Historical biogeography and post-glacial recolonization of South American temperate rain forest by the relictual marsupial Dromiciops gliroides

Aim Long‐term climatic variation has generated historical expansions and contractions of species ranges, with accompanying fragmentation and population bottlenecks, which are evidenced by spatial variation in genetic structure of populations. We examine here hypotheses concerning dispersal and vicariance in response to historical geoclimatic change and potential isolation produced by mountains and water barriers. Location The temperate rain forest of southern South America, which is distributed from coastal Chile, including the large continental island of Chiloé, across the Andes into Argentina. Methods We investigated our hypotheses in the phylogenetically and biogeographically relictual marsupial Dromiciops gliroides. We examined 56 specimens, which resulted from field samples and museum study skins from 21 localities. We evaluated the influence of two major barriers, the Andean cordillera and the waterway between the mainland and the large island of Chiloé, by performing Bayesian and maximum‐likelihood phylogenetic analyses on sequences of 877 base pairs of mitochondrial DNA. We further tested the contribution of the proposed geographical barriers using analysis of molecular variance (amova ). We also evaluated the responses of populations to historical north–south shifts of habitat associated with glacial history and sea‐level change. Results Our analyses revealed a phylogeny with three clades, two of which are widespread and contain nearly all the haplotypes: a northern clade (36–39° S) and a southern clade (40–43° S). These two clades contain forms from both sides of the Andes. Within the southern clade, island and mainland forms were not significantly differentiated. Tests of recent demographic change revealed that southern populations have experienced recent expansion, whereas northern populations exhibit long‐term stability. The direction of recent gene flow and range expansion is predominantly from Chile to Argentina, with a modest reciprocal exchange across the Andes. Recent gene flow from the island of Chiloé to the mainland is also supported. Main conclusions The genetic structure of contemporary D. gliroides populations suggests recent gene flow across the Andes and between the mainland and the island of Chiloé. Differences in demographic history that we detected between northern and southern populations have resulted from historical southward shifts of habitat associated with glacial recession in South America. Our results add to a growing literature that demonstrates the value of genetic data to illuminate how environmental history shapes species range and population structure.     

Environmental Controls of Cryptogam Composition and Diversity in Anthropogenic and Natural Peatland Ecosystems of Chilean Patagonia

Peatlands exhibit highly characteristic ecological traits and are unique complex ecosystems. Nevertheless, knowledge about southern South American peatlands is very limited. In this study, we analyzed species composition of bryophytes and lichens of Southern Hemisphere peatlands, specifically from eight peatlands of Isla Grande de Chiloé (Chiloé Island) in southern Chile (42°–43°S and 75°–73°W). Two kinds of Sphagnum peatlands were studied: natural and anthropogenic peatlands. Our results indicate the existence of clear environmental gradients affecting the structure of bryo-lichenic communities in the Sphagnum peatlands of Chiloé. Canonical correspondence analysis suggests that variation in bryophyte and lichen species composition mainly follows ombrotrophic–minerotrophic and lithotrophic-thalassotrophic gradients. Surface-water chemistry is the most significant factor accounting for changes in floristic composition among our study sites. In contrast to our expectations, bog origin (natural or anthropic) was not the most significant factor accounting for changes in floristic composition among peatlands. Other elements, such as the water source supplying peatlands or the influence of sea spray, were more relevant in the bryo-lichenic flora species occurrence in the peatlands of Chiloé. We also observed clear differences in ecological niches among species in general additive model response curves. Therefore, our results show that despite the origin, the ecology of peatlands follows common rules with peatlands from the Northern Hemisphere.     

