Genetic homogeneity between Korean and Japanese populations of the broad-leaved evergreen tree Machilus thunbergii (Lauraceae): A massive post-glacial immigration through the Korea Strait or something else?

The warm-temperate vegetation of Korea, currently limited to southern coastal areas, shifted during the Last Glacial Maximum (LGM) towards glacial refugia, putatively located in southern Japan. We hypothesized two scenarios of post-glacial re-colonization of warm-temperate species in relation to current levels of genetic diversity within their populations. If extant Korean populations originated from a single source (a single glacial refugium), we expect significantly lower levels of genetic diversity relative to those from Japan due to founder effects. Alternatively, if they were derived from multiple source populations, levels of genetic diversity within Korean populations will not be significantly reduced compared to those of Japanese ones. To test which of these scenarios is more likely, we investigated the patterns of genetic diversity in 14 populations (seven from southern Korea and seven from southern Japan) of the broad-leaved evergreen tree Machilus thunbergii, employing 11 allozyme loci. High levels of genetic variation in M. thunbergii were found both in southern Korea and southern Japan, with a considerable genetic homogeneity not only between the two regions but also between populations within the two regions. These results suggest a pattern of re-colonization after the LGM fitting the second scenario (immigration from multiple refugia), probably through multiple waves and/or with large founder populations.     

Evidence for spontaneous polyploidization in cassava Manihot esculenta Crantz

Since high levels of genetic diversity may ensure long-term survival of a plant species, it is essential to preserve the genetic diversity of the species. Tipularia japonica and Epipactis papillosa are rare terrestrial orchids in southern Korea with fewer than 50 mature individuals in a population and southern Japan and considered to be threatened (endangered or vulunerable). To obtain knowledge of how the genetic variation of these species is partitioned within and among populations in Korea, I used enzyme electrophoresis to examine the genetic diversity of each eight known populations of the two species from South Korea. Twenty-three (E. papillosa) and 24 putative loci (T. japonica) resolved from 15 enzyme systems revealed no variation either within or among populations of each species (0.0% of the percentage of polymorphic loci, %P). Previous studies, in contrast, showed that their more widely distributed disjunct congeners T. discolor and E. helleborine harbored high allozyme-based genetic diversity within populations in eastern United States (%P = 75%) and in Denmark (%P = 73.6%), respectively. In theory, small population size leads to allelic fixation at many loci over generations within a population, resulting in population genetic divergence or differentiation. In this regard, the complete lack of genetic differences between conspecific populations of T. japonica and E. papillosa cannot be explained by genetic drift. Instead, the present allozyme data suggest that recent origin from the same genetically depauperate ancestral or source population could result in this observation. The current status of T. japonica and E. papillosa (rarity and lack of genetic variation) significantly threatens the long-term survival of the species in Korea.     

Patterns of Genetic Diversity in Rare and Common Orchids Focusing on the Korean Peninsula: Implications for Conservation

To provide basic information for orchid conservation, we surveyed the plant allozyme literature to summarize genetic diversity and structure data for (i) rare orchids native to the Korean Peninsula, and (ii) their congeners irrespective of being common and rare or Korean or not. A total of 68 taxa (32 taxa in Korea and 37 outside Korea; Goodyera repens being included in both datasets) were considered in this study. Overall, rare Korean orchid species had significantly lower levels of genetic diversity than their common congeners and common orchids in general at both population and species levels. However, mean values of G _ST (or F _ST) for rare and common orchids (Korean or not) did not differ significantly from each other. We found patterns of both low and high genetic diversity in rare Korean orchids. Many rare orchids harbored a complete lack of allozyme variation or extremely low within-population variation, perhaps due to rarity associated with random genetic drift and/or, for the case of warm-temperate orchids, to founder effects during post-glacial re-colonization. In contrast, high levels of genetic variation were found for a few orchids that have become recently rare (due to over-collection during the past several decades), probably because there have not been sufficient generations for the initial diversity to be substantially eroded. In addition, several orchids occurring in the main mountain system of the Korean Peninsula (the Baekdudaegan), that served as a glacial refugium, maintained moderate to high levels of within-population genetic diversity. Based on our genetic data, conservation priority should be given to rare orchid species. Particularly, urgent measures should be implemented on Jeju Island, a popular vacation spot, because it also a hotspot for threatened orchids with low levels of genetic diversity.     

