Long‐term social structure of a resident community of Atlantic spotted dolphins,Stenella Frontalis,in the Bahamas 1991–2002

Long‐term social structure data on small delphinids is lacking for most species except the bottlenose dolphin. This study describes the long‐term social structure of one community of Atlantic spotted dolphins, Stenella frontalis, divided into three social clusters. Data from 12 yr were analyzed using SOCPROG 2.3. Coefficients of association (CoA) were calculated using the half‐weight index. The overall mean community CoA ranged from 0.09 to 0.12. Temporal analyses and mantel tests revealed significant differences between sex class associations due to high male‐male CoA (0.12–0.23) compared to female‐female and mixed sex CoA (0.08–0.10). Female associations were strongly influenced by reproductive status, calf care, and social familiarity, but not by age class. Male associations were strongly influenced by age, access to females, and alliance formation. Males showed two levels of alliance formation, long‐term first order pairs/trios (CoA 0.70–1.00) and shorter‐term second order alliances between two or more first order alliances (CoA 0.45–0.69), and a possible third level during interspecies interactions. Mating strategies, sex, and cluster formation shaped the social structure in this spotted dolphin community. Similar to many bottlenose dolphin studies, long‐term affiliations for spotted dolphins were correlated with age, sex, and reproductive status.     

Community structure and cluster definition of Atlantic spotted dolphins,Stenella frontalis,in the Bahamas

Fission‐fusion dynamics typical of many delphinid populations allow for a variety of social grouping patterns. Identifying these groupings is crucial before conducting a detailed social structure analysis. This study analyzed the structure of a population of Bahamian spotted dolphins, Stenella frontalis. Through long‐term observations and preliminary analysis, three clusters were defined: Northern, Central, and Southern. To quantitatively investigate these delineations, we conducted analysis on 12 yr of sighting data using SOCPROG 2.3. Coefficients of association (CoA) were calculated using the half‐weight index, with individuals sighted six or more times per pooled period (3 yr each). Nonmetric multidimensional scaling (MD), hierarchical agglomerative cluster analysis and Mantel tests were conducted to determine if any divisions were present. Mantel tests and MD plots analysis supported the delineations into the three clusters. Cluster analysis showed cluster groupings, but with less clear distinctions between the clusters. The amount and strength of associations were significantly higher within clusters than between clusters. Based on behavioral and geographic overlap, these clusters did not meet the definition of separate communities and thus were termed social clusters. These fine scale, within community divisions, are biologically and socially important aspects of their community and are crucial in understanding the dolphins’ social structure.     

High site fidelity,strong associations,and long‐term bonds: Short‐finned pilot whales off the island of Hawai‘i

Studies of short‐finned pilot whales suggest they travel in stable mixed‐sex groups composed of strongly associated individuals; however, temporal analyses of social structure are lacking. To examine site fidelity, association patterns, and temporal relationships, we analyzed data from 267 encounters of this species off the island of Hawai‘i from 2003 through 2007, identifying 448 distinctive individuals (68.1% seen more than once). About 72% of the whales were linked by association into a single social network, suggesting the possibility of multiple populations using the area. Sighting histories suggested that only some individuals exhibit high site fidelity. Individuals demonstrated preferential associations and community division was strongly supported by average‐linkage hierarchical cluster analysis of the association data. Nine longitudinally stable social units composed of key individuals and their constant companions were identified. Qualitative assignment of age and sex classes of unit members indicated that some segregation between adult males and female/calf pairs may occur. Temporal analyses of individuals encountered on the same day indicate stable long‐term associations. Differential patterns of residency and site fidelity were unexpected and may be indicative of multiple populations around the main Hawaiian Islands. The presence of a resident population demonstrating strong, long‐term site fidelity and associations off Hawai‘i Island may warrant special management considerations.     

Occurrence and social structure of Baird's beaked whales,Berardius bairdii,in the Commander Islands,Russia

The social structure of Baird's beaked whales is completely unstudied, and it is unknown if either females or males form long‐term social associations or occur in stable groups. In this paper we summarize our observations of individually identified animals over the span of 6 yr to provide insight on their long‐term social structure. We have identified 122 whales, with 28 of them encountered three times or more and thus included in the analysis of social structure. We found that the whales exhibited nonrandom patterns of social associations with some individuals preferentially associating with each other. Whales with more scarred skin had higher maximum association coefficients, which indicates that older animals and/or males were more inclined to form stable associations. Cluster analysis with a modularity test for gregariousness divided the whales into four clusters. Whales from the same clusters did not always occur together, but some individuals retained stable associations over several years. The strength of social relationships decayed over periods of months, with between‐year relationships showing little deviation from what would be expected if association was random. Generally these findings do not correspond to a stable society with fixed groups but instead suggest a fission‐fusion society with some stable alliances.     

