In the Cook Islands in 2024, the population decreased by about 2.24 percent compared to the previous year, making it the country with the highest population decline rate in 2024. Of the 20 countries with the highest rate of population decline, the majority are island nations, where emigration rates are high (especially to Australia, New Zealand, and the United States), or they are located in Eastern Europe, which suffers from a combination of high emigration rates and low birth rates.

Antarctic fur seals (AFS) are an ecologically important predator and a focal indicator species for ecosystem-based Antarctic fisheries management. This species suffered intensive anthropogenic exploitation until the early 1900s, but recolonized most of its former distribution, including the southern-most colony at Cape Shirreff, South Shetland Islands (SSI). The IUCN describes a single, global AFS population of least concern; however, extensive genetic analyses clearly identify four distinct breeding stocks, including one in the SSI. To update the population status of SSI AFS, we analyzed 20 years of field-based data including population counts, body size and condition, natality, recruitment, foraging behaviors, return rates, and pup mortality at the largest SSI colony. Our findings show a precipitous decline in AFS abundance (86% decrease since 2007), likely driven by leopard seal predation (increasing since 2001, p << 0.001) and potentially worsening summer foraging conditions. We estimated that leopard seals consumed an average of 69.3% (range: 50.3–80.9%) of all AFS pups born each year since 2010. AFS foraging-trip durations, an index of their foraging habitat quality, were consistent with decreasing krill and fish availability. Significant improvement in the age-specific over-winter body condition of AFS indicates that observed population declines are driven by processes local to the northern Antarctic Peninsula. The loss of SSI AFS would substantially reduce the genetic diversity of the species, and decrease its resilience to climate change. There is an urgent need to reevaluate the conservation status of Antarctic fur seals, particularly for the rapidly declining SSI population.

This is the replication package for our paper titled "Did the colonial mita cause a population collapse? What current surnames reveal in Peru". We present quantitative evidence that the mita introduced by the Spanish crown in 1573 caused the decimation of the native-born male population. The mass baptisms after the conquest of Peru in 1532 resulted in the assignation of surnames for the first time. We argue that past mortality displacement and mass out-migration were responsible for differences in the surnames observed in mita and non-mita districts today. Using a regression discontinuity and data from the Peruvian Electoral Roll of 2011, we find that mita districts have 47 log points fewer surnames than non-mita districts, 65 log points fewer surnames that are present in only one district, and 93 log points fewer surnames that are solely present in one area (mita or non-mita).

It is well known that temporal fluctuations in small populations deeply influence evolutionary potential. Less well known is whether fluctuations can influence the evolutionary potentials of species with large census sizes. Here, we estimated genetic population parameters from as survey of polymorphic microsatellite DNA loci in archived otoliths from Adriatic European anchovy (Engraulis encrasicolus), a fish with large census sizes that supports numerous local fisheries. Stocks have fluctuated greatly over the past few decades, and the Adriatic fishery collapsed in 1987. Our results show a significant reduction of mean genetic parameters as a consequence of the population collapse. In addition, estimates of effective population size (Ne) are much smaller than those expected in a fishes with large population census sizes (Nc). Estimates of Ne indicate low effective population sizes, even before the population collapse. The ratio Ne/Ne ranged between 10−6 and 10−8, indicating a large discrepancy between the anchovy gene pool and population census size. Therefore, anchovy populations may be more vulnerable to fishery effort and environmental change than previously thought.

Abstract
Both landscape structure and population size fluctuations influence population genetics. While independent effects of these factors on genetic patterns and processes are well studied, a key challenge is to understand their interaction, as populations are simultaneously exposed to habitat fragmentation and climatic changes that increase variability in population size. In a population network of an alpine butterfly, abundance declined 60–100% in 2003 because of low over-winter survival. Across the network, mean microsatellite genetic diversity did not change. However, patch connectivity and local severity of the collapse interacted to determine allelic richness change within populations, indicating that patch connectivity can mediate genetic response to a demographic collapse. The collapse strongly affected spatial genetic structure, leading to a breakdown of isolation-by-distance and loss of landscape genetic pattern. Our study reveals important interactions between landscape structure and temporal demographic variability on the genetic diversity and genetic differentiation of populations. Projected future changes to both landscape and climate may lead to loss of genetic variability from the studied populations, and selection acting on adaptive variation will likely occur within the context of an increasing influence of genetic drift.

