Diversity Of Animal Populations Research Articles

The Impact Of Palm Oil Plantations On Bird Diversity In Palm Oil Estates In Nagari Salareh Aia, Palembayan Sub-District, Agam District

This study aimed to see the effect of the existence of oil palm agricultural land on bird populations in the Agam area of West Sumatra Province. Observations were made directly by taking primary and secondary data.The species of birds that were identified during the observations were Pycnonotus goiaver (Merbah Cerocok) important value index 68.75 %, Streptopelia chinensis (Tekukur) IVI 42.50, Prinia familiaris (Prenjak Java) IVI 35.00 %, Colocalia esculenta (Cow Swallow) IVI 18.75 %, Copsychus saularis musicus (Murai) IVI 13.75 %, Halcyon smyrnensis (Javanese gecko) IVI 8.75 %, Rhipidura javanica (Stripe fan) IVI 6.25 % and Porzana cinerea (White Eyebrow Rat) with IVI 6.25%. The diversity of bird species in the oil palm plantations is low because only 8 bird species were found. The results of this study were basic data that need to be developed because there are effects that need to be multiplied further. The existence of oil palm plantations has an effect on the diversity of animal populations, especially birds around the land.

Alternative model systems for cognitive variation: eusocial-insect colonies.

Understanding the origins and maintenance of cognitive variation in animal populations is central to the study of the evolution of cognition. However, the brain is itself a complex, hierarchical network of heterogeneous components, from diverse cell types to diverse neuropils, each of which may be of limited use to study in isolation or prohibitively challenging to manipulate in situ. Consequently, highly tractable alternative model systems may be valuable tools. Eusocial-insect colonies display emergent cognitive-like properties from relatively simple social interactions between diverse subunits that can be observed and manipulated while operating collectively. Here, we review the individual-scale mechanisms that cause group-level variation in how colonies solve problems analogous to cognitive challenges faced by brains, like decision-making, attention, and search.

Biometric variation of domestic animals in Rome from the Orientalizing/Archaic period to the Middle Ages

A large number of assemblages of animal remains have come to light in the modern city of Rome and have been studied over the past forty years, providing a large amount of information on animal consumption and exploitation from the Early Iron Age (9th c. BC) to the Late Middle Ages (13th c. AD). This long chronological period witnesses the succession of important historical events that have profoundly influenced all aspects, among them the urban landscape, the demography, but also the diet and all economic activities involving animals. Some papers devoted to the discussion of faunal data from single context or on particular topics and some overviews on animal consumption and management in ancient Rome have been already published, but a detailed analysis of biometric data has not yet completely carried out. Biometry is an important tool used in zooarchaeological studies that provides data on size variation in animal populations, contributing to our understanding of husbandry practices, focusing on breeding control and improvement in ancient time. This paper is devoted to the discussion of the results of the biometric analyses carried out with the LSI (Logarithm Size Index) method, in order to investigate on the variation of domestic animals in Rome from the Orientalizing/Archaic period to the Late Middle Ages.

Epigenetic variation in animal populations: Sources, extent, phenotypic implications, and ecological and evolutionary relevance

Laboratory experiments and fieldwork with asexually reproducing invertebrates and vertebrates clearly revealed that animal populations can produce substantial phenotypic variation despite genetic identity. This epigenetically caused phenotypic variation comes from two different sources, namely directional environmental induction and bed-hedging developmental stochasticity. Both occur together and are mediated by molecular epigenetic mechanisms like DNA methylation, histone modifications and microRNAs. These epigenetic mechanisms are also involved in insect polyphenism, phenotypic changes in early domestication, and gene expression change and chromatin rearrangement during speciation. Epigenetic variation is particularly important for asexual populations helping them to stay in the game of life when the environmental conditions change. However, it is also relevant for sexually reproducing populations, as shown for genetically impoverished invasive groups, cave animals and sessile taxa that cannot evade unfavourable environmental conditions. Experiments revealed that epigenetic marks can be transgenerationally inherited and persist for several generations. First evidence suggests that inherited epimutations with phenotypic effects may end-up in phenotype-fixing genetic mutations by accelerated mutation of methylated nucleotides. Refined concepts, suitable animal models, fast and affordable new omics techniques that require only small tissue samples, and appropriate data interpretation tools are now available enabling future investigations in ecological and evolutionary epigenetics with high accuracy.

