Physiological consequences of captive conditions in water voles (Arvicola terrestris)

Re-introductions of captive-bred animals are increasingly common in wildlife conservation and it is important that they fulfil their potential. To foster this goal we examined variations in stress levels in a captive-bred population of water voles Arvicola terrestris in response to housing conditions and radio-collaring, using weight loss and leukocyte coping capacity (LCC) as measures of relative stress, to investigate the impacts of housing conditions, handling and radio-collaring on this species. Thirty-eight water voles (22 males and 16 females) were used in the investigation, 25 housed in outdoor enclosures and 13 in laboratory cages. During the 6-week study, LCC, body weight and urine refractive index (URI, an indicator of hydration levels) were recorded once a week for each individual in weeks 1, 2, 4 and 6. After the first sample, radio-collars were attached to 20 individuals (10 males and 10 females) taken from both housing types. Throughout the experiment laboratory-cage housed voles weighed less, had lower LCC scores – indicating a reduced ability to combat infection – and had higher URIs than outdoor-enclosure voles. This suggests that the laboratory-cage voles were more stressed and dehydrated than the outdoor-enclosure voles. Weights and LCC scores of both housing groups decreased as the study progressed, suggesting that elements of the study, such as repeated handling, may have caused stress to both groups. Evidence suggested a short-term effect of radio-collaring on immuno-competence. We conclude that captive housing conditions, repeated manipulation and radio-collaring had demonstrable physiological effects on the water voles studied. We recommend that the effects of husbandry and tagging practices upon captive-bred mammals be closely studied as part of the quest to improve the success of the re-introductions to which they contribute.     

Genetic structure,ecological versatility,and skull shape differentiation in Arvicola water voles (Rodentia,Cricetidae)

Water voles from the genus Arvicola display an amazing ecological versatility, with aquatic and fossorial populations. The Southern water vole (Arvicola sapidus) is largely accepted as a valid species, as well as the newly described Arvicola persicus. In contrast, the taxonomic status and evolutionary relationships within Arvicola amphibiussensu lato had caused a long-standing debate. The phylogenetic relationships among Arvicola were reconstructed using the mitochondrial cytochrome b gene. Four lineages within A. amphibiuss.l. were identified with good support: Western European, Eurasiatic, Italian, and Turkish lineages. Fossorial and aquatic forms were found together in all well-sampled lineages, evidencing that ecotypes do not correspond to distinct species. However, the Western European lineage mostly includes fossorial forms whereas the Eurasiatic lineage tends to include mostly aquatic forms. A morphometric analysis of skull shape evidenced a convergence of aquatic forms of the Eurasiatic lineage toward the typically aquatic shape of A. sapidus. The fossorial form of the Western European lineage, in contrast, displayed morphological adaptation to tooth-digging behavior, with expanded zygomatic arches and proodont incisors. Fossorial Eurasiatic forms displayed intermediate morphologies. This suggests a plastic component of skull shape variation, combined with a genetic component selected by the dominant ecology in each lineage. Integrating genetic distances and other biological data suggest that the Italian lineage may correspond to an incipient species (Arvicola italicus). The three other lineages most probably correspond to phylogeographic variations of a single species (A. amphibius), encompassing the former A. amphibius, Arvicola terrestris, Arvicola scherman, and Arvicola monticola.     

Widespread gene flow and high genetic variability in populations of water voles Arvicola terrestris in patchy habitats

Theory predicts that the impact of gene flow on the genetic structure of populations in patchy habitats depends on its scale and the demographic attributes of demes (e.g. local colony sizes and timing of reproduction), but empirical evidence is scarce. We inferred the impact of gene flow on genetic structure among populations of water voles Arvicola terrestris that differed in average colony sizes, population turnover and degree of patchiness. Colonies typically consisted of few reproducing adults and several juveniles. Twelve polymorphic microsatellite DNA loci were examined. Levels of individual genetic variability in all areas were high ( H _O= 0.69–0.78). Assignments of juveniles to parents revealed frequent dispersal over long distances. The populations showed negative F _IS values among juveniles, F _IS values around zero among adults, high F _ST values among colonies for juveniles, and moderate, often insignificant, F _ST values for parents. We inferred that excess heterozygosity within colonies reflected the few individuals dispersing from a large area to form discrete breeding colonies. Thus pre-breeding dispersal followed by rapid reproduction results in a seasonal increase in differentiation due to local family groups. Genetic variation was as high in low-density populations in patchy habitats as in populations in continuous habitats used for comparison. In contrast to most theoretical predictions, we found that populations living in patchy habitats can maintain high levels of genetic variability when only a few adults contribute to breeding in each colony, when the variance of reproductive success among colonies is likely to be low, and when dispersal between colonies exceeds nearest-neighbour distances.     

