Population Extinction Risk Research Articles

Living Beyond the Edge: Impacts of Climate Change on Rock Lizards at the Niche Margin

ABSTRACTEctotherms are particularly threatened by climate change because they are strictly reliant on environmental conditions for homeostasis. Increasing environmental temperatures may approach the species' critical thermal maximum, with deleterious effects on individual thermoregulation capacities. This study tests the hypothesis developed in a recent work that under ongoing global warming populations living in sites at the warm edge of the species' thermal niche will suffer a disruption of the thermoregulation process, with detrimental effects at the individual and population level. We collected individual measurements and temperature data for Mediterranean endemic rock lizards, across the entire distribution range of the species and during two different sampling periods ~20 years apart to compare thermoregulation coefficient (C), body condition index (BCI) and population size under different climatic conditions. We found that C and BCI vary across space and time following a linear pattern along the thermal niche gradient (Niche Margin Effect, NME) until a threshold temperature, beyond which the NME is disrupted. This threshold temperature indicates the warm edge of the species' thermal niche. A slightly higher temperature marks the threshold at which we observed significant population declines over the 20‐year study period in the warmest sites. This suggests a lagged response of population trends to climate warming. This study suggests a mechanism of disruption of homeostatic processes when the warm margin of the thermal niche is reached and indicates that individual parameters such as thermoregulation coefficient and body condition, rather than demographic trends, are key indicators for an early detection of population extinction risk. The multipopulation approach implemented in our study allows to identify the niche edge that underlies species' vulnerability to global warming, and to identify populations suffering negative effects of climate change before demographic collapse. This might allow to plan appropriate mitigation measures and management strategies to avoid local extinctions.

Dynamics of predator-prey system with the consequences of double Allee effect in prey population.

A underlying complex dynamical behavior of double Allee effects in predator-prey system is studied in this article to understand the predator-prey relation more intensely from different aspects. We first propose a system with the Caputo sense fractional-order predator-prey system incorporating the Allee effect in prey populations to explain how the memory effect can change the different emergent states. Local stability analysis is analyzed by applying Matignon's condition for the FDE system. Further, we consider a discrete-time system to show the influence of double Allee effects in non-overlapping generations. For discrete-time system, different bifurcations like Neimark-Sacker, flip bifurcations, irregularity in periodic oscillations, are observed. Irregularity occurs through a period-doubling cascade which is a common route to chaos in a dynamical sense. Maximum Lyapunov exponent (MLE) is shown to illustrate the irregular behaviors of discrete-time systems. The Allee effect influences system stability where the strong Allee effect enhances system stability whereas the stability is lost for the weak Allee effect. The extinction risk of populations in the presence of the Allee effect is a concerning issue. We have insight into how all populations survive along with stable extinction equilibrium. Our proposed systems exhibit different alternative states. Multiple stable attractor basins are plotted to depict the different alternative states of the FDE system as well as the discrete-time system. Initial population densities play a key role in the coexistence of all the populations otherwise there is a risk of species extinction. Besides analytical results, numerical simulation is performed to valid our analytical findings of different dynamical states like bifurcation, stability, irregularity as well as multi-stability.

Nutrient-rich spatial refuges buffer against extinction and promote evolutionary rescue in evolving microbial populations.

Microbial populations are often exposed to long-term abiotic disturbances, which can reduce population viability and cause local extinction. Eco-evolutionary theory suggests that spatial refuges can facilitate persistence and evolutionary rescue. However, one drawback of spatial refuges is reduced exposure to nutrients such as carbon and oxygen, suggesting the protective effect of refuges depends on the interplay between environmental conditions and the degree of stress. Here, we test this general idea using mathematical modelling, and experimental evolution of the model bacterium Pseudomonas fluorescens SBW25 under salinity stress. As our model predicted, we find that the ability of spatial refuges to rescue evolving populations from extinction crucially depends on nutrient availability. Populations evolving under salinity stress where nutrient-rich spatial refuges were available, harboured clones that displayed enhanced salt resistance, indicating that nutrient-rich spatial refuges can facilitate evolutionary rescue. Furthermore, while control-salinity-evolved populations adapted to spatial structure by evolving enhanced motility (likely through parallel mutations in PFLU_4551, a predicted aerotaxis response regulator), this phenotype was constrained under high salinity, because increased motility negates the benefits of a spatial refuge. Our results reveal a general interplay between spatial refuges and nutrient availability that could be leveraged to reduce extinction risk in natural populations.