Spatio-temporal processes drive fine-scale genetic structure in an otherwise panmictic seabird population

When and where animals breed can shape the genetic structure and diversity of animal populations. The importance of drivers of genetic diversity is amplified in island populations that tend to have more delineated gene pools compared to continental populations. Studies of relatedness as a function of the spatial distribution of individuals have demonstrated the importance of spatial organisation for individual fitness with outcomes that are conditional on the overall genetic diversity of the population. However, few studies have investigated the impact of breeding timing on genetic structure. We characterise the fine-scale genetic structure of a geographically-isolated population of seabirds. Microsatellite markers provide evidence for largely transient within-breeding season temporal processes and limited spatial processes, affecting genetic structure in an otherwise panmictic population of sooty terns Onychoprion fuscatus. Earliest breeders had significantly different genetic structure from the latest breeders. Limited evidence was found for localised spatial structure, with a small number of individuals being more related to their nearest neighbours than the rest of the population. Therefore, population genetic structure is shaped by heterogeneities in collective movement in time and to a lesser extent space, that result in low levels of spatio-temporal genetic structure and the maintenance of genetic diversity.

The Role of Stochasticity in the Origin of Epigenetic Variation in Animal Populations.

Epigenetic mechanisms such as DNA methylation modulate gene expression in a complex fashion are consequently recognized as among the most important contributors to phenotypic variation in natural populations of plants, animals, and microorganisms. Interactions between genetics and epigenetics are multifaceted and epigenetic variation stands at the crossroad between genetic and environmental variance, which make these mechanisms prominent in the processes of adaptive evolution. DNA methylation patterns depend on the genotype and can be reshaped by environmental conditions, while transgenerational epigenetic inheritance has been reported in various species. On the other hand, DNA methylation can influence the genetic mutation rate and directly affect the evolutionary potential of a population. The origin of epigenetic variance can be attributed to genetic, environmental, or stochastic factors. Generally less investigated than the first two components, variation lacking any predictable order is nevertheless present in natural populations and stochastic epigenetic variation, also referred to spontaneous epimutations, can sustain phenotypic diversity. Here, potential sources of such stochastic epigenetic variability in animals are explored, with a focus on DNA methylation. To this day, quantifying the importance of stochasticity in epigenetic variability remains a challenge. However, comparisons between the mutation and the epimutation rates showed a high level of the latter, suggesting a significant role of spontaneous epimutations in adaptation. The implications of stochastic epigenetic variability are multifold: by affecting development and subsequently phenotype, random changes in epigenetic marks may provide additional phenotypic diversity, which can help natural populations when facing fluctuating environments. In isogenic lineages and asexually reproducing organisms, poor or absent genetic diversity can hence be tolerated. Further implication of stochastic epigenetic variability in adaptation is found in bottlenecked invasive species populations and populations using a bet-hedging strategy.

Genome-Wide Association Study of Meat Quality Traits in Hanwoo Beef Cattle Using Imputed Whole-Genome Sequence Data.

The discovery of single nucleotide polymorphisms (SNP) and the subsequent genotyping of large numbers of animals have enabled large-scale analyses to begin to understand the biological processes that underpin variation in animal populations. In beef cattle, genome-wide association studies using genotype arrays have revealed many quantitative trait loci (QTL) for various production traits such as growth, efficiency and meat quality. Most studies regarding meat quality have focused on marbling, which is a key trait associated with meat eating quality. However, other important traits like meat color, texture and fat color have not commonly been studied. Developments in genome sequencing technologies provide new opportunities to identify regions associated with these traits more precisely. The objective of this study was to estimate variance components and identify significant variants underpinning variation in meat quality traits using imputed whole genome sequence data. Phenotypic and genomic data from 2,110 Hanwoo cattle were used. The estimated heritabilities for the studied traits were 0.01, 0.16, 0.31, and 0.49 for fat color, meat color, meat texture and marbling score, respectively. Marbling score and meat texture were highly correlated. The genome-wide association study revealed 107 significant SNPs located on 14 selected chromosomes (one QTL region per selected chromosome). Four QTL regions were identified on BTA2, 12, 16, and 24 for marbling score and two QTL regions were found for meat texture trait on BTA12 and 29. Similarly, three QTL regions were identified for meat color on BTA2, 14 and 24 and five QTL regions for fat color on BTA7, 10, 12, 16, and 21. Candidate genes were identified for all traits, and their potential influence on the given trait was discussed. The significant SNP will be an important inclusion into commercial genotyping arrays to select new breeding animals more accurately.

Can metric data be an effective tool for galliform skull identification in archaeological contexts?

