The molecular population structure of the tall forb Cicerbita alpina (Asteraceae) supports the idea of cryptic glacial refugia in central Europe

There is an ongoing debate about the glacial history of non‐arctic species in central and northern Europe. The two main hypotheses are: (1) postglacial colonization from refugia outside this region; (2) glacial survival in microclimatically favourable sites within the periglacial areas. In order to clarify the glacial history of a boreo‐montane tall forb, we analysed AFLPs from populations of Cicerbita alpina through most of its range (Scandinavia, the mountains of central Europe, the Alps, the Pyrenees and the Balkan Peninsula). We found a major differentiation between the Pyrenean population and all others, supported by principal coordinate, neighbour joining and STRUCTURE analyses. Furthermore, three populations from the central and north‐eastern Alps were genetically distinct from the bulk of populations from Scandinavia, central Europe, the Alps and the Balkan Peninsula. Most populations, including those from central and northern Europe, had moderate to high levels of genetic diversity (mean Shannon index H_Sh = 0.292, mean percentage of polymorphic loci P = 54.1%, mean Nei's gene diversity H = 0.195). The results indicate separate glacial refugia in the Pyrenean region and the Italian Alps. Furthermore, they provide evidence of glacial persistence in cryptic refugia north of the Alps, from where Scandinavia and most of the Alps are likely to have been colonized following deglaciation. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 142–154.     

Rhytidium rugosum (Bryophyta) colonized Scandinavia from at least two glacial refugial source populations

The Scandinavian post‐glacial history of the moss Rhytidium rugosum is traced on the basis of information from the nuclear markers ITS and gpd for 229 Scandinavian and 81 other specimens. Some haplotypes, groups or lineages identified in a NeighborNet split network are predominantly northern Scandinavian, whereas others are southern. With the distributions of individual haplotypes and the timing of the deglaciation in different parts of Scandinavia, this implies colonization from the south and from the north or north‐east. High haplotype and nucleotide diversity and the occurrence of certain private haplotypes in the north suggest that the species may have survived the Last Glacial Maximum in local refugia. Slightly higher numbers of private haplotypes in Scandinavia than in central or north‐eastern Europe also favour an explanation with at least some local glacial survival. Low diversity in the southernmost contiguous region of the Scandinavian mountain range is probably a result of recent land uplift and late colonization. The Scandinavian lowland regional populations probably represent remains of an earlier widespread population that became increasingly restricted to small and isolated areas when the vegetation closed during the post‐glacial period. Some of the lowland populations require extensive management to survive. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 635–657.     

Multiple autopolyploidizations and range expansion of Allium przewalskianum Regel. (Alliaceae) in the Qinghai‐Tibetan Plateau

We used the Allium przewalskianum diploid–tetraploid complex on the Qinghai‐Tibetan Plateau (QTP) as a model to examine how this complex responded to the Quaternary climatic oscillations, and whether multiple autopolyploidizations have occurred. We sequenced five chloroplast DNA (cpDNA) fragments (accD‐psaI, trnH‐psbA, trnL‐trnF, trnS‐trnG and rpl16‐intron) in 306 individuals (all of known ploidy level) from 48 populations across the distribution of this species complex. We identified a total of 32 haplotypes—11 in diploids only, 13 in tetraploids only, and 8 found in both cytotypes. This, plus network analyses, indicated that tetraploids have arisen independently from diploids at least eight times. Most populations in the eastern QTP contained multiple haplotypes, but only a single haplotype was found for 17 tetraploid populations on the western QTP, suggesting a recent colonization of the western QTP. We further found that this species complex underwent an earlier range expansion around 5–150 thousand years ago (kya), after the largest glacial period (800–170 kya) in the QTP. In addition, the high frequencies of tetraploids in the QTP suggested that the tetraploid A. przewalskianum cytotype has evolutionary advantages over diploids in colonizing and/or surviving the arid habitats of the QTP.     