Predicted range shifts in North American boreal forest birds and the effect of climate change on genetic diversity in blackpoll warblers (Setophaga striata)

As North American species’ ranges shift northward in response to climate change, populations isolated in high-elevation habitat “islands” at the southern edge of distributions are predicted to decrease in size or be extirpated. Levels of genetic structure and gene flow and the number of private alleles held within these peripheral populations can be used as a measure of the potential loss of genetic diversity due to climate change. We use GIS-based climate niche models to project geographic distributions of 15 boreal forest bird species for the year 2080 under two carbon emissions scenarios to predict the extent to which ranges will shift, leading to the extirpation of isolated populations at the southern periphery of the boreal forest. Breeding distributions of nearly all boreal bird species are predicted to expand as they shift northward, but will dramatically decrease or be completely lost from mountain populations in New York, Vermont, and New Hampshire by 2080. To examine the effect of these shifts on gene pools of migratory bird species we genotyped 178 blackpoll warblers (Setophaga striata) at nine microsatellite loci, sampling four imperiled high-elevation populations and four northern populations. In S. striata 10.4 % of microsatellite alleles were confined to populations expected to be lost due to climate change. However, these accounted for a nonsignificant percent of the genetic structure, and loss of these alleles would not significantly erode species heterozygosity or allelic richness. Our results indicate that isolated southern populations of S. striata, and possibly other migratory species with high gene flow, do not represent genetically isolated, independently evolving units. Efforts to mitigate the effect of climate change on boreal forest birds should focus on species in which peripheral populations harbor significant genetic diversity.     

Pollination biology and breeding systems in the terrestrial orchid Bletilla striata

The levels of fruit set in different habitats (three inland populations vs. three coastal populations) and the breeding system in the terrestrial orchid Bletilla striata were examined in two groups of populations in Haenam-gun, Jollanam-do Province in southern Korea. In total inland populations (mean fruit set=13.3%) showed about eight-fold higher fruit set per plant than the coastal populations (1.6%), probably due to mild climatic conditions in the inland populations during the flowering period. Honey bee workers Apis mellifera were observed in the inland populations, but no visitors were found in the coastal populations. However, a great increase in fruit set was achieved by hand-pollination: the percentage of fruit set through artificial self-pollination and geitonogamous pollination were close to 90%, indicating that B. striata is self-compatible. Agamospermy and spontaneous autogamy (automatic self-pollination) were not detected in this study. These indicate that pollinia vectors are essential for achieving fruit set in natural populations of B. striata. Except in one inland population examined in 2001, there was no significant correlation between the patch size per population and the average percentage of fruit set, which might reflect deception-pollination of B. striata and/or paucity of pollinators. Overall levels of fruit sets within and among patches in each population were homogeneous during a two-year period.     

Phylogeography of East Asian <Emphasis Type="Italic">Lespedeza buergeri</Emphasis> (Fabaceae) based on chloroplast and nuclear ribosomal DNA sequence variations

