Nuclear vs. plastid data: complex Pleistocene history of a circumpolar key species

To fully understand the contemporary genetic structure of plants, both nuclear and plastid markers are needed. Three chloroplast DNA (cpDNA) lineages, which probably diverged before the major Pleistocene glaciations, have been identified in the circumpolar/circumboreal Vaccinium uliginosum. Here we investigate its nuclear DNA variation using nuclear ribosomal internal transcribed spacer (ITS) sequences, DNA ploidy level measurements and amplified fragment length polymorphisms (AFLPs). We also extend the cpDNA dataset. Two ITS lineages, corresponding to diploids and tetraploids, respectively, were identified. However, both main sequence types apparently occurred in most individual plants but showed ploidy-biased homogenization and possibly reflect paralogy predating the origin of V. uliginosum. The ploidy levels were largely consistent with the cpDNA lineages, suggesting that the initial cpDNA divergence followed early polyploidizations. Five main AFLP groups were identified, consistent with recent glacial refugia in Beringia, western Siberia, the southern European mountains and areas south/east of the Scandinavian and Laurentide ice sheets. Except from the southern European mountains, there has been extensive expansion from all refugia, resulting in several contact zones. Surprisingly, the presumably older ploidy and cpDNA patterns were partly inconsistent with the main AFLP groups and more consistent with AFLP subgroups. A likely major driver causing the inconsistencies is recent nuclear gene flow via unreduced pollen from diploids to tetraploids. This may prevent cytoplasmic introgression and result in overlayed patterns formed by processes dominating at different time scales. The data also suggest more recent polyploidizations, as well as several chloroplast capture events, further complicating this scenario. This study highlights the importance of combining different marker systems to unravel intraspecific histories.     

Molecular diversity and derivations of populations of Silene acaulis and Saxifraga oppositifolia from the high Arctic and more southerly latitudes

A survey of allozyme diversity within and between populations of Silene acaulis from Spitsbergen, Norway, Iceland and Scotland, showed that populations from the high Arctic (Spitsbergen, > 76°N) contained high levels of diversity and were genetically similar to populations from more southern locations. Indirect measures of gene flow (Nm), calculated from Wrigh's F indicated that there had been extensive gene flow between Spitsbergen and some Norwegian populations. A restriction site analysis of chloroplast DNA (cpDNA) in S. acaulis revealed that all populations contained a single identical cpDNA haplotype, except one population from Norway which also contained a second haplotype. In contrast, five different cpDNA haplotypes were distinguished in a more limited survey of cpDNA variation in Saxifraga oppositifolia, with all five haplotypes present in one of two Spitsbergen populations surveyed. The contrasting cpDNA results for the two species suggest that whereas high-Arctic populations of Silene acaulis have most likely been derived from immigrants which arrived from the south after the last glacial period, high-Arctic populations of Saxifraga oppositifolia may be derived, in part, from ancient northern stocks which survived the last glaciation in high-Arctic refugia.     

Glacial Refugia of Ginkgo biloba and Human Impact on Its Genetic Diversity： Evidence from Chloroplast DNA

Variations in the trnK region of chloroplast DNA were investigated in the present study using polymerase chain reactionrestriction fragment length polymorphism to detect the genetic structure and to infer the possible glacial refugia of Ginkgo biloba L. in China. In total, 220 individuals from 12 populations in China and three populations outside China were analyzed, representing the largest number of populations studied by molecular markers to date. Nineteen haplotypes were produced and haplotype A was found in all populations. Populations in south-western China, including WC, JF, PX, and SP, contained 14 of the 19 haplotypes and their genetic diversity ranged from 0.771 4 to 0.867 6. The TM population from China also showed a high genetic diversity （H = 0.848 5）. Most of the genetic variation existed within populations and the differentiation among populations was low （GsT = 0.2）. According to haplotype distribution and the historical record, we suggest that populations of G. biloba have been subjected to extensive human impact, which has compounded our attempt to infer glacial refugia for Ginkgo. Nevertheless, the present results suggest that the center of genetic diversity of Ginkgo is mainly in south-western China and in situ conservation is needed to protect and preserve the genetic resources.     