Functional morphology of the ear in fossorial rodents, Microtus arvalis and Arvicola terrestris

Functionally relevant features and parameters of the outer, middle, and inner ear were studied morphologically and morphometrically in two species of voles, smaller Microtus arvalis and larger Arvicola terrestris. The findings in these fossorial (i.e., burrowing) rodents with components of surface activity were compared with respective findings reported for taxonomically related muroid rodents representing the same size classes but different eco-morphotypes: obligate subterranean rodents (Ellobius talpinus and Spalax ehrenbergi superspecies) and generalized rodents (Mus domesticus and Rattus norvegicus). The ear in voles was characterized by traits reported for subterranean rodents. The eardrum was round, without a distinct pars flaccida, and had an area of 5.4 mm2 in M. arvalis and 9 mm2 in A. terrestris. The middle ear exhibited reduced goniale, enlarged incus nearly parallel to the manubrium of the malleus. The malleus-incus lever ratio amounted to 2.1 (M. arvalis) and 2.0 (A. terrestris). The malleus-incus complex weighed about 0.8 mg in both vole species. The stapedial footplate had an area of 0.3 mm2 in M. arvalis and 0.4 mm2 in A. terrestris. The cochlea had 2.3 coils in both vole species; the basilar membrane was 8.5 mm and 10.5 mm long in M. arvalis and A. terrestris, respectively. There were on average 1,030 (M. arvalis) and 1,220 (A. terrestris) inner hair cells, and 3,760 (M. arvalis) and 4,250 (A. terrestris) outer hair cells in the organ of Corti. In quantitative terms, all these (as well as some further) traits and parameters were intermediate (related to body size) between those reported for generalized rodents on the one hand and subterranean ones on the other. The sound transmission system of the ear seems to be best tuned to frequencies of about 8-16 kHz with a high-frequency cut-off at about 50-60 kHz. The ear of A. terrestris seems to be tuned to somewhat lower frequencies than that in M. arvalis. In this aspect as well as regarding hearing sensitivity (as judged from the mechanical transmission parameters), voles can be considered intermediate not only in their lifestyle but also in their hearing abilities between the subterranean rodents (mole-vole and blind mole-rat) and the surface dwellers (house mouse and Norway rat).     

Parentage assignment detects frequent and large-scale dispersal in water voles

Estimating the rate and scale of dispersal is essential for predicting the dynamics of fragmented populations, yet empirical estimates are typically imprecise and often negatively biased. We maximized detection of dispersal events between small, subdivided populations of water voles (Arvicola terrestris) using a novel method that combined direct capture-mark-recapture with microsatellite genotyping to identify parents and offspring in different populations and hence infer dispersal. We validated the method using individuals known from trapping data to have dispersed between populations. Local populations were linked by high rates of juvenile dispersal but much lower levels of adult dispersal. In the spring breeding population, 19% of females and 33% of males had left their natal population of the previous year. The average interpopulation dispersal distance was 1.8 km (range 0.3-5.2 km). Overall, patterns of dispersal fitted a negative exponential function. Information from genotyping increased the estimated rate and scale of dispersal by three- and twofold, respectively, and hence represents a powerful tool to provide more realistic estimates of dispersal parameters.     

