Fragmented Populations Research Articles

Living at the edge: home range patterns of the Buraiga Chimpanzee Community, Kibale National Park, Uganda

Data on space-use patterns are essential for understanding species ecology and conservation. Individual chimpanzee communities are known to vary in home range size and habitat use dynamics, reflecting site-specific strategies to differences in resource availability on different landscapes. Here we present home range estimates for the Buraiga chimpanzees of Kibale National Park, Uganda, a community of eastern chimpanzees (Pan troglodytes schweinfurthii) living within the largest remaining population fragment in Uganda. The Buraiga chimpanzees are currently undergoing habituation for research and tourism under the direction of the Uganda Wildlife Authority (UWA). We analyzed 15 months of GPS data (August 2019 – March 2020, and January – July 2022), calculating overall and seasonal home range and core area estimates with two methods, minimum convex polygon (MCP) and kernel density estimates (KDE). Home range was estimated to cover an area of 15.77 km2 (95% KDE), and 24.90 km2 (100% MCP). Additionally, we found that 15.82% of the Buraiga chimpanzee’s home range overlaps with community-managed land, primarily the Kanyanchu Swamp corridor and adjacent agricultural land. Seasonally, we found that Buraiga chimpanzees used a larger area during dry season months, compared with rainy season months. Documenting how great ape populations utilize increasingly anthropogenically influenced landscapes is important in order to facilitate long-term survival in the face of climate change, habitat fragmentation, and other ongoing threats.

Sexual selection buffers the negative consequences of population fragmentation on adaptive plastic responses to increasing temperatures.

Whether sexual selection facilitates or hampers the ability to plastically respond to novel environments might depend on population structure, via its effects on sexual interactions and associated fitness payoffs. Using experimentally evolved lines of the seed beetle Callosobruchus maculatus, we tested whether individuals evolving under different sexual selection (monogamy vs. polygamy) and population spatial structure (metapopulation vs. undivided populations) treatments differed in their response across developmental thermal conditions (control, hot, or stressful) in a range of fitness and fitness-associated traits. We found that individuals from subdivided populations had lower lifetime reproductive success at hot temperatures, but only in lines evolving under relaxed sexual selection, revealing a complex interaction between sexual selection, population structure, and thermal environmental stress on fitness. We also found an effect of population structure on several traits, including fertility and adult emergence success, under exposure to high thermal conditions. Finally, we found a strong negative effect of hot and stressful temperatures on fitness and associated traits. Our results show that population structure can exacerbate the impact of a warming climate, potentially leading to declines in population viability, but that sexual selection can buffer the negative influence of population subdivision on adaptation to warm temperatures.

Episodic population fragmentation and gene flow reveal a trade-off between heterozygosity and allelic richness.

In episodic environments like deserts, populations of some animal species exhibit irregular fluctuations such that populations are alternately large and connected or small and isolated. Such dynamics are typically driven by periodic resource pulses due, for example, to large but infrequent rainfall events. The repeated population bottlenecks resulting from fragmentation should lower genetic diversity over time, yet species undergoing these fluctuations appear to maintain high levels of genetic diversity. To resolve this apparent paradox, we simulated a metapopulation of constant size undergoing repeat episodes of fragmentation and change in gene flow to mimic outcomes experienced by mammals in an Australian desert. We show that episodic fragmentation and gene flow have contrasting effects on two measures of genetic diversity: heterozygosity and allelic richness. Specifically, fragmentation into many, small subpopulations, coupled with periods of infrequent gene flow, preserves allelic richness at the expense of heterozygosity. In contrast, fragmentation into a few, large subpopulations maintains heterozygosity at the expense of allelic richness. The strength of the trade-off between heterozygosity and allelic richness depends on the amount of gene flow and the frequency of gene flow events. Our results imply that the type of genetic diversity maintained among species living in strongly fluctuating environments will depend on the way populations fragment, with our results highlighting different mechanisms for maintaining allelic richness and heterozygosity in small, fragmented populations.