Galliforms, or game birds, are commonly found in zooarchaeological assemblages but several taxa within the order (e.g. chicken, pheasant and grouse) are difficult to distinguish from one another morphologically. Osteometrics is a tool for understanding skeletal variation in animal populations that has been shown to be useful in distinguishing between closely related genera in galliform post-cranial elements. In this paper, we test whether metrics are also effective in identifying galliform skulls (crania and mandibles) to the genus level. Using osteometric data collected from nine North American gallinaceous genera, we found that size was the greatest source of variation within the order. Several dimensions (greatest height, smallest breadth between orbits and length of incisivum) on the cranium were successful in distinguishing Domestic chicken (Gallus gallus domesticus) from Ring-necked pheasant (Phasianus colchicus), while measurements on the mandible were not very effective in separating closely related taxa. The application of osteometrics to fragmentary bird skulls from an historic era site assemblage in New York was not effective in identifying birds beyond general size-classes even with the aid of morphology and comparative collections. This suggests that previous work identifying fragmentary skull remains to the species level is not accurate, and that more advanced methods need to be developed to identify morphological and metric variation between taxa in these fragmentary elements.

The gut microbiome as a driver of individual variation in cognition and functional behaviour.

Research into proximate and ultimate mechanisms of individual cognitive variation in animal populations is a rapidly growing field that incorporates physiological, behavioural and evolutionary investigations. Recent studies in humans and laboratory animals have shown that the enteric microbial community plays a central role in brain function and development. The 'gut-brain axis' represents a multi-directional signalling system that encompasses neurological, immunological and hormonal pathways. In particular it is tightly linked with the hypothalamic-pituitary-adrenal axis (HPA), a system that regulates stress hormone release and influences brain development and function. Experimental examination of the microbiome through manipulation of diet, infection, stress and exercise, suggests direct effects on cognition, including learning and memory. However, our understanding of these processes in natural populations is extremely limited. Here, we outline how recent advances in predominantly laboratory-based microbiome research can be applied to understanding individual differences in cognition. Experimental manipulation of the microbiome across natal and adult environments will help to unravel the interplay between cognitive variation and the gut microbial community. Focus on individual variation in the gut microbiome and cognition in natural populations will reveal new insight into the environmental and evolutionary constraints that drive individual cognitive variation.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

The Role of Introgressive Hybridization in Hypoxia Adaptation of the Tibetan Mastiff

The role of introgressive hybridization as a source of adaptive genetic variation in animal populations is generally unclear, although recent findings suggest it may be more important than previously anticipated. While there are a number of tools to detect introgression, a major challenge is to experimentally confirm that it has played a role in adaptation by documenting the phenotypic effects of introgressed alleles. Animals native to high‐altitude are excellent models for such experimental studies, as it is often possible to formulate clear a priori hypotheses about the adaptive significance of particular changes in phenotype (for example, increases or decreases in the oxygen affinity of hemoglobin [Hb]). There is evidence to suggest that the high‐altitude adaptation of the Tibetan mastiff is, in part, the result of adaptive introgresssion with the Tibetan wolf. One of the introgressed regions between the Tibetan wolf and mastiff spans the entire β‐Hb gene cluster and the upstream cis‐regulatory elements. This has resulted in two non‐synonymous amino acid substitutions in the Tibetan mastiff, with respect to domestic dogs, in each of the adult expressed β‐type globin genes. To assess the functional effects of these mutations, we have measured the Hb‐O2 affinity of Tibetan wolves, Tibetan mastiffs and domestic dogs. These analyses revealed that the high‐altitude canids have Hb‐O2 affinity that is increased relative to domestic dogs (Figure 1). Thus, introgressive hybridization with the Tibetan wolf has resulted in a phenotypic change to the Tibetan mastiff that increases blood‐O2 saturation under hypoxia.Support or Funding InformationThis work is supported by the National Institutes of Health, the National Science foundation, and the Chinese Academy of Sciences.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The sex-specific effects of diet quality versus quantity on morphology in Drosophila melanogaster.

Variation in the quality and quantity of nutrition is a major contributor to phenotypic variation in animal populations. Although we know much of how dietary restriction impacts phenotype, and of the molecular-genetic and physiological mechanisms that underlie this response, we know much less of the effects of dietary imbalance. Specifically, although dietary imbalance and restriction both reduce overall body size, it is unclear whether both have the same effect on the size of individual traits. Here, we use the fruit fly Drosophila melanogaster to explore the effect of dietary food versus protein-to-carbohydrate ratio on body proportion and trait size. Our results indicate that body proportion and trait size respond differently to changes in diet quantity (food concentration) versus diet quality (protein-to-carbohydrate ratio), and that these effects are sex specific. While these differences suggest that Drosophila use at least partially distinct developmental mechanisms to respond to diet quality versus quantity, further analysis indicates that the responses can be largely explained by the independent and contrasting effects of protein and carbohydrate concentration on trait size. Our data highlight the importance of considering macronutrient composition when elucidating the effect of nutrition on trait size, at the levels of both morphology and developmental physiology.

