行政院國家科學委員會專題研究計畫 期中進度報告
台灣柯及柳葉柯(殼斗科) 之親緣地理及保育研究(2/3)
計畫類別： 個別型計畫
計畫編號： NSC91-2313-B-006-002-
執行期間： 91 年 08 月 01 日至 92 年 07 月 31 日 執行單位： 國立成功大學生物學系（所）
計畫主持人： 蔣鎮宇
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中 華 民 國 92 年 6 月 2 日
行政院國家科學委員會補助專題研究計畫 □成果報告
■ 期 中 進度
報告
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※※ 台灣柯及柳葉柯(殼斗柯)之親緣地理及保育研 究(2/3) ※
※ Phylogeography and conservation of pasania
※
※
formosanus
and P. dodoniifolius (Fagaceae)※
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※
計畫類別：▓個別型計畫 □整合型計畫 計畫編號：NSC91-2313-B-006-002
執行期間：91 年 08 月 01 日至 92 年 07 月 31 日 計畫主持人：蔣鎮宇
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中 華 民 國 92 年 5 月 29 日
行政院國家科學委員會專題研究計畫成果報告
台灣柯及柳葉柯(殼斗柯)之親緣地理及保育研究(2/3) Phylogeography and conservation of Pasania formosanus
and
P. dodoniifolius (Fagaceae)
計畫編號：NSC 91-2313-B-006-002
執行期限：91 年 08 月 01 日至 92 年 07 月 31 日 主持人：蔣鎮宇
執行機構及單位名稱:國立成功大學生物系
一、中文摘要
本研究利用核 DNA ITS region 重建台 灣柯以及柳葉柯的親緣關係，重建台灣柯 以及柳葉柯的親緣關係,結果顯示不論在 種間以及族群間皆具有較高的遺傳歧異度, 但其分化程度卻相對低,此一結果與所重 建的親源樹狀圖中顯現兩物種多起源的現 象一致,利用親緣網狀圖顯示出兩個主要 的支系(A and A’clades),其中 A’支系包 含 3 個支系(B, C, D),而且沒有任何一個 族群各自形成一各支系,支系 D 中並無台灣 柯的個體出現,B 以及 C 支系中則無柳葉柯 中的兩個小族群的個體存在,此種分布情 形主要是由於 lineage sorting 所造成的, 反之在 RAPD 的結果則顯示不論在種間以及 族群間皆具有高度分化的情形,就目前而 言其種子長距離的傳播似乎不太可能,因 此在葉綠體 DNA 中較高的 Nm 值應該是歷史 上長距離傳播所造成的,再輔以地質證據 顯示兩者的共祖在冰河時期時避入冰河避 難所,於後冰河時期才擴散至現今分布地, 由於分布至不同的棲地使的兩者在開花時 間上有所差異,進而導致升殖隔離以及種 化
關鍵詞：核 DNA、台灣柯、柳葉柯避難所、
種化 Abstract
Gene genealogy of the ITS region of nrDNA was reconstructed to assess the phylogeographic pattern of two closely related
oaks, Pasania formosanus andP. dodoniifolius.
High levels of nucleotide and haplotype diversities, high levels of genetic differentiation between species but lower level of genetic differentiation among populations were detected. The result consistent with a neighbor-joining analysis.
Monophyly of P. formosanus and P. dodoniifolius was suggested by the NJ tree. According to
geological evidence, during the deglaciation period, common ancestral populations were possibly
forced to migrate into refugia at local peaks.
Invading and adapting to habitats of different elevations, two oaks flower with a lag interval of about half a month, which may have triggered the reproductive isolation and speciation.
Keyword: ITS、lineage soting、neighbor-joining analysis、refugia、speciation
二、緣由與目的
Genetic diversity in natural populations is a major concern of evolutionary biologists because distributions of genetic diversity are likely to affect the evolutionary potential of species and /or populations (Futuyma 1986).
