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375 results for “island population”
Data from: Small but connected islands can maintain populations and genetic diversity under climate change
<p>In response to the striking effects of environmental change, conservation strategies often include the identification of conservation areas that can effectively maintain vulnerable species. Consequently, identifying system-specific conditions that maintain the demographic and genetic viability of species of conservation concern is essential. Connectivity plays a critical role in the persistence of populations. Islands have been model systems to understand connectivity and metapopulation processes and have emerged as particularly favorable targets for conservation. While islands can be isolated from mainland disturbances, it is unknown what degree of isolation is necessary to avoid unfavorable changes but remain sufficiently connected to maintain population viability. To test this question, we explored connectivity within the Apostle Islands, an archipelago of 22 islands within Lake Superior, by comparing historical and contemporary trends in ice bridge connectivity and by simulating the effect of reduced connectivity within this system. We developed a demographically informed individual-based model to explicitly test the role of connectivity to influence the persistence and genetic diversity of American marten (<em>Martes americana</em>), a forest carnivore at risk across its southern range boundary. We found that genetic diversity was resilient to moderate changes in ice cover, but a complete loss of connectivity resulted in rapid genetic erosion. Despite genetic erosion, populations persisted as long as nominal connectivity occurred between islands. Our work suggests that connectivity will decline, but martens would be resilient to moderate changes, and, in the short term, the Apostle Islands can act as a refuge along this species' southern range boundary. Identifying thresholds in connectivity that maintain populations but allow for isolation from disturbance will be necessary to identify suitable areas for species conservation across space and time.</p>
Polyandry and non-random fertilisation maintain long-term genetic diversity in an isolated island population of adders (Vipera berus)
<p>Conservation genetic theory suggests that small and isolated populations should be subjected to reduced genetic diversity i.e., heterozygosity and allelic diversity. Our 34 years study of an isolated island population of adders (<em>Vipera berus</em>) in southern Sweden challenges this notion. Despite a lack of gene flow and a yearly mean estimated reproductive adult population size of only 65 adult adders (range 12 to 171), the population has been able to maintain high levels of heterozygosity and allelic diversity similar to that observed in two mainland populations. Even a 14-year major "bottleneck" i.e., a reduction in adult adder numbers, encompassing at least four adder generations, did not result in any reduction in the island adders' heterozygosity and allelic diversity. Female adders are polyandrous, and fertilisation is non-random, which our empirical data and modelling suggest underpinning the island adders' ability to maintain a high level of heterozygosity. Our empirical results and subsequent modelling suggest that the positive genetic effects of polyandry in combination with non-random fertilisation, often overlooked in conservation genetic analyses, deserve greater consideration when predicting long-term survival of small and isolated populations.</p>
Coupling and de-coupling of the El Niño Southern Oscillation to the supply of larval fishes to benthic populations in the Hawaiian Islands
<p>Several recent high intensity ENSO events have caused strong negative impacts on the adult phases of foundational species in coral reef ecosystems, but comparatively little is known about how climatic variables related to recent ENSOs are impacting the supply of larvae to benthic populations. In marine fishes and invertebrates, reproductive adults and planktonic larvae are generally more sensitive to environmental variability than older, non-reproductive adults. Further, the transport of larvae in ocean currents may also be strongly ENSO dependent. The interactions between the dynamics of larval survivorship and larval transport could lead to population bottlenecks as stronger ENSO events become more common. We tested the predictions of this hypothesis around the Main Hawaiian Islands (MHI) by constructing a correlation matrix of physical and biological time series variables that spanned 11 years (2007 – 2017) and multiple ENSO events. Our correlation matrix included four types of variables: i. published ENSO indices, ii. satellite-derived sea surface temperature (SST) and chlorophyll