below 1200 m altitude, and in the (Table 6) indicate that the legume shrub Adeno- southern areas of the island. Population 165 was carpus foliolosus which is also a member of the in the north west of the island but at an altitude Genisteae had high positive scores along the sec- of 450 m. This distribution was in agreement with ond axis whereas Micromeria varia had low nega- the species scores along the first axis (Table 6). tive values on this axis. Those species usually found in areas which have the influence of the trade winds (e.g. Myricafaya) had large negative scores on the first axis. High El Hierro positive values were only obtained for arid areas (e.g. Kleinia neriifolia or Euphorbia obtusifolia). The three stands of escobon of EI Hierro were This axis showed a transition within the Cistus located on the cliffs of EI Golfo caldera in the monspeliensisscrub from semi-arid areas to those north of this island at an altitude of 1000 m. which receive the effect of the trade winds. These stands were clearly linked to the heath belt

SOl

Fig. 6. DECORANA ordination for La Gomera.The two TWINSPAN end groupsare also indicated 14 and species usually found on cliff plant commu- areas which are under the influence of the trade nities such as Greenoviaaurea, Silene sabinosaeor winds (Santos-Guerra 1984), a situation previ- Toipis proustii were also recorded. It was never ously described by Fernandez-Galvan (1983), in observed forming dense scrubs and could not be La Gomera, an island with lower altitude than La regarded as a common species. No populations Palma, Tenerife and Gran Canaria, and where of C. proliferus were associated with the pine for- the trade winds can have a great influence on est, despite the extensive floristic survey carried some slopes of the south. This factor coupled out in the south of the island. with the fact that there are no real pine forest formations in the island, means that in the south there are zones which reflect a transition between Discussion the heath belt and plant communities from arid zones. In relation to that, one of the main features Chamaecytisusproliferus should be regarded as a of C. prolifelUs in La Gomera is that it was never species which grows under a broad range of eco- located within the true laurel wood zone. Acebes- logical conditions. Previous reports (Ceballos & Ginoves (pers. comm.) considers it likely that a Ortufio 1951; Esteve-Chueca 1969; Sunding 1972 form of C. prolifelUs similar to the white escobon and Rivas-Martinez 1987) which indicated that of Tenerife or Gran Canaria could exist on the the whole complex is restricted to the Canary pine cliffs of the laurel wood of this island. Despite the life-zone have been misleading. The different survey carried out during field studies and inter- morphological forms of the complex are also views with farmers and forest rangers from the found in the thermo-s:anarian zone, and some area, such a morphological form was never found. populations were also identified towards the high The fact that narrow-leaved escobon was never altitude scrub ofTenerife or in the semi-arid infra- observed within the limits of the laurel wood of canarian zone from the south of Tenerife and La Gomera confirms that this morphological form Gran Canaria. The classification and ordination has achieved ecological differentiation, and is of the stands demonstrate that the speciesfollows clearly adapted to dry areas which were not under an ecological cline through Tenerife, Gran Ca- the influence of the north-eastern trade winds. naria and La Palma, with distinct morphological ChamaecytisusprolifelUs does not conform to forms in the extremes of this cline. Typical taga- the same ecological trends in each island. The saste in La Palma, white escobon of Tenerife and two morphological forms from Gran Canaria white escobon of Gran Canaria are only located were observed colonising and forming massive in laurel wood/heath belt zones of these islands, scrubs in all areas where both the pine forest and whereas white tagasaste in La Palma, narrow- the laurel wood have vanished. On some occa- leaved escobon in Tenerife and escobon of south- sions, this colonising ability has led to the