The dynamic changes in land configuration during the Quaternary that were accompanied by climatic oscillations have significantly influenced the current distribution and genetic structure of warm-temperate forests in East Asia. Although recent surveys have been conducted, the historical migration of forest species via land bridges and, especially, the origins of Korean populations remains conjectural. Here, we reveal the genetic structure of Lespedeza buergeri, a warm-temperate shrub that is disjunctively distributed around the East China Sea (ECS) at China, Korea, and Japan. Two non-coding regions (rpl32-trnL, psbA-trnH) of chloroplast DNA (cpDNA) and the internal transcribed spacer of nuclear ribosomal DNA (nrITS) were analyzed for 188 individuals from 16 populations, which covered almost all of its distribution. The nrITS data demonstrated a genetic structure that followed geographic boundaries. This examination utilized AMOVA, comparisons of genetic differentiation based on haplotype frequency/genetic mutations among haplotypes, and Mantel tests. However, the cpDNA data showed contrasting genetic pattern, implying that this difference was due to a slower mutation rate in cpDNA than in nrITS. These results indicated frequent migration by this species via an ECS land bridge during the early Pleistocene that then tapered gradually toward the late Pleistocene. A genetic isolation between western and eastern Japan coincided with broad consensus that was suggested by the presence of other warm-temperate plants in that country. For Korean populations, high genetic diversity indicated the existence of refugia during the Last Glacial Maximum on the Korean Peninsula. However, their closeness with western Japanese populations at the level of haplotype clade implied that gene flow from western Japanese refugia was possible until post-glacial processing occurred through the Korea/Tsushima Strait land bridge.     

Colonization history of Scots pine in Eastern Europe and North Asia based on mitochondrial DNA variation

During Quaternary glaciations, the ranges of Northern Eurasia forest species periodically experienced contraction followed by subsequent re-colonizations in the interglacial intervals. However, unlike the broadleaf trees of temperate forests, taiga species seem not to have retreated fully to southern regions in unfavorable periods and possibly survived at mid-latitudes in multiple refugia. Here, we report a study of genetic variation of three mitochondrial DNA markers in 90 populations of Scots pine (Pinus sylvestris) located from Eastern Europe to Eastern Siberia. The geographic distribution of seven mitotypes demonstrated the split between western and eastern populations approximately along the 38th meridian. Genetic diversity in the western part was significantly higher than in the eastern one. Five mitotypes were western- and one eastern-specific. One mitotype was common in both regions, but in the eastern part it occurred only in the South Urals and adjacent areas. The geographic structure in the mitotype distribution supports a hypothesis of post-glacial re-colonization of the studied territory from the European and Ural refugia.     

Contrasting levels of genetic diversity between the historically rare orchid Cypripedium japonicum and the historically common orchid Cypripedium macranthos in South Korea

Many terrestrial orchids are historically rare and occur in small, spatially isolated populations. Theory predicts that such species will harbour low levels of genetic variation within populations and will exhibit a high degree of population genetic divergence, primarily as a result of genetic drift. If the origin of the present‐day populations is relatively recent from the same genetically depauperate source population, a complete lack of genetic differentiation between conspecific populations is expected. If a terrestrial orchid was historically common with moderate or high levels of genetic diversity, but has experienced more recent anthropogenic disturbance as a result of over‐collection, it would still exhibit initial levels of genetic variation within populations and a low degree of genetic divergence between populations. To test these predictions, we examined the genetic diversity in six populations (N = 131) of the historically and currently rare Cypripedium japonicum and in four populations (N = 94) of the historically common but now rare C. macranthos from South Korea. Fourteen putative allozyme loci resolved from eight enzyme systems revealed no variation either within or among populations of C. japonicum, which supports the first prediction. In contrast, populations of C. macranthos harboured high levels of genetic variation (mean percentage of polymorphic loci %P = 46.7; mean expected heterozygosity H_e = 0.185) and exhibited a low degree of population genetic divergence (G_ST = 0.059), supporting the second prediction. The lack of genetic variation both within and among conspecific populations of C. japonicum may suggest that populations originated from the same genetically depauperate ancestral population. The high levels of genetic diversity maintained in populations of C. macranthos suggest that the collection‐mediated decrease in the number of individuals is still too recent for long‐term effects on genetic variation. Based on current demographic and genetic data, in situ and ex situ conservation strategies should be provided to preserve genetic variation and to ensure the long‐term survival of the two species in the Korean Peninsula. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 119–129.     

