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1.
    
The arctic phytoplankton spring bloom, which is often diatom‐dominated, is a key event that provides the high latitude communities with a fundamental flux of organic carbon. During a bloom, phytoplankton may increase its biomass by orders of magnitude within days. Yet, very little is known about phytoplankton bloom dynamics, including for example how blooming affects genetic composition and diversity of a population. Here, we quantified the genetic composition and temporal changes of the diatom Fragilariopsis cylindrus, which is one of the most important primary producers in the Arctic, during the spring bloom in western Greenland, using 13 novel microsatellite markers developed for this study. We found that genetic differentiation (quantified using sample‐specific FST) decreased between time points as the bloom progressed, with the most drastic changes in FST occurring at the start of the bloom; thus the genetic structure of the bloom is characterized by isolation by time. There was little temporal variation in genetic diversity throughout the bloom (mean HE = 0.57), despite marked fluctuations in F. cylindrus cell concentrations and the temporal change in sample‐specific FST. On the basis of this novel pattern of genetic differentiation, we suggest that blooming behavior may promote genetic diversity of a phytoplankton population.  相似文献   

2.
    
Nineteen polymorphic microsatellite loci were identified and developed for Natrix maura. Polymorphism was assessed for 120 individuals sampled across four sampling sites from the French Pyrenees Mountains. The number of alleles per locus ranged from 3 to 15, and expected heterozygosity per locus ranged from 0.227 to 0.863. We tested for deviation from Hardy–Weinberg equilibrium and linkage disequilibrium and assessed the presence of null alleles for all loci, resulting in a selection of 14 high‐quality polymorphic markers. These markers will be extremely useful in identifying fine‐scale genetic structures and providing insight into conservation management plans of this species.  相似文献   

3.
    
Understanding levels of connectivity among scleractinian coral populations over a range of temporal and spatial scales is vital for managing tropical coral reef ecosystems. Here, we use multilocus microsatellite genotypes to assess the spatial genetic structure of two molecular operational taxonomic units (MOTUs, types α and β) of the widespread coral Pocillopora damicornis on the Great Barrier Reef (GBR) and infer the extent of connectivity on spatial scales spanning from local habitat types to latitudinal sectors of the GBR. We found high genetic similarities over large spatial scales spanning > 1000 km from the northern to the southern GBR, but also strong genetic differentiation at local scales in both MOTUs. The presence of a considerable number of first‐generation migrants within the populations sampled (12% and 27% for types α and β, respectively) suggests that genetic differentiation over small spatial scales is probably a consequence of stochastic recruitment from different genetic pools into recently opened up spaces on the reef, for example, following major disturbance events. We explain high genetic similarity among populations over hundreds of kilometres by long competency periods of brooded zooxanthellate larvae and multiple larval release events each year, combined with strong longshore currents typical along the GBR. The lack of genetic evidence for predominantly clonal reproduction in adult populations of P. damicornis, which broods predominantly asexually produced larvae, further undermines the paradigm that brooded larvae settle close to parent colonies shortly after the release.  相似文献   

4.
    
It is generally assumed that species with low population sizes have lower genetic diversities than larger populations and vice versa. However, this would not be the case for long‐lived species with long generation times, and which populations have declined due to anthropogenic effects, such as the blue whale (Balaenoptera musculus). This species was intensively decimated globally to near extinction during the 20th century. Along the Chilean coast, it is estimated that at least 4288 blue whales were hunted from an apparently pre‐exploitation population size (k) of a maximum of 6200 individuals (Southeastern Pacific). Thus, here, we describe the mtDNA (control region) and nDNA (microsatellites) diversities of the Chilean blue whale aggregation site in order to verify the expectation of low genetic diversity in small populations. We then compare our findings with other blue whale aggregations in the Southern Hemisphere. Interestingly, although the estimated population size is small compared with the pre‐whaling era, there is still considerable genetic diversity, even after the population crash, both in mitochondrial (N = 46) and nuclear (N = 52) markers (Hd = 0.890 and Ho = 0.692, respectively). Our results suggest that this diversity could be a consequence of the long generation times and