Long live the cat: Ocelot population viability in a planned reintroduced population in Texas, USA

AbstractReintroductions are often needed to recover carnivore populations and restore ecological processes. Felids are common subjects of reintroduction efforts, but published population models informing felid reintroduction plans are uncommon, and poor planning has sometimes caused issues in felid reintroduction programs. In the United States, ocelots (Leopardus pardalis pardalis) are classified as endangered, and recovery requires population expansion into historic habitat. A multi‐organization effort is underway to establish a new ocelot population in Texas by releasing ocelots into an area of 478 km2 of suitable habitat in ocelots' historic but now unoccupied range. In this study, we used population viability analyses to compare different ocelot reintroduction strategies for the identified reintroduction area. Based on a potential ocelot breeding program's limitations, we modeled reintroduction using a founding population of no more than six ocelots and no more than four ocelots released per year for no more than 15 subsequent years. Within these limitations, we assessed projected population abundances and extinction risks after 30 years for 20 different reintroduction strategies. We found that long‐term releases are necessary to establish a viable population; under conservative model assumptions, releasing six ocelots in the initial year and then releasing four individuals annually for an additional 10–15 years is necessary for attaining a projected population greater than 36.62 ocelots (baseline) with <6% extinction risk. We also found that ocelot population abundance is about equally sensitive to post‐release mortality and inbreeding depression. This highlights the importance of not only supporting reintroduced ocelots' survival but also managing for high genetic diversity in the reintroduction program. Further, we found that realistic but more liberal assumptions on the carrying capacity of the reintroduction area and the age of first reproduction for ocelots increase projected population abundances (53.95 individuals and 61.26 individuals, respectively), and thus reintroduction success. The model's sensitivity to carrying capacity suggests that long‐term habitat protection and expansion are among the most important management actions to support ocelot reintroduction. Our study establishes the first population viability model for an ocelot reintroduction plan anywhere across the species' wide geographic range, and it reinforces several key considerations for wildlife reintroduction efforts worldwide.

Increased incidences of cervical ribs in deer indicate extinction risk

Mammals as a rule have seven cervical vertebrae, a number which remains remarkably conserved. Occasional deviations of this number are usually due to the presence of cervical ribs on the seventh vertebra, indicating a homeotic transformation from a cervical rib-less vertebra into a thoracic rib-bearing vertebra. These transformations are often associated with major congenital abnormalities or pediatric cancers (pleiotropic effects) that are, at least in humans, strongly selected against. Based on data from Late Pleistocene mammoths (Mammuthus primigenius) and woolly rhinoceroses (Coelodonta antiquitatis) from the North Sea, we hypothesized that high incidences of cervical ribs in declining populations are due to inbreeding and/or adverse conditions impacting early pregnancies. In this study, we investigated the incidence of cervical ribs in an extinct Late Pleistocene megaherbivore, giant deer (Megaloceros giganteus) from Ireland and in the extant highly inbred Père David deer (Elaphurus davidianus) and in twenty other extant species. We show that the incidence of cervical ribs is exceptionally high in both the Irish giant deer and the Père David deer and much higher than in extant outbred deer. Our data support the hypothesis that inbreeding and genetic drift increase the frequencies of maladaptive alleles in populations at risk of extinction. The high incidence of cervical ribs indicates a vulnerable condition, which may have contributed to the extinction of megaherbivore species in the Late Pleistocene. We argue that cervical rib frequency may be a good proxy for extinction risk in inbred populations.