variables, iii. abundance and diversity of larval fishes sampled during the late winter spawning season off Oahu, and iv. abundance and diversity of coral reef fish recruits sampled on the western shore of the Big Island of Hawaii. We found that the abundance and diversity of larval fishes was negatively correlated with the Multivariate El Niño Index (MEI), and that larval variables were positively correlated with measures of fall recruitment (September & November), but not correlated with spring-summer recruitment (May & July). In the MHI, SST variables were not correlated with the MEI, but two successive El Niño events of 2014-15 and 2015-2016 were characterized by SST maxima approaching 30 °C. Two large pulses of benthic recruitment occurred in the 2009 and 2014 recruitment seasons, with > 8000 recruits observed by divers over the summer and fall months. Both events were characterized by either neutral or negative MEI indices measured during the preceding winter months. These patterns suggest that La Niña and the neutral phases of the ENSO cycle are generally favorable for adult reproduction and larval development in the spring and summer, while El Niño phases may limit recruitment in the late summer and fall. We hypothesize that episodic recruitment during non-El Niño phases is related to favorable survivorship and transport dynamics that are associated with the formation of pairs of anticyclonic and cyclonic eddies on the leeward sides (western shores) of the Main Hawaiian Islands.</p>
An assemblage-level comparison of genetic diversity and population genetic structure between island and mainland ant populations
<p>Island biotas provide unparalleled opportunities to examine evolutionary processes. Founder effects and bottlenecks, for example, typically decrease genetic diversity in island populations, while selection for reduced dispersal can increase population structure. Given that support for these generalities mostly comes from single-species analyses, assemblage-level comparisons are needed to clarify how (i) colonization affects the gene pools of interacting insular organisms, and (ii) patterns of genetic differentiation vary within assemblages of organisms. Here, we use genome-wide sequence data from ultraconserved elements (UCEs) to compare genetic diversity and population structure of mainland and island populations of nine ant species in coastal southern California with respect to genetic diversity and population structure. As expected, island populations (from Santa Cruz Island) had lower than expected heterozygosity and Watterson's theta compared to mainland populations (from the Lompoc Valley). Island populations, however, exhibited smaller genetic distances among samples, indicating less population subdivision and a higher capacity for dispersal compared to mainland populations. Within the focal assemblage, pairwise F<sub>st</sub> values revealed pronounced interspecific variation in mainland-island differentiation, which increases with gyne body size. Our results reveal differences in genetic diversity and population genetic structure across an assemblage of interacting species, and illuminate general patterns of insularization in ants. Compared to single-species studies, our analysis of nine species pairs from the same island-mainland system offers a powerful approach to studying fundamental evolutionary processes.</p>
Figure 3 in The population structure of Mesobuthus gibbosus (Scorpiones: Buthidae) on Koufonisi Island (central Aegean Archipelago, Greece)
Figure 3: The population per sampling.
Figure 6 in The population structure of Mesobuthus gibbosus (Scorpiones: Buthidae) on Koufonisi Island (central Aegean Archipelago, Greece)
Figure 6: The Relative Surface Density per sampling.
Figure 5 in The population structure of Mesobuthus gibbosus (Scorpiones: Buthidae) on Koufonisi Island (central Aegean Archipelago, Greece)
Figure 5: The number of animals joining/leaving the population from one sampling to the next.
Figure 4 in The population structure of Mesobuthus gibbosus (Scorpiones: Buthidae) on Koufonisi Island (central Aegean Archipelago, Greece)
Figure 4: The proportion of marked scorpions per sampling.
Figure 2 in The population structure of Mesobuthus gibbosus (Scorpiones: Buthidae) on Koufonisi Island (central Aegean Archipelago, Greece)
Figure 2: Northern (top) and western (bottom) view of the study site at Pori bay.
Plate 1 in Population status and distribution assessment of Nicobar Long-Tailed Macaque Macaca Fascicularis Umbrosus (Miller, 1902) in Nicobar Group of Islands
Plate 1. Nicobar Long tailed Macaque in its natural forested habitat.
Fig. 1 in Population size, distribution and daylight behaviour of Irrawaddy dolphins (Orcaella brevirostris) in Penang Island, Malaysia
Fig. 1. Penang Island. Shown are the survey trackline west of island and fishing villages.