Multiple glacial refugia and postglacial colonization routes inferred for a woodland geophyte,Cyclamen purpurascens: patterns concordant with the Pleistocene history of broadleaved and coniferous tree species

The phylogeographical history of mid‐altitude woodland herbs that depend on moist and shaded forest habitats is poorly understood. Here, we analysed the genetic structure of Cyclamen purpurascens, a mountainous calcicolous perennial, to test hypotheses regarding its glacial survival in single or multiple refugia and postglacial colonization routes, and to explore how they are congruent with the histories inferred for temperate trees and other mountainous herbs. We gathered AFLP data and chloroplast DNA sequences (trnD‐trnT region) from 68 populations spanning the entire distribution range (the Jura Mountains, Alps, western Carpathians, Dinarides). Both genetic markers revealed two main phylogeographical groups (phylogroups) in C. purpurascens. Additionally, AFLP data detected a more detailed structure of five phylogroups: two widespread, showing east?west geographical separation, and three local ones, restricted to somewhat disjunct, marginal regions of the species range. We suggest that C. purpurascens survived the last glaciation in two main regions, the foothills of the Southern Limestone Alps and the Karst area of the north‐western Dinarides, and possibly also in microrefugia in the Western Carpathians. The glacial persistence and colonization routes of this woodland herb are highly concordant with those inferred for several temperate trees, especially the European beech. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 741–760.     

Phylogeography of a subalpine tall‐herb Ranunculus platanifolius (Ranunculaceae) reveals two main genetic lineages in the European mountains

A phylogeographical analysis of Ranunculus platanifolius, a typical European subalpine tall‐herb species, indicates the existence of two main genetic lineages based on amplified fragment length polymorphism (AFLP) markers. One group comprises populations from the Balkan Peninsula and the south‐eastern Carpathians and the other includes the remaining part of the range of the species, encompassing the western Carpathians, Sudetes, Alps, Pyrenees and Scandinavia. The main phylogeographical break observed in this species runs across the Carpathians and separates the main parts of this range (western and south‐eastern Carpathians), supporting a distinct glacial history of populations in these areas. The high genetic similarity of the Balkan Peninsula and south‐eastern Carpathian populations could indicate a common glacial refugium for these contemporarily isolated areas of species distribution. The western and northern part of the species range displays an additional weak differentiation into regional phylogeographical groups, which could have been shaped by isolation in glacial refugia or even by a postglacial isolation. The observed weak phylogeographical structure could also be linked with ecological requirements, allowing survival along streams in relatively low, forested mountain ranges. © 2013 The Linnean Society of London     

Northern richness and southern poverty: contrasting genetic footprints of glacial refugia in the relictual tree Sciadopitys verticillata (Coniferales: Sciadopityaceae)

Sciadopitys verticillata is amongst the most relictual of all plants, being the last living member of an ancient conifer lineage, the Sciadopityaceae, and is distributed in small and disjunct populations in high rainfall regions of Japan. Although mega‐fossils indicate the persistence of the species within Japan through the Pleistocene glacial–interglacial cycles, how the species withstood the colder and drier climates of the glacials is not well known. The present study utilized phylogeography and palaeodistribution modelling to test whether the species survived within pollen‐based coastal temperate forest glacial refugia or within previously unidentified refugia close to its current range. Sixteen chloroplast haplotypes were found that displayed significant geographical structuring. Unexpectedly, northern populations in central Honshu most distant from coastal refugia had the highest chloroplast diversity and were differentiated from the south, a legacy of glacial populations possibly in inland river valleys close to its current northern range. By contrast, populations near putative coastal refugia in southern Japan, harboured the lower chloroplast diversity and were dominated by a single haplotype. Fragment size polymorphism at a highly variable and homoplasious mononucleotide repeat region in the trnT‐trnL intergenic spacer reinforced the contrasting patterns of diversity observed between northern and southern populations. The divergent histories of northern and southern populations revealed in the present study will inform the management of this globally significant conifer. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 263–277.     