Cloudy with a chance of survival: Simulating the effects of climate, habitat, and management on the population viability of an at-risk lizard species

The spot-tailed earless lizards (STEL) are small, phrynosomatid lizards in the Holbrookia genus. Historically, these were considered two subspecies, the Plateau (Holbrookia lacerata lacerata) and Tamaulipan STEL (Holbrookia lacerata subcaudalis); however, each are now recognized as a distinct species (i.e., H. lacerata (plateau STEL) and H. subcaudalis (Tamaulipan STEL)). Recently, the plateau STEL was considered but not awarded federal protection under the Endangered Species Act by the U.S. Fish and Wildlife Service; however, much uncertainty remains about the status of the Tamaulipan STEL and a conclusive policy decision has not been made. In this study, we developed a hybrid theoretic-empirical demographic model and conducted a population viability analysis (PVA) of the Tamaulipan STEL (H. subcaudalis). We evaluated the role of multiple demographic, environmental, and anthropogenic parameters and assessed population-level effects and extinction risks via sensitivity experiments. The baseline simulation demonstrated that Tamaulipan STEL have a relatively low probability of extinction under best case scenario conditions; however, results of elasticity analysis of the baseline simulation and sensitivity analysis of demographic parameters demonstrated that increases in juvenile mortality had the greatest effect on population growth rate and extinction risk. Simulations of anthropogenic impacts showed that small increases in habitat loss (e.g., 2 %) had drastic negative effects on population size and persistence. Results from this study demonstrate the need for conservation and management actions aimed at protecting and increasing populations of young individuals (i.e., decreasing juvenile mortality) and promoting the conservation of available and suitable habitat for STEL throughout their range. These results must be considered in future conservation initiatives focused on this species to achieve successful conservation outcomes.

Generalism in species interactions is more the consequence than the cause of ecological success.

Generalism in resource use is commonly considered a critical driver of population success, species distribution and extinction risk. This idea can be questioned as generalism may be a result rather than the cause of species abundance and range size. We tested these contrasting causal hypotheses focusing on host use in three databases encompassing approximately 44,000 mutualistic (hummingbird-plant), commensalistic (lichen-plant) and parasitic (flea-mammal) interactions in 617 ecological communities across the Americas and Eurasia. Across all interaction types, our analyses indicated that range size and abundance influence the probability of encountering hosts and set the arena for species to express generalism potentials or adapt to new hosts. Hence, our findings support the hypothesis that generalism is a consequence of species ecological success. This highlights the importance of ecological opportunity in driving species characteristics considered key for their survival and conservation.

Isolation management to protect threatened native galaxiid fish species: Lessons from Aotearoa New Zealand

Abstract The use of barriers in freshwater systems to mitigate invasions, known as isolation management, has been increasingly implemented as a protection strategy for native fish. Barriers are crucial for securing vulnerable populations, but much remains to be learnt about the drivers of success and the implications of deliberate fragmentation. In Aotearoa‐New Zealand, henceforth Aotearoa, native non‐migratory galaxiid (NMG) fishes are characterized by a disproportionate number of threatened species with introduced salmonids (trout) identified as a key driver of NMG declines. We conducted a qualitative review of barriers protecting NMG in Aotearoa, illustrating varying outcomes and current knowledge gaps with case studies. Barrier types ranged from natural bedrock waterfalls, shallow velocity chutes and drying reaches to deliberately engineered structures (known commonly as exclusion barriers). Barriers were typically located in headwater streams or spring systems. NMG species secured by fragmentation often have high conservation value and barriers are essential for their protection. Despite the critical role of these barriers, the isolated NMG populations above them are at risk of stochastic extirpation, invasion, or re‐invasion. Exclusion barriers may restrict access to habitat for native migratory fish species and can sometimes alter or remove ideal mesohabitat from protected populations. Overall, when using exclusion barriers, managers must assess extinction risk for individual populations by isolation or invasion, balancing benefits and consequences. However, these assessments are frequently based on incomplete data and hindered by lack of general understanding of the underpinning processes. Despite well‐documented benefits to NMG population survival, key knowledge gaps such as long‐term viability of isolated populations, combinations of physical barrier parameters conferring exclusion under all flow regimes and extent of habitat loss to other native species still exist.