In the last three decades, a huge amount of researches on genetic diversity of species and populations has assessed (Hamrick and Godt 1989). Genetically sound conservation requires a robust understanding of the processes by which species display genetic diversity in local population and the patterns of these species (Falk and Holsinger 1991;
Hamrick and Godt 1996). The theoretical relationship between the severity of a population bottleneck and the subsequent loss of genetic variability and increase in
genetic differentiation is well established (Wright, 1969; Nei et al. 1975). However, empirical validation of the genetic
consequences of well documented bottlenecks in natural populations are relatively scarce (Leberg 1991; Taylor et al.
1994) While some species recovering from bottlenecks are known to have limited genetic variarility (Ellegren et al. 1993), bottlenecked populations that retain appreciably high levels of variability have also been described (Carson 1990;
Dinerstaein & McCracken 1990; Robinson et al 1993). In addition, the recovery of
endangered species from severe population bottlenecks now frequently involves human intervention ( Hambler 1994; Hartman 1994;
Russell et al 1994), but the genetic
consequences of natural damages are largely unknown.
Population genetic studies over the last decade have revealed that populations of many organisms are structured into phylogenetic units, and these units often correspond to geographical regions (e.g.
Avise et al. 1987; Avise 1992 ; Riddle 1995).
Avise et al. (1987) hypothesized that phylogeographic pattern results either from physical barriers that restrict gene flow between geographical regions or from the localized extinction of haplotypes in widely distributed taxa with limited capacity for dispersal. The recovery of congruent phylogeographic patterns across distantly related taxa suggests that the genetic structuring results from broadly acting physical processes and not localized extinction (Avise et al. 1987; Avise 1992 ; Riddle 1995). Congruent patterns of genetic structuring, however, are not always
observed. The genetic structuring of populations is dependent on demographic, genetic, and historical factors (Slatkin 1994).
These factors can vary so much that even closely related taxa in a common
environment have different patterns of genetic structure (e.g. Meyer et al. 1996;
Patton et al. 1996) making it difficult to determine phylogeographic structure of closely related species. Because the formation of phylogeographic structure
within a single species is a potentially important step in the process leading to population differentiation, it is also important to understand speciation. In the absence of congruent patterns across taxa, the
examination of patterns of gene flow may provide an equally valid alternative method for understanding the origins of
phylogeographic structure within a species.
Morphologically, trees of 4-9 m in height of both taxa shared entire and revolute leaf margins, obtuse leaf apex, and nuts encrusted with cupule at bottom. A single extant population of P. formosanus, with no more than 100 constituting plants, is
remained in the wild, although several scattered populations were previously recorded (cf. Lu, 1996). The population is distributed along the Nanjen Stream in the Kengting National Park. Two subpopulations occurring along ridges about 400 m alt. are separated by a stream. Only the ob-lanceolate leaf shape of P. dodoniifolius is distinct from the oblong to obovate leaf shape of P.
formosanus. In contrast the P. formosanus , three populations of P. dodoniifolius are distributed along the Central Mountain Range of the island: Mt. Weiliaoshan (ca.
1,200 m alt.) with about 100 individuals, Chingshuiying (ca. 1,500 m alt.) with about 200 individuals and Dazen (ca. 600 m alt.) with about 9 individuals. Two species are about 30 km apart geographically.
Populations of P. dodoniifolius are also isolated with distance between 20 km and 60 km. Ecologically, plants of both species usually grow on wind-facing slopes, mixing with other fagaceous and lauraceous species in tropical or subtropical forests. Pollen dispersal is wind-mediated, while seeds are usually carried by small mammals, such as squirrel (Chiang & Hong, 1999).
In order to determine the level of ongoing gene flow between populations, which are mostly amplified from the ITS region nrDNA DNA , were utilized to assess the extent of migration.
三、結果與討論
Oaks survived glacial cycles (cf.