Predicting the geographical distribution of the Persian leopard, Panthera pardus tulliana, a rare and endangered species

The endangered Persian Leopard, Panthera pardus tulliana, is a top predator and keystone species whose small, fragmented population is still distributed across the Zagros Mountain regions of northeastern Iraq. Their population is under threat from habitat loss and fragmentation, illegal hunting, prey depletion, minefields, and conflicts with humans. Conservation efforts require accurate information on the current and future distribution patterns of this species. Therefore, this study aimed at establishing new baseline data based on the maximum entropy model (Maxent) combined with GIS techniques, field surveys (i.e., camera traps, kill reports, carcasses), and relevant environmental variables obtained from multiple sources. Modeling demonstrated that the current suitable habitat distribution of the species comprises 12.4 % (6318 km2) of the total area of the study area (50971 km2). Of these suitable areas, 0.8 % (431 km2) were categorized as high suitable, 3.8 % (1935 km2) as medium suitable, and 7.8 % (3953 km2) as low suitable. Overall, as demonstrated by modeling under the preselected environmental predictors, the suitable habitat distribution of the Persian Leopard would contract by 1.3 % (666 km2) and 1.7 % (843 km2) in 2070 under the RCP2.6 and RCP8.5 climate change scenarios, respectively. There would be a latitudinal shift, and the distance between the current and future centroids would be around 43.492 km. This spatial shift would be mostly towards the Zagros Mountains in the northeast of Iraq, alongside the Iran-Iraq border. The most important variables that contributed significantly to the distribution of the species across the study area included slope (47.3 %), temperature seasonality (bio4) (27.9 %), land cover (7.7 %), human population density (4.2 %), soil pH (2.7 %), temperature (Bio2) (2.7 %), and NDVI (1.8 %). These results could have great implications for establishing strategic protected areas not only for the target species of this study but for a wide range of plant communities and prey species (e.g., goats, wild boar) across the mountain ecosystem.

Purebred dogs show higher levels of genomic damage compared to mixed breed dogs

Inbreeding is a common phenomenon in small, fragmented or isolated populations, typical conditions of many threatened species. In the present paper, we used a new non-invasive approach based on the buccal micronucleus assay to evaluate the possible relationships between inbreeding and genomic damage using the dog as model species. In particular, we assessed the frequencies of micronuclei and other nuclear aberrations in a group of purebred dogs (n = 77), comparing the obtained data with those from a control group represented by mixed breed dogs (n = 75). We found a significant increase of micronuclei, nuclear buds and total nuclear aberrations frequencies in purebred dogs compared to mixed-bred dogs. The absence of significant differences in the frequency of micronuclei and other nuclear aberrations amongst different breeds reinforces the hypothesis that the observed increased genomic damage amongst purebred dogs may not be due to a different genomic instability typical of a particular breed, but to inbreeding itself. This hypothesis is further confirmed by the fact that other endogen confounding factors, such as sex, age and weight, do not contribute significantly to the increase of genomic damage observed amongst purebred dogs. In conclusion, results presented in this study showed that, in purebred dogs, inbreeding may increase the levels of genomic damage. Considering that genomic damage is associated with increased physiological problems affecting animal health, the results we obtained may represent a stimulus to discourage the use of intensive inbreeding practices in captive populations and to reduce the fragmentation of wild populations.

Comparative genetic and demographic responses to climate change in three peatland butterflies in the Jura massif

Climate is a main driver of species distributions, but all species are not equally affected by climate change, and their differential responses to similar climatic constraints might dramatically affect the local species composition. In the context of climate warming, a better knowledge of the ability of dispersal-limited and habitat-specialist species to track climate change at local scale is urgently needed. Comparing the population genetic and demographic impacts of past climate cycles in multiple co-distributed species with similar ecological requirements help predicting the community-scale response to climate warming, but such comparative studies remain rare. Here, we studied the relationship between demographic history and past changes in spatial distribution of three protected peatland butterfly species (Boloria aquilonaris, Coenonympha tullia, Lycaena helle) in the Jura massif (France), using a genomic approach (ddRAD sequencing) and species distribution modeling (SDM). We found a similar and narrow thermal niche among species, and shared demographic histories of post-glacial decline and recent fragmentation of populations. Each species functions as a single metapopulation at the regional scale, with a North-South gradient of decreasing genetic diversity that fits the local dynamics of the ice cover over time. However, we found no correlation between changes in the quantity or the quality of suitable areas and changes in effective population size over time. This suggests that species ranges moved beyond the Jura massif during the less favorable climatic periods, and/or that habitat loss and deterioration are major drivers of the current dramatic decline observed in the three species. Our findings allow better understanding how history events and contemporary dynamics shape local biodiversity, providing valuable knowledge to identify appropriate conservation strategies.