Haplotype variation of relevance to global and European phylogeography in Sarmentypnum exannulatum (Bryophyta: Calliergonaceae)

Abstract

Haplotype variation is explored for Sarmentypnum exannulatum (Schimp.) Hedenäs, based on the nuclear ITS, and the chloroplast trnL–trnF, rpl16 and tRNA-Gly in 179 specimens (176 for chloroplast markers). The focus is Europe (124 samples), and especially Scandinavia (79), but most regions of the species' distribution area except northern Eurasia were sampled. Haplotype variation appears greater in Scandinavia than in Central Europe, with five of the European haplotype groups found only in Scandinavia compared with one unique to Central Europe. The Central European haplotype group probably survived the glaciations in one or several of the well-known refugia of the northern Mediterranean, but this seems unlikely for the Scandinavian haplotypes. The latter could have survived in northern refugia or immigrated from the east or north-east. On a global scale, several haplotype groups have restricted distributions, which could be due to sparse sampling in some regions, or the evolution or extinction of haplotypes. Some haplotypes were perfectly bipolar, whereas the species as a whole is imperfectly bipolar. These were absent from more southern parts of the northern temperate zone and from the sampled tropical mountains. It thus seems unlikely that representatives of these haplotypes dispersed from north to south (or vice versa) by stepwise migration.     

Phylogeography and palaeodistribution modelling in the Patagonian steppe: the case of Mulinum spinosum (Apiaceae)

Aim An integrative study of the endemic, yet ubiquitous, Patagonian shrub Mulinum spinosum (Apiaceae) was performed: (1) to assess the historical processes that influenced its geographical pattern of genetic variation; (2) to test hypotheses of its survival in situ or in glacial refugia during glacial cycles; and (3) to model its extant and palaeoclimatic distributions to assess support for the phylogeographical patterns recovered. Location Chilean and Argentinian Andean region and Patagonian steppe. Methods Chloroplast DNA sequences, trnH–psbA, trnS–trnG and 3′trnV–ndhC, were obtained for 314 individuals of M. spinosum from 71 populations. The haplotype data matrix was analysed using nested clade analysis (NCA) to construct a network. Analysis of molecular variance (AMOVA), spatial analysis of molecular variance (SAMOVA) and neutrality tests were also used to test for genetic structure and range expansion in the species. The present potential geographical distribution of M. spinosum was modelled and projected onto a Last Glacial Maximum (LGM) model. Results Amongst the 29 haplotypes observed, one was widely distributed, but most were restricted to either northern or southern regions. The populations with highest haplotype diversity were found in southern Patagonia, the high Andean region, and northern Patagonia. AMOVA and SAMOVA showed latitudinal structure for Argentinian populations. NCA implied patterns of restricted gene flow or dispersal but with some long‐distance dispersal and also long‐distance colonization and/or past fragmentation. Neutrality tests did not support range expansions. The current distribution model was a fairly good representation of the extant geographical distribution of the species, and the distribution model for the LGM did not show important shifts of the extant range to lower latitudes, except for a shift towards the palaeoseashore. Main conclusions Based on agreement amongst phylogeographical patterns, distribution of genetic variability, equivocal evidence of putative refugia and palaeodistribution modelling, it is probable that glaciations did not greatly affect the distribution of Mulinum spinosum. Our results are consistent with the in situ survival hypothesis, and not with the latitudinal migration of plant communities to avoid adverse climate conditions during Pleistocene glaciations. It is possible that populations of northern Patagonia may have been isolated from the southern ones by the Chubut and Deseado basins.     