Population genetic structure of the bank vole Myodes glareolus within its glacial refugium in peninsular Italy

It is now well established that Southern European peninsulas have been major glacial refugia for temperate species during Pleistocene climatic oscillations. However, substantial environmental changes occurred also within these peninsulas throughout the Pleistocene, raising questions about the role and interplay of various microevolutionary processes in shaping patterns of intraspecific diversity within these areas. Here, we investigate the patterns of genetic variation in the bank vole Myodes glareolus within the Italian peninsula. By using a panel of 13 microsatellite loci, we found more intraspecific variation than expected based on previous assessments. Indeed, both Bayesian and ordination‐based clustering analyses of variation recovered five main geographic/genetic clusters along the peninsula, with three clusters geographically restricted to the southern portion of the peninsula. This clustering is supported by previous evidences of some morphological distinctiveness among these populations. This pattern can be explained by a refugia‐within‐refugia scenario, with the occurrence of multiple sub‐refugia for the bank vole within the Italian peninsula, likely promoted by the major palaeo‐environmental changes which affected forested habitats within this area during the Pleistocene. Moreover, our results support a scenario whereby the high levels of intraspecific diversity observed within major Pleistocene refugia are better explained by dynamic microevolutionary processes occurred within these areas, rather than by long‐term demographic stability of refugial population. Finally, the narrow and isolated distribution of some of the identified lineages suggests the need for future assessments of their conservation and taxonomic status.     

Variation in offspring sex ratio of a long‐lived sexually dimorphic raptor,the Eastern Imperial Eagle Aquila heliaca

Sex ratio theory attempts to explain observed variation in offspring sex ratio at both the population and the brood levels. In the context of low‐fecundity organisms producing high‐investment offspring, the drivers of adaptive variation in sex ratio are incompletely understood. For raptors that display reverse sexual dimorphism (RSD), preferential allocation of resources to the putatively cheaper sex (male) may be a response to environmental, social or demographic stressors. To assess the extent of skew in offspring sex ratios and to evaluate possible dietary, environmental and demographic correlates of such skew to long‐lived RSD avian species, we evaluated the offspring sex ratio of 219 chicks from 119 broods in 30 territories of Eastern Imperial Eagles Aquila heliaca across 7 years and four regions at a nature reserve in Kazakhstan. Only in one region in 1 year of our study did the offspring sex ratio differ significantly from parity (10 males : 1 female in 11 territories). Whereas offspring sex ratios were independent of dietary diversity, precipitation, temperature and productivity, we found that year had a moderate effect on brood sex ratio within territories. Our results provide limited evidence of brood sex manipulation in these populations of Eastern Imperial Eagles, and no mechanistic insight into predictions associated with it. Stochastic variation is likely to explain much of the fluctuation we observed in sex ratios, but our observations are also consistent with the hypothesis that sex‐ratio manipulation may occur irregularly, in concurrence with atypical environmental or demographic conditions that fluctuate at a time scale longer than that of our 7‐year study.     

Bottlenose dolphin (Tursiops truncatus) social structure in the Shannon Estuary,Ireland, is distinguished by age‐ and area‐related associations

Social and network analyses that incorporate information on individuals within a population enhance our knowledge of complex species. In this study, the social structure of wild bottlenose dolphins in the Shannon Estuary, Ireland, was analyzed by examining the dynamics of the whole population and then of individuals classed by sex, age, and area. One hundred and twenty‐one dolphins were identified during 522 sightings between 2012 and 2015. The mean half‐weight association index (HWI) of the population was 0.07 ± 0.02. The highest HWIs for individuals of known sex were for female‐male pairs. Mean within‐class HWI was significantly higher than mean between‐class HWI for both age and area classes. Ordinations and sociograms were used to visualize social networks. Permutation tests revealed nonrandom associations for the population overall and both between and within classes. Temporal analyses showed associations persisting for >1,000 d. The whole population's best fit model was for two levels of casual acquaintances. Movement analyses demonstrated the use of the inner estuary by only 25% of the population revealing a potential community division by area. The difference between mean HWI when socializing (0.09 ± 0.03) compared to foraging (0.06 ± 0.03) was significant. These results highlight the importance of localized research, reflecting the complexity found in bottlenose dolphin societies globally.     