For the purpose of reproducibility, we here provide the datasets and R script supporting the analyses of the paper “Population collapse in viviparid gastropods of the Lake Victoria ecoregion started before the Last Glacial Maximum†by Van Bocxlaer et al. This paper has been accepted for publication in Molecular Ecology on 31 July 2020. In this study, we examine the population structure of the clade of Bellamya gastropods that occupies the Lake Victoria ecoregion with the aim to relate past environmental change with demography and diversification dynamics. The here provided datasets include 1) an alignment of a fragment of the gene cytochrome c oxidase subunit 1 for 60 specimens; 2) genotype data for 321 individuals from 39 localities for 15 microsatellite loci (total dataset); 3) a regrouped genotype dataset (282 specimens from 21 localities for 15 microsatellite loci), which was used for some analyses in our study. Analyses were performed with various programs as reported in our paper....

Bold values are significant after a sequential Bonferroni correction [42] for 36 multiple tests (P < 0.0014).

Population declines may promote interspecific hybridization due to the shortage of conspecific mates (Hubb’s ‘desperation’ hypothesis), thus greatly increasing the risk of species extinction. Yet, confirming this process in the wild has proved elusive. Here we combine camera-trapping and molecular surveys over seven years to document demographic processes associated with introgressive hybridization between the critically endangered giant sable antelope (Hippotragus niger variani), and the naturally sympatric roan antelope (H. equinus). Hybrids with intermediate phenotypes, including backcrosses with roan, were confirmed in one of the two remnant giant sable populations. Hybridization followed population depletion of both species due to severe wartime poaching. In the absence of mature sable males, a mixed herd of sable females and hybrids formed and grew progressively over time. To prevent further hybridization and recover this small population, all sable females were confined to a larg...

The dataset contains the Raw data and the annotated code to create all the Figures and Statistical analysis included in the associated manuscript.

NG = number of generations between a pair of samples. Ne = effective population size estimate. Lower and Upper 95% CI = represents a 95% Confidence Interval (CI) for Ne estimated for a pair of samples. Ne MAX = maximum prior effective population size defined in coalescent-based simulations. Values in bold represent the most likely coalescent estimates based on higher 95% CI limit per simulation.

The supplied data represents key environmental variables for collection sites included in a population genomic study of black abalone. These data include measures of sea surface temperature (SST), pH, and ROMS connectivity (PLD 5, 10, 15 days) generated or synthesized for this study that are not readily available on public databases.

Anticipating critical transitions in spatially extended systems is a key topic of interest to ecologists. Gradually declining metapopulations are an important example of a spatially extended biological system that may exhibit a critical transition. Theory for spatially extended systems approaching extinction that accounts for environmental stochasticity and coupling is currently lacking. Here, we develop spatially implicit two-patch models with additive and multiplicative forms of environmental stochasticity that are slowly forced through population collapse, through changing environmental conditions. We derive patch-specific expressions for candidate indicators of extinction and test their performance via a simulation study. Coupling and spatial heterogeneities decrease the magnitude of the proposed indicators in coupled populations relative to isolated populations, and the noise regime and the degree of coupling together determine trends in summary statistics. This theory may be readily applied to other spatially extended ecological systems, such as coupled infectious disease systems on the verge of elimination.

Ocean acidification is forecast to drive a decline in populations of calcifying species, including sea urchins, particularly through its negative effects on reproduction and recruitment. Evidence for these predictions rests predominantly on laboratory experiments, which cannot fully incorporate the influence of ecological complexity in the natural environment. Therefore, we used natural volcanic CO2 seeps on a temperate reef, to test the prediction that ocean acidification drives a decline in urchin reproductive potential across their naturally occurring densities. We observed the opposite of this prediction, with urchins showing an increase in per capita reproductive potential under elevated CO2, with this effect enhanced at the decreased urchin densities observed at the seeps. This influence on reproductive potential appears to be an indirect effect of CO2 enrichment boosting the nutritional value and abundance of their algal food. Hence, the commonly observed direct negative effects of elevated CO2 in the laboratory may be countered by such positive effects that can only be observed in the field. So, whilst ocean acidification might put pressure on vulnerable early life stages to drive population decline, as observed in the laboratory, our field observations suggest that increasing reproductive potential may buffer the magnitude of these declines to maintain population persistence. Therefore, this study highlights the duality of ocean acidification to potentially suppress population sizes, whilst facilitating population persistence.