From Mediterranean shores to central Saharan mountains: key phylogeographical insights from the genus Myrtus

Aim The Mediterranean region is often regarded as a crossroads where species of various origins meet. However, the biogeographical relationships between this region and contiguous Saharan, Macaronesian and Irano‐Turanian regions have not been investigated in detail. The aim of this study was to characterize the phylogeography of the circum‐Mediterranean species Myrtus communis and to investigate the origin of isolated central Saharan populations of Myrtus nivellei. Location The distribution ranges of M. communis from Macaronesia to the Irano‐Turanian region (173 sampled populations) and of M. nivellei in the mountains (Hoggar, Tassili n’Ajjer, Immidir, Tibesti) of the central Sahara (23 populations). Methods Nuclear ribosomal DNA (nrDNA) sequences of Myrtaceae were used to root the phylogeny of Myrtus, and to date its crown node, according to a detailed review of the palaeobotanical records used for multiple fossil calibration. Chloroplast DNA (cpDNA) sequences were analysed through the determination of genetic diversity indices and by statistical phylogeography. Results Both cpDNA and nrDNA markers indicated east–west genetic differentiation within M. communis. During the late Miocene, a key vicariance event affected the previous circum‐Mediterranean distribution of Myrtus, leading to the isolation of eastern populations. During the late Miocene or early Pliocene, two clades diverged: one is now scattered in the Mediterranean Basin and adjacent regions, whereas the other evolved in the western Mediterranean region. The differentiation of lineages during the Plio‐Pleistocene occurred mainly in the western part of the Mediterranean Basin, which has been at the origin of migrations towards Macaronesian islands and Saharan mountains. This is one of the first plant phylogeographical studies to report migrations from the Mediterranean to the Sahara. Main conclusions The genus Myrtus has persisted in the Mediterranean region since at least the Neogene and its biogeography reflects the cumulation of the species’ responses to successive palaeoenvironmental changes. The current distribution of the genus Myrtus in the Mediterranean Basin and in isolated areas, such as the Macaronesian islands and Saharan mountains, can be explained by the striking ability of this plant not only to persist locally in various refugia, but also to migrate.     

基于叶绿体微卫星研究鄂报春谱系遗传结构

鄂报春Primula obconica作为一种广泛栽培的园艺植物,其野生居群的遗传多样性及遗传结构的研究还少见报道。本文通过叶绿体微卫星分析了17个鄂报春野生居群(共278个个体),共发现4个多态性位点(16个等位基因),得到14个单倍型。结果表明鄂报春具有很高的总基因多样性(HT=0.971)和极低的居群内基因多样性(HS=0.028);分子方差分析(AMOVA)显示98%的变异存在于居群间。这些结果说明早期的生境片断化及有限的种子传播能力是造成当前遗传结构的重要原因。Nst值显著大于Gst值,表明关系相近的单倍型会出现在相同的地区内,同时最小生成树(MST)的分析结果证实了这样的结论。我们在最小生成树的两个组中推断出一些古老单倍型,并推测在冰期时湖北和我国的西南地区可能是该物种的避难所。     

When east meets west: population structure of a high-latitude resident species,the boreal chickadee (Poecile hudsonicus)

The population genetic structure of northern boreal species has been strongly influenced both by the Quaternary glaciations and the presence of contemporary barriers, such as mountain ranges and rivers. We used a combination of mitochondrial DNA (mtDNA), nuclear microsatellites and spatial distribution modelling to study the population genetic structure of the boreal chickadee (Poecile hudsonicus), a resident passerine, and to investigate whether historical or contemporary barriers have influenced this northern species. MtDNA data showed evidence of eastern and western groups, with secondary admixture occurring in central Canada. This suggests that the boreal chickadee probably persisted in multiple glacial refugia, one in Beringia and at least one in the east. Palaeo-distribution modelling identified suitable habitat in Beringia (Alaska), Atlantic Canada and the southern United States, and correspond to divergence dates of 60–96 kya. Pairwise F_ST values for both mtDNA and microsatellites were significant for all comparisons involving Newfoundland, though mtDNA data suggest a more recent separation. Furthermore, unlike mtDNA data, nuclear data support population connectivity among the continental populations, possibly due to male-biased dispersal. Although both are significant, the isolation-by-distance signal is much stronger for mtDNA (r²=0.51) than for microsatellites (r²=0.05), supporting the hypothesis of male-biased dispersal. The population structure of the boreal chickadee was influenced by isolation in multiple refugia and contemporary barriers. In addition to geographical distance, physical barriers such as the Strait of Belle Isle and northern mountains in Alaska are restricting gene flow, whereas the Rocky Mountains in the west are a porous barrier.     