Dusky dolphin (Lagenorhynchus obscurus) social structure characterized by social fluidity and preferred companions

Many coastal delphinids exhibit social structures with a high degree of fission‐fusion dynamics. However, little is known about fission‐fusion dynamics in semipelagic delphinids such as dusky dolphins (Lagenorhynchus obscurus). We analyzed dusky dolphin social structure in a winter foraging habitat in New Zealand. We examined the population‐level societal attributes of preferred/avoided companions, behaviorally specific preferred/avoided companions, and simple ratio (SR) association index strength and distribution and the dyad‐level societal attribute of temporal patterning of associations. We identified 741 individuals; 99 met inclusion criteria for analysis. Long‐term and short‐term preferred/avoided companions were present in the pooled (6 yr) and annual samples. Individuals were observed to form long‐term but not short‐term preferred/avoided companions during all behavioral states. Mean and maximum SRs were 0.03 ± 0.01 SD and 0.40 ± 0.20 SD, respectively. Temporal analysis indicated that individuals associated preferentially throughout the study period. Dusky dolphins exhibited high social fluidity, as indicated by many weak and few strong associations. However, there was stability as individuals were observed to form behaviorally specific preferred/avoided companions and associate preferentially throughout the 6 yr period. Dusky dolphins thus display a dynamic social structure where overall low levels of bonding are juxtaposed against a subset of the population that forms strong bonds.     

Population genetic structure,migration, and polyploidy origin of a medicinal species Gynostemma pentaphyllum (Cucurbitaceae)

Gynostemma pentaphyllum, a member of family Cucurbitaceae, is a perennial creeping herb used as a traditional medicinal plant in China. In this study, six polymorphic nSSR and four EST‐SSR primers were used to genotype 1,020 individuals in 72 wild populations of G. pentaphyllum. The genetic diversity and population structure were investigated, and ecological niche modeling was performed to reveal the evolution and demographic history of its natural populations. The results show that G. pentaphyllum has a low level of genetic diversity and high level of variation among populations because of pervasive asexual propagation, genetic drift, and long‐term habitat isolation. Results of the Mantel test demonstrate that the genetic distance and geographic distance are significantly correlated among G. pentaphyllum natural populations. The populations can be divided into two clusters on the basis of genetic structure. Asymmetrical patterns of historical gene flow were observed among the clusters. For the contemporary, almost all the bidirectional gene flow of the related pairs was symmetrical with slight differences. Recent bottlenecks were experienced by 34.72% of the studied populations. The geographic range of G. pentaphyllum continues to expand northward and eastward from Hengduan Mountains. The present distribution of G. pentaphyllum is a consequence of its complex evolution. Polyploidy in G. pentaphyllum is inferred to be polygenetic. Finally, G. pentaphyllum is a species in need of protection, so in situ and ex situ measures should be considered in the future.     

Evolution of sociality in spiders leads to depleted genomic diversity at both population and species levels

Across several animal taxa, the evolution of sociality involves a suite of characteristics, a “social syndrome,” that includes cooperative breeding, reproductive skew, primary female‐biased sex ratio, and the transition from outcrossing to inbreeding mating system, factors that are expected to reduce effective population size (Ne). This social syndrome may be favoured by short‐term benefits but come with long‐term costs, because the reduction in Ne amplifies loss of genetic diversity by genetic drift, ultimately restricting the potential of populations to respond to environmental change. To investigate the consequences of this social life form on genetic diversity, we used a comparative RAD‐sequencing approach to estimate genomewide diversity in spider species that differ in level of sociality, reproductive skew and mating system. We analysed multiple populations of three independent sister‐species pairs of social inbreeding and subsocial outcrossing Stegodyphus spiders, and a subsocial outgroup. Heterozygosity and within‐population diversity were sixfold to 10‐fold lower in social compared to subsocial species, and demographic modelling revealed a tenfold reduction in Ne of social populations. Species‐wide genetic diversity depends on population divergence and the viability of genetic lineages. Population genomic patterns were consistent with high lineage turnover, which homogenizes the genetic structure that builds up between inbreeding populations, ultimately depleting genetic diversity at the species level. Indeed, species‐wide genetic diversity of social species was 5–8 times lower than that of subsocial species. The repeated evolution of species with this social syndrome is associated with severe loss of genomewide diversity, likely to limit their evolutionary potential.     