Modelling decisions and density dependence in monarch butterflies: A comment on Meehan and Crossley (2023)

Abstract Decisions about which processes to include in a population model can have substantial impact on estimates of population trends and extinction risk. This is particularly important for species of conservation concern, whose conservation status is decided in part on the basis of these models. In their recent paper, Meehan and Crossley (2023) Insect Conservation and Diversity, 16, 566–573 revisit a time series of overwintering monarch butterfly abundances, which previous assessments had characterised as rapidly declining and at risk of extinction. The authors, in contrast, reported no evidence for declines in the past 10 years and characterised extinction risk as low. A primary reason for the difference between these conclusions was that Meehan and Crossley used a more complex model that included a parameter for density dependence. While negative density dependence may play a role in monarch population regulation, there are a variety of unresolved issues with how and if density dependence should be included in models of monarch populations, including widely known issues with separating observation error from density dependence in noisy time series and taxon‐specific issues with fitting models to data surveyed every fourth generation and pooled at continental scales. These issues make the conclusions of Meehan and Crossley about monarch population viability much less robust than implied in their article. They do not provide convincing evidence that density dependence reduces extinction risk in monarch butterflies. Our commentary supports their general conclusion that population viability projections depend on model assumptions, but the ways in which monarch butterfly populations are regulated remains an open question.

Small translocations of endangered Gallinula galeata sandvicensis (Hawaiian Common Gallinule) may be sufficient to generate a viable reintroduced population

Abstract Where stable source populations of at-risk species exist, translocation may be a reasonable strategy for re-establishing extirpated populations. However, the success rates of such efforts are mixed, necessitating thorough preliminary investigation. Stochastic population modeling can be a useful method of assessing the potential success of translocations. Here, we report on the results of modeling translocation success for the Gallinula galeata sandvicensis or ‘alae ‘ula (Hawaiian Common Gallinule), an endangered waterbird endemic to the Hawaiian Islands. Using updated vital rates, we constructed a model simulating 3 existing extant (wild) source populations and a hypothetical recipient site on another island. We then projected the effects of 6 different translocation scenarios and sensitivity of the results to variation of three important demographic parameters on the probability of extinction (PE) of the reintroduced and donor populations. Larger translocations, of at least 30 birds, had low probability of extinction in the reintroduced population, but raised extinction risk of the smallest source population. Spacing out translocations in time (e.g., 10 birds translocated in total in 3 installments over 9 years), led to lower PE than translocating all individuals at once (i.e., bulk translocations) for both the source and reintroduced populations. Brood size and hatch-year juvenile survival had a disproportionate impact on reintroduced population viability. Importantly, the reported juvenile survival rate is very near the threshold for population failure. This suggests that post-introduction and subsequent management of wetlands, particularly predator control, could be critical to reintroduction success. We recommend that individuals should be translocated from multiple, genetically distinct subpopulations to reduce the possibility of inbreeding depression. Based on this analysis, the recipient wetland should be sufficiently large that it can support at least 25 pairs of gallinules. Based on recent estimates of population densities on O‘ahu, such a wetland would need to be between 3.75 and 74.6 ha.

Impacts of Habitat Fragmentation on Terrestrial Biodiversity in Tropical Forests in Democratic Republic of Congo

Purpose: The aim of the study was to examine impacts of habitat fragmentation on terrestrial biodiversity in tropical forests in Democratic Republic of Congo Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study found that habitat fragmentation poses a significant threat to terrestrial biodiversity in tropical forests, particularly in the Democratic Republic of Congo (DRC). The fragmentation of forest habitats due to human activities such as logging, agriculture, and infrastructure development leads to the isolation of species populations, loss of genetic diversity, and disruption of ecological processes. As a result, endemic species in the DRC, including primates, birds, and large mammals, face heightened risks of population decline and extinction. Moreover, habitat fragmentation exacerbates other environmental challenges, such as climate change and invasive species encroachment, further compromising biodiversity conservation efforts in the region. Unique Contribution to Theory, Practice and Policy: Metapopulation Theory, Landscape Ecology Theory & Island Biogeography Theory may be used to anchor future studies on impacts of habitat fragmentation on terrestrial biodiversity in tropical forests in Democratic Republic of Congo. Implement habitat corridors that physically link fragmented habitats, facilitating the movement of species and genetic exchange. These corridors should be strategically placed based on ecological modeling to maximize effectiveness. Develop and enforce integrated land-use policies that consider both conservation and development needs. Policies should promote land-use planning that minimizes habitat fragmentation and incorporates ecological networks.