Genomic diversity and differentiation between island and mainland populations of White‐tailed Eagles (Haliaeetus albicilla)
<p>Using whole genome shotgun sequences from 92 white-tailed eagles (<em>Haliaeetus albicilla</em>) sampled from Greenland, Iceland, Norway, Denmark, Estonia, and Turkey between 1885–1950 and after 1990, we investigate the genomic variation within countries over time, and between countries. Clear signatures of ancient biogeographic substructure across Europe and the North‐East Atlantic are observed. The greatest genomic differentiation was observed between island (Greenland and Iceland) and mainland (Denmark, Norway and Estonia) populations. The two island populations share a common ancestry from a single mainland population, distinct from the other sampled mainland populations, and despite the potential for high connectivity between Iceland and Greenland they are well separated from each other and are characterized by inbreeding and little variation. Temporal differences also highlight a pattern of regional populations persisting despite the potential for admixture. All sampled populations generally showed a decline in effective population size over time, which may have been shaped by four historical events: I) isolation of refugia during the last glacial period 110‐115,000 years ago, II) population divergence following the colonization of the deglaciated areas ~10,000 years ago, III) human population expansion, which led to the settlement in Iceland ~1,100 years ago, and IV) human persecution and exposure to toxic pollutants during the last two centuries.</p>
Runs of homozygosity reveal past bottlenecks and contemporary inbreeding across diverging populations of an island-colonizing bird
<p>Genomes retain evidence of the demographic history and evolutionary forces that have shaped populations. Across island systems, contemporary patterns of genetic diversity reflect complex population demography, including colonisation events, bottlenecks, gene flow and genetic drift. Here, we investigate whether island founder events have prolonged effects on genome-wide diversity and runs of homozygosity (ROH) distributions, using whole genome resequencing from six populations across three archipelagos of Berthelot's pipit (<em>Anthus</em> <em>berthelotii</em>) – a passerine which has undergone island speciation relatively recently. Pairwise sequential Markovian coalescent (PSMC) analyses estimated divergence from its sister species approximately two million years ago. Results indicate that all Berthelot's pipit populations had shared ancestry until approximately 50,000 years ago, when the Madeiran archipelago populations were founded, while the Selvagens were colonised within the last 8,000 years. We identify extensive long ROH (>1 Mb) in genomes in the most recently colonised populations of Madeira and Selvagens which have experienced sequential island founder events and population crashes. Population expansion within the last 100 years may have eroded long ROH in the Madeiran archipelago, resulting in a prevalence of short ROH (<1 Mb). Extensive long and short ROH in the Selvagens reflects strong recent inbreeding, small contemporary effective population size and past bottleneck effects, with as much as 37.7% of the autosomes comprised of ROH >250 kb in length. These findings highlight the importance of demographic history, as well as selection and genetic drift, in shaping contemporary patterns of genomic diversity across diverging populations. </p>
Dataset for density estimation for an island population of raccoon dogs in Japan
<p><span>Estimation of the population</span><span> size</span><span> is essential for understanding population dynamics</span><span>. Estimating animal density using multiple methods and/or multiple attempts is required for accurate estimations. Raccoon dog (<em>Nyctereutes</em> <em>procyonoides</em>) is native to East Asia, including Japan, and has become an invasive species in Europe. Information on raccoon dog density in their native range is important to understand their invasion; however, relatively few studies have been conducted on raccoon dog density in their native range. In this study, we extracted DNA from fecal samples of raccoon dogs inhabiting a small island in Japan and conducted density estimation over two periods using DNA capture-recapture methods: CAPWIRE and SECR. We also investigated sex ratio</span> <span>using genetic sex identification. Density estimates using SECR were approximately threefold different between the two study periods: </span><span>17.2</span><span> individuals per km<sup>2</sup> in 2018 and </span><span>49.0 </span><span>individuals per km<sup>2</sup> in 2020. In contrast, estimates using CAPWIRE were relatively stable: </span><span>21.7</span><span> individuals per km<sup>2</sup> in 2018 and </span><span>24.3</span><span> individuals per km<sup>2</sup> in 2020. A drastic increase or decrease is not expected during the study period, and thus</span><span>, density estimates using CAPWIRE are more reasonable than </span><span>those using SECR. The small number of samples per individual might result in low accuracy of density estimates by SECR. The density estimated by CAPWIRE was similar to that in the main island in Japan</span> <span>and higher than that in Europe. Feeding competition with other omnivorous carnivores and/or predation risk by wolves might maintain the low density in Europe. The sex ratio of raccoon dogs was 1:1, which was similar to </span><span>the values in invasive raccoon dogs and </span><span>other canids. Further genetic census</span><span>, including sex identification in various landscapes in their native and invasive range, will enable us to understand not only the ecology of raccoon dogs but also their adaptations to </span><span>their invading areas.</span></p>
A major myna problem; invasive predator removal benefits female survival and population growth of a translocated island endemic