The Diverse Reticulate Genetic Set-Up of Endangered Gladiolus palustris in Southern Germany Has Consequences for the Development of Conservation Strategies

Gladiolus palustris (marsh Gladiolus) of wet grasslands is an extremely rare and highly endangered species in Central Europe. Ongoing loss of habitat, population fragmentation, drought, and higher mean annual temperatures caused by global warming have all contributed to a severe decline in its population over the past few decades. Additionally, hybridization with other species, such as G. imbricatus and G. illyricus, and genetic depletion may pose a significant threat to the species’ survival. The focus of this study is to characterize major gene pools of the species in southern and southwestern Germany. Using molecular AFLP markers and ITS DNA sequencing, this study shows that past hybridization and introgression in Central Europe are more extensive than previously thought, posing a challenge to conservation strategies targeting taxonomically defined species. The region of the Rhine River in southwestern Germany (Upper Rhine Valley) has seen the emergence of various scattered populations of G. palustris over the past three decades, which are believed to have been introduced by humans. Introduced populations in this area (comprising the German Federal States of Baden–Württemberg and Rhineland–Palatinate) likely descend from a large source population near Lake Constance. Therefore, the study suggests promoting and protecting these new populations, given their long-standing presence in the region. Furthermore, the research proposes that naturally occurring hybrids and introgressed populations should also be the primary target of conservation efforts.

Balancing selection shapes population differentiation of major histocompatibility complex genes in wild golden snub-nosed monkeys.

Small and isolated populations face several intrinsic risks, such as genetic drift, inbreeding depression, and reduced gene flow. Thus, patterns of genetic diversity and differentiation have become an important focus of conservation genetics research. The golden snub-nosed monkey Rhinopithecus roxellana, an endangered species endemic to China, has experienced rapid reduction in population size and severe population fragmentation over the past few decades. We measured the patterns of genetic diversity and population differentiation using both neutral microsatellites and adaptive major histocompatibility complex (MHC) genes in 2 R. roxellana populations (DPY and GNG) distributed on the northern and southern slopes of the Qinling Mountains, respectively. Eight MHC-linked haplotypes formed by 5 DQA1 alleles, 5 DQB1 alleles, 5 DRB1 alleles, and 4 DRB2 alleles were detected in the 2 populations. The larger GNG population showed higher genetic variation for both MHC and microsatellites than the smaller DPY population, suggesting an effect of genetic drift on genetic variation. Genetic differentiation index (F ST) outlier analyses, principal coordinate analysis (PCoA), and inferred population genetic structure showed lower genetic differentiation in the MHC variations than microsatellites, suggesting that pathogen-mediated balancing selection, rather than local adaptation, homogenized the MHC genes of both populations. This study indicates that both balancing selection and genetic drift may shape genetic variation and differentiation in small and fragmented populations.

Mechanistic understanding of perianth traits hindering pollination in Aristolochia contorta Bunge.