Bennett, 1990; Chiang & Peng, 1998), like many angiosperm tree species (e.g., oaks, Ferris et al., 1995; Petit et al., 1997;
Dumolin-Lapègue et al., 1997; beech, Koike et al., 1998; and beets, Desplanque et al., 2000) and gymnosperms, such as
Cunninghamia (Lu et al., 1999) and Pinus (Strauss et al., 1993). According to
geological record, since the late Pleistocene, Taiwan had been the southeastern edge of the Asian continent before the formation of Taiwan Strait about 100,000 years ago (Lin, 1966; Tsukada, 1966; Kizaki & Oshiro, 1977). This continental island was linked to the mainland via a land bridge and was not completely isolated until the last glacial retreat some 18,000 to 20,000 years ago (Lin, 1966). Geological evidence indicates that ice ages have occurred at regular intervals of approximately 100,000 years followed by warm periods of about 20,000 years (Milankovitch cycles) (cf. Bennett, 1990;
King & Ferris, 1998). During the glacial maximum many fagaceous plants and conifers previously dominated in northern part of east Asia were forced to migrate into refugia in southern China and Taiwan (Chiang et al., 1999), which were mostly distributed at low elevations (cf. Tsukada, 1966). During the subsequent deglaciation, raised global temperatures forced the lowland plants to migrate to high elevations or local peaks. Pollen records reveal the migration routes of many relic and endemic species, which constitute a large portion of Taiwan’s flora (Shaw, 1997). The current geographical distribution of L. dodoniifolius and L.
formosanus is possibly a result of such a migration history.
Extinction and recolonization regulated by geological events, however, were thought to enhance genetic differentiation among populations (cf. Wright, 1977) owing to founder events resulting from the
colonization by a small number of surviving individuals. Recently, Wade and McCauley (1990) further suggested that the results of extinction / recolonization on genetic
differentiation among populations depend on the number of founders as well as the level of heterogeneity of genetic composition within populations according to coalescence theory.
When the colonist size is small and the genetic heterogeneity is low, genetic differentiation among populations will be reached fast, via stochastic processes alone.
Due to limited area and available habitats of the island, the population size of Taiwan’s oaks is apparently smaller than that of continental species. Under near neutrality, a longer period of lineage sorting for cpDNA chlorotypes in small populations may be likely ascribed to higher levels of
heterogeneity in genetic composition.
Interestingly, observations indicated that greater genetic variation exists in southern refugia (such as Italy, Balkans, and Iberians) than in northern populations (e.g., Central Europe) (European oaks cf.
Dumolin-Lapègue et al., 1997, 1998e.g., European Alnus King & Ferris 1998; Fagus, Demesure et al., 1996; and Japanese Abies, Tsumura & Suyama 1998). The
continent-island discrepancy may be
associated with the more southern location of Taiwan, today’s subtropics to tropics, than most areas of European and American continents. In other words, Taiwan may have provided more fitting habitats for surviving plants during the glacial maximum than mainland refugia. Accordingly, “invaders”
from north area of mainland Asia, during the glacial expansion, may have carried much genetic variation into Taiwan. In addition, the high level of heterogeneity in oak
populations must have been regulated by the process of apportioning of genetic variation between and within populations as well. Such process, however, may have been constrained by the ragged topography of the island. As stated above, during the glacial expansion, ancestral populations may have distributed in lowlands west of the central mountain range as well as the land bridge. Some sporadic local crests in both middle and low elevations provided refugia during the deglaciation period. In contrast to the huge plains in continents, where settlement of individuals from the same or neighboring populations was likely and thereafter resulted in patchy structure, the mountainous landscape of the continental island may have limited
migratory routes for the survived. Most migrants were forced to enter into the
scattered and limited refugia. Invasions with highly diverged resources inevitably
increased the level of heterogeneity in genetic composition, which therefore may have prolonged the period for coalescence of the cpDNA and resulted in low genetic differentiation among populations, despite the small population size relative to continental populations.
Apparently, the level of genetic variation is not only regulated by the real population size, but also determined by the geological history that the species and populations evolved through. High level of organelle variation, given no homologous crossing over, can be possibly maintained even within species with limited population size and number, as a result of the
migrant-pool dispersal model. In contrast, variation of nuclear genome can be swept, due to the effect of genetic drift and
crossing-over between homologous loci, in smaller populations.