Mate choice for neutral and MHC genetic characteristics in Alpine marmots: different targets in different contexts?

Sexual selection through female mate choice for genetic characteristics has been suggested to be an important evolutionary force maintaining genetic variation in animal populations. However, the genetic targets of female mate choice are not clearly identified and whether female mate choice is based on neutral genetic characteristics or on particular functional loci remains an open question. Here, we investigated the genetic targets of female mate choice in Alpine marmots (Marmota marmota), a socially monogamous mammal where extra‐pair paternity (EPP) occurs. We used 16 microsatellites to describe neutral genetic characteristics and two MHC loci belonging to MHC class I and II as functional genetic characteristics. Our results reveal that (1) neutral and MHC genetic characteristics convey different information in this species, (2) social pairs show a higher MHC class II dissimilarity than expected under random mate choice, and (3) the occurrence of EPP increases when social pairs present a high neutral genetic similarity or dissimilarity but also when they present low MHC class II dissimilarity. Thus, female mate choice is based on both neutral and MHC genetic characteristics, and the genetic characteristics targeted seem to be context dependent (i.e., the genes involved in social mate choice and genetic mate choice differ). We emphasize the need for empirical studies of mate choice in the wild using both neutral and MHC genetic characteristics because whether neutral and functional genetic characteristics convey similar information is not universal.

Genome-wide linkage disequilibrium and genetic diversity in five populations of Australian domestic sheep

BackgroundKnowledge of the genetic structure and overall diversity of livestock species is important to maximise the potential of genome-wide association studies and genomic prediction. Commonly used measures such as linkage disequilibrium (LD), effective population size (Ne), heterozygosity, fixation index (FST) and runs of homozygosity (ROH) are widely used and help to improve our knowledge about genetic diversity in animal populations. The development of high-density single nucleotide polymorphism (SNP) arrays and the subsequent genotyping of large numbers of animals have greatly increased the accuracy of these population-based estimates.MethodsIn this study, we used the Illumina OvineSNP50 BeadChip array to estimate and compare LD (measured by r2 and D′), Ne, heterozygosity, FST and ROH in five Australian sheep populations: three pure breeds, i.e., Merino (MER), Border Leicester (BL), Poll Dorset (PD) and two crossbred populations i.e. F1 crosses of Merino and Border Leicester (MxB) and MxB crossed to Poll Dorset (MxBxP).ResultsCompared to other livestock species, the sheep populations that were analysed in this study had low levels of LD and high levels of genetic diversity. The rate of LD decay was greater in Merino than in the other pure breeds. Over short distances (<10 kb), the levels of LD were higher in BL and PD than in MER. Similarly, BL and PD had comparatively smaller Ne than MER. Observed heterozygosity in the pure breeds ranged from 0.3 in BL to 0.38 in MER. Genetic distances between breeds were modest compared to other livestock species (highest FST = 0.063) but the genetic diversity within breeds was high. Based on ROH, two chromosomal regions showed evidence of strong recent selection.ConclusionsThis study shows that there is a large range of genome diversity in Australian sheep breeds, especially in Merino sheep. The observed range of diversity will influence the design of genome-wide association studies and the results that can be obtained from them. This knowledge will also be useful to design reference populations for genomic prediction of breeding values in sheep.Electronic supplementary materialThe online version of this article (doi:10.1186/s12711-015-0169-6) contains supplementary material, which is available to authorized users.