Genetic diversity and historical migration patterns of an endemic evergreen oak,Quercus acuta,across Korea and Japan,inferred from nuclear microsatellites

Forests dominated by broad-leaved evergreen trees cover a narrow zone of the southern coast of Korea as well as warm-temperate and subtropical regions of Japan. However, little is known about their establishment history, especially in Korea. Endemic Quercus acuta grows in Korea and Japan. We evaluated its genetic diversity, population structure, and degree of lineage admixture in terms of its distribution history. Analyses utilized seven nuclear microsatellites that were genotyped from 330 individuals of 16 populations. Genetic diversity was highest for the Japanese Kyushu populations. The allelic diversity of populations was similar between Jeju Island and Kyushu, implying that they are putative refugia. Although the mean F _ST value was very low, patterns for isolation-by-distance were strong and significant. Results from Bayesian clustering and Monmonier’s algorithm indicated that populations are roughly partitioned from west (Korea and Kyushu) to east (Japanese Honshu). Therefore, the two divisions within this species are demographically independent and may have arisen due to past fragmentation. In considering the mixed genetic structure between Korea and Kyushu populations, and the higher levels of genetic diversity in mainland Korea relative to Honshu, we hypothesized that this species has been able to survive within Jeju Island and Kyushu. Consequently, mainland Korea populations might have been shaped by range expansion that kept them well mixed from a continuous and large genetic resource.     

Population Genetic Structure of a Centipede Species with High Levels of Developmental Instability

European populations of the geophilomorph centipede Haplophilus subterraneus show a high proportion of individuals with morphological anomalies, suggesting high levels of developmental instability. The broad geographic distribution of this phenomenon seems to exclude local environmental causes, but the source of instability is still to be identified. The goal of the present study was to collect quantitative data on the occurrence of phenodeviants in different populations, along with data on the patterns of genetic variation within and between populations, in order to investigate possible association between developmental instability and genetic features. In a sample of 11 populations of H. subterraneus, distributed in western and central Europe, we looked for phenodeviants, in particular with respect to trunk morphology, and studied genetic variation through the genotyping of microsatellite loci. Overall, no support was found to the idea that developmental instability in H. subterraneus is related to a specific patterns of genetic variation, including inbreeding estimates. We identified a major genetic partition that subdivides French populations from the others, and a low divergence among northwestern areas, which are possibly related to the post-glacial recolonization from southern refugia and/or to recent anthropogenic soil displacements. A weak correlation between individual number of leg bearing segments and the occurrence of trunk anomalies seems to support a trade-off between these two developmental traits. These results, complemented by preliminary data on developmental stability in two related species, suggest that the phenomenon has not a simple taxonomic distribution, while it exhibits an apparent localization in central and eastern Europe.     

Phylogeographic Pattern of the Striped Snakehead,Channa striata in Sundaland: Ancient River Connectivity,Geographical and Anthropogenic Singnatures

A phylogeographic study of an economically important freshwater fish, the striped snakehead, Channa striata in Sundaland was carried out using data from mtDNA ND5 gene target to elucidate genetic patterning. Templates obtained from a total of 280 individuals representing 24 sampling sites revealed 27 putative haplotypes. Three distinct genetic lineages were apparent; 1)northwest Peninsular Malaysia, 2)southern Peninsular, east Peninsular, Sumatra and SW (western Sarawak) and 3) central west Peninsular and Malaysian Borneo (except SW). Genetic structuring between lineages showed a significant signature of natural geographical barriers that have been acting as effective dividers between these populations. However, genetic propinquity between the SW and southern Peninsular and east Peninsular Malaysia populations was taken as evidence of ancient river connectivity between these regions during the Pleistocene epoch. Alternatively, close genetic relationship between central west Peninsular Malaysia and Malaysian Borneo populations implied anthropogenic activities. Further, haplotype sharing between the east Peninsular Malaysia and Sumatra populations revealed extraordinary migration ability of C. striata (>500 km) through ancient connectivity. These results provide interesting insights into the historical and contemporary landscape arrangement in shaping genetic patterns of freshwater species in Sundaland.     