Amplified fragment length polymorphism (AFLP) suggests old and recent immigration into the Alps by the arctic-alpine annual Comastoma tenellum (Gentianaceae)

Aim This study aims to elucidate the phylogeography of the arctic‐alpine annual Comastoma tenellum (Rottb.) Toyok. (Gentianaceae) and to unravel the history of its immigration into the Alps. Location Although samples from Alaska and Central Asia were also included, our study focusses on Europe, especially on the Alps. Methods We applied amplified fragment length polymorphism (AFLP) fingerprinting on 37 populations (162 individuals) of C. tenellum and analysed the results phenetically. Results As C. tenellum is mainly inbreeding, there is typically little to no intrapopulational genetic variation. Two populations from Alaska and Altai are strongly separated from all other accessions. The majority of the populations from the Alps group together with high bootstrap support. They fall into an unsupported Alps I group (northwards of Gran Paradiso) and a well‐supported Alps II group (south‐western Alps). The remaining European populations form a weakly‐supported branch constituting accessions from the Carpathians, Scandinavia and two populations from the Eastern Alps. Main conclusions Comastoma tenellum reached the Alps at least twice. The first immigration event resulted in a lineage that is clearly separated from the other European accessions. The immigration must have occurred well before the last glaciation because this lineage shows further phylogeographical structuring into two groups (Alps II in the south‐western Alps and Alps I in the rest of the Alps). This pattern is presumably due to isolation in different glacial refugia. In addition to the old immigration event, the species reached the Alps in recent times either from Scandinavia or from the Carpathians via long‐distance dispersal. These immigrations resulted in (at least) two populations that are spatially small and poor in individuals.     

Multiple periglacial refugia in the Patagonian steppe and post‐glacial colonization of the Andes: the phylogeography of Calceolaria polyrhiza

Aim We perform a phylogeographical study of an endemic Patagonian herbaceous plant to assess whether geographical patterns of genetic variation correspond to in situ Pleistocene survival or to glacial retreat and post‐glacial expansion. We also seek to determine the locations of potential glacial refugia and post‐glacial colonization routes. Location Southern Andes and Patagonian steppe. Methods We used Calceolaria polyrhiza, a widely distributed Patagonian herbaceous plant that occurs mainly in the understorey of Nothofagus rain forests and in the arid Patagonian steppe, as our model system. The chloroplast intergenic spacer trnH–psbA was sequenced for 590 individuals from 68 populations. Sequence data were analysed using phylogenetic (maximum parsimony, maximum likelihood and Bayesian inference) and population genetic (spatial analyses of molecular variance, mismatch distributions and neutrality tests) methods. Nested clade phylogeographic analyses, and divergence time estimates using a calibrated molecular clock, were also conducted. Results A total of 27 haplotypes identified in the present study clustered into four primary genealogical lineages, revealing three significant latitudinal phylogeographical breaks. The two high Andean lineages probably split first, during the late Miocene, and the Patagonian lineage split around 4 Ma, coincident with the establishment of the Patagonian steppe. Within each haplogroup, major diversification occurred in the Pleistocene. The Patagonian groups show a pattern consistent with a rapid post‐glacial expansion and colonization of the Andean flanks, achieved independently by four lineages. The highest haplotype diversity was found along a longitudinal transect that is remarkably congruent with the limit of the ice‐sheet extension during the Greatest Patagonian Glaciation. A north‐east expansion is evident, which is probably associated with the ‘Arid Diagonal’ fluctuations. Main conclusions Glacial climate fluctuations had a substantial impact on the diversification, distribution and demography of the study species. A scenario of multiple periglacial Pleistocene refugia and subsequent multiple recolonization routes, from eastern Patagonia to the Andean flanks, may explain the phylogeographical patterns observed. However, current genetic structure also preserves the imprints of older events that probably occurred in the Miocene and Pliocene, providing evidence that multiple processes, operating at different spatial and temporal scales, have moulded biodiversity in Patagonia.     

Multilocus phylogeography and population structure of common eiders breeding in North America and Scandinavia