Phylogeography of a Patagonian lizard and frog: Congruent signature of southern glacial refuges

Pleistocene glaciations produced significant increases in continental ice cover in polar and mid‐latitude temperate areas, sea‐level declines and shifts and reshuffling of biomes, all of which promote either isolation, coalescence or fragmentation in the distribution of land biota. If populations of several taxa have been co‐distributed for a prolonged time, and if the periods between perturbation or vicariance processes have been more or less stable, it is expected that divergence patterns of closely related and ecologically similar species will be congruent because of their similar biological and demographic characteristics. Based on this premise, we analysed the phylogeographic structure (cytochrome b) of Liolaemus pictus and Batrachyla leptopus, two widely co‐distributed lizard and frog species, respectively, in the Chiloé Archipelago of southern Chile, to decipher their genetic structure in response to a common climatic and environmental history. Haplotype network analysis and Bayesian inference suggest an evolutionary pattern of genetic diversity for the two species that is consistent with the Quaternary glacial history of southern Chile, and suggests a complex phylogeographic history in the Liolaemus and Batrachyla species. High‐divergence levels among haplotypes in some island populations of the archipelago also suggest genetic connectivity between putative refuges from Chiloé Island and the mainland along the exposed continental shelf during sea level minima associated with the most recent Quaternary glaciations. Our results are consistent with our hypothesis that two species have responded to parallel historical events in which the historical process during the last glacial maximum (approximately 41°S) has been sufficient to influence their phylogeographic structure.     

mtDNA microevolution in Southern Chile's archipelagos

The genetic variability of four predominantly Indian populations of southern Chile's archipelagos was examined by determining the frequencies of four mitochondrial DNA haplogroups that characterize the American Indian populations. Over 90% of the individuals analyzed presented Native American mtDNA haplogroups. By means of an unweighted group pair method with arithmetic mean (UPGMA) dendrogram, a principal component analysis (PCA) derived from a distance matrix of mtDNA, and the exact test of population differentiation, we are able to prove the existence of a North‐South cline. The populations in the northern part of the archipelagos are genetically similar to the Huilliche tribe, while the groups from the South are most closely related to the Fueguino tribe from the extreme South of Chile, and secondarily to the Pehuenche and Mapuche, who are found to the North and East of Chiloé archipelago. These results are consistent with a colonization of the southern archipelagos from Tierra del Fuego. We evaluate the evolutionary relationships of the population of the Chiloé area to groups from other geographic areas of Chile, using analysis of molecular variance (AMOVA). Three Amerindian clusters are identified: one formed by the Aymará and Atacameño, a second by the Huilliche, and a third including the Mapuche, Pehuenche, and Fueguino tribes, and the population inhabiting the South of the Chiloé arcipelago. These groups exhibit a North‐South gradient in the frequency of haplogroup B, confirmed by F_ST tests. Am J Phys Anthropol, 2006 © 2005 Wiley‐Liss, Inc.     

Leucocytozoon toddi and Haemoproteus tinnunculi (Protozoa: Haemosporina) in the Chimango caracara (Milvago chimango) in southern Chile.

Two species of blood protozoans were identified from blood smears collected from 15 specimens of the Chimango caracara (Milvago chimango) on Isla Grande de Chiloé in southern Chile. These included Leucocytozoon toddi in 13 birds, including all 5 of the 4-6 week old nestlings examined, and 8 of the subadults or adults. One of the nestlings also had a dual infection of L. toddi and Haemoproteus tinnunculi. These are the first reports of blood parasites from M. chimango.     

Phylogeography of the Patagonian otter Lontra provocax: adaptive divergence to marine habitat or signature of southern glacial refugia?

Background  

A number of studies have described the extension of ice cover in western Patagonia during the Last Glacial Maximum, providing evidence of a complete cover of terrestrial habitat from 41°S to 56°S and two main refugia, one in south-eastern Tierra del Fuego and the other north of the Chiloé Island. However, recent evidence of high genetic diversity in Patagonian river species suggests the existence of aquatic refugia in this region. Here, we further test this hypothesis based on phylogeographic inferences from a semi-aquatic species that is a top predator of river and marine fauna, the huillín or Southern river otter (Lontra provocax).     