Phylogeography and Pleistocene refugia of the Little OwlAthene noctuainferred from mtDNA sequence data

Pleistocene glaciations greatly affected the distribution of genetic diversity in animal populations. The Little Owl is widely distributed in temperate regions and could have survived the last glaciations in southern refugia. To describe the phylogeographical structure of European populations, we sequenced the mitochondrial cytochrome c oxidase I (COI) and control region (CR1) in 326 individuals sampled from 22 locations. Phylogenetic analyses of COI identified two deeply divergent clades: a western haplogroup distributed in western and northwestern Europe, and an eastern haplogroup distributed in southeastern Europe. Faster evolving CR1 sequences supported the divergence between these two main clades, and identified three subgroups within the eastern clade: Balkan, southern Italian and Sardinian. Divergence times estimated from COI with fossil calibrations indicate that the western and eastern haplogroups split 2.01–1.71 Mya. Slightly different times for splits were found using the standard 2% rate and 7.3% mtDNA neutral substitution rate. CR1 sequences dated the origin of endemic Sardinian haplotypes at 1.04–0.26 Mya and the split between southern Italian and Balkan haplogroups at 0.72–0.21 Mya, coincident with the onset of two Pleistocene glaciations. Admixture of mtDNA haplotypes was detected in northern Italy and in central Europe. These findings support a model of southern Mediterranean and Balkan refugia, with postglacial expansion and secondary contacts for Little Owl populations. Central and northern Europe was predominantly recolonized by Little Owls from Iberia, whereas expansion out of the Balkans was more limited. Northward expansion of the Italian haplogroup was probably prevented by the Alps, and the Sardinian haplotypes remained confined to the island. Results showed a clear genetic pattern differentiating putative subspecies. Genetic distances between haplogroups were comparable with those recorded between different avian species.

Relative importance of prey abundance and habitat structure as drivers of shorebird breeding success and abundance

AbstractUnderstanding large‐scale drivers of animal breeding densities and demography has a range of important uses, including informing conservation management. Given the threat of climate change, the importance of developing a process‐based understanding of variation in animal populations is increased to inform adaptive management. For a climate‐change sensitive species, the European Golden Plover Pluvialis apricaria, we use novel field‐collected data on large‐scale spatial variation in prey abundance and vegetation structure to understand drivers of breeding abundance and breeding success, and inform potential management responses. The abundance of the key prey, crane flies (Tipulidae), increased with altitude (a surrogate for temperature) and peat depth (a surrogate for soil moisture). Golden plover breeding densities were highest where vegetation was shortest, probably reflecting greater prey accessibility. In contrast, breeding success was not strongly related to vegetation height, but positively correlated with both crane fly abundance and daily minimum temperatures. When combined to model the number of likely successful pairs in any 1 year, the magnitude of vegetation height effect far exceeded that of crane fly abundance. Thus, for golden plover and other shorebirds sharing similar habitats, management to optimize breeding habitat (grazing or burning to promote short vegetation) may differ from management to promote breeding success (drain blocking to increase soil moisture and prey abundance). Adaptive management in the face of climate change should therefore include appropriate vegetation management, as well as maximizing prey abundance. More broadly, as the drivers of breeding density and demographic parameters may differ, we advocate that conservation practitioners collect not just information on species' distributions but also underpinning demographic processes when using science to inform management.

Combination of genetics and spatial modelling highlights the sensitivity of cod (Gadus morhua) population diversity in the North Sea to distributions of fishing

AbstractConserving genetic diversity in animal populations is important for sustaining their ability to respond to environmental change. However, the “between-population” component of genetic diversity (biocomplexity) is threatened in many exploited populations, particularly marine fish, where harvest management regions may be larger than the spatial extent of genetically distinct subpopulations. Using single-nucleotide polymorphism data, we delineated the geographic limits of three population units of Atlantic cod (Gadus morhua) in northwest European waters. Two of the populations cohabit the North Sea, and trawl survey data showed differing trends in their abundances. We developed a spatial model of these units to simulate population dynamics under spatial patterns of harvesting. Competition between units during the pelagic juvenile stages in the model led to suppression of the more localized northern North Sea (Viking) unit by the more widespread (Dogger) unit, and its premature extinction under some spatial patterns of fishing. Fishery catch limits for cod are set at the scale of the whole North Sea without regard to such subpopulation dynamics. Our model offers a method to quantify adjustments to regional fishing mortality rates to strike a balance between maximizing sustainable yield and conserving vulnerable populations.