Aim Glacial refugia during the Pleistocene had major impacts on the levels and spatial apportionment of genetic diversity of species in northern latitude ecosystems. We characterized patterns of population subdivision, and tested hypotheses associated with locations of potential Pleistocene refugia and the relative contribution of these refugia to the post‐glacial colonization of North America and Scandinavia by common eiders (Somateria mollissima). Specifically, we evaluated localities hypothesized as ice‐free areas or glacial refugia for other Arctic vertebrates, including Beringia, the High Arctic Canadian Archipelago, Newfoundland Bank, Spitsbergen Bank and north‐west Norway. Location Alaska, Canada, Norway and Sweden. Methods Molecular data from 12 microsatellite loci, the mitochondrial DNA (mtDNA) control region, and two nuclear introns were collected and analysed for 15 populations of common eiders (n = 716) breeding throughout North America and Scandinavia. Population genetic structure, historical population fluctuations and gene flow were inferred using F‐statistics, analyses of molecular variance, and multilocus coalescent analyses. Results Significant inter‐population variation in allelic and haplotypic frequencies were observed (nuclear DNA F_ST = 0.004–0.290; mtDNA Φ_ST = 0.051–0.927). Whereas spatial differentiation in nuclear genes was concordant with subspecific designations, geographic proximity was more predictive of inter‐population variance in mitochondrial DNA haplotype frequency. Inferences of historical population demography were consistent with restriction of common eiders to four geographic areas during the Last Glacial Maximum: Belcher Islands, Newfoundland Bank, northern Alaska and Svalbard. Three of these areas coincide with previously identified glacial refugia: Newfoundland Bank, Beringia and Spitsbergen Bank. Gene‐flow and clustering analyses indicated that the Beringian refugium contributed little to common eider post‐glacial colonization of North America, whereas Canadian, Scandinavian and southern Alaskan post‐glacial colonization is likely to have occurred in a stepwise fashion from the same glacial refugium. Main conclusions Concordance of proposed glacial refugia used by common eiders and other Arctic species indicates that Arctic and subarctic refugia were important reservoirs of genetic diversity during the Pleistocene. Furthermore, suture zones identified at MacKenzie River, western Alaska/Aleutians and Scandinavia coincide with those identified for other Arctic vertebrates, suggesting that these regions were strong geographic barriers limiting dispersal from Pleistocene refugia.     

Phylogeography and genetic diversity of East Asian Neolitsea sericea (Lauraceae) based on variations in chloroplast DNA sequences

Neolitsea sericea is an evergreen broad leaved tree in the warm-temperate regions of East Asia. This area is a hotspot for plant species richness and endemism caused by dynamic changes in land configuration during the Quaternary. However, the historical migration of such evergreen tree species is still poorly understood. In an attempt to reconstruct the phylogeographic history of N. sericea during the Quaternary, we identified the chloroplast DNA haplotypes of 287 individuals from 33 populations covering almost all of its geographic range. Analyses were based on sequence data from the trnL–F, psbC–trnS, and rps16 regions. Nine haplotypes were identified. The majority included ancestral types in the southwestern part of the main islands of Japan, with other region-specific haplotypes being found in populations on the Korean Peninsula, Taiwan (Isl. Lanyu), and elsewhere in Japan. A statistical parsimony network revealed two lineages derived from Japanese main islands. One was represented on the Korean Peninsula, the other on Isl. Lanyu. The current distribution of N. sericea has been shaped by colonization via land bridges. During the glacial periods, two primary, but separate migration routes were followed—from the southwestern part of the Japanese main islands to either the Korean Peninsula or Taiwan. In addition, we believe the Zhoushan populations were shaped by post-glacial processes through an ECS land bridge (East China Sea basin) from northern refugia that existed during the late Pleistocene.     

History and evolution of alpine plants endemic to the Qinghai-Tibetan Plateau: Aconitum gymnandrum (Ranunculaceae)