Genetic Variation and Geographic Differentiation in Mitochondrial DNA of the Horseshoe Crab, LIMULUS POLYPHEMUS

Restriction site variation in mitochondrial DNA (mtDNA) of the horseshoe crab (Limulus polyphemus) was surveyed in populations ranging from New Hampshire to the Gulf Coast of Florida. MtDNA clonal diversity was moderately high, particularly in southern samples, and a major genetic "break" (nucleotide sequence divergence approximately 2%) distinguished all sampled individuals which were north vs. south of a region in northeastern Florida. The area of genotypic divergence in Limulus corresponds to a long-recognized zoogeographic boundary between warm-temperate and tropical marine faunas, and it suggests that selection pressures and/or gene flow barriers associated with water mass differences may also influence the evolution of species widely distributed across such transition zones. On the other hand, a comparison of the mtDNA divergence patterns in Limulus with computer models involving stochastic lineage extinction in species with limited gene flow demonstrates that deterministic explanations need not necessarily be invoked to account for the observations. Experiments to distinguish stochastic from deterministic possibilities are suggested. Overall, the pattern and magnitude of mtDNA differentiation in horseshoe crabs is very similar to that typically reported for freshwater and terrestrial species assayed over a comparable geographic range. Results demonstrate for the first time that, geographically, at least some continuously distributed marine organisms can show considerable mtDNA genetic differentiation.     

High genetic variation in marginal fragmented populations at extreme climatic conditions of the Patagonian Cypress Austrocedrus chilensis

Knowledge about current patterns of genetic structure of populations together with the evolutionary history of a species helps to understand and predict the adaptation of populations to future climate change. We assayed variation at nuclear microsatellite markers among peripheral vs. continuous populations of the temperate South American species Austrocedrus chilensis, to investigate the role of historical vs. demographical forces in shaping population genetic structure. This species occurs in continuous populations in the west and central distribution range, but becomes highly fragmented at the eastern limit, which comprised ice-free areas during Quaternary glaciations and has extreme climatic conditions at present times. Bayesian analysis methods identified two contrasting patterns of genetic structure; (I) populations from humid, mesic and peri-glacial regions formed a single deme with relatively low genetic differentiation and high admixture levels whereas (II) a highly heterogeneous genetic structure with low level of admixture was found in the steppe, towards the east and northeast limit of the distribution range. In the steppe, population fragmentation, restricted gene flow and isolation-by-distance were also inferred. In addition, several small steppe populations showed high genetic diversity and divergent gene pools, suggesting that they constitute ancient refuges from pre-Holocene glaciations with just a subgroup of them contributing significantly to post-glacial spread. These results are discussed in relation to patterns of genetic variation found for other temperate species and the contribution of the particular southern Andes topography and climate to post-glacial spread.     

Parapatric diversification after post-glacial range expansion in the gall fly Urophora cardui (Tephritidae)

Aim Primary and secondary genetic clines in post-glacial colonized regions have different implications for biogeographic distributions and the origin of species. Primary clines arise in situ after colonization as adaptive responses to environmental gradients, while secondary clines are caused by contact between vicariant lineages. Here we analyse primary versus secondary origin of a genetic cline in the tephritid fly Urophora cardui in Jutland, Denmark, in a post-glacial landscape. Location Western Palaearctic. Methods Phylogeographic and demographic analyses of U. cardui based on mitochondrial DNA (mtDNA) genealogies, hierarchical genetic variance tests based on allozymes and distribution analysis of a rare allele from the Jutland cline. Results There was no phylogeographic divergence between the Jutland population of U. cardui north of the cline and neighbouring western European regional populations, which all shared the common western European mtDNA haplotype H1. At nuclear loci, by contrast, the North Jutland population was diverged above the mean level of divergence among regional populations and had no loss of genetic variation. A rare allozyme allele that was frequent in the cline area (up to 45%) and was missing north of the cline also occurred at low frequency (0–14%) elsewhere in the sampling range. Shallow phylogeographic divergence was observed between Russian and western European populations and between English and continental populations. Main conclusions The genetic variation patterns support primary cline evolution and parapatric divergence in Jutland following a demographic expansion of a western European ancestral source population of U. cardui, and suggest cryptic refugia and/or selection in other European population assemblages. The patterns of intra-specific regional divergence are discussed with respect to the interpretation of cryptic refugia in Europe after the most recent ice age.     