<p>Invasive predators are a major driver of extinctions and continue to threaten native populations worldwide. Island eradications of (mostly mammalian) invasive predators have facilitated the reestablishment of numerous island-endemic populations. Other invasive taxa, such as some predatory birds, could pose a more persistent threat due to their ability to fly and actively re-invade even remote and isolated islands. However, the impact of invasive predatory birds has been largely overlooked. We report on a novel sex-specific impact of an invasive-nest predator, the common myna (<span><em>Acridotheres</em> <em>tristis</em></span>), on a reintroduced population of Seychelles warblers (<span><em>Acrocephalus</em> <em>sechellensis</em></span>); translocated from Cousin Island to Denis Island in 2004. Regular post-translocation monitoring revealed that female mortality was 20 % higher than males, leading to a 60<span>–</span>70 % male-biased population sex-ratio between 2005 and 2015. This was attributed to common mynas inflicting severe injuries to incubating female Seychelles warblers while attempting to prey upon eggs in their nests. These effects likely contributed to the slower-than-expected population growth observed (relative to previous translocations of Seychelles warblers to other islands) over the same period. An eradication programme beginning in 2011 removed all common mynas from Denis by 2015. Subsequently, we observed a balancing of sex-specific survival and the population sex-ratio of Seychelles warblers and, consequently, accelerated population growth. This study demonstrates the importance of assessing the threat posed by all invasive taxa (not just mammals) to island conservation. Furthermore, we show how extended monitoring is needed to identify problems and develop solutions, post-translocation.</p>
Data for: A novel cricket morph has diverged in song and wing morphology across island populations
<p class="MsoNormal"><span>Divergence of sexual signals between populations can lead to speciation, yet opportunities to study the immediate aftermath of novel signal evolution are rare. The recent emergence and spread of a new mating song, purring, in Hawaiian populations of the Pacific field cricket (<em>Teleogryllus oceanicus</em>) allows us to investigate population divergence soon after the origin of a new signal. Male crickets produce songs with specialized wing structures to attract mates from afar (calling) and entice them to mate when found (courtship). However, in Hawaii, these songs also attract an eavesdropping parasitoid fly (<em>Ormia ochracea</em>) that kills singing males. The novel purring song, produced with heavily modified wing morphology, attracts female crickets but not the parasitoid fly, acting as a solution to this conflict between natural and sexual selection. We've since observed increasing numbers of purring males across Hawaii. In this integrative field study, we investigated the distribution of purring and the proportion of purring males relative to other morphs in six populations on four islands and compared a suite of phenotypic traits (wing morphology, calling song, and courtship song) that make up this novel signal across populations of purring males. We show that purring is found in varying proportions across five, and is locally dominant in four, Hawaiian populations. We also show that calling songs, courtship songs, and wing morphology of purring males differ geographically. Our findings demonstrate the rapid pace of evolution in island populations and provide insights into the emergence and divergence of new sexual signals over time.</span></p>
Phenotypic and genetic diversity data recorded in island and mainland populations worldwide
<p><span>We used this dataset to assess the strength of isolation due to geographic and macroclimatic distance across island and mainland systems, comparing published measurements of phenotypic traits and neutral genetic diversity for populations of plants and animals worldwide. </span>The dataset includes 112 studies of 108 species (72 animals and 36 plants) in 868 island populations and 760 mainland populations, with population-level taxonomic and biogeographic information, totalling 7438 records.</p>
Data from: Evolutionarily labile dispersal behavior and discontinuous habitats enhance population differentiation in island vs continentally distributed swallows
<p class="MsoNormal"><span>The causes of population divergence in vagile groups remain a paradox in evolutionary biology: dispersive species should be able to colonize new areas, a prerequisite for allopatric speciation, but dispersal also facilitates gene flow, which erodes population differentiation. Strong dispersal ability has been suggested to enhance divergence in patchy habitats and inhibit divergence in continuous landscapes, but empirical support for this hypothesis is lacking. Here we compared patterns of population divergence in a dispersive clade of swallows distributed across both patchy and continuous habitats. The Pacific Swallow (</span><em>Hirundo tahitica</em><span>) has an insular distribution throughout Southeast Asia and the Pacific, while its sister species, the Welcome Swallow (</span><em>H. neoxena</em><span>), has a continental distribution in Australia. We used whole-genome data to demonstrate strong genetic structure and limited introgression among insular populations, but not among continental populations. Demographic models show that historic changes in habitat connectivity have contributed to population structure within the cl</span>ade. Swallows appear to exhibit evolutionarily labile dispersal behavior in which they reduce dispersal propensity after island colonization despite retaining strong flight ability. Our data support the hypothesis that fragmented habitats enhance population differentiation in vagile groups, and suggest that labile dispersal behavior is a key mechanism underlying this pattern.</p>
Data from: Evolutionarily labile dispersal behavior and discontinuous habitats enhance population differentiation in island vs continentally distributed swallows
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Data from: Adaptive landscape genetics and malaria across divergent island bird populations
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