Phylogeographic analysis delimits three evolutionary significant units of least chipmunks in North America and identifies unique genetic diversity within the imperiled Peñasco population

Although least chipmunks (Neotamias minimus) are a widely distributed North American species of least concern, the southernmost population, N. m. atristriatus (Peñasco least chipmunk), is imperiled and a candidate for federal listing as a subspecies. We conducted a phylogeographic analysis across the N. minimus range to assess genomic differentiation and distinctiveness of the N. m. atristriatus population. Additionally, we leveraged the historical component of sampling to conduct a temporal analysis of N. minimus genetic diversity and also considered climate change effects on range persistence probability by projecting a species distribution model into the IPCC5 RCP 2.6 and 8.5 scenarios. We identified three geographically structured groups (West, North, and South) that were supported by both mitochondrial and nuclear data. N. m. atristriatus grouped within a unique South subclade but were not reciprocally monophyletic from N. m. operarius, and nuclear genome analyses did not separate N. m. atristriatus, N. m. caryi, and N. m. operarius. Thus, while least chipmunks in the Southwest represent an evolutionary significant unit, subspecies distinctions were not supported and listing of the Peñasco population as a Distinct Population Segment of N. m. operarius may be warranted. Our results also support consideration of populations with North and West mitogenomes as two additional evolutionary significant units. We found that N. minimus genetic diversity declined by ~87% over the last century, and our models predicted substantial future habitat contraction, including the loss of the full contemporary ranges of N. m. atristriatus, N. m. arizonensis, and N. m. chuskaensis.     

Colonization history of north European field voles (Microtus agrestis) revealed by mitochondrial DNA

The genetic structure of field vole (Microtus agrestis) populations from northern Europe was examined by restriction fragment length polymorphisms of mitochondrial DNA (mtDNA) in 150 individuals from 67 localities. A total of 83 haplotypes was observed, most of which were rare and highly localized geographically. Overall nucleotide diversity was high (134%), but showed a tendency to decrease with higher latitude. Two major mtDNA lineages differing by 2% in nucleotide sequence were identified. A southern mtDNA lineage was observed in field voles from Britain, Denmark and southern and central Sweden, whereas voles from Finland and northern Sweden belonged to a northern lineage. The strict phylogeographic pattern suggests that the present population generic structure in field voles reflects glacial history: the two groups are derived from different glacial refugia, and recolonized Fennoscandia from two directions. A 150–200-km-wide secondary contact zone between the two mtDNA groups was found in northern Sweden. Distinct phylogeographic substructuring was observed within both major mtDNA groups.     

A multiplex panel of dinucleotide microsatellite markers for the water vole,Arvicola terrestris

We isolated and characterized nine polymorphic dinucleotide microsatellite loci in the fossorial vole Arvicola terrestris Scherman (Shaw). A multiplex panel comprising all nine loci was developed and its application to a set of 31 individuals allowed clear and easy characterization of allele sizes. The number of alleles range from three to 14 per locus with the observed heterozygosity ranging from 0.42 to 0.90. These markers will be useful for analysis of questions concerning population genetic structure and reproductive behaviour.     

Phylogeographic differentiation in the mitochondrial control region in the koala, Phascolarctos cinereus (Goldfuss 1817)

The koala, Phascolarctos cinereus, is a geographically widespread species endemic to Australia, with three currently recognized subspecies: P.c. adustus, P.c. cinereus, and P.c. victor. Intraspecific variation in the mitochondrial DNA (mtDNA) control region was examined in over 200 animals from 16 representative populations throughout the species’ range. Eighteen different haplotypes were defined in the ≈ 860 bp mtDNA control region, as determined by heteroduplex analysis/temperature gradient gel electrophoresis (HDA/TGGE). Any single population typically possessed only one or two haplotypes yielding an average within-population haplotypic diversity of 0.180 ± 0.003, and nucleotide diversity of 0.16%. Overall, mtDNA control region sequence diversity between populations averaged 0.67%, and ranged from 0% to 1.56%. Nucleotide divergence between populations averaged 0.51%, and ranged from 0% to 1.53%. Neighbour-joining methods revealed limited phylogenetic distinction between geographically distant populations of koalas, and tentative support for a single evolutionarily significant unit (ESU). This is consistent with previous suggestions that the morphological differences formalized by subspecific taxonomy may be interpreted as clinal variation. Significant differentiation in mtDNA-haplotype frequencies between localities suggested that little gene flow currently exists among populations. When combined with microsatellite analysis, which has revealed substantial differentiation among koala populations, we conclude that the appropriate short-term management unit (MU) for koalas is the local population.     

