Population Extinction Risk Research Articles

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

AbstractMaternally‐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.

Genetic erosion reduces biomass temporal stability in wild fish populations

Genetic diversity sustains species adaptation. However, it may also support key ecosystems functions and services, for example biomass production, that can be altered by the worldwide loss of genetic diversity. Despite extensive experimental evidence, there have been few attempts to empirically test whether genetic diversity actually promotes biomass and biomass stability in wild populations. Here, using long-term demographic wild fish data from two large river basins in southwestern France, we demonstrate through causal modeling analyses that populations with high genetic diversity do not reach higher biomasses than populations with low genetic diversity. Nonetheless, populations with high genetic diversity have much more stable biomasses over recent decades than populations having suffered from genetic erosion, which has implications for the provision of ecosystem services and the risk of population extinction. Our results strengthen the importance of adopting prominent environmental policies to conserve this important biodiversity facet.

In search of the Goldilocks zone for hybrid speciation II: hard times for hybrid speciation?

Hybridization opens a unique window for observing speciation mechanisms and is a potential engine of speciation. One controversially discussed outcome of hybridization is homoploid hybrid speciation by reciprocal sorting, where a hybrid population maintains a mixed combination of the parental genetic incompatibilities, preventing further gene exchange between the newly formed population and the two parental sources. Previous work showed that, for specific linkage architectures (i.e., the genomic location and order of hybrid incompatibilities), reciprocal sorting could reliably result in hybrid speciation. Yet, the sorting of incompatibilities creates a risk of population extinction. To understand how the demographic consequences of the purging of incompatibilities interact with the formation of a hybrid species, we model an isolated hybrid population resulting from a single admixture event. We study how population size, linkage architecture, and the strength of the incompatibility affect survival of the hybrid population, resolution/purging of the genetic incompatibilities and the probability of observing hybrid speciation. We demonstrate that the extinction risk is highest for intermediately strong hybrid incompatibilities. In addition, the linkage architecture displaying the highest hybrid speciation probabilities changes drastically with population size. Overall, this indicates that population dynamics can strongly affect the outcome of hybridization and the hybrid speciation probability.

Meta-analysis reveals impacts of disturbance on reptile and amphibian body condition.

Ecosystem disturbance is increasing in extent, severity and frequency across the globe. To date, research has largely focussed on the impacts of disturbance on animal population size, extinction risk and species richness. However, individual responses, such as changes in body condition, can act as more sensitive metrics and may provide early warning signs of reduced fitness and population declines. We conducted the first global systematic review and meta-analysis investigating the impacts of ecosystem disturbance on reptile and amphibian body condition. We collated 384 effect sizes representing 137 species from 133 studies. We tested how disturbance type, species traits, biome and taxon moderate the impacts of disturbance on body condition. We found an overall negative effect of disturbance on herpetofauna body condition (Hedges' g = -0.37, 95% CI: -0.57, -0.18). Disturbance type was an influential predictor of body condition response and all disturbance types had a negative mean effect. Drought, invasive species and agriculture had the largest effects. The impact of disturbance varied in strength and direction across biomes, with the largest negative effects found within Mediterranean and temperate biomes. In contrast, taxon, body size, habitat specialisation and conservation status were not influential predictors of disturbance effects. Our findings reveal the widespread effects of disturbance on herpetofauna body condition and highlight the potential role of individual-level response metrics in enhancing wildlife monitoring. The use of individual response metrics alongside population and community metrics would deepen our understanding of disturbance impacts by revealing both early impacts and chronic effects within affected populations. This could enable early and more informed conservation management.

Giant pandas are losing their edge: Population trend and distribution dynamic drivers of the giant panda.

Comprehending the population trend and understanding the distribution range dynamics of species are necessary for global species protection. Recognizing what causes dynamic distribution change is crucial for identifying species' environmental preferences and formulating protection policies. Here, we studied the rear-edge population of the flagship species, giant pandas (Ailuropoda melanoleuca), to (1) assess their population trend using their distribution patterns, (2) evaluate their distribution dynamics change from the second (1988) to the third (2001) survey (2-3 Interval) and third to the fourth (2013) survey (3-4 Interval) using a machine learning algorithm (eXtremely Gradient Boosting), and (3) decode model results to identify driver factors in the first known use of SHapley Additive exPlanations. Our results showed that the population trends in Liangshan Mountains were worst in the second survey (k = 1.050), improved by the third survey (k = 0.97), but deteriorated by the fourth survey (k = 0.996), which indicates a worrying population future. We found that precipitation had the most significant influence on distribution dynamics among several potential environmental factors, showing a negative correlation between precipitation and giant panda expansion. We recommend that further research is needed to understand the microenvironment and animal distribution dynamics. We provide a fresh perspective on the dynamics of giant panda distribution, highlighting novel focal points for ecological research on this species. Our study offers theoretical underpinnings that could inform the formulation of more effective conservation policies. Also, we emphasize the uniqueness and importance of the Liangshan Mountains giant pandas as the rear-edge population, which is at a high risk of population extinction.