forma- ern Gran Canaria have their distribution range tion of dense scrubs in which escobon of south- linked with the Canary pine forest area. ern Gran Canaria or white escobon of Gran Such a gradient was not detected in El Hierro, Canaria are the dominant species. Furthermore, where C. proliferus was restricted to the cliffs of these two morphological forms also exhibit a the heath belt of El Golfo. A similar situation was weedy habit, being detected on abandoned found in La Gomera, where narrow-leaved esco- cultivated sites. This ability to thrive under vari- bon was always associated with Cistus monspe- ous ecological conditions was only shown by liensis, forming a kind of scrub which also oc- narrow-leaved escobon in Tenerife where this curred in localities of southern T enerife. However, morphological type also forms dense scrubs some of the stands from La Gomera had species (TWINSP AN end group E) and grows on aban- such as Erica arborea or Myrica faya which were doned cultivated sites. All the other morphologi- not found in their homologues from the south of cal forms have a more restricted ecological range; Tenerife. These species usually occur in northern white escobon of EI Hierro, white escobon of 15

Tenerifeand typical tagasastewere only observed forms have played an important role during the on cliffs and sunnyareas of the laurel wood/heath floristic changes which the pine forests ofTenerife belt. and Gran Canaria and the laurel wood/heath belt White tagasastewas confined to the pine for- of Gran Canaria have suffered because of human est of northern La Palma and to La Caldera de impact since the conquest of the Canary Islands, Taburiente and did not show the weedyhabit of late in the 14th century. Then intense pastoralism its ecologicallyhomologous narrow-leaved esco- and agriculture resulted in large-scale deforesta- bon and escobonof southernGran Canaria. Al- tion (Parsons 1981). Once such forests were cut though it was observedas an understorey species down these forms of C. proliferus colonised the of the pine forest it shows a tendencyto form area and formed scrub, as the habitats became densescrubs alongthe bottoms of the numerous sunnier and competition with other species was gullies which dissectthe huge eroded caldera of dramatically reduced. Furthermore, wild C. pro- the La Caldera de Taburiente.This morphologi- liferus is broadly utilised as a fodder plant. In our cal form was observedneither in the pine forest study, 80 % of the stands were found to have of southernLa Palma nor linked to low altitude heavily pruned escobon shrubs (Francisco-Or- plant communities of Euphorbia obtusifolia or tega 1992). This means that only in exceptional Kleinia neriifolia. These distribution patterns re- cases can C. proliferus form a dense shrub. Its present a more restricted ecologicalrange than competition with other species of the scrub and escobon of southern Gran Canaria or narrow- its colonisation ability and its density is severely leavedescobon. reduced by its utilisation as fodder by peasant Results shownhere indicate that the ability of farmers. Eventually the scrub is not so dense and the speciesto grow under wider ecologicalcon- a ground layer is mainly formed by Micromeria ditions is demonstratedmore in the easternis- spp., Bystropogonoriganifolius or Sideritis spp. In lands (Gran Canaria and Tenerife-La Gomera) the few places where escobon is not pruned it has than in the western islands (La Palma and El become the dominant species, and even in some Hierro). This accords with previous studies of situations other shrubs, such as Adenocarpusspp. genetic diversity, based on results from ten which have similar ecological requirements to C. isozyme loci, where only populations from the proliferus could barely compete with escobon. Our easternislands had unique alleles and also the observations indicate that prior to the massive highestvalues of Nei's index of genetic diversity destruction of the Canary pine forest and the lau- (Francisco-Ortega1992). Similarly, it was also in rel wood, C. proliferus may have been found thoseislands where a greaternumber of morpho- mainly in those areas where the forest was not so logical variants were