Cryptic divergent lineages of Pultenaea pauciflora M.B. Scott (Fabaceae: Mirbelieae) exhibit different evolutionary history

Genetic structure among disjunct population groups of Pultenaea pauciflora was assessed to determine the evolutionary history of this species as a basis for conservation management strategies. Analysis of individuals from all extant populations using 1737 amplified length polymorphism markers revealed two highly divergent genetic entities with strong geographical structuring. Populations located at Narrogin and Brookton clustered together in Bayesian assignment analysis with every individual optimally placed in a single cluster with complete membership. Genetic differentiation between populations in these two areas was very low. Populations at Boddington were highly divergent from those located at Narrogin and Brookton. All individuals from Boddington populations were optimally placed into a second cluster with complete membership. Populations located at Boddington maintain lower levels of allelic diversity, yet greater levels of mean heterozygosity than populations located at Narrogin and Brookton. The degree of genetic differentiation and different patterns of genetic diversity strongly suggest historical divergence and separate evolutionary influences on the two lineages that occur in different ecological habitat. These Evolutionary Significant Units are likely to represent two cryptic sister taxa in the extant populations currently recognized as P. pauciflora, and the reassessment of taxonomic and conservation status of both lineages is required. © 2013 State of Western Australia. Biological Journal of the Linnean Society © 2013 The Linnean Society of London     

Phylogeographic structure and past history of the circum-Mediterranean species Tomicus destruens Woll. (Coleoptera: Scolytinae)

Phylogeographic studies are often focused on temperate European species with relict footholds in the Mediterranean region. Past climatic oscillations usually induced range contractions and expansions from refugial areas located in southern Europe, and spatial distribution of genetic diversity show that northward expansions were usually pioneer-like. Actually, few studies have focused on circum-Mediterranean species, which probably were not influenced in the same way by climatic oscillations. We present the phylogeography of the bark beetle Tomicus destruens, which is restricted to the whole Mediterranean basin and the Atlantic coasts of North Africa and Portugal. We systematically sequenced 617 bp of the mitochondrial genes COI and COII for 42 populations (N = 219). Analysis revealed 53 haplotypes geographically structured in two clades, namely eastern and western clades, that diverged during the Pleistocene. A contact zone was identified along the Adriatic coast of Italy. Interestingly, we found contrasting levels of genetic structure within each clade. The eastern group was characterized by a significant phylogeographic pattern and low levels of gene flow, whereas the western group barely showed a spatial structure in haplotype distribution. Moreover, the main pine hosts were different between groups, with the Aleppo-brutia complex in the east and the maritime pine in the west. Potential roles of host species, climatic parameters and geographical barriers are discussed and the phylogeographic patterns are compared to classical models of postglacial recolonization in Europe.     

Metapopulation genetic structure in the water vole, Arvicola terrestris, in NE Scotland

The genetic structure of nine colonies of the water vole, Arvicola terrestris , in one area of NE Scotland was studied. Non-destructive samples from 478 individuals (mostly immature animals) were typed for 12 microsatellites. Cases of Hardy-Weinberg disequilibrium were frequent within all colonies. The five colonies in the inland part of the study area also showed frequent cases of linkage disequilibrium. All colonies showed high levels of genetic diversity (unbiased H = 0.52-0.74). All five colonies sampled in successive years showed significant annual changes in genetic composition. All colonies showed genetic differentiation from each other, whether measured by average 6, pairwise 9 or pairwise Nei's genetic distance. The spatial pattern of genetic differentiation was consistent with either a stepping-stone model over the whole study area or an island model within the coastal and inland parts and an intervening barrier to gene flow. The study suggested that the genetic structure of colonies of A. terrestris often departs from the equilibrium states assumed by traditional mefhods for the study of gene flow, and that a parentage-based approach would be fruitful.     