Sea level rise causes habitat loss and is considered to be a key threat to coastal species globally. Sea level rise also reduces habitat quality, potentially threatening populations already before habitat drowns and is lost. The extent and timing of changes in habitat quality for wildlife actively adapting to sea level rise, and how this affects population numbers under different emission scenarios, is unknown. Here, we combine long-term field data with models of sea level rise, marsh geomorphology, adaptive behaviour, and population dynamics to show that habitat quality is already declining on three islands due to increased flooding of shorebird nests. Also, population collapses are projected well before habitat drowns. Habitat loss, a widely used proxy, thus severely underestimates population impacts of sea level rise and coastal species will suffer much sooner than previously thought. Despite shorebirds adapting by moving to higher grounds, sea level rise will result in up to 79% fewer birds in a century, eventually leading to extinction in their prime habitat. Local gas mining exacerbates matters, as deep soil subsidence makes habitat even more vulnerable to sea level rise, effectively halving the window of opportunity for conservation action. Climate change ultimately jeopardizes the biodiversity value of this UNESCO World Heritage Area, and nature management needs to take this long-term perspective on board by in the short-term, boosting the accretion of tidal marshes or developing flood-safe alternative habitat elsewhere. Methods See paper for a detailed description of the datasets.

NG = number of generations between a pair of samples. Ne = effective genetic size estimate. Lower and upper 95% CI represents a 95% Confidence Interval (CI) for Ne estimated for each pair of samples. Ne/Nc ratio = ratio between effective population size (estimated from temporal moment-based method) and census size (obtained from MEDIAS acoustic survey data; Fig 2). NA = not available data.

Fen_dataThe file 'Fen_data' consists of following Matsalu Bay perch information used in phenotypic analysis: sampling date, gear, total and standard length, total and standard weight, age, sex, maturity status and back-calculated length at different ages (SL1 to SL10).Gen_dataThe file 'Gen_data' consists of information used in population genetic analysis and includes: sampling site, sampling year, cohort and loci information.

no abstract provided

1.Emerging and invasive pathogens can have long-lasting impacts on susceptible wildlife populations, including localised collapse and extirpation. Management of threatening disease is of widespread interest and requires knowledge of spatiotemporal patterns of pathogen spread.

2.Theory suggests disease spread often occurs via two patterns: homogenous mixing and travelling waves. However, high resolution empirical data demonstrating localised (within population) disease spread patterns are rare.

3.This study examined the spread of sarcoptic mange (aetiological agent Sarcoptes scabiei) in a population of bare-nosed wombats (Vombatus ursinus), and investigated whether pathogen spread occurred by homogenous mixing or a travelling wave.

4.Using seven years of population surveys and four years of disease severity surveys, we show that mange was first detected in the east of a wombat population in northern Tasmania, and progressed westward as a travelling wave. Wombat mortality rates reached...

Severe bottlenecks significantly diminish the amount of genetic diversity and the speed at which it accumulates (i.e. evolutionary rate). They further compromise the efficiency of natural selection to eliminate deleterious variants, which may reach fixation in the surviving populations. Consequently, expanding and adapting to new environments may pose a significant challenge when strong bottlenecks result in genetic pauperization. Herein, we surveyed the patterns of nucleotide diversity, molecular adaptation and genetic load across hundreds of loci in a circum-Mediterranean conifer (Pinus pinea L.) that represents one of the most extreme cases of genetic pauperization in widespread outbreeding taxa. We found very little genetic variation in both hypervariable non-coding (nuSSRs) and gene-coding loci, which translated into genetic diversity estimates one order of magnitude lower than those previously reported for pines. Such values were consistent with a strong population decline that be...

The population of the Yellow-breasted Bunting Emberiza aureola, a formerly widely distributed and abundant songbird of northern Eurasia, suffered a catastrophic decline and a strong range contraction between 1980 and 2013. There is evidence that the decline was driven by illegal trapping during migration, but potential contributions of other factors to the decline, such as land-use change, have not yet been evaluated. Before effects of land-use change can be evaluated, a basic understanding of the ecological requirements of the species is needed. We therefore compared habitat use in ten remaining breeding regions across the range, from European Russia to Japan and the Russian Far East. We also assessed large-scale variation in habitat parameters across the breeding range.

We found large variation in habitat use, within and between populations. Differences were related to the cover and height of trees and shrubs at Yellow-breasted Bunting territories. In many regions, Yellow-breasted Buntings occupied early successional stages, including anthropogenic habitats characterized by mowing, grazing or fire regimes. We found that the probability of presence can be best predicted with the cover of shrubs, herbs and grasses. Highest probabilities were found at shrub cover values of 40 to 70 %.

Differences in habitat use along a longitudinal gradient were small, but we found strong differences across latitudes, possibly related to habitat availability. We conclude that the remaining Yellow-breasted Bunting populations are not limited to specific habitat types. Our results provide important baseline information to model the range-wide distribution of this critically endangered species and to guide targeted conservation measures.