Contrasting Demographic Structure of Short‐ and Long‐lived Pioneer Tree Species on Amazonian Forest Edges

Although tropical forests have been rapidly converted into human‐modified landscapes, tree species response to forest edges remains poorly examined. In this study, we addressed four pioneer tree species to document demographic shifts experienced by this key ecological group and make inferences about pioneer response to forest edges. All individuals with dbh ≥ 1 cm of two short‐lived (Bellucia grossularioides and Cecropia sciadophylla) and two long‐lived species (Goupia glabra and Laetia procera) were sampled in 20 1‐ha forest edge plots and 20 1‐ha forest interior plots in Oiapoque and Manaus, Northeast and Central Amazon, respectively. As expected, pioneer stem density with dbh ≥ 1 cm increased by around 10–17‐fold along forest edges regardless of species, lifespan, and study site. Edge populations of long‐lived pioneers presented 84–94 percent of their individuals in sapling/subadult size classes, whereas edge populations of short‐lived pioneers showed 56–97 percent of their individuals in adult size classes. These demographic biases were associated with negative and positive net adult recruitment of long‐ and short‐lived pioneers, respectively. Our population‐level analyses support three general statements: (1) native pioneer tree species proliferate along forest edges (i.e., increased density), at least in terms of non‐reproductive individuals; (2) pioneer response to edge establishment is not homogeneous as species differ in terms of demographic structure and net adult recruitment; and (3) some pioneer species, particularly long‐lived ones, may experience population decline due to adult sensitivity to edge‐affected habitats.     

Unsustainable anthropogenic mortality disrupts natal dispersal and promotes inbreeding in leopards

Anthropogenic mortality of wildlife is typically inferred from measures of the absolute decline in population numbers. However, increasing evidence suggests that indirect demographic effects including changes to the age, sex, and social structure of populations, as well as the behavior of survivors, can profoundly impact population health and viability. Specifically, anthropogenic mortality of wildlife (especially when unsustainable) and fragmentation of the spatial distribution of individuals (home‐ranges) could disrupt natal dispersal mechanisms, with long‐term consequences to genetic structure, by compromising outbreeding behavior and gene flow. We investigate this threat in African leopards (Panthera pardus pardus), a polygynous felid with male‐biased natal dispersal. Using a combination of spatial (home‐range) and genetic (21 polymorphic microsatellites) data from 142 adult leopards, we contrast the structure of two South African populations with markedly different histories of anthropogenically linked mortality. Home‐range overlap, parentage assignment, and spatio‐genetic autocorrelation together show that historical exploitation of leopards in a recovering protected area has disrupted and reduced subadult male dispersal, thereby facilitating opportunistic male natal philopatry, with sons establishing territories closer to their mothers and sisters. The resultant kin‐clustering in males of this historically exploited population is comparable to that of females in a well‐protected reserve and has ultimately led to localized inbreeding. Our findings demonstrate novel evidence directly linking unsustainable anthropogenic mortality to inbreeding through disrupted dispersal in a large, solitary felid and expose the genetic consequences underlying this behavioral change. We therefore emphasize the importance of managing and mitigating the effects of unsustainable exploitation on local populations and increasing habitat fragmentation between contiguous protected areas by promoting in situ recovery and providing corridors of suitable habitat that maintain genetic connectivity.     

Familial social structure and socially driven genetic differentiation in Hawaiian short‐finned pilot whales

Social structure can have a significant impact on divergence and evolution within species, especially in the marine environment, which has few environmental boundaries to dispersal. On the other hand, genetic structure can affect social structure in many species, through an individual preference towards associating with relatives. One social species, the short‐finned pilot whale (Globicephala macrorhynchus), has been shown to live in stable social groups for periods of at least a decade. Using mitochondrial control sequences from 242 individuals and single nucleotide polymorphisms from 106 individuals, we examine population structure among geographic and social groups of short‐finned pilot whales in the Hawaiian Islands, and test for links between social and genetic structure. Our results show that there are at least two geographic populations in the Hawaiian Islands: a Main Hawaiian Islands (MHI) population and a Northwestern Hawaiian Islands/Pelagic population (F_ST and Φ_ST p < .001), as well as an eastern MHI community and a western MHI community (F_ST p = .009). We find genetically driven social structure, or high relatedness among social units and clusters (p < .001), and a positive relationship between relatedness and association between individuals (p < .0001). Further, socially organized clusters are genetically distinct, indicating that social structure drives genetic divergence within the population, likely through restricted mate selection (F_ST p = .05). This genetic divergence among social groups can make the species less resilient to anthropogenic or ecological disturbance. Conservation of this species therefore depends on understanding links among social structure, genetic structure and ecological variability within the species.     