Molecular systematics of the Amazonian endemic genus Hylexetastes (Aves: Dendrocolaptidae): taxonomic and conservation implications

Hylexetastes woodcreepers are endemic to the terra firme forests of the Amazon basin. Currently, most taxonomic sources recognize two species of Hylexetastes (H. perrotii and H. stresemanni), each divided into three subspecies. Some authors maintain that the H. perrotii subspecies should be elevated to full species status. In particular, Hylexetastes perrotii brigidai is endemic to the eastern Amazon, the second Amazonian area of endemism (Xingu) most affected by deforestation and habitat degradation. Consequently, the taxonomic status of H. p. brigidai is of particular concern for conservation. Thus far, only morphological characters have been evaluated for the taxonomic delimitation of species and subspecies of Hylexetastes. We present a molecular phylogenetic analysis of all subspecies to help delimit Hylexetastes interspecific limits. Fragments of two mitochondrial (Cytb and ND2) and three nuclear genes (FGB5, G3PDH and MUSK) from 57 Hylexetastes specimens were sequenced. An ecological niche model was estimated to describe more accurately the potential distributions of taxa and to evaluate their vulnerability to ongoing deforestation. Phylogenetic analyses support the paraphyly of the polytypic H. perrotii as currently delimited and the elevation of Hylexetastes perrotii uniformis to full species rank, as well as the presence of three evolutionary significant units (ESUs) within this newly delimited species, including one grouping all H. p. brigidai specimens. Alternatively, under lineage-based species concepts, our results support at least five evolutionary species in Hylexetastes: H. stresemanni, H. undulatus, H. perrotii, H. uniformis and H. brigidai. Each of these taxa and ESUs are distributed in different interfluvial areas of the Amazon basin, which have different degrees of disturbance. Because they occupy the most heavily impacted region among all Hylexetastes ESUs, regular assessments of the conservation statuses of H. p. brigidai and both H. uniformis ESUs are paramount.     

Post‐weaning ontogeny of the mandible in fossorial water voles: ecological and evolutionary implications

Ventura, J. and Casado‐Cruz, M. 2011. Post‐weaning ontogeny of the mandible in fossorial water voles: ecological and evolutionary implications. —Acta Zoologica (Stockholm) 92 : 12–20. Geometric morphometrics was applied to the mandible of fossorial water voles (Arvicola terrestris monticola) to determine size and shape variations in this structure during post‐weaning ontogeny. The sample consisted of collection specimens obtained in the Aran Valley (Spain), which were grouped into six age classes. Mandible size and shape did not differ significantly between sexes, but between age classes. Mandible size accounted significantly for the shape variation. After the size‐related differences were removed, the mandible shape did not show significant sexual dimorphism but differences by age remained significant. The main shape changes occur between the third and tenth weeks of life and are related to the shift from suckling to a herbivorous diet. Although mandible shape was less remodelled after that age, an appreciable variation also occurs during adulthood. Age‐related changes lead to enhancing the digging potential of the mandible, which in adults becomes a robust structure with an increased surface and stronger crests for muscle insertion. As part of the mandible shape variation was not related to the size‐dependent adjustment and diet does not vary significantly between juvenile and adult voles, shape changes that occur during adulthood can be related to the mechanical stress derived from digging activities.     

Phylogeographic analysis of the threatened and endangered superconglutinate-producing mussels of the genus Lampsilis (Bivalvia: Unionidae)