五、參考文獻
AVISE, J. C. 1999. Phylogeography:
The history and formation of species.
Harvard University Press. Cambridge.
Massachusetts.
BENNETT, K. D. 1990. Milankovitch cycles and their effects on species in ecological and evolutionary time. Paleobiology 16:11-21.
DEMESURE, B., B. COMPS, & R. PETIT. 1996. Chloroplast DNA phylogeography of the common
beech (Fagus sylvatica L.) in Europe. Evolution 50: 2515-2520.
DESPLANQUE, B., F. VIARD, J. BERNARD, D.
FORCIOLI, P. SAUMITOU-LAPRADE, J.
CUGUEN, & H. VAN DIJK. 2000. The linkage disequilibrium between chloroplast DNA and mitochondrial DNA haplotypes in Beta vulgaris ssp. maritima (L.): the usefulness of both genomes for population genetic studies. Mol. Ecol. 9: 141-154.
DUMOLIN, S., B. DEMESURE, & R. J. PETIT. 1995.
Inheritance of chloroplast and
mitochondrial genomes in pedenculate oak investigated with an efficient PCR method.
Theor. Appl. Genet. 91: 1253-1256.
FELSENSTEIN, J. 1985. Confidence limits on phylogenies: an approach using the bootstrap.
Evolution 39: 783-791.
FERRIS, C., P. OLIVER, A. J. DAVY, &G. M.
HEWITT. 1995. Using chloroplast DNA to trace postglacial migration routes of oaks into Britain. Mol. Ecol. 4: 731-738.
FORCIOLI, D., P. SAUMITOU-LAPRADE, M.
VALERO, P. VERNET, &J .CUGUEN. 1998.
Distribution of chloroplast DNA diversity within and among populations in
gynodioecious Beta vulgaris ssp. maritima (Chenopodiaceae). Mol. Ecol. 7:
1183-1204.
KING, R. A., &C. FERRIS. 1998. Chloroplast DNA phylogeography of Alnus glutinosa (L.) Gaertn. Mol. Ecol. 7: 1151-1161.
KIZAKI, K., AND I. OSHIRO. 1977.
Paleogeography of the Ryukyu Islands. Mar.
Sci. Month.
9: 542-549.
LI, H. L. 1953. Taxonomic notes on the Fagaceae of Formosa. Bull. Torrey Club 80: 317-324.
LIAO, J. C. 1996. Fagaceae. Pp. 51-123. in Editorial Committee of the Flora of Taiwan (editor), Flora of Taiwan. 2nd Edn. Taipei.
LELANDAIS, C., B. ALBERT, & S. GUTIERES. 1998.
Organization and expression of the mitochondrial genome in the Nicotoanum sylvestris CMSII mutant. Genetics 150:
873-882.
MANEN, J. F., & A. NATALI. 1995. Comparison of the evolution of ribulose-1,
5-biphosphate carboxylase (rbcL) and atpB-rbcL noncoding spacer sequences in a recent plant group, the tribe Rubieae
(Rubiaceae). J. Mol. Evol. 41: 920-927.
MANOS, P. S., J. J. DOYLE, & K. C. NIXON. 1999.
Phylogeny, biogeography, and processes of molecular differentiation in Quercus subgenus Quercus (Fagaceae). Mol.
Phylogenet. Evol. 12: 333- 349.
STRAND, A. E., B. G. MILLIGAN, & C. M. PRUITT. 1996. Are populations islands? Analysis of chloroplast DNA variation in Aquilegia.
Evolution 50: 1822-1829.
STRAUSS, M., Y. P. HONG, &V. D. HIPKINS. 1993.
High levels of population
differentiation for mitochondrial DNA haplotypes in Pinus radiata, muricata, and attenuata. Theor. Appl. Genet. 86: 605-611.
STUESSY, T. F., & M. ONO. 1998Evolution and speciation of island plants. Cambridge University Press, Cambridge.