Survey of Heritable Endosymbionts in Southern Mexico Populations of the Fruit Fly Species Anastrepha striata and A. ludens

Heritable endosymbiotic bacteria associated with insects are ubiquitous and taxonomically diverse. Many of these endosymbionts influence the fitness of their hosts and/or manipulate their host reproduction. Exploiting the effects of endosymbionts on hosts for pest control is a growing research area, but requires knowledge of endosymbionts associated with the target pest population. In this study, we used molecular methods to screen southern Mexico populations of two species of tephritid fruit fly pests, Anastrepha ludens and A. striata, for heritable bacteria. The only heritable endosymbiont found was Wolbachia in A. striata. Based on multilocus sequence typing and phylogenetic analyses, this Wolbachia strain is new and belongs to the Wolbachia supergroup B. Wolbachia strains previously reported in members of the genus Anastrepha in South America belong to supergroup A. We discuss the potential implications for pest control of the presence of a different Wolbachia strain in southern Mexico.     

Genetic variation in populations of Populus davidiana Dode based on microsatellite marker analysis

Populus davidiana Dode, the only aspen in Korea, is useful for restoration because of its fast growth and vigorous reproduction. This study was conducted to estimate the genetic diversity and subdivision in populations of P. davidiana in South Korea using microsatellite markers. DNA from 113 individuals from five populations was amplified using five microsatellite primers. Fifty-three alleles were detected, and the expected heterozygosity was 0.603. The populations of P. davidiana in Korea have high genetic variation despite their peripheral distribution. R _ST (0.213) indicated a significant level of genetic subdivision among populations compared to the differentiation among other aspen populations. The high conservation value of the populations is attributed to its ecological and commercial importance.     

白芨SSR引物筛选及群体遗传多样性研究

白芨(Bletilla striata Rchb.)为中国珍稀濒危植物,重要的药用植物。该研究基于Illumina测序技术构建白芨基因组文库和微卫星文库,设计白芨微卫星引物,用白芨4个野生种群80个个体对引物进行多态性检测,应用4个白芨近缘种中进行引物的通用性检测,并在此基础上分析了白芨的遗传多样性和遗传分化,以探讨白芨的遗传结构和进化潜能。结果表明:(1)白芨基因组中微卫星片断丰富,共检测出17 841条微卫星片断。基于白芨微卫星库对100个位点设计了引物对,经PCR扩增和检测筛选出能够稳定扩增的多态性位点20个,每个位点的复等位基因数(Na)在2~6之间,平均为3.85;20对引物的大部分能够在4个白芨近缘种中成功扩增。(2)白芨在物种水平均有较高的遗传多样性(Na=3.85,I=1.07,H=0.614 7),白芨种群遗传分化强烈(Gst=0.43),居群间的基因流较弱(Nm=0.867 6),居群聚类分析结果均表明地理距离较近的居群具有较近的遗传关系。     

Extremely Low Levels of Allozyme Variation in Southern Korean Populations of the Two Rare and Endangered Lithophytic or Epiphytic <Emphasis Type="Italic">Bulbophyllum Drymoglossum</Emphasis> and <Emphasis Type="Italic">Sarcanthus Scolopendrifolius</Emphasis> (Orchidaceae): Implications for Conservation