How Quaternary climatic oscillations affected range distributions and intraspecific divergence of alpine plants on the Qinghai‐Tibetan Plateau (QTP) remains largely unknown. Here, we report a survey of chloroplast DNA (cpDNA) and nuclear ribosomal internal transcribed spacer (ITS) DNA variation aimed at exploring the phylogeographical history of the QTP alpine endemic Aconitum gymnandrum. We sequenced three cpDNA fragments (rpl20–rps12 intergenic spacer, the trnV intron and psbA‐trnH spacer) and also the nuclear (ITS) region in 245 individuals from 23 populations sampled throughout the species’ range. Two distinct lineages, with eastern and western geographical distributions respectively, were identified from a phylogenetic analysis of ITS sequence variation. Based on a fast substitution rate, these were estimated to have diverged from each other in the early Pleistocene approximately 1.45 Ma. The analysis of cpDNA variation identified nine chlorotypes that clustered into two major clades that were broadly congruent in geographical distribution with the two ITS lineages. The east–west split of cpDNA divergence was supported by an amova which partitioned approximately half of the total variance between these two groups of populations. Analysis of the spatial distribution of chlorotypes showed that each clade was subdivided into two groups of populations such that a total of four population groups existed in the species. It is suggested that these different groups derive from four independent glacial refugia that existed during the Last Glacial Maximum (LGM), and that three of these refugia were located at high altitude on the QTP platform itself at that time. Coalescent simulation of chlorotype genealogies supported both an early Pleistocene origin of the two main cpDNA clades and also the ‘four‐refugia’ hypothesis during the LGM. Two previous phylogeographical studies of QTP alpine plants indicated that such plants retreated to refugia at the eastern/south‐eastern plateau edge during the LGM and/or previous glacial maxima. However, the results for A. gymnandrum suggest that at least some of these cold‐tolerant species may have also survived centrally on the QTP platform throughout the Quaternary.     

Patterns of chloroplast DNA variation in <Emphasis Type="Italic">Cycas debaoensis</Emphasis> (Cycadaceae): conservation implications

Climate changes during glacial periods have had significant effects on the current distribution of plant species. Palaeontologial data suggest that modern cycads originated in southwest China. Cycas debaoensis (Cycadaceae) is an endangered species restricted to a small area of southwest China. This species has been classified into two types: sand and karst, according to the soil matrix they grow on. To determine the locations of its glacial refugia and its genetic structure, we examined chloroplast sequence variation of the atpB-rbcL and psbA-trnH intergenic spacers. Four chloroplast DNA haplotypes were obtained from 120 individuals collected from 11 populations covering the entire extant distribution range of the species. Significant population subdivision was detected (G _ST = 0.684 and F _ST = 0.74160), suggesting low levels of gene flow between regions and populations. There was marked haplotype differentiation between populations in the sand and karst regions, with only one haplotype being present in both. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest that C. debaoensis experienced range contraction during glacial periods, and that the current populations are still confined to the areas of the original refugia. These results implied that isolated refugia might have maintained in both sand and karst regions during the last glacial maximum and even earlier glaciations. The low within-population diversity of C. debaoensis suggested that there were strong bottleneck events or founder effects within each separate region during the Quaternary climatic oscillations. These findings are important for the conservation of this endangered species.     

Nuclear and mitochondrial phylogeography of the European fire-bellied toads Bombina bombina and Bombina variegata supports their independent histories

Exact location and number of glacial refugia still remain unclear for many European cold‐blooded terrestrial vertebrates. We performed a fine‐scaled multilocus phylogeographic analysis of two Bombina species combining mitochondrial variation of 950 toads from 385 sites and nuclear genes (Rag‐1, Ncx‐1) from a subset of samples to reconstruct their colonization and contemporary variation patterns. We identified the lowlands northwest of the Black Sea and the Carpathians to be important refugial areas for B. bombina and B. variegata, respectively. This result emphasizes the importance of Central European refugia for ectothermic terrestrial species, far north of the Mediterranean areas regarded as exclusive glacial refugia for the animals. Additional refugia for B. variegata have been located in the southern Apennines and Balkans. In contrast, no evidence for the importance of other east European plains as refugial regions has been found. The distribution of mtDNA and Ncx‐1 variation suggests the presence of local refugia near the Black Sea for B. bombina; however, coalescent simulations did not allow to distinguish whether one or two refugia were present in the region. Strong genetic drift apparently accompanied postglacial expansions reducing diversity in the colonization areas. Extended sampling, coupled with the multilocus isolation with migration analysis, revealed a limited and geographically restricted gene flow from the Balkan to Carpathian populations of B. variegata. However, despite proximity of inferred B. bombina and B. variegata refugia, gene exchange between them was not detected.     