Fire and ice: volcanic and glacial impacts on the phylogeography of the New Zealand forest fern Asplenium hookerianum

In the Southern Hemisphere there has been little phylogeographical investigation of forest refugia sites during the last glacial. Hooker's spleenwort, Asplenium hookerianum, is a fern that is found throughout New Zealand. It is strongly associated with forest and is a proxy for the survival of woody vegetation during the last glacial maximum. DNA sequence data from the chloroplast trnL-trnF locus were obtained from 242 samples, including c. 10 individuals from each of 21 focal populations. Most populations contained multiple, and in many cases unique, haplotypes, including those neighbouring formerly glaciated areas, while the predominant inference from nested clade analysis was restricted gene flow with isolation by distance. These results suggest that A. hookerianum survived the last glacial maximum in widespread populations of sufficient size to retain the observed phylogeography, and therefore that the sheltering woody vegetation must have been similarly abundant. This is consistent with palynological interpretations for the survival in New Zealand of thermophilous forest species at considerably smaller distances from the ice sheets than recorded for the Northern Hemisphere. Eastern and central North Island populations of A. hookerianum were characterized by a different subset of haplotypes to populations from the remainder of the country. A similar east-west phylogeographical pattern has been detected in a diverse array of taxa, and has previously been attributed to recurrent vulcanism in the central North Island.     

Phylogeographic insights of the lowland species Cheirolophus sempervirens in the southwestern Iberian Peninsula

The southwestern Iberian Peninsula is an important biogeographic region, showing high biodiversity levels and hosting several putative glacial refugia for European flora. Here, we study the genetic diversity and structure of the Mediterranean, thermophilous plant Cheirolophus sempervirens (Asteraceae) across its whole distribution range in SW Iberia, as a tool to disentangle some of the general biogeographic patterns shaping this southern refugia hotspot. Null genetic diversity was observed in the cpDNA sequencing screening. Nonetheless, AFLP data revealed high levels of among-population genetic differentiation correlated to their geographic location. Our results suggest longer species persistence in southern Iberian refugia during glacial periods and subsequent founder effects northwards due to colonizations in warmer stages (i.e., the southern richness to northern purity pattern). Additionally, our phylogeographic analyses indicate the presence of two separate genetic lineages within Ch. sempervirens, supporting the hypothesis of multiple minor refugia for SW Iberia in agreement with the refugia within refugia model.     

Southern crossroads of the Western Palaearctic during the Late Pleistocene and their imprints on current patterns of genetic diversity: insights from the mosquito Aedes caspius