detected(i.e. morphological dense, such as along the small and numerous clines for seed colour, juvenile characters,leaf ravines which dissectedthe forest, or on cliffs shapeand keel petal length in Gran Canaria and where taller trees are not dominant. It is also for leaf hairiness,leaf shapeand keelpetal length perceived that due to the abrupt and rough geog- in Tenerife).These results suggestthat there is a raphy of the islands the species could find many relationshipbetween germplasm provenance and ecological niches because of these features where ecogeographicalvariation measuredin terms of it thrived in association with other species of the ecology,morphology and allozymes.In this rela- forest. tionship, germplasmfrom the easternislands was We also find that C. proliferus should be re- more variable than that collected in the western garded as a pyrophytic species. Many young islands. plants of narrow-leaved escobon, tagasaste and Thereis anothermajor consequenceof the high escobon of southern Gran Canaria were observed colonising ability of narrow-leavedescobon, es- growing in stands which had been burnt recently cobon of southernGran Canaria and white es- and this is confirmed by Perez de Paz et al. (1986). cobon of Gran Canaria. These morphological Being a pyrophyte C. proliferus grows better on 16

habitats which becomesunnier with less compe- Appendix A tition from other species.Furthermore, as P. ca- nariensisis able to continue growth after a fire, a TWINSPAN characteristicspecies for Tenerife,Gran Ca. real scrubhas not actuallyreplaced the pine for- naria and La Palma. est, and only some young plants of C. proliferus 1. Adenocarpusfoliolosus 14. LaulUsazorica have survived in competition with the Canary .2. Adenocarpusviscosus 15. Micromeriabenthamii pine. Therefore an equilibrium, in which fire is 3. Bystropogonoriganifolius 16. Nepetateydea one of the regulators,is establishedbetween C. 4. Carlinaxeranthemoides 17. Phyllisnabla proliferusand P. canariensis. 5. ChamaecytisusprolifelUs s.l. 18. Pinuscanariensis 6. Cistusmonspeliensis 19. Rumexlunaria From a combinedecogeographical and genetic 7. Cistussymphytifolius 20. Seneciowebbii resource perspective the seven morphological 8. Echiumonosmifolium 21. Sideritiscretica types of C. proliferushave different ecologicalre- 9. Erica arborea 22. Sideritisdasygnaphalla quirementsand effectivein situ conservationand 10. Erysimumscoparium 23. Spartocytisussupranubius utilisation of the plant genetic resourcesof the 11. Euphorbiaobtusifolia 24. Telinemicropylla 12. flex canariensis 25. Festucaagustini speciesneeds to take account of its phytogeog- 13. Kleinia neriifolia raphy. The two morphologicalforms endemicin Gran Canaria, and narrow-leaved escobon in Tenerifeand La Gomeraare not endangeredspe- cies.Also they can withstand continuouspruning References by farmers and many of their plant communities Acebes-Ginoves, J.R. 1990. Contribuci6n al estudio de los have arisenas a result of human interventionupon generos ChamaecytisusLink y Dorycnium Mill en el archip- the forest. As a consequenceof the rather limited ielago canario (Ph.D. Thesis, unpublished). Universidad de distribution range of white tagasastemost of its La Laguna, La Laguna, Tenerife. populationsare confinedto La Calderade Tabur- Alridge, A.E. 1980. Anatomy and evolution in Macaronesian iente National Park where they correctlyhave an Echium (Boraginaceae). Plant Syst. Evol. 138: 9-22. Bramwell, D. 1972. Endemism in the flora of the Canary Is- in situ conservationstatus. Other priorities for in lands. In: Valentine, D.H. (ed), Taxonomy, phytogeogra- situ conservationshould be focusedtowards the phy and evolution, pp. 258-294. Academic Press, London. other three morphological forms, namely typical Bramwell, D. (ed) 1979. Plants and islands. Academic Press, tagasaste,white escobonofTenerife and escobon London. of EI Hierro. They have restricted ecologicalre- Ceballos, L. & Ortufto, F. 1951. Estudio sobre la vegetaci6n y la flora de las Canarias occidentales. Instituto Forestal de quirements and also have lower adaptation to Investigaciones y Experiencias, Madrid. those disturbed habitats which have arisen after Cristofolini, G. 1991. Taxonomic