Insects are vital pollinators for angiosperms, playing a crucial role in their reproductive success and fruit production. Aristolochia contorta is a perennial herbaceous vine that occurs in fragmented populations across East Asia. One notable feature of this plant is its trap flower, which employs a unique mechanism to attract, trap, retain, and release insects, ensuring effective pollination. The presence of this trap flower significantly influences the pollination system of A. contorta. Field surveys and pollination experiments were conducted to understand the processes and effectiveness of its pollination mechanism. It was allogamous and was pollinated by the species from Ceratopogonidae. During the insect attraction stage, 11.57% of the flowers contained insects, primarily Ceratopogonidae spp. Most Ceratopogonidae spp. concentrated in few flowers, indicating that although overall attraction might be modest, specific flowers acted as significant focal points for gathering. Trichomes effectively trapped Ceratopogonidae spp. inside flower tubes. In the retention stage, 26.16% of Ceratopogonidae spp. were loaded with pollen grains, but only 7.91% of those exited the flowers in the release stage. The sticky texture of the perianth's internal cavity posed challenges during this release, leading to adhesion and clogging of the narrow perianth tube. Consequently, a significant portion of Ceratopogonidae spp. became trapped on the perianth wall and perished. This highlights that despite the significant energy and resources invested in flower development, the perianth contributes to the low pollination effectiveness. This study revealed additive factors with negative effects on pollination, including the densely clustered distribution of its pollinators within only a few flowers, insufficient pollen loading onto pollinators, hindered release of entrapped pollinators due to the perianth adhesive surface, and a high rate of defective pollen grains in A. contorta. These factors account for the observed phenomenon of low fruit set (7.7%) and contribute to the diminished rate of sexual reproduction in A. contorta populations. This might lead the species to heavily rely on asexual reproduction, which could potentially lead to gene erosion within populations. The implications of these findings extend to the ecological and conservation aspects, emphasizing the need to understand and conserve the unique pollination system of A. contorta.

Ultra-short cell-free DNA fragments enhance cancer early detection in a multi-analyte blood test combining mutation, protein and fragmentomics.

Cancer morbidity and mortality can be reduced if the cancer is detected early. Cell-free DNA (cfDNA) fragmentomics emerged as a novel epigenetic biomarker for early cancer detection, however, it is still at its infancy and requires technical improvement. We sought to apply a single-strand DNA sequencing technology, for measuring genetic and fragmentomic features of cfDNA and evaluate the performance in detecting multiple cancers. Blood samples of 364 patients from six cancer types (colorectal, esophageal, gastric, liver, lung, and ovarian cancers) and 675 healthy individuals were included in this study. Circulating tumor DNA mutations, cfDNA fragmentomic features and a set of protein biomarkers were assayed. Sensitivity and specificity were reported by cancer types and stages. Circular Ligation Amplification and sequencing (CLAmp-seq), a single-strand DNA sequencing technology, yielded a population of ultra-short fragments (<100 bp) than double-strand DNA preparation protocols and reveals a more significant size difference between cancer and healthy cfDNA fragments (25.84 bp vs. 16.05 bp). Analysis of the subnucleosomal peaks in ultra-short cfDNA fragments indicates that these peaks are regulatory element "footprints" and correlates with gene expression and cancer stages. At 98 % specificity, a prediction model using ctDNA mutations alone showed an overall sensitivity of 46 %; sensitivity reaches 60 % when protein is added, sensitivity further increases to 66 % when fragmentomics is also integrated. More improvements observed for samples representing earlier cancer stages than later ones. These results suggest synergistic properties of protein, genetic and fragmentomics features in the identification of early-stage cancers.

Preservation of genetic diversity in a highly fragmented population of the gray-sided vole Myodes rufocanus in an intensive farming region.

Individual dispersal plays an important role in preserving genetic diversity in density-fluctuating populations of arvicoline rodents. When habitats are fragmented and dispersal between habitats is severely constrained, genetic diversity can be lost. Here, I investigated whether genetic diversity in the gray-sided vole Myodes rufocanus was preserved in an intensive farming region in Japan, where voles inhabited isolated windbreak forests along the borders of plowed lands. Genetic structure was examined in 673 vole samples (330 in spring and 343 in fall) collected at 34 windbreak forests located 0.35-20 km apart. A part of the control region (425 bp) of mitochondrial DNA (mtDNA) was sequenced in 673 voles, yielding 76 haplotypes. Genetic differentiation of maternally inherited mtDNA among trapping sites was markedly lower in males than in females in both seasons, indicating strong male-biased dispersal. Genotypes at six microsatellite DNA loci were determined in 494 voles (245 in spring and 249 in fall) from 18 trapping sites, and loci harbored 16-24 alleles. The mean number of alleles per locus (allelic diversity) at trapping sites was positively correlated with the number of examined individuals (density) in both seasons, and the relationship was very similar to that of a previous study performed in much less fragmented populations. The genetic differentiation of microsatellite DNA among trapping sites decreased considerably from spring to fall. In a STRUCTURE analysis with a most probable cluster number of two, closer trapping sites showed more similar mean values of cluster admixture proportions. The present findings indicate that gene flow among isolated windbreak forests, which occurred mainly by dispersal of males, was not restrained in this intensive farming region. Furthermore, the results suggest that genetic diversity in the study population was preserved as well as in less fragmented populations.