Sex ratio distorting microbes exacerbate arthropod extinction risk in variable environments.

Maternally-inherited sex ratio distorting microbes (SRDMs) are common among arthropod species. Typically, these microbes cause female-biased sex ratios in host broods, either by; killing male offspring, feminising male offspring, or inducing parthenogenesis. As a result, infected populations can experience drastic ecological and evolutionary change. The mechanism by which SRDMs operate is likely to alter their impact on host evolutionary ecology; despite this, the current literature is heavily biased towards a single mechanism of sex ratio distortion, male-killing. Furthermore, amidst the growing concerns surrounding the loss of arthropod diversity, research into the impact of SRDMs on the viability of arthropod populations is generally lacking. In this study, using a theoretical approach, we model the epidemiology of an understudied mechanism of microbially-induced sex ratio distortion-feminisation-to ask an understudied question-how do SRDMs impact extinction risk in a changing environment? We constructed an individual-based model and measured host population extinction risk under various environmental and epidemiological scenarios. We also used our model to identify the precise mechanism modulating extinction. We find that the presence of feminisers increases host population extinction risk, an effect that is exacerbated in highly variable environments. We also identified transmission rate as the dominant epidemiological trait responsible for driving extinction. Finally, our model shows that sex ratio skew is the mechanism driving extinction. We highlight feminisers and, more broadly, SRDMs as important determinants of the resilience of arthropod populations to environmental change.

A stage-based life cycle implementation for individual-based population viability analyses of grey wolves (Canis lupus) in Europe

Population viability analyses (PVA) are important tools for decision-making and planning of adaptive wildlife management actions. While earlier approaches on individual based PVAs have often been age-based, analyses of species with strong social structure might benefit from a stage-based model approach. In this study, we designed an individual-based and stage-based PVA within the software Vortex. As a case study, we applied our model to the German part of the European wolf population, making use of comprehensive data sets originating from the German monitoring regime including individual genotypes. Genetic diversity and inbreeding were important considerations in our analysis, as they could greatly impact population dynamics. We aimed to assess the population's trajectory, extinction risk, and genetic integrity under different scenarios while analyzing factors that could affect its survival. We found that mortality rates at different life cycle stages had varying effects on population growth. Higher mortality rates among pups and dispersers led to negative growth and increased the risk of extinction. In comparison, higher mortality rates among yearlings and subdominant wolves still resulted in positive growth but at a slower rate. Mortality among the breeding individuals within the pack (territorials) had the highest impact on population trajectory. Although the German wolves represent a rather recently founded population, our simulations predicted generally good genetic diversity as long as the population was not held at artificially low numbers.Ultimately, we present a generic, easy-to-use-and-adapt model built within the Vortex environment, that after appropriate modification, calibration and testing could be used within conservation practice and management in collaboration with scientific research. Our study highlights the importance of stage-based modeling for understanding the demographic traits of social species like wolves.

Unclear relationships between mean survival rate and its environmental variance in vertebrates.

Current environmental changes may increase temporal variability of life history traits of species thus affecting their long-term population growth rate and extinction risk. If there is a general relationship between environmental variances (EVs) and mean annual survival rates of species, that relationship could be used as a guideline for analyses of population growth and extinction risk for populations, where data on EVs are missing. For this purpose, we present a comprehensive compilation of 252 EV estimates from 89 species belonging to five vertebrate taxa (birds, mammals, reptiles, amphibians and fish) covering mean annual survival rates from 0.01 to 0.98. Since variances of survival rates are constrained by their means, particularly for low and high mean survival rates, we assessed whether any observed relationship persisted after applying two types of commonly used variance stabilizing transformations: relativized EVs (observed/mathematical maximum) and logit-scaled EVs. With raw EVs at the arithmetic scale, mean-variance relationships of annual survival rates were hump-shaped with small EVs at low and high mean survival rates and higher (and widely variable) EVs at intermediate mean survival rates. When mean annual survival rates were related to relativized EVs the hump-shaped pattern was less distinct than for raw EVs. When transforming EVs to logit scale the relationship between mean annual survival rates and EVs largely disappeared. The within-species juvenile-adult slopes were mainly positive at low (<0.5) and negative at high (>0.5) mean survival rates for raw and relativized variances while these patterns disappeared when EVs were logit transformed. Uncertainties in how to interpret the results of relativized and logit-scaled EVs, and the observed high variation in EV's for similar mean annual survival rates illustrates that extrapolations of observed EVs and tests of life history drivers of survival-EV relationships need to also acknowledge the large variation in these parameters.