Several species of freshwater unionid mussels in the genus Lampsilis exhibit a remarkable reproductive strategy. Female mussels of these species enclose their larvae in a minnow-like lure, called a 'superconglutinate', to attract piscivorous fishes. When a fish attempts to ingest the superconglutinate the lure ruptures and the larvae are released to parasitize the fish. Of the four species of mussel which exhibit this strategy and are endemic to the Gulf Coast drainages of the southeastern United States, three are protected under the Endangered Species Act, and one is recognized as imperiled. Phylogenetic analysis of nucleotide sequences of the mitochondrial 16S ribosomal RNA and the first subunit of the cytochrome oxidase c genes was conducted on 18 individual specimens representing these four species and six outgroup taxa. Phylogenetic analyses of these data support the monophyly of the superconglutinate-producing mussels, and indicates a strong geographical component to the data. The zoogeographic patterns of the four taxa included in the study are congruent with those seen in freshwater vertebrates, and are consistent with a vicariant pattern resulting from fluctuations in sea level during the Pleistocene. Despite the strong geographical structuring of the data, only one species, Lampsilis subangulata, was recovered as monophyletic. The authors attribute the lack of support for the monophyly of the remaining species to insufficient sequence variation and the recent origin of the ancestor of these taxa. Based on these data, any future captive breeding projects aimed at augmenting or re-establishing populations should do so only from the appropriate source populations so as to maintain the genetic integrity of these nascent species.     

Phylogeographic structure of brown trout Salmo trutta in Britain and Ireland: glacial refugia,postglacial colonization and origins of sympatric populations

The phylogeographical structure of brown trout Salmo trutta in Britain and Ireland was studied using polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis of four mitochondrial DNA segments (16S/ND1, ND5/6, COXIII/ND5 and ND5/12S). Analysis of 3636 individuals from 83 sites–morphotypes revealed a total of 25 haplotypes. These haplotypes were nested in seven two‐step clades. Although there was a clear geographical patterning to the occurrence of derived clades, admixture among ancestral clades was extensive throughout the studied area. A relevant feature of the data was that some populations contained mixtures of highly divergent clades. This type II phylogeographic pattern is uncommon in nature. Clade intermixing is likely to have taken place during earlier interglacials as well as since the Last Glacial Maximum. The anadromous life history of many S. trutta populations has probably also contributed to clade mixing. Based on the data presented here and published data, postglacial colonization of Britain and Ireland most likely involved S. trutta from at least five potential glacial refuges. Probable locations for such refugia were: south of England–western France, east of the Baltic Sea, western Ireland, Celtic Sea and North Sea. Ferox S. trutta, as defined by their longevity, late maturation and piscivory, exhibited a strong association with a particular clade indicating that they share a common ancestor. Current evidence indicates that the Lough Melvin gillaroo S. trutta and sonaghen S. trutta sympatric types diverged prior to colonization of Lough Melvin and, although limited gene flow has occurred since secondary contact, they have remained largely reproductively isolated due to inlet and outlet river spawning segregation. Gillaroo S. trutta may reflect descendents of a previously more widespread lineage that has declined due to habitat alterations particularly affecting outlet rivers. The mosaic‐like distribution of mtDNA lineages means that conservation prioritization in Britain and Ireland should be based on the biological characteristics of local populations rather than solely on evolutionary lineages.     

Phylogeographic structure in long‐tailed voles (Rodentia: Arvicolinae) belies the complex Pleistocene history of isolation,divergence, and recolonization of Northwest North America's fauna

Quaternary climate fluctuations restructured biodiversity across North American high latitudes through repeated episodes of range contraction, population isolation and divergence, and subsequent expansion. Identifying how species responded to changing environmental conditions not only allows us to explore the mode and tempo of evolution in northern taxa, but also provides a basis for forecasting future biotic response across the highly variable topography of western North America. Using a multilocus approach under a Bayesian coalescent framework, we investigated the phylogeography of a wide‐ranging mammal, the long‐tailed vole, Microtus longicaudus. We focused on populations along the North Pacific Coast to refine our understanding of diversification by exploring the potentially compounding roles of multiple glacial refugia and more recent fragmentation of an extensive coastal archipelago. Through a combination of genetic data and species distribution models (SDMs), we found that historical climate variability influenced contemporary genetic structure, with multiple isolated locations of persistence (refugia) producing multiple divergent lineages (Beringian or northern, southeast Alaska or coastal, and southern or continental) during glacial advances. These vole lineages all occur along the North Pacific Coast where the confluence of numerous independent lineages in other species has produced overlapping zones of secondary contact, collectively a suture zone. Finally, we detected high levels of neoendemism due to complex island geography that developed in the last 10,000 years with the rising sea levels of the Holocene.