Genetic differentiation of the Thorn‐tailed Rayadito Aphrastura spinicauda (Furnariidae: Passeriformes) revealed by ISSR profiles suggests multiple palaeorefugia and high recurrent gene flow

Nucleotide sequence data (cytochrome b) and ISSR genomic fingerprints were used to analyse the genetic variation and population differentiation in Thorn‐tailed Rayadito, a widespread Patagonian forest bird. We included samples from eight populations of Thorn‐tailed Rayadito covering most of the distribution range of the species: from fragmented patches of Olivillo forest in northern Chile to Isla Navarino forests in the extreme south of South America. Low levels of genetic diversity were found among populations, with a large within‐population molecular variance indicating high levels of gene flow. The multivariate and cluster analyses based on ISSR markers show that the subspecies bullocki (from Mocha Island) differs significantly from all other populations. The subspecies fulva (Chiloé Island) shows less differentiation than bullocki, sharing several alleles with continental populations. Bayesian analyses suggest that the Mocha Island population contributes most to the total genetic diversity observed in the species. Mantel tests revealed no significant correlation between geographical distance and pairwise genetic distance and cytochrome b sequence analyses failed to detect differentiation among subspecies. Mocha Island might have been a palaeorefuge and this population may have diversified by genetic drift after the last glacial maximum. There is also the possibility of a postglacial colonization of the Thorn‐tailed Rayadito from an austral palaeorefugium, supporting a multiple refugia hypothesis. This study illustrates the usefulness of the rarely used ISSR genomic fingerprint method in avian phylogeography.     

Refugial races and postglacial colonization history of the freshwater amphipod Gammarus lacustris in Northern Europe

The systematic structure and postglacial population history of the freshwater amphipod Gammarus lacustris were explored in an allozyme survey of 65 populations across Northern Europe. A strong multilocus pattern of differentiation discriminated populations of the north‐east (north‐eastern Norway, northern Finland) from those in the west and the south (southern and central Scandinavia, Denmark, Poland). This principal division is attributed to postglacial colonization of the area by two main refugial races or lineages, one from the east (Russia), the other from the south (north‐western European continent). The strongly diverged Eastern and Western races (Nei's D= 0.3, from 22 loci) now meet in a secondary contact zone across a narrow sector of northernmost Norway. Genetic population compositions in this zone vary in a mosaic pattern, and show no evidence of reproductive incompatibility. Similar contacts of eastern and western lineages, far older than the latest glaciation, are now known from a number of taxa and they constitute a general pattern in Fennoscandian phylogeography. Within the Western Gammarus race, the populations through coastal north‐western Norway are further distinguished from those in southern Scandinavia and Denmark by a set of unique alleles at high frequencies (D = 0.12). This suggests an independent early colonization of the coastal region by another distinct stock, either along an early deglaciated coastal corridor from the south‐west, or directly from the ice‐free continental shelf off the Norwegian coast – a hypothesis that has also previously been presented for G. lacustris, and parallels controversial suggestions of local refugia for other taxa in Scandinavia. The coastal population type only later could come into contact with Gammarus invading over the mountains from the south; these two population types now smoothly intergrade. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 79, 523–542.     

Philopatry and faithfulness to nest site in Cory's Shearwaters Calonectris diomedea at Selvagem Grande

Mougin, J.-L., Granadeiro, J. P., Jouanin, C. & Roux, F. 1999. Philopatry and faithfulness to nest site in Cory's Shearwaters Calonectris diomedea at Selvagem Grande. Ostrich 70 (3&4): 229–232.

Nearly fledged Cory's Shearwater Calonectris diomedea chicks at Selvagem Grande occasionally desert their nest sites during the night, but generally return before dawn. The temporary use of other nest sites is rare and lasts less than two days. Almost all chicks from Selvagem Grande return to the island for their first breeding attempt; very few breed at islands outside the archipelago. On Selvagem Grande, almost half the males return to their native colony whereas more than 90% of females recruit to other colonies. Inter-colony movements sometimes exceed 1 km, but, if they return to their native colony, both sexes settle within 20 m of their natal site. From the second breeding attempt onwards, most birds of both sexes are faithful to the nest site. On average, less than 20% of birds desert their former nest site each year, with a shift of about 4 m only. Most nest shifts follow a breeding failure or a temporary respite from breeding, and are accompanied by a switch in partners.