Genomic exploration of the endangered oriental stork, Ciconia boyciana, sheds light on migration adaptation and future conservation.

The oriental stork, Ciconia boyciana, is an endangered migratory bird listed on the International Union for Conservation of Nature's Red List. The bird population has experienced a rapid decline in the past decades, with nest locations and stop-over sites largely degraded due to human-bird conflicts. Multipronged conservation efforts are required to secure the future of oriental storks. We propose that a thorough understanding of the genome-wide genetic background of this threatened bird species is critical to make future conservation strategies. In this study, the first chromosome-scale reference genome was presented for the oriental stork with high quality, contiguity, and accuracy. The assembled genome size was 1.24 Gb with a scaffold N50 of 103 Mb, and 1.23 Gb contigs (99.32%) were anchored to 35 chromosomes. Population genomic analysis did not show a genetic structure in the wild population. Genome-wide genetic diversity (π = 0.0012) of the oriental stork was at a moderate to high level among threatened bird species, and the inbreeding risk was also not significant (FROH = 5.56% ± 5.30%). Reconstruction of demographic history indicated a rapid recent population decline likely driven by human activities. Genes that were under positive selection associated with the migratory trait were identified in relation to the long-term potentiation, photoreceptor cell organization, circadian rhythm, muscle development, and energy metabolism, indicating the essential interplay between genetic and ecological adaptation. Our study presents the first chromosome-scale genome assembly of the oriental stork and provides a genomic basis for understanding a genetic background of the oriental stork, the population's extinction risks, and the migratory characteristics, which will facilitate the decision of future conservation plans for this species.

Discharge‐Mediated Temperature Management in a Large, Regulated River, With Implications for Management of Endangered Fish

AbstractFor large, regulated rivers, operators can impact abiotic conditions for the benefit of the ecosystem, primarily by controlling the volume of discharge from upstream reservoirs. Understanding the decision space around discharge is necessary for evaluating tradeoffs between environmental and other objectives. As a result of climate change, warming water temperatures are increasingly becoming a concern for thermally‐sensitive fauna. In California's largest river, the Sacramento, extinction risk of salmon populations is linked to high water temperatures. Yet, little is known about how much water temperature in lower reaches can be affected by reservoir discharge operations, and the potential benefits to salmon. We used a process‐based water temperature model to estimate the ability of reservoir discharge to mediate river temperature heating processes impacting downstream locations (discharge‐mediated temperature management). To bound this analysis, we used historical forcings over a recent 29‐year span. Results indicate reservoir discharge increases of up to 340 cms over the historical record could have decreased water temperature in the lower reaches by up to 3.6°C. Salmon require water below 20°C during most stages of their lifecycle, and we found that normative water operations could ensure 20°C was rarely exceeded for two potential management seasons, in late‐spring and early‐fall. These periods coincide with important rearing and migratory periods for salmon, during which they frequently experience excessive temperatures under the management status‐quo. This analysis provides stakeholders tools to manage conditions for native fauna in the face of a warming climate, and a framework for developing similar tools in other large, regulated rivers.

How environmental drivers of spatial synchrony interact

Spatial synchrony, the tendency for populations across space to show correlated fluctuations, is a fundamental feature of population dynamics, linked to central topics of ecology such as population cycling, extinction risk, and ecosystem stability. A common mechanism of spatial synchrony is the Moran effect, whereby spatially synchronized environmental signals drive population dynamics and hence induce population synchrony. After reviewing recent progress in understanding Moran effects, we here elaborate a general theory of how Moran effects of different environmental drivers acting on the same populations can interact, either synergistically or destructively, to produce either substantially more or markedly less population synchrony than would otherwise occur. We provide intuition for how this newly recognized mechanism works through theoretical case studies and application of our theory to California populations of giant kelp. We argue that Moran interactions should be common. Our theory and analysis explain an important new aspect of a fundamental feature of spatiotemporal population dynamics.