Aim Climatic changes have strongly reshaped the Western Palaearctic biota throughout the Late Pleistocene. For animals, most studies so far have focused on species having low to moderate dispersal abilities, while strong dispersers have remained understudied, despite their abundance. With the aim of contributing to filling this gap, we here investigate the Late Pleistocene evolutionary history of one such species, the mosquito Aedes caspius. Location Western Palaearctic. Methods Sequences of the cytochrome c oxidase subunits I and II mitochondrial DNA genes were analysed in individuals from 16 sampling localities. The phylogeographic structure was investigated using phylogenetic network analysis, permutational contingency tests, spatial analysis of molecular variance, and correlation of genetic and geographic distances between populations. Historical demographic changes were investigated by analysing the mismatch distributions, the Bayesian skyline plot method and Fu’s F_S statistic. Results We observed 67 haplotypes over all 112 individuals analysed (haplotype diversity = 0.971; nucleotide diversity = 0.0067). Despite the substantial genetic diversity, we found neither strong phylogenetic divergence among haplotypes (uncorrected mean sequence divergence 0.8%) nor any phylogeographic structure across the study area. The historical demographic analyses suggested that the species maintained a stable population size until roughly 25,000 years ago, when it underwent a sudden demographic expansion. Main conclusions Our data suggest that during the last glacial stage, A. caspius did not undergo dramatic range fragmentation in separate glacial refugia. Rather, the species is likely to have persisted in largely interconnected populations throughout most of the region, in areas with suitable environmental conditions. This scenario adds to similar patterns emerging for other temperate regions of the world, suggesting that an important component of the evolutionary history of temperate biotas has hitherto been largely overlooked.     

Choosing and using diversity indices: insights for ecological applications from the German Biodiversity Exploratories

Biodiversity, a multidimensional property of natural systems, is difficult to quantify partly because of the multitude of indices proposed for this purpose. Indices aim to describe general properties of communities that allow us to compare different regions, taxa, and trophic levels. Therefore, they are of fundamental importance for environmental monitoring and conservation, although there is no consensus about which indices are more appropriate and informative. We tested several common diversity indices in a range of simple to complex statistical analyses in order to determine whether some were better suited for certain analyses than others. We used data collected around the focal plant Plantago lanceolata on 60 temperate grassland plots embedded in an agricultural landscape to explore relationships between the common diversity indices of species richness (S), Shannon's diversity (H'), Simpson's diversity (D₁), Simpson's dominance (D₂), Simpson's evenness (E), and Berger–Parker dominance (BP). We calculated each of these indices for herbaceous plants, arbuscular mycorrhizal fungi, aboveground arthropods, belowground insect larvae, and P. lanceolata molecular and chemical diversity. Including these trait‐based measures of diversity allowed us to test whether or not they behaved similarly to the better studied species diversity. We used path analysis to determine whether compound indices detected more relationships between diversities of different organisms and traits than more basic indices. In the path models, more paths were significant when using H', even though all models except that with E were equally reliable. This demonstrates that while common diversity indices may appear interchangeable in simple analyses, when considering complex interactions, the choice of index can profoundly alter the interpretation of results. Data mining in order to identify the index producing the most significant results should be avoided, but simultaneously considering analyses using multiple indices can provide greater insight into the interactions in a system.     

Genetic consequences of glacial survival: the late Quaternary history of balsam poplar (Populus balsamifera L.) in North America

Aim Beringia, the unglaciated region encompassing the former Bering land bridge, as well as the land between the Lena and Mackenzie rivers, is recognized as an important refugium for arctic plants during the last ice age. Compelling palaeobotanical evidence also supports the presence of small populations of boreal trees within Beringia during the Last Glacial Maximum. The occurrence of balsam poplar (Populus balsamifera) in Beringia provides a unique opportunity to assess the implications of persistence in a refugium on present‐day genetic diversity for this boreal tree species. Location North America. Methods We sequenced three variable non‐coding regions of the chloroplast genome (cpDNA) from 40 widely distributed populations of balsam poplar across its North American range. We assessed patterns of genetic diversity, geographic structure and historical demography between glaciated and unglaciated regions of the balsam poplar’s range. We also utilized a coalescent model to test for divergence between regions. Results Levels of genetic diversity were consistently greater for populations at the southern margin (θ_W = 0.00122) than in the central (θ_W = 0.00086) or northern (θ_W = 0.00034) regions of the current distribution of balsam poplar, and diversity decreased with increasing latitude (R² = 0.49, P < 0.01). We detected low, but significant, structure (F_CT = 0.05, P = 0.05), among regions of P. balsamifera’s distribution. The cpDNA genealogy was shallow, however, showing an absence of highly differentiated chloroplast haplotypes. Coalescent analyses supported a model of divergence between the southern ice margin and the northern unglaciated region of balsam poplar’s distribution, but analyses of other regional comparisons did not converge. Main conclusions The palaeobotanical record supports the presence of a Beringian refugium for balsam poplar, but we were unable to definitively identify the presence of known refugial populations based on genetic data alone. Balsam poplar populations from Beringia are not a significant reservoir of cpDNA diversity today. Unique alleles that may have been present in the small, isolated populations that survived within Beringia were probably lost through genetic drift or swamped by post‐glacial, northward migration from populations south of the ice sheets.     