Genetic diversity and structure of mongolian gazelle (Procapra gutturosa) populations in fragmented habitats

BackgroundThe Mongolian gazelle (Procapra gutturosa) population has shown a considerable range of contractions and local extinctions over the last century, owing to habitat fragmentation and poaching. A thorough understanding of the genetic diversity and structure of Mongolian gazelle populations in fragmented habitats is critical for planning effective conservation strategies.ResultIn this study, we used eight microsatellite loci and mitochondrial cytochrome b (Cytb) to compare the levels of genetic diversity and genetic structure of Mongolian gazelle populations in the Hulun Lake National Nature Reserve (HLH) with those in the China-Mongolia border area (BJ). The results showed that the nucleotide diversity and observed heterozygosity of the HLH population were lower than those of the BJ population. Moreover, the HLH and BJ populations showed genetic differentiation. We concluded that the HLH population had lower genetic diversity and a distinct genetic structure compared with the BJ population.ConclusionThe genetic diversity of fragmented Mongolian gazelle populations, can be improved by protecting these populations while reinforcing their gene exchange with other populations. For example, attempts can be made to introduce new individuals with higher genetic diversity from other populations to reduce inbreeding.

Contribution of small rodent communities (Muridae) to the history of West Central African savannas (case of Gabonese savannas): diversity, biogeographic affinities, phylogeography and paleoenvironmental analyses

Savannas of West Central Africa stand around or inside the large rainforest block. They result from paleo-climatic fluctuations, but the details of their history remain poorly known. The aim of the present study is to explain the present distribution of savannas in West Central Africa, considering the two classic anthropic or paleoclimatic hypotheses about their origin. The study was focused on Gabonese savannas and based on small terrestrial mammal patterns. The phylogeography of small species of strictly savanicolous rodents was compared using nested clade analysis of haplotype networks based on cytochrome b mitochondrial DNA, coupled with other approaches. The data were also compared with literature data on vegetation changes in tropical West Africa over the last 150,000 years to test scenarios on the origin and history of Gabonese savannas. The results showed several fragmentation events of small rodent populations and revealed redundant biogeographic relationships. These events were dated, and the results about the history of rodent species were congruent with palaeobiological data about the successive phases of savanna expansion and fragmentation: the results support the hypothesis of a paleoclimatic origin of the Western Congolian forest-savanna mosaic. These rodent population fragmentation events occurred more than 50,000 years ago.

Genomic approaches to mitigating genetic diversity loss in declining populations.

The accelerating pace of global biodiversity loss is exacerbated by habitat fragmentation and subsequent inbreeding in small populations. To address this problem, conservation practitioners often turn to assisted breeding programmes with the aim of enhancing genetic diversity in declining populations. Although genomic information is infrequently included in these efforts, it has the potential to significantly enhance the success of such programmes. In this study, we showcase the value of genomic approaches for increasing genetic diversity in assisted breeding efforts, specifically focusing on a highly inbred population of Western burrowing owls. To maximize genetic diversity in the resulting offspring, we begin by creating an optimal pairing decision tree based on sex, kinship and patterns of homozygosity across the genome. To evaluate the effectiveness of our strategy, we compare genetic diversity, brood size and nestling success rates between optimized and non-optimized pairs. Additionally, we leverage recently discovered correlations between telomere length and fitness across species to investigate whether genomic optimization could have long-term fitness benefits. Our results indicate that pairing individuals with contrasting patterns of homozygosity across the genome is an effective way to increase genetic diversity in offspring. Although short-term field-based metrics of success did not differ significantly between optimized and non-optimized pairs, offspring from optimized pairs had significantly longer telomeres, suggesting that genetic optimization can help reduce the risk of inbreeding depression. These findings underscore the importance of genomic tools for informing efforts to preserve the adaptive potential of small, inbred populations at risk of further decline.