Subspecies delineation amid phenotypic,geographic and genetic discordance in a songbird

Understanding the processes that drive divergence within and among species is a long‐standing goal in evolutionary biology. Traditional approaches to assessing differentiation rely on phenotypes to identify intra‐ and interspecific variation, but many species express subtle morphological gradients in which boundaries among forms are unclear. This intraspecific variation may be driven by differential adaptation to local conditions and may thereby reflect the evolutionary potential within a species. Here, we combine genetic and morphological data to evaluate intraspecific variation within the Nelson's (Ammodramus nelsoni) and salt marsh (Ammodramus caudacutus) sparrow complex, a group with populations that span considerable geographic distributions and a habitat gradient. We evaluated genetic structure among and within five putative subspecies of A. nelsoni and A. caudacutus using a reduced‐representation sequencing approach to generate a panel of 1929 SNPs among 69 individuals. Although we detected morphological differences among some groups, individuals sorted along a continuous phenotypic gradient. In contrast, the genetic data identified three distinct clusters corresponding to populations that inhabit coastal salt marsh, interior freshwater marsh and coastal brackish–water marsh habitats. These patterns support the current species‐level recognition but do not match the subspecies‐level taxonomy within each species—a finding which may have important conservation implications. We identified loci exhibiting patterns of elevated divergence among and within these species, indicating a role for local selective pressures in driving patterns of differentiation across the complex. We conclude that this evidence for adaptive variation among subspecies warrants the consideration of evolutionary potential and genetic novelty when identifying conservation units for this group.     

Distinct haplotype structure at the innate immune receptor Toll‐like receptor 2 across bank vole populations and lineages in Europe

Parasite‐mediated selection may contribute to the maintenance of genetic variation at host immune genes over long time scales. To date, the best evidence for the long‐term maintenance of immunogenetic variation in natural populations comes from studies on the major histocompatibility complex (MHC) genes, whereas evidence for such processes from other immune genes remains scarce. In the present study, we show that, despite pronounced population differentiation and the occurrence of numerous private alleles within populations, the innate immune gene Toll‐like receptor 2 (TLR2) displays a distinct haplotype structure in 21 bank vole (Myodes glareolus) populations across Europe. Haplotypes from all populations grouped in four clearly differentiated clusters, with the three main clusters co‐occurring in at least three previously described mitochondrial lineages. This pattern indicates that the distinct TLR2 haplotype structure may precede the split of the mitochondrial lineages 0.19–0.56 Mya and suggests that haplotype clusters at this innate immune receptor are maintained over prolonged time in wild bank vole populations.     

Long‐term decline despite conservation efforts questions Eurasian Stone‐curlew population viability in intensive farmlands

Agricultural intensification over the past decades has led to a generalized decline in farmland biodiversity. Farmland birds are particularly exposed to rapid changes in habitat and reduced food resources or availability. Understanding how farmland specialists can be preserved and their populations enhanced are major challenges for this century. Based on a long‐term (19‐year) study of a Eurasian Stone‐curlew Burhinus oedicnemus population, we estimated the demographic parameters, including clutch size, egg volume, hatching success, survival rate and apparent population size. Demographic rates found for this French population were, on average, comparable to those found elsewhere in Europe. However, all demographic parameters showed negative trends, including a dramatic decline in the local population (26% decline over 14 years) and a 10% decline in adult survival rate over 11 years. Such a long‐term decline, despite on‐going conservation efforts, calls into question the overall sustainability of arable Stone‐curlew populations. We infer some of the possible causes of this decline, in particular food shortage, and discuss how this pattern could be reversed through conservation measures applicable at very large spatial scales.     

Fine‐scale genetic structuring in a group‐living lizard,the gidgee skink (Egernia stokesii)

By constraining gene flow, group living and natal philopatry can result in fine‐scale genetic structure. Although the genetic structure of some group‐living lizards has been characterised, studies are few compared with those for group‐living bird and mammal species. The Egerniinae group of lizards exhibits a high diversity of social structures, making it a useful group for comparative studies of genetic structure across a broader range of social taxa. A well‐studied member of Egerniinae is Egernia stokesii, a lizard that forms long‐term pair bonds and stable social groups and exhibits natal philopatry and limited dispersal. Evidence exists for consistent E. stokesii social structure across seven close but disconnected rocky outcrops within a 40 × 10 km area. We used summary statistics, analysis of molecular variance, Bayesian clustering, and discriminant analysis of principal components to assess if E. stokesii exhibit a consistent pattern of fine‐scale genetic structure across the same seven outcrops. Due to E. stokesii social structure and constrained dispersal, we predicted significant genetic structuring – based on microsatellite markers – among outcrops. We found significant fine‐scale genetic structuring and evidence for two genetic clusters. We discuss features of E. stokesii biology and ecology that may explain our findings. Some rocky outcrops, and some social groups, contained lizards from both genetic clusters. An examination of the composition of mixed cluster social groups did not detect any notable patterns. Therefore, further work is necessary to identify how the observed patterns may have arisen. Future investigations in E. stokesii and other group‐living lizard species are likely to contribute greatly to our understanding of the genetic consequences of group living.     