Species delimitation and phylogeography of the Abies chensiensis complex inferred from morphological and molecular data

Species delimitation in the Abies chensiensis complex, consisting of A. chensiensis, A. recurvata, A. ernestii and A. ernestii var. salouenensis, has been the subject of a long‐term dispute, as various taxonomic combinations have been proposed. We combined different lines of evidence, including morphological characters and mitochondrial and plastid DNA sequence data, to assess species delimitation. Plastid DNA sequence variation was highly consistent with the morphological result and separated A. recurvata from the other three taxa, but the mitochondrial DNA genealogy was more strongly related to geographical distribution rather than species delimitation, as proposed in previous studies. On the basis of morphological characters and plastid DNA sequence variation, the current species status of A. recurvata was well supported, and we also accepted A. ernestii and A. ernestii var. salouenensis as varieties of A. chensiensis. Furthermore, the phylogeographical history of A. chensiensis was surveyed by molecular data and ecological niche modelling. On the basis of molecular data, the current phylogeographical pattern of the A. chensiensis complex was probably shaped by recent rapid expansions from multiple refugia in the Hengduan Mountains and habitat contraction after the last glaciation. This hypothesis was supported by the results of ecological niche modelling and previous fossil records. Our findings suggest that these fir taxa might have continued to expand their range after the largest glaciation until the end of the last glaciation, but have contracted since then with the increasing temperature and habitat changes. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 175–188.     

Phylogeography of Camassia quamash in western North America: postglacial colonization and transport by indigenous peoples

Recent human activities have spread numerous plant species across the globe, yet it is unclear to what degree historical human activities influenced plant dispersal. In western North America, Camassia quamash was one of the most important food plants for indigenous peoples, who transported its propagules either intentionally or accidentally. We investigated how human and natural dispersal might have contributed to the current pattern of spatial genetic structure in C. quamash by performing phylogeographical surveys at two geographical scales. We sequenced two noncoding regions of chloroplast deoxyribonucleic acid (DNA) in 226 individuals from 53 populations of C. quamash as well as 126 individuals from 21 populations of the non-food plant Zigadenus venenosus . Contrary to the expectation of anthropogenic transport, C. quamash populations did not exhibit weaker genetic structure than Z. venenosus populations. We also failed to find convincing evidence for signatures of transport. Instead, our data showed strong effects of past glaciation and geographical barriers of the mountains in the Cascade Range, Olympic Peninsula and Vancouver Island. West of the Cascades, the species appears to have largely migrated northward from a southern refugium after deglaciation, whereas few populations having a highly divergent haplotype might have survived in southwestern Washington. Our data suggest that despite substantial ethnobotanical evidence for anthropogenic transport, the current pattern of genetic structure of C. quamash does not show any detectable signatures of transport by indigenous peoples and is better understood as the result of natural dispersal processes.     

The southwestern Carpathians as an ancient centre of diversity of freshwater gammarid amphipods: insights from the Gammarus fossarum species complex