Mougin, J.-L., Granadeiro, J. P. Jouanin, C. & Roux, F. 1999. Philopatrie et fidélité au nid chez le Puffin cendré Calonectris diomedea de Selvagem Grande. Ostrich 70 (3&4): 229–232.

Le poussin en fin de croissance du Puffin cendré Calonectris diomedea de Selvagem Grande déserte parfois son nid pendant la nuit, mais y revient généralement avant le jour. L'utilisation temporaire d'un autre site de nid est rare et dure moins de deux jours. Les jeunes adultes nés à Selvagem Grande reviennent presque toujours nicher sur l'île et extrêmement rarement en dehors de l'archipel. A Selvagem Grande, près de la moitié des mâles reviennent à leur colonie de naissance, mais moins de 10% des femelles. Le déplacement est parfois supérieur à 1 km mais, s'ils reviennent à leur colonie natale, les deux sexes s'établissent à moins de 20 m du nid où ils sont nés. A partir de leur deuxième reproduction, les deux sexes sont fidèles à leur nid. Moins de 20% des oiseaux changent de nid d'une année à l'autre, avec un déplacement de 4 m seulement, le plus souvent à la suite d'un échec ou d'une interruption temporaire de la reproduction, ce déplacement étant le plus souvent accompagne d'un changement de partenaire.     

Phylogeography of the introduced species Rattus rattus in the western Indian Ocean,with special emphasis on the colonization history of Madagascar

Aim To describe the phylogeographic patterns of the black rat, Rattus rattus, from islands in the western Indian Ocean where the species has been introduced (Madagascar and the neighbouring islands of Réunion, Mayotte and Grande Comore), in comparison with the postulated source area (India). Location Western Indian Ocean: India, Arabian Peninsula, East Africa and the islands of Madagascar, Réunion, Grande Comore and Mayotte. Methods Mitochondrial DNA (cytochrome b, tRNA and D‐loop, 1762 bp) was sequenced for 71 individuals from 11 countries in the western Indian Ocean. A partial D‐loop (419 bp) was also sequenced for eight populations from Madagascar (97 individuals), which were analysed in addition to six previously published populations from southern Madagascar. Results Haplotypes from India and the Arabian Peninsula occupied a basal position in the phylogenetic tree, whereas those from islands were distributed in different monophyletic clusters: Madagascar grouped with Mayotte, while Réunion and Grand Comore were present in two other separate groups. The only exception was one individual from Madagascar (out of 190) carrying a haplotype that clustered with those from Réunion and South Africa. ‘Isolation with migration’ simulations favoured a model with no recurrent migration between Oman and Madagascar. Mismatch distribution analyses dated the expansion of Malagasy populations on a time‐scale compatible with human colonization history. Higher haplotype diversity and older expansion times were found on the east coast of Madagascar compared with the central highlands. Main conclusions Phylogeographic patterns supported the hypothesis of human‐mediated colonization of R. rattus from source populations in either the native area (India) or anciently colonized regions (the Arabian Peninsula) to islands of the western Indian Ocean. Despite their proximity, each island has a distinct colonization history. Independent colonization events may have occurred simultaneously in Madagascar and Grande Comore, whereas Mayotte would have been colonized from Madagascar. Réunion was colonized independently, presumably from Europe. Malagasy populations may have originated from a single successful colonization event, followed by rapid expansion, first in coastal zones and then in the central highlands. The congruence of the observed phylogeographic pattern with human colonization events and pathways supports the potential relevance of the black rat in tracing human history.     