revision of Cytisus Desf. deforestation. sect. TubocytisusDC. (Fabaceae). Webbia 45: 187-219. Esteve-Chueca, F. 1969. Estudio de las alianzas y asocia- ciones del orden Cytiso-Pinetalia en las Canarias orientales. Bol. R. Soc. Esp. Hist. Nat. Secc. Bioi. 67: 77-104. Acknowledgements Feoli-Chiapella, L. & Feoli, E. 1977. A numerical phytoso- ciological study of the summits of the Majella massive Financial support for this work was received (Italy). Vegetatio 34: 21-39. through a personal grant (JFO) from the Minis- Fernandez-Galvan, M. 1983. Esquema de la vegetaci6n po- terio de Educacion y Ciencia (Spain), Plan Na- tencial de la isla de La Gomera. In: Comunica~oes apre- sentadas ao II Congreso Internacional pro Flora Macaro- cional de Formacion de Personal Investigador nesica 19-25 Junho de 1977, pp. 269-293. Funchal. (grantno. PG88 42044506)and from the IBPGR. Francisco-Ortega, J. 1992. An ecogeographical study within Thanks are due to J.R. Acebes-Ginoves(Univer- the Chamaecytisus proliferus (L.fiI.) Link complex (Fa- sidad de La Laguna, Tenerife)for critical reading baceae: Genisteae) in the Canary Islands (Ph.D. Thesis, of this manuscript.P.O. Machin (Universidadde unpublished). The University of Birmingham, Birmingham. Francisco-Ortega, J., Jackson, M. T., Santos-Guerra, A. & La Laguna, Tenerife) provided technical assis- Fernandez-Galvan, M. 1990. Genetic resources of the fod- tance. der legumes tagasaste and escobon (Chamaecytisusprolif- 17

elUS(L.fi1.) Link sensulato). FAO/IBPGR PI. Genet. Re- evolution of plant forms in the Canary Islands: Aeonium. sources Newsl. 81/82: 27-32. Ecology 41: 1-17. Harlan, J.R. 1983. The scope for collection and improvement Mohler, C.L. 1987. Cornell ecology programs. Microcom- of forage plants. In: McIvor, J.G. & Bray, R.A. (eds), Ge- puter Power, Ithaca. netic resources of forage plants, pp. 3-14. Commonwealth Parsons, J.J. 1981. Human influences in the pine and laurel Science and Industrial Research Organization, East Mel- forest of the Canary Islands. Geogr. Rev. 71: 253-271. bourne. Perez de Paz, P.L., Del Arco, M., Acebes-Ginoves, J.R. & Hernandez-Gonzalez, M. 1987. Comarca Guia-Juncalillo, Wildpret, W. 1986. Leguminosas forrajeras de Canarias. estudio forrajero (B.Sc. Thesis, unpublished). Universidad Cabildo Insular de Tenerife, Santa Cruz de Tenerife. Politecnica de Las Palmas Gran Canaria, La Laguna, Ten- Rivas-Martinez, S. 1987. Memoria del mapa de series de erife. vegetaci6n de Espafta 1:400,000. Instituto para la Conser- Hill, M.O. 1979a. TWINSPAN -A fortran program for ar- vaci6n de La Naturaleza, Madrid. ranging multivariate data in an ordered two-way table clas- Santos-Guerra, A. 1983a. Vegetaci6n y flora de La Palma. sification of the individuals and attributes. Ecology and Editorial Interinsular Can aria, Santa Cruz de Tenerife. Systematics, Cornell University, Ithaca, New York. Santos-Guerra, A. 1983b. Vegetaci6n de la region macaron- Hill, M.O. 1979b. DECORANA -A fortran program for esica. In: Comunica~oes apresentadas ao II Congreso In- detrented correspondence analysis and reciprocal averag- ternacionalpro Flora Macaronesica 19-25 Junho de 1977, ing. Ecology and Systematics, Cornell University, Ithaca, pp. 185-203. Funchal. New York. Santos-Guerta, A. 1984. Flora y vegetaci6n. In: Afonso, A. Humphries, C.J. 1976. A revision of the Macaronesian genus (ed), GeografIa de Canarias. Vol. 1, geografIa fisica, Argyranthemum Webb ex Schultz Bip. (Compo sitae- pp. 258-294. Editorial Interinsular Canaria, Santa Cruz de Anthemidae). Bull. Br. Mus. (Nat. His.) Bot. 5: 145- Tenerife. 240. Santos-Guerra, A. & Fernandez-Galvan, M. 1980. Vegeta- Jackson, D.A & Somers, K.M. 1991. Putting things in order: ci6n. In: Afonso, L. (ed), Atlas basico de Canarias, pp. 38- the ups and downs of detrended correspondence analysis. 47. Interinsular Can aria, Santa Cruz de Tenerife. Am. Nat. 137: 704-712. Sunding, P. 1972. The vegetation of Gran Can aria. Univer- Kunkel, G. (ed) 1976. Biogeography and ecology in the Ca- sitetsforlaget, Oslo. nary Islands. W. Junk, The Hague. Webb, P.B. & Berthelot, S. 1836-1850. Histoire naturelle des Lems, K. 1960. Botanical notes on the Canary Islands II. The Iles Canaries. Paris.