Gammarus fossarum is a diverse species complex of epigean freshwater amphipods throughout Europe. Due to their poor dispersal capabilities and ubiquity, these crustaceans may serve as a model for investigating the influence of historical factors on the contemporary distribution and diversity patterns of freshwater macrozoobenthos. Here, we investigate the fine‐scale phylogeographic structure of this complex across its range in the southwestern Carpathian Mountains, which comprises two areas that are geographically isolated from its main European distribution area as well as from each other. Given the Tertiary age of many freshwater Gammarus species, we hypothesize that the southwestern Carpathian populations reflect a relict distribution pattern. We used two mitochondrial and three nuclear markers from 32 localities to reconstruct phylogenetic relationships and estimate the timings of divergence among southwestern Carpathian and non‐Carpathian lineages. Cryptic diversity was evaluated from mitochondrial markers by employing phylogenetic and distance‐based methods. We distinguished at least 16 cryptic microendemic taxa, some of them coexisting, distributed in the southwestern Carpathians in a mosaic‐like pattern. These lineages form a monophyletic group together with several lineages from southeastern Europe. Estimated divergence times indicate a Middle Miocene origin of this clade, with many deep splits dating back to more than 10 Ma. This time frame corresponds with a period of intense geological subsidence in the region that gave birth to the Pannonian Basin. We conclude that subsidence could have been an important driver of diversification in freshwater Gammarus and that the southwestern Carpathians represent an ancient centre of diversity for these crustaceans.     

Phylogeographic patterns and high levels of chloroplast DNA diversity in four Packera (asteraceae) species in southwestern Alberta

Chloroplast DNA (cpDNA) haplotype variation is compared among alpine and prairie/montane species of Packera from a region in southwestern Alberta that straddles the boundary of Pleistocene glaciation. The phylogeny of the 15 haplotypes identified reveals the presence of two groups: one generally found in coastal and northern species and the other from species in drier habitats. The presence of both groups in all four species and most populations from southwestern Alberta is evidence of past hybridization involving species or lineages that may no longer be present in the region. With the exception of the alpine P. subnuda (phiST = 1.0), interpopulational subdivision of haplotype variation is low (phiST < 0.350), suggesting that interpopulational gene flow is high. However, based on haplotype distribution patterns, we propose that Pleistocene hybridization and incomplete lineage sorting have resulted in reduced subdivision of interpopulational variation so that gene flow may not be as high as indicated. Drift has been more important in the alpine species populations, especially P. subnuda.     

Rapid extraction and purification of environmental DNA for molecular cloning applications and molecular diversity studies

A rapid method for the extraction and purification of DNA from environmental samples for molecular cloning applications was developed. The indigenous cells from plant debris, organic materials, sediments, and soils were lysed directly by using DAS-I^Z solution and the nucleic acids were precipitated with isopropanol. A simple purification step using DAS-II^Z solution without binding matrix produced highly pure, colorless and undegraded DNA with molecular weight of more than 20 kb. The superiority of this method was tested for wide applications in molecular cloning, i.e., construction of genomic library by using Lambda DASH^(R)II Vector and Gigapack^(R)III XL, plasmid library, cloning of gene encoding protease, and molecular microbial diversity analysis. An additional advantage of this method is that only 0.1 g of sample is required, if analysis of many samples in short time should be done. To extract large amounts of environmental DNA for molecular cloning lasts only 30 min and to purify it less than 1 h.     

Comparative study of the phylogenetic structure in six Apodemus species (Mammalia,Rodentia) inferred from ISSR-PCR data

The utility of the Inter Simple Sequence Repeat-Polymerase Chain Reaction (ISSR-PCR) was explored in order to determine genetic variation in six species of the genus Apodemus (A. flavicollis, A. sylvaticus, A. uralensis, A. agrarius, A. mystacinus and A. epimelas) at the individual level, population level, in separate geographic samples and in the species as a whole. Six optimized primers produced highly reproducible and polymorphic DNA markers with 98.3% polymorphic bands on a total sample of 91 individuals from 32 localities in Europe and Asia. Moreover, each primer allowed for an exact diagnosis of each of the six Apodemus species and thus provides a simple and reliable tool for the hitherto problematic discrimination of species from the subgenus Sylvaemus. Genetic distances between species ranged from 0.079, among the closely related A. flavicollis and A. sylvaticus, to 0.203 between A. mystacinus and A. agrarius. A. flavicollis, A. uralensis and A. sylvaticus display a strong population substructure. The range of genetic distances among geographic samples within last two species reaches the values obtained for closely related species. ISSR markers proved to be a simple and reliable tool for species diagnosis, as well as for estimating genetic diversity below the species level and for closely related species, but they showed questionable reliability for larger genetic distances.     