Mitochondrial DNA variation in Koryaks and Itel'men: Population replacement in the Okhotsk Sea–Bering Sea region during the neolithic

In this study, we analyzed the mitochondrial DNA (mtDNA) variation in 202 individuals representing one Itel'men and three Koryak populations from different parts of the Kamchatka peninsula. All mtDNAs were subjected to high resolution restriction (RFLP) analysis and control region (CR) sequencing, and the resulting data were combined with those available for other Siberian and east Asian populations and subjected to statistical and phylogenetic analysis. Together, the Koryaks and Itel'men were found to have mtDNAs belonging to three (A, C, and D) of the four major haplotype groups (haplogroups) observed in Siberian and Native American populations (A–D). In addition, they exhibited mtDNAs belonging to haplogroups G, Y, and Z, which were formerly called “Other” mtDNAs. While Kamchatka harbored the highest frequencies of haplogroup G mtDNAs, which were widely distributed in eastern Siberian and adjacent east Asian populations, the distribution of haplogroup Y was restricted within a relatively small area and pointed to the lower Amur River–Sakhalin Island region as its place of origin. In contrast, the pattern of distribution and the origin of haplogroup Z mtDNAs remained unclear. Furthermore, phylogenetic and statistical analyses showed that Koryaks and Itel'men had stronger genetic affinities with eastern Siberian/east Asian populations than to those of the north Pacific Rim. These results were consistent with colonization events associated with the relatively recent immigration to Kamchatka of new tribes from the Siberian mainland region, although remnants of ancient Beringian populations were still evident in the Koryak and Itel'men gene pools. Am J Phys Anthropol 108:1–39, 1999. © 1999 Wiley‐Liss, Inc.     

Experimental comparison of laboratory-reared vs. wild-typeTrichogramma chilonis [Hym.: Trichogrammatidae] II. Tolerance of non-optimal temperatures

A comparative study was made of the tolerance of wild-type (WT) vs. laboratory-reared (LR)Trichogramma chilonis Ishii (=T. confusum Vigg.) for low (2°C) and high (35°C) temperatures. The wild-type populations orginated from two geographical regions viz., Vijayapura (near Bangalore) and Hyderabad. Probit analysis of the data to determine the precise LT₅₀ showed that the WT populations survived high and low temperatures better than the LR populations.

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Résumé Une étude comparative a été effectuée sur la tolérance à des températures basses (2°C) et élevées (35°C) deTrichogramma chilonis Ishii provenant de la nature par rapport à une souche de laboratoire. Les populations sauvages provenaient de 2 régions: Vijayupara (près de Bangalore) et Hyderabad. Une analyse probit des données destinée à déterminer le temps létal 50 a montré que les populations sauvages survivent mieux aux températures extrêmes que la population d'élevage.

     

Phylogeography of Rhinichthys cataractae (Teleostei: Cyprinidae): pre‐glacial colonization across the Continental Divide and Pleistocene diversification within the Rio Grande drainage

The longnose dace, Rhinichthys cataractae, is a primary freshwater fish inhabiting riffle habitats in small headwater rivers and streams across the North American continent, including drainages east and west of the Continental Divide. The mitochondrially encoded cytochrome b gene (1140 bp) and 2298–2346 bp of the nuclear‐encoded genes S7 and RAG1 were obtained from 87 individuals of R. cataractae (collected from 17 sites throughout its range) and from several close relatives. Phylogenetic analyses recovered a monophyletic R. cataractae species‐group that contained Rhinichthys evermanni, Rhinichthys sp. ‘Millicoma dace’, and a non‐exclusive R. cataractae. Within the R. cataractae species‐group, two well‐supported lineages were identified, including a western lineage (containing R. evermanni, R. sp. ‘Millicoma dace’ and individuals of R. cataractae from Pacific slope drainages) and an eastern lineage (containing individuals of R. cataractae from Arctic, Atlantic, and Gulf slope drainages). Within the eastern lineage of R. cataractae, two well‐supported groups were recovered: a south‐eastern group, containing individuals from the Atlantic slope, southern tributaries to the Mississippi River, and the Rio Grande drainage; and a north‐eastern group, containing individuals from the Arctic slope and northern tributaries to the Mississippi River. Estimates of the timing of divergence within the R. cataractae species‐group, combined with ancestral area‐reconstruction methods, indicate a separation between the eastern and western lineages during the Pliocene to early‐Pleistocene, with a direction of colonization from the west of the Continental Divide eastward. Within the southern portion of its range, R. cataractae likely entered the Rio Grande drainage during the Pleistocene via stream capture events between the Arkansas River (Mississippi River drainage) and headwaters of the Rio Grande. A close relationship between populations of R. cataractae in the Rio Grande drainage and the adjacent Canadian River (Mississippi River drainage) is consistent with hypothesized stream capture events between the Pecos (Rio Grande drainage) and Canadian rivers during the late‐Pleistocene. The population of R. cataractae in the lower Rio Grande may have become separated from other populations in the Rio Grande drainage (upper Rio Grande and Pecos River) and Canadian River during the late‐Pleistocene, well before initiation of recent and significant anthropogenic disturbance within the Rio Grande drainage. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 317–333.     