Identification of glacial refugia in south-eastern North America by phylogeographical analyses of a forest understorey plant, Trillium cuneatum

Aim We examine several hypotheses emerging from biogeographical and fossil records regarding glacial refugia of a southern thermophilic plant species. Specifically, we investigated the glacial history and post‐glacial colonization of a forest understorey species, Trillium cuneatum. We focused on the following questions: (1) Did T. cuneatum survive the Last Glacial Maximum (LGM) in multiple refugia, and (if so) where were they located, and is the modern genetic structure congruent with the fossil record‐based reconstruction of refugia for mesic deciduous forests? (2) What are the post‐glacial colonization patterns in the present geographical range? Location South‐eastern North America. Methods We sampled 45 populations of T. cuneatum throughout its current range. We conducted phylogeographical analyses based on maternally inherited chloroplast DNA (cpDNA haplotypes) and used TCS software to reconstruct intraspecific phylogeny. Results We detected six cpDNA haplotypes, geographically highly structured into non‐overlapping areas. With one exception, none of the populations had mixed haplotype composition. TCS analysis resulted in two intraspecific cpDNA lineages, with one clade subdivided further by shallower diversification. Main conclusions Our investigation revealed that T. cuneatum survived the LGM in multiple refugia, belonging to two (western, eastern) genealogical lineages geographically structured across south‐eastern North America. The western clade is confined to the south‐western corner of T. cuneatum’s modern range along the Lower Mississippi Valley, where fossil records document a major refugium of mesic deciduous forest. For the eastern clade, modern patterns of cpDNA haplotype distribution suggest cryptic vicariance, in the form of forest contractions and subsequent expansions associated with Pleistocene glacial cycles, rather than simple southern survival and subsequent northward colonization. The north–south partitioning of cpDNA haplotypes was unexpected, suggesting that populations of this rather southern thermophilic species may have survived in more northern locations than initially expected based on LGM climate reconstruction, and that the Appalachian Mountains functioned as a barrier to the dispersal of propagules originating in more southern refugia. Furthermore, our results reveal south‐west to north‐east directionality in historical migration through the Valley and Ridge region of north‐west Georgia.     

Conservation genetics and geographic patterns of genetic variation of the endangered officinal herb Fritillaria pallidiflora

Fritillaria pallidiflora is an endangered officinal herb distributed in the Tianshan Mountains of northwestern China. We examined its phylogeography to study evolutionary processes and suggest implications for conservation. Six haplotypes were detected based on three chloroplast non‐coding spacers (psbA‐trnH, rps16, and trnS‐trnG); genetic variation mainly occurred among populations and SAMOVA groups. This species is distributed in different deep valleys, and we speculate that these fragmented habitats cause gene flow barriers among populations and groups. We also speculate that during glacial periods, extremely low temperatures and aridity caused additional range shrinkage and fragmentation, factors consequently resulting in significant intraspecific differentiation in allopatric regions. For setting a conservation management plan, we identified the Lucaogou region as the most important area, and we designated two ESUs for separate management.     

Population genomic evidence for plant glacial survival in Scandinavia

Quaternary glaciations have played a major role in shaping the genetic diversity and distribution of plant species. Strong palaeoecological and genetic evidence supports a postglacial recolonization of most plant species to northern Europe from southern, eastern and even western glacial refugia. Although highly controversial, the existence of small in situ glacial refugia in northern Europe has recently gained molecular support. We used genomic analyses to examine the phylogeography of a species that is critical in this debate. Carex scirpoidea Michx subsp. scirpoidea is a dioecious, amphi‐Atlantic arctic–alpine sedge that is widely distributed in North America, but absent from most of Eurasia, apart from three extremely disjunct populations in Norway, all well within the limits of the Weichselian ice sheet. Range‐wide population sampling and variation at 5,307 single nucleotide polymorphisms show that the three Norwegian populations comprise unique evolutionary lineages divergent from Greenland with high between‐population divergence. The Norwegian populations have low within‐population genetic diversity consistent with having experienced genetic bottlenecks in glacial refugia, and host private alleles that probably accumulated in long‐term isolated populations. Demographic analyses support a single, pre‐Weichselian colonization into Norway from East Greenland, and subsequent divergence of the three populations in separate refugia. Other refugial areas are identified in North‐east Greenland, Minnesota/Michigan, Colorado and Alaska. Admixed populations in British Columbia and West Greenland indicate postglacial contact. Taken together, evidence from this study strongly indicates in situ glacial survival in Scandinavia.     