Low genetic diversity and shallow population structure in the broom hare, Lepus castroviejoi (Lagomorpha: Leporidae)

Abstract The broom hare (Lepus castroviejoi) is a threatened Iberian endemic, for which there is limited knowledge. We use genetic non-invasive sampling (gNIS; N = 185 faeces samples) and specimens from hunting and roadkills (N = 22) in conjunction with a 15-microsatellite panel and a 541-bp fragment of cytochrome-b to assess the genetic diversity, population structure and evolutionary history of this species. Populations from the other four European hare species were also analysed to accurately compare the genetic diversity patterns and infer admixture. Species identification from gNIS was inferred using small fragments of cytochrome-b and transferrin genes and individual identification was obtained using microsatellites. The broom hare population showed the lowest level of nuclear DNA diversity of all analysed hare species (N = 76; Na = 2.53, He = 0.186 and Fis = 0.341) and very low mitochondrial DNA diversity (N = 64; Hd = 0.743 and π = 0.01543). Only the Italian hare (L. corsicanus) showed a similar pattern of low genetic diversity. No hybridization with the neighbouring hare species was detected. However, two mitochondrial DNA lineages, corresponding to two ancient events of introgression of mountain hare (L. timidus) origin, were characterized. There was evidence for shallow spatial population differentiation of the broom hare. The described reduced genetic diversity, associated with a narrow distribution range and recent population declines, represents a risk of population extinction, and highlights the need for conservation measures of this endemic threatened hare species.

Sexually-selected male weapon increases the risk of population extinction under environmental change: an experimental evidence.

Exaggerated sexually-selected traits, occurring more commonly in males, help individuals to increase reproductive success, but are costly to produce and maintain. These costs on the one hand may improve population fitness by intensifying selection against maladapted males, but on the other hand may increase the risk of extinction under environmental challenge. However, the impact of sexually selected traits on extinction risk have not been investigated experimentally. We used replicate populations of a male-dimorphic mite, Rhizoglyphus robini, to test if prevalence of a sexually-selected weapon affected the risk of extinction under temperature increase (2 0C per each of three consecutive generations). In two independent experiments that utilized either inbred lines or lines mass selected for or against the weapon to establish experimental replicate populations differing in the prevalence of the weapon, we found that populations with high weapon prevalence were more likely to go extinct. Extinctions occurred despite partial suppression of the weapon expression at increased temperature and were not explained by increased male mortality. Our results provide the first, to our knowledge, experimental evidence demonstrating dramatic effect of elaborated sexual traits on the risk of extinction under environmental challenge.

Identifying global research and conservation priorities for Columbidae: a quantitative approach using random forest models

The family of Columbidae, including pigeons and doves, remains understudied despite their patrimonial value and high ecological and conservation relevance. Currently, 353 extant columbid species are listed in the IUCN red list, with about 20% of them being threatened with extinction. However, there has been little effort so far to synthetize the available information on factors influencing extinction risk and the allocation of research effort among columbid species. In this context, using random forest models, the present study aims at quantitatively assessing to what extent environmental, life history and socio-political factors may drive the extinction risk of pigeons and doves and explain differences in scientific attention among species. We found that high risk of extinction in columbids is associated with small historical range, exposure to invasive alien mammals and living in isolated islands and/or at low altitudes, while the probability of population decline is associated with species body size, surrounding human density and narrow habitat breadth. We also evidenced a large disparity between species or population extinction risk and scientific interest. Indeed, most of the studies on columbids have been conducted by scientists from North America and Western Europe on their local species, whereas species from biodiversity hotspots, which are more at risk of extinction, have comparatively received little attention. This unequal acquisition of knowledge creates gaps that deserve to be filled in order to have a good appreciation of extinction risk in columbids and associated threats, through fair transnational cooperation, academic training and regional coordination in conservation-oriented research on columbids.