Shed skin as a source of DNA for genotyping-by-sequencing (GBS) in reptiles

Over a fifth of reptile species are classified as ‘Threatened’ and conservation efforts, especially those aimed at recovery of isolated or fragmented populations, will require genetic and genomic data and resources. Shed skins of snakes and other reptiles contain DNA; are a safe and ethical way of non-invasively sampling large numbers of individuals; and provide a simple mechanism by which to involve the public in scientific research. Here we test whether the DNA in dried shed skin is suitable for reduced representation sequencing approaches, specifically genotyping-by-sequencing (GBS). Shed skin-derived libraries resulted in fewer sequenced reads than those from snap-frozen muscle samples, and contained slightly fewer variants (70,685 SNPs versus 97,724), but this issue can easily be rectified with deeper sequencing of shed skin-derived libraries. Skin-derived libraries also have a very slight (but significantly different) profile of transitions and transversions, most likely as a result of DNA damage, but the impact of this is minimal given the large number of single nucleotide polymorphisms (SNPs) involved. SNP density tends to scale with chromosome length, and microchromosomes have a significantly higher SNP density than macrochromosomes, most likely because of their higher GC content. Overall, shed skin provides DNA of sufficient quality and quantity for the identification of large number of SNPs, but requires greater sequencing depth, and consideration of the GC richness of microchromosomes when selecting restriction enzymes.

Cryophilic Tardigrada have disjunct and bipolar distribution and establish long-term stable, low-density demes

Glaciers are inhabited by various cryophilic organisms ranging from single celled to multicellular, like Tardigrada (water bears). Owing to their scattered distribution, glaciers represent extremely fragmented habitats, and it remains unclear how their inhabitants survive and disperse among such isolated patches. This study investigates the biogeography of the tardigrade genus Cryoconicus, whose distribution, population stability, and interregional connectivity are examined by screening the collections from ~ 60 glaciers worldwide and by a phylogeographic analysis. We found that two Cryoconicus species occur at low densities on two Arctic glaciers in Svalbard, far from their previously reported Antarctic and Central Asian ranges. Screening of worldwide databases and DNA metabarcoding indicated that these species are absent or rare in the intermediate areas, suggesting large disjunctions in their ranges. In particular, the genetic data and multiyear resampling showed that Cryoconicus kaczmareki established a stable population on the Ebba Glacier (Svalbard), which has been isolated from its Asian core range since before the last glacial maximum. Our findings suggest that glacial invertebrates may possess wide yet largely disjunctive ranges. Interpolar- or intercontinental-scale movements of cryophilic meiofauna may occur, but migration connectivity is not sufficient to mitigate the differentiation of the local population. Revealed biogeographic patterns further demonstrate that inhabitants of extreme environments may establish isolated and highly fragmented populations that persist long term, even if at very low densities.

Can flowers help to disentangle the Vriesea oligantha complex (Bromeliaceae: Tillandsioideae)? Taxonomic implications and contributions to the floral anatomy and biology of Stigmatodon

Abstract The Vriesea oligantha complex comprises Vriesea lancifolia, Vriesea oligantha, and Vriesea pseudoligantha, which were recently transferred to Stigmatodon. Such species exhibit strong morphological convergence to live in rocky fields, which makes difficult their identification in the wild or in herbarium specimens. In a previous work, leaf characters helped in the species delimitation and evidenced a new taxon. Considering that morphology, anatomy, and aspects of floral biology can contribute to better define species limits and to indicate potential pollinators, individuals from nine populations of V. oligantha complex were comparatively studied. The typical V. oligantha is mainly distinguished by tubular flowers, with simple petal appendages and diurnal anthesis. The remaining individuals studied from different populations exhibit campanulate corollas, with denticulate petal appendages and nocturnal anthesis, not allowing for the separation of V. lancifolia, V. pseudoligantha, and a fourth taxon. Floral anatomy is less variable than the external morphology, with little contribution to the species delimitation; however, it is helpful in the circumscription of Stigmatodon. The infralocular septal nectaries and the floral features provide evidence that the main pollinators of campanulate and tubular flowers are bats and hummingbirds, respectively. Specific pollinator guilds in combination with fragmented populations may explain the limited gene flow amongst populations.