Allozyme variation was investigated in two local populations of Bulbophyllum drymoglossum and three populations Sarcanthus scolopendrifolius, two rare and endangered lithophytes and epiphytes from South Korea. Genetic diversity was extremely low within populations (mean H _e = 0.011 for B. drymoglossum; 0.002 for S. scolopendrifolius). Among the putative screened 21 loci, we found only one polymorphic locus for each species. Only one polymorphic locus, detected just one population of each species, revealed significantly high degree of population differentiation between and among populations (F _ST = 0.253 for B. drymoglossum and F _ST = 0.899 for S. scolopendrifolius). These results suggest that genetic drift (consequence of a very small effective population size), coupled with a limited gene flow would play a major role in shaping population genetics of these species in South Korea. The current status of both species (small population sizes, spatially isolated populations, and highly localized habitats) in addition to the extremely low levels of genetic diversity and reckless collection of endangered orchids by plant sellers, significantly threaten the long-term survival of these species in Korea. Conservation of the two species requires both in situ strategies, by introducing of genets to increase effective population sizes by minimizing adverse effects (e.g., outbreeding depression and genetic swamping by non-native genotypes), and ex situ strategies, such as collection of genets from clonal ramets.     

Moisture variables, and not temperature, are responsible for climate filtering and genetic bottlenecks in the South African endemic terrestrial mollusc Prestonella (Orthalicoidea)

Non-vagile taxa such as terrestrial molluscs are susceptible to stochastic environmental events that can cause local extinctions or population declines, and extinctions of terrestrial mollusc species are among the highest documented. Many terrestrial snails are habitat specialists, and genetic studies using both allozyme and DNA sequence data have indicated that many species contain substantial and geographically structured genetic variation. In this study, we assess the genetic variation within two species of the rare terrestrial snail genus Prestonella, an inhabitant of rocky areas along water courses in the southern Great Escarpment of South Africa, and correlate genetic diversity to climatic variables. DNA sequence data from mitochondrial 16S rDNA and partial cytochrome oxidase I genes indicate that neither species is monophyletic, and that populations are deeply divergent, even over distances of a few hundred metres. Principal components anaylsis of climatic variables derived from two databases indicates that genetic diversity of the populations is correlated to moisture-related climatic variables. Populations with little or no diversity occur in more arid regions, and are thus most at risk from any future climatic changes that would increase aridification. These moisture variables are thus potent drivers of genetic bottlenecks and may have resulted in historical climate filtering or limitation of the distribution of these species. Temperature appears to be a less important variable, a finding supported by physiological data based on heart rates that show that death occurs only at temperatures far higher than found in their environment.     

Rapid genetic differentiation between ex situ and their in situ source populations: an example of the endangered Silene otites (Caryophyllaceae)

Ex situ cultivation in botanic gardens could be one possibility to preserve plant species diversity and genetic variation. However, old ex situ populations are often sparsely documented. We were able to retrieve three different ex situ populations and their source in situ populations of the endangered plant species Silene otites after 20–36 years of isolation. Furthermore, three additional wild populations were included in the analysis. Population genetic diversity and differentiation were analysed using AFLP markers. Genetic variation in the ex situ populations was lower than the variation found in the in situ populations. Strong differentiation (F_ST = 0.21–0.36) between corresponding in situ and ex situ populations was observed. Bayesian clustering approach also showed a distinct genetic separation between in situ and ex situ populations. The high genetic differentiation and loss of genetic diversity during spatial and temporal isolation in the ex situ populations can be attributable to small population sizes and unconscious selection during cultivation. Therefore, adequate sampling prior to ex situ cultivation and large effective population sizes are important to preserve genetic diversity. Near‐natural cultivation allowing for generation overlap and interspecific competition without artificial selection is recommended as being best for the maintenance of the genetic constitution. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, ??, ??–??.