Phylogeography of Plathymenia reticulata (Leguminosae) reveals patterns of recent range expansion towards northeastern Brazil and southern Cerrados in Eastern Tropical South America

Little is known about past vegetation dynamics in Eastern Tropical South America (ETSA). Here we describe patterns of chloroplast (cp) DNA variation in Plathymenia reticulata, a widespread tree in the ETSA Atlantic Forest and Cerrado biomes, but not found in the xeromorphic Caatinga. Forty one populations, comprising 220 individuals, were analysed by sequencing the trnS‐trnG and trnL‐trnL‐trnF cpDNA regions. Combined, they resulted in 18 geographically structured haplotypes. The central region of the sampling area, comprising Minas Gerais and Goiás Brazilian states, is a centre of genetic diversity and probably the most longstanding area of the distribution range of the species. In contrast, populations from northeastern Brazil and the southern Cerrados showed very low diversity levels, almost exclusively with common haplotypes which are also found in the central region. Coupled with a long‐branched star‐like network, these patterns suggest a recent range expansion of P. reticulata to those regions from central region sources. The recent origin of the species (in the early Pleistocene) or the extinction of some populations due to drier and cooler climate during the last glacial maximum could have been responsible for that phylogeographic pattern. The populations from northeastern Brazil originated from two colonization routes, one eastern (Atlantic) and one western (inland). Due to its high diversity and complex landscape, the central region, especially central‐north Minas Gerais (between 15°–18° S and 42°–46° W), should be given the highest priority for conservation.     

Genetic and morphometric differentiation among island populations of two Norops lizards (Reptilia: Sauria: Polychrotidae) on independently colonized islands of the Islas de Bahia (Honduras)

Aim Anole lizards (Reptilia: Sauria: Polychrotidae) display remarkable morphological and genetic differentiation between island populations. Morphological differences between islands are probably due to both adaptive (e.g. differential resource exploitation and intra‐ or interspecific competition) and non‐adaptive differentiation in allopatry. Anoles are well known for their extreme diversity and rapid adaptive speciation on islands. The main aim of this study was to use tests of morphological and genetic differentiation to investigate the population structure and colonization history of islands of the Islas de Bahia, off the coast of Honduras. Location Five populations of Norops bicaorum and Norops lemurinus were sampled, four from islands of the Islas de Bahia and one from the mainland of Honduras. Methods Body size and weight differentiation were measured in order to test for significant differences between sexes and populations. In addition, individuals were genotyped using the amplified fragment length polymorphism technique. Bayesian model‐based and assignment/exclusion methods were used to study genetic differentiation between island and mainland populations and to test colonization hypotheses. Results Assignment tests suggested migration from the mainland to the Cayos Cochinos, and from there independently to both Utila and Roatán, whereas migration between Utila and Roatán was lacking. Migration from the mainland to Utila was inferred, but was much less frequent. Morphologically, individuals from Utila appeared to be significantly different in comparison with all other localities. Significant differentiation between males of Roatán and the mainland was found in body size, whereas no significant difference was detected between the mainland and the Cayos Cochinos. Main conclusions Significant genetic and morphological differentiation was found among populations. A stepping‐stone model for colonization, in combination with an independent migration to Utila and Roatán, was suggested by assignment tests and was compatible with the observed morphological differentiation.     