Physiological, Behavioral and Maternal Factors That Contribute to Size Variation in Larval Amphibian Populations

Size variance among similarly aged individuals within populations is a pattern common to many organisms that is a result of interactions between intrinsic and extrinsic traits of individuals. While genetic and maternal effects, as well as physiological and behavioral traits have been shown to contribute to size variation in animal populations, teasing apart the influence of such factors on individual growth rates remain a challenge. Furthermore, tracing the effects of these interactions across life stages and in shaping adult phenotypes also requires further exploration. In this study we investigated the relationship between genetics, hatching patterns, behaviors, neuroendocrine stress axis activity and variance in growth and metamorphosis among same-aged larval amphibians. Through parallel experiments we found that in the absence of conspecific interactions, hatch time and to a lesser extent egg clutch identity (i.e. genetics and maternal effects) influenced the propensity for growth and development in individual tadpoles and determined metamorphic traits. Within experimental groups we found that variance in growth rates was associated with size-dependent foraging behaviors and responses to food restriction. We also found an inverse relationship between glucocorticoid (GC) hormone levels and body mass and developmental stage among group-reared tadpoles, which suggests that GC expression plays a role in regulating differing within-population growth trajectories in response to density-dependent conditions. Taken together these findings suggest that factors that influence hatching conditions can have long-term effects on growth and development. These results also raise compelling questions regarding the extent to which maternal and genetic factors influence physiological and behavioral profiles in amphibians.

MHC‐disassortative mate choice and inbreeding avoidance in a solitary primate

Sexual selection theory suggests that choice for partners carrying dissimilar genes at the major histocompatibility complex (MHC) may play a role in maintaining genetic variation in animal populations by limiting inbreeding or improving the immunity of future offspring. However, it is often difficult to establish whether the observed MHC dissimilarity among mates drives mate choice or represents a by-product of inbreeding avoidance based on MHC-independent cues. Here, we used 454-sequencing and a 10-year study of wild grey mouse lemurs (Microcebus murinus), small, solitary primates from western Madagascar, to compare the relative importance on the mate choice of two MHC class II genes, DRB and DQB, that are equally variable but display contrasting patterns of selection at the molecular level, with DRB under stronger diversifying selection. We further assessed the effect of the genetic relatedness and of the spatial distance among candidate mates on the detection of MHC-dependent mate choice. Our results reveal inbreeding avoidance, along with disassortative mate choice at DRB, but not at DQB. DRB-disassortative mate choice remains detectable after excluding all related dyads (characterized by a relatedness coefficient r>0), but varies slightly with the spatial distance among candidate mates. These findings suggest that the observed deviations from random mate choice at MHC are driven by functionally important MHC genes (like DRB) rather than passively resulting from inbreeding avoidance and further emphasize the need for taking into account the spatial and genetic structure of the population in correlative tests of MHC-dependent mate choice.

The genetic structure of a relict population of wood frogs

Habitat fragmentation and the associated reduction in connectivity between habitat patches are commonly cited causes of genetic differentiation and reduced genetic variation in animal populations. We used eight microsatellite markers to investigate genetic structure and levels of genetic diversity in a relict population of wood frogs (Lithobates sylvatica) in Rocky Mountain National Park, Colorado, where recent disturbances have altered hydrologic processes and fragmented amphibian habitat. We also estimated migration rates among subpopulations, tested for a pattern of isolation-by-distance, and looked for evidence of a recent population bottleneck. The results from the clustering algorithm in Program STRUCTURE indicated the population is partitioned into two genetic clusters (subpopulations), and this result was further supported by factorial component analysis. In addition, an estimate of FST (FST = 0.0675, P value <0.0001) supported the genetic differentiation of the two clusters. Estimates of migration rates among the two subpopulations were low, as were estimates of genetic variability. Conservation of the population of wood frogs may be improved by increasing the spatial distribution of the population and improving gene flow between the subpopulations. Construction or restoration of wetlands in the landscape between the clusters has the potential to address each of these objectives.

Habitat islands, genetic diversity, and gene flow in a Patagonian rodent.

The effects of terrestrial habitat islands on gene flow and genetic diversity in animal populations have been predicted and discussed in theoretical terms, but empirical data are needed to test these predictions and provide an understanding of the relationships of life-history characteristics to genetics of insular species. We studied saxicolous mice (Phyllotis xanthopygus) in Patagonia to explore genetic structure, phylogeography, and gene flow in a species inhabiting natural habitat islands. Phylogeographic analyses based on mtDNA sequences revealed two haplotype clades, which presumably reflect early Pleistocene factors that temporarily separated the mice into two geographically isolated groups. The Río Chubut, which lies within a glacial drainage basin bisecting northern Patagonia, might have affected gene flow in the species. Although we anticipated isolation by distance and founder phenomena associated with habitat islands, in some habitat patches we found evidence of high local genetic diversity. The amount of divergence in the mitochondrial cytochrome b gene (approximately 3.4%) in animals at a single locality could best be explained through a combination of historical factors and metapopulation source-sink theory. Demographic shifts, dispersal, and episodic recolonization are important in the life history and genetic population structure of P. xanthopygus.