Climatic niche and neutral genetic diversity of the six Iberian pine species: a retrospective and prospective view

Quaternary climatic fluctuations have left contrasting historical footprints on the neutral genetic diversity patterns of existing populations of different tree species. We should expect the demography, and consequently the neutral genetic structure, of taxa less tolerant to particular climatic extremes to be more sensitive to long‐term climate fluctuations. We explore this hypothesis here by sampling all six pine species found in the Iberian Peninsula (2464 individuals, 105 populations), using a common set of chloroplast microsatellite markers, and by looking at the association between neutral genetic diversity and species‐specific climatic requirements. We found large variation in neutral genetic diversity and structure among Iberian pines, with cold‐enduring mountain species (Pinus uncinata, P. sylvestris and P. nigra) showing substantially greater diversity than thermophilous taxa (P. pinea and P. halepensis). Within species, we observed a significant positive correlation between population genetic diversity and summer precipitation for some of the mountain pines. The observed pattern is consistent with the hypotheses that: (i) more thermophilous species have been subjected to stronger demographic fluctuations in the past, as a consequence of their maladaptation to recurrent glacial cold stages; and (ii) altitudinal migrations have allowed the maintenance of large effective population sizes and genetic variation in cold‐tolerant species, especially in more humid regions. In the light of these results and hypotheses, we discuss some potential genetic consequences of impending climate change.     

Putative glacial refugia of Cedrus atlantica deduced from Quaternary pollen records and modern genetic diversity

Aim To investigate the impact of past environmental changes on Cedrus atlantica and its current genetic diversity, and to predict its future distribution. Location Morocco, Algeria and Tunisia. Methods Eleven fossil pollen records from these three countries were used to locate putative glacial refugia and to reconstruct past climate changes. A mechanistic vegetation distribution model was used to simulate the distribution of C. atlantica in the year 2100. In addition, a genetic survey was carried out on modern Moroccan C. atlantica. Results Pollen records indicate that Cedrus was present during the last glacial period, probably in scattered refugia, in Tunisia, Algeria and Morocco. In the Tunisian and Algerian sites, cedar expanded during the late glacial and the early Holocene, then disappeared after c. 8000 yr bp . Reconstructed mean annual precipitation and January temperature show that the last glacial period in Morocco was cooler by 10–15°C and drier by c. 300–400 mm year^?1 than the climate today. Modern chloroplast microsatellites of 15 C. atlantica populations in Morocco confirm the presence of multiple refugia and indicate that cedar recolonized the Moroccan mountains fairly recently. Model simulation indicates that by the year 2100 the potential distribution of C. atlantica will be much restricted with a potential survival area located in the High Atlas. Main conclusions Environmental changes in northern Africa since the last glacial period have had an impact on the geographical distribution of C. atlantica and on its modern genetic diversity. It is possible that by the end of this century C. atlantica may be unable to survive in its present‐day locations. To preserve the species, we suggest that seedlings from modern C. atlantica populations located in the High Atlas mountains, where a high genetic diversity is found, be transplanted into the western High Atlas.     

Legacy lost: genetic variability and population size of extirpated US grey wolves (Canis lupus)

By the mid 20th century, the grey wolf (Canis lupus) was exterminated from most of the conterminous United States (cUS) and Mexico. However, because wolves disperse over long distances, extant populations in Canada and Alaska might have retained a substantial proportion of the genetic diversity once found in the cUS. We analysed mitochondrial DNA sequences of 34 pre-extermination wolves and found that they had more than twice the diversity of their modern conspecifics, implying a historic population size of several hundred thousand wolves in the western cUS and Mexico. Further, two-thirds of the haplotypes found in the historic sample are unique. Sequences from Mexican grey wolves (C. l. baileyi) and some historic grey wolves defined a unique southern clade supporting a much wider geographical mandate for the reintroduction of Mexican wolves than currently planned. Our results highlight the genetic consequences of population extinction within Ice Age refugia and imply that restoration goals for grey wolves in the western cUS include far less area and target vastly lower population sizes than existed historically.