Population genetic patterns among social groups of the endangered Central American spider monkey (Ateles geoffroyi) in a human‐dominated landscape

Spider monkeys (Genus: Ateles) are a widespread Neotropical primate with a highly plastic socioecological strategy. However, the Central American species, Ateles geoffroyi, was recently re‐listed as endangered due to the accelerated loss of forest across the subcontinent. There is inconsistent evidence that spider monkey populations could persist when actively protected, but their long‐term viability in unprotected, human‐dominated landscapes is not known. We analyzed noninvasive genetic samples from 185 individuals in 14 putative social groups on the Rivas Isthmus in southwestern Nicaragua. We found evidence of weak but significant genetic structure in the mitochondrial control region and in eight nuclear microsatellite loci plus negative spatial autocorrelation in Fst and kinship. The overall pattern suggests strong localized mating and at least historical female‐biased dispersal, as is expected for this species. Heterozygosity was significantly lower than expected under random mating and lower than that found in other spider monkey populations, possibly reflecting a recent decline in genetic diversity and a threat from inbreeding. We conclude that despite a long history of human disturbance on this landscape, spider monkeys were until recently successful at maintaining gene flow. We consider the recent decline to be further indication of accelerated anthropogenic disturbance, but also of an opportunity to conserve native biodiversity. Spider monkeys are one of many wildlife species in Central America that is threatened by land cover change, and an apt example of how landscape‐scale conservation planning could be used to ensure long‐term persistence.     

Extreme genetic structure in a social bird species despite high dispersal capacity

Social barriers have been shown to reduce gene flow and contribute to genetic structure among populations in species with high cognitive capacity and complex societies, such as cetaceans, apes and humans. In birds, high dispersal capacity is thought to prevent population divergence unless major geographical or habitat barriers induce isolation patterns by dispersal, colonization or adaptation limitation. We report that Iberian populations of the red‐billed chough, a social, gregarious corvid with high dispersal capacity, show a striking degree of genetic structure composed of at least 15 distinct genetic units. Monitoring of marked individuals over 30 years revealed that long‐distance movements over hundreds of kilometres are common, yet recruitment into breeding populations is infrequent and highly philopatric. Genetic differentiation is weakly related to geographical distance, and habitat types used are overall qualitatively similar among regions and regularly shared by individuals of different populations, so that genetic structure is unlikely to be due solely to isolation by distance or isolation by adaptation. Moreover, most population nuclei showed relatively high levels of genetic diversity, suggesting a limited role for genetic drift in significantly differentiating populations. We propose that social mechanisms may underlie this unprecedented level of genetic structure in birds through a pattern of isolation by social barriers not yet described, which may have driven this remarkable population divergence in the absence of geographical and environmental barriers.     

Population viability analysis of Walia ibex (Capra walie) at Simien Mountains National Park (SMNP), Ethiopia

Population viability analysis (PVA) has been applied to the management of many threatened populations. The objective of this study was, therefore, to estimate the PVA of Walia ibex at the Simen Mountains National Park, in the north‐central highlands of Ethiopia, with respect to population growth parameters, the probability of the population reaching a lower extinction threshold and the mean time to extinction. Direct census of the population was carried out in 2009. Secondary census data were also collected from park authorities and the literature reviews. The result revealed that the estimates of the infinitesimal mean, μ (0.04117) was greater than the infinitesimal variance, σ² (0.0219). The probability that the population reaches the extinction threshold was very low (0.15%). The mean time required for the counts to decline from the existing population size to one individual animal was 160 years. But threatened species are adversely affected by changes in landscape. These changes can be brought by short‐ and long‐term human and climate change impacts, respectively. Therefore, with the absence of environmental and demographic stochasticity and, with the application of appropriate reproductions and habitat management, the population of Walia ibex will be viable and reaches its mean time of extinctions after 160 years.