Pre‐Columbian population dynamics in coastal southern Peru: A diachronic investigation of mtDNA patterns in the Palpa region by ancient DNA analysis

Alternative models have been proposed to explain the formation and decline of the south Peruvian Nasca culture, ranging from migration or invasion to autochthonous development and ecological crisis. To reveal to what extent population dynamic processes accounted for cultural development in the Nasca mainland, or were influenced by them, we analyzed ancient mitochondrial DNA of 218 individuals, originating from chronologically successive archaeological sites in the Palpa region, the Paracas Peninsula, and the Andean highlands in southern Peru. The sampling strategy allowed a diachronic analysis in a time frame from approximately 800 BC to 800 AD. Mitochondrial coding region polymorphisms were successfully analyzed and replicated for 130 individuals and control region sequences (np 16021–16408) for 104 individuals to determine Native American mitochondrial DNA haplogroups and haplotypes. The results were compared with ancient and contemporary Peruvian populations to reveal genetic relations of the archaeological samples. Frequency data and statistics show clear proximity of the Nasca populations to the populations of the preceding Paracas culture from Palpa and the Peninsula, and suggest, along with archaeological data, that the Nasca culture developed autochthonously in the Rio Grande drainage. Furthermore, the influence of changes in socioeconomic complexity in the Palpa area on the genetic diversity of the local population could be observed. In all, a strong genetic affinity between pre‐Columbian coastal populations from southern Peru could be determined, together with a significant differentiation from ancient highland and all present‐day Peruvian reference populations, best shown in the differential distribution of mitochondrial haplogroups. Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.     

The post‐Pleistocene population genetic structure of a western North American passerine: the chestnut‐backed chickadee Poecile rufescens

The population genetic structure of many high‐latitude species in North America was affected by the last glaciation, and current structure reflects isolation in refugia and colonisation patterns. Large ice‐free areas, both south of the ice sheets and in the north‐west, supported numerous flora and fauna throughout this period. Fossil evidence suggests additional western glacial refugia existed both on Haida Gwaii (the Queen Charlotte Islands) and in northern Idaho. The chestnut‐backed chickadee Poecile rufescens is a songbird found along the western edge of Canada and the United States, with a linear distribution along the coast, and an isolated interior population. Mitochondrial DNA sequence data (control region and ATPase 6–8) from 10 populations (n = 122) were used to test for population genetic structure. The data supported a general north/south separation. Haida Gwaii was found to be genetically distinct from the rest of the populations, and the two northern British Columbia populations separated from all but Alaska. The interior population showed evidence of both historical isolation and secondary colonisation by birds from coastal populations. Neutrality tests suggested a past population expansion in all populations from previously glaciated areas, and a stable population in areas believed to be unglaciated. This pattern supports the use of multiple glacial refugia by the chestnut‐backed chickadee. We could not reject the use of Haida Gwaii or the interior (i.e. Clearwater Basin) as glacial refugia.     

Historical demography and spatial genetic structure of the subterranean rodent Ctenomys magellanicus in Tierra del Fuego (Argentina)

Ctenomys (tuco‐tuco) is the most numerous genus of South American subterranean rodents and one of the most genetically diverse clades of mammals known. In particular, the genus constitutes a very interesting model for evolutionary studies of genetic divergence and conservation. Ctenomys magellanicus is the southernmost species of the group and the only one living in Isla Grande de Tierra del Fuego (Argentina). This species presents two chromosomal forms (Cm34 and Cm36) fragmented into demes distributed from the north region (steppe) to the south region (ecotone) of the island, respectively; no hybrids or overlapping areas were detected. To study the historical demography and the spatial genetic structure of the C. magellanicus population we used mitochondrial DNA (mtDNA) (D‐loop and cytochrome b) and microsatellite loci. Nine mtDNA haplotypes were identified, three of them belonging to the north and the other six to the south. Shared haplotypes between regions were not detected. mtDNA and microsatellite genotypes showed a marked pattern of population structure with low values of genetic flow between regions. The south is made up of small populations or isolated demes making up an endogamic metapopulation with unique alleles and haplotypes. Also, the results suggest a northward expansion process starting from an ancestral haplotype from the south. That population might have lived at a refuge through the adverse Pleistocene environmental conditions that took place at Tierra del Fuego. Results of this study are relevant to the conservation of C. magellanicus, suggesting that each region (north and south) might be considered as an Evolutionarily Significant Unit. © 2013 The Linnean Society of London     