Meta‐ and subpopulation estimation with disparate data: coconut crabs in the Western Indian Ocean

AbstractWidely dispersed fragmented populations are a challenge to monitor because subpopulation sizes may be very small, difficult to access and time consuming to sample regularly. We use the coconut crab (Birgus latro) on Pemba, United Republic of Zanzibar as a case study for estimating highly fragmented populations and metapopulation sizes. The species is a very large terrestrial decapod threatened by exploitation and habitat alteration and now classified as vulnerable. We developed an integrated model to analyse capture‐mark‐recapture (CMR) data from five sites jointly with count data from 24 sites to estimate site‐level densities and population sizes, predicted total population size across the Pemba archipelago, and investigated the effect of six predictors of human influence on density. We fitted separate models to test the effect of the same predictors on raw counts and individual body mass. We estimate the total population of coconut crabs on the Pemba archipelago to be c. 6700 terrestrial individuals. We show that government protection generally affects crabs positively, whereas presence of agriculture negatively affects their densities. This study highlights that time‐consuming CMR data can be leveraged to estimate densities on less visited sites, and that fully protected islands are critical for maintaining relatively high population densities. Our overall population estimate suggests that Pemba still hosts a viable coconut crab population in a part of its range where the species is otherwise in steep decline.

The impact of habitat loss and population fragmentation on genomic erosion

Habitat loss and population fragmentation pose severe threats to biodiversity and the survival of many species. Population isolation and the decline in effective population size lead to increased genetic drift and inbreeding. In turn, this reduces neutral diversity, and it also affects the genetic load of deleterious mutations. Here, we analyse the effect of such genomic erosion by designing a spatially explicit, individual based model in SLiM, simulating the effects of the recorded habitat loss in Mauritius over the past ~ 250 years. We show that the loss of neutral diversity (genome-wide heterozygosity) was barely noticeable during the first 100 years of habitat loss. Changes to the genetic load took even more time to register, and they only became apparent circa 200 years after the start of habitat decline. Although a considerable number of deleterious mutations were lost by drift, others increased in frequency. The masked load was thus converted into a realised load, which compromised individual fitness and population viability after much of the native habitat had been lost. Importantly, genomic erosion continued after the metapopulation had stabilised at low numbers. Our study shows that historic habitat loss can pose a sustained threat to populations also in future generations, even without further habitat loss. The UN’s Decade on Ecosystem Restoration needs to lead to transformative change to save species from future extinction, and this requires the urgent restoration of natural habitats.

Patterns and drivers of vector-borne microparasites in a classic metapopulation.

Many organisms live in fragmented populations, which has profound consequences on the dynamics of associated parasites. Metapopulation theory offers a canonical framework for predicting the effects of fragmentation on spatiotemporal host–parasite dynamics. However, empirical studies of parasites in classical metapopulations remain rare, particularly for vector-borne parasites. Here, we quantify spatiotemporal patterns and possible drivers of infection probability for several ectoparasites (fleas, Ixodes trianguliceps and Ixodes ricinus) and vector-borne microparasites (Babesia microti, Bartonella spp., Hepatozoon spp.) in a classically functioning metapopulation of water vole hosts. Results suggest that the relative importance of vector or host dynamics on microparasite infection probabilities is related to parasite life-histories. Bartonella, a microparasite with a fast life-history, was positively associated with both host and vector abundances at several spatial and temporal scales. In contrast, B. microti, a tick-borne parasite with a slow life-history, was only associated with vector dynamics. Further, we provide evidence that life-history shaped parasite dynamics, including occupancy and colonization rates, in the metapopulation. Lastly, our findings were consistent with the hypothesis that landscape connectivity was determined by distance-based dispersal of the focal hosts. We provide essential empirical evidence that contributes to the development of a comprehensive theory of metapopulation processes of vector-borne parasites.