Refugia and phylogeography of Taiwania in East Asia

Aim The East Asia endemic Taiwania cryptomerioides Hayata is an iconic and relictual monotypic conifer whose main extant populations are now restricted to the Yunnan–Myanmar border, northern Vietnam and Taiwan. It has also been reported from several localities in Guizhou, Hubei and Fujian Provinces, China. Its fossil record indicates that, while it was more widely distributed in the Northern Hemisphere and grew under a range of different ecological conditions, it has remained almost unchanged in its morphology for over 100 Myr. We investigate whether these remaining extant, disjunct populations have diverged genetically; when such a divergence may have occurred; and which, if any, of the extant populations exhibit refugial characteristics. Location East Asia. Methods Sequences of five chloroplast DNA markers (petG–trnP, trnH–psbA, trnV–trnM, trnC–ycf6 and trnL–trnF) from all extant populations of T. cryptomerioides were analysed to reveal their phylogeography. Molecular clock models with fossil calibrations were used to estimate divergence times between extant populations. Results Extremely low nucleotide diversity was found in the overall population (π = 0.00077) with only nine haplotypes distinguished. The mainland Asia populations share one major ancestral haplotype. The insular populations in Taiwan all possess a unique haplotype with at least an eight‐mutational‐step difference to the mainland Asia haplotype. Molecular clock estimations demonstrated that the mean divergence time between the predominant insular population haplotype and the mainland Asia haplotype occurred at c. 3.23–3.41 Ma, followed by a split into Vietnamese and Yunnan–Myanmar populations (c. 1.0–1.39 Ma). Main conclusions Strong genetic differentiation exists between insular (Taiwan) and mainland Asia populations. The split between insular and mainland haplotypes can be dated back to the end of the Pliocene. The Yunnan–Myanmar border area, northern Vietnam and Taiwan are identified here as potential refugia for T. cryptomerioides. Other populations in mainland China are unlikely to be the result of historical fragmentation and their origins require further investigation.     

The Tanaka Line shaped the phylogeographic pattern of the cotton tree (Bombax ceiba) in southwest China

The Tanaka Line is considered to be an important phytogeographic boundary in southwest China, especially in Yunnan province. This Line has been deemed to separate East Asia's Sino-Himalayan and Sino-Japanese floras. However, it is not clear whether there is a special phylogeographic pattern for plants occurring across the Tanaka Line. To better understand the role of the Tanaka Line in shaping genetic structure of plant species occurring either side of this line, we employed Bombax ceiba, an economically and ecologically important tree species with a distribution across the Tanaka Line, as a proxy to study whether or not the Tanaka Line acts as a boundary to gene flow. We scanned and analyzed genetic variation at three chloroplast DNA fragments (psbB-psbF, trnL-rpl32 and psbI-psbK) within and among 17 natural populations (201 individuals). We identified eight chloroplast haplotypes (A-H) in total. Geographically, seven haplotypes were found southwest of the Tanaka Line, but only two haplotypes (B and H) were located northeast of the Tanaka Line. Meanwhile, both mismatch distribution analysis and environmental niche modeling (ENM) analysis suggested that multiple glacial refugia were maintained in the southwest range of B. ceiba during the last glacial maximum and that northeastern populations underwent strenuous retreatment during the Quaternary climatic oscillations. The present study highlights the importance of historical climate change and topographical circumstances in shaping population structure across the Tanaka Line.