A time‐calibrated phylogenetic approach to assessing the phylogeography,colonization history and phenotypic evolution of snakes in the Japanese Izu Islands

Aim We infer the biogeography and colonization history of a dispersal‐limited terrestrial vertebrate, the Japanese four‐lined ratsnake (Elaphe quadrivirgata), to reveal the number of times mainland populations have invaded the Izu Archipelago of Japan, the mainland sources of these colonists, and the time‐scale of colonization. We compare these results with those of past studies in an attempt to uncover general biogeographical patterns. Moreover, we briefly examine the significance of colonization history when evaluating the evolution of body size and melanism of the Izu Island E. quadrivirgata populations. Location The Izu Islands (Oshima, Toshima, Niijima, Shikine, Kozu, Tadanae and Mikura), a volcanic archipelago off the Pacific coast of central Japan. Methods We obtained DNA sequences of the mitochondrial cytochrome b gene (1117 base pairs) from 373 individual snakes sampled from seven of the Izu Islands and 25 mainland localities. We employed partitioned Bayesian phylogenetic analyses assuming a relaxed molecular clock to estimate phylogenetic relationships among extant haplotypes and to give an explicit temporal scale to the timing of clade divergence, colonization history and tempo of body‐size evolution. Moreover, we employed model‐based biogeographical analysis to calculate the minimum number of times E. quadrivirgata colonized the Izu Islands. Results We found evidence that three separate regions of the Izu Archipelago have been colonized independently from mainland ancestors within the past 0.58–0.20 Ma. The Izu Peninsula plus Oshima and Mikura were both colonized independently from lineages inhabiting eastern mainland Japan. The Toshima, Niijima, Shikine, Kozu and Tadanae populations all derive from a single colonization from western mainland Japan. Oshima has been subject to three or possibly four colonizations. Main conclusions These results support the hypothesis that the extreme body‐size disparity among island populations of this ratsnake evolved in situ. Moreover, the fact that the dwarf, melanistic population inhabiting Oshima descends from multiple mainland colonization events is evidence of an extremely strong natural selection pressure resulting in the rapid evolution of this unique morphology. These results contrast with theoretical predictions that natural selection pressures should play a decreased role on islands close to the mainland and/or subject to frequent or recent immigration.     

The role of disjunction and postglacial population expansion on phylogeographical history and genetic diversity of the circumboreal plant Chamaedaphne calyculata

In the last decade a number of studies has illustrated quite different phylogeographical patterns amongst plants with a northern present‐day geographical distribution, spanning the entire circumboreal region and/or circumarctic region and southern mountains. These works, employing several marker systems, have brought to light the complex evolutionary histories of this group. Here I focus on one circumboreal plant species, Chamaedaphne calyculata (leatherleaf), to unravel its phylogeographical history and patterns of genetic diversity across its geographical range. A survey of 29 populations with combined analyses of chloroplast DNA (cpDNA), internal transcribed spacer (ITS) and AFLP markers revealed structuring into two groups: Eurasian/north‐western North American, and north‐eastern North American. The present geographical distribution of C. calyculata has resulted from colonization from two putative refugial areas: east Beringia and south‐eastern North America. The variation of chloroplast DNA (cpDNA) and ITS sequences strongly indicated that the evolutionary histories of the Eurasian/north‐western North American and the north‐eastern North American populations were independent of each other because of a geographical disjunction in the distribution area and ice‐sheet history between north‐eastern and north‐western North America. Mismatch analysis using ITS confirmed that the present‐day population structure is the result of rapid expansion, probably since the last glacial maximum. The AFLP data revealed low genetic diversity of C. calyculata (P = 19.5%, H = 0.085) over the whole geographical range, and there was no evidence of loss of genetic diversity within populations in the continuous range, either at the margins or in formerly glaciated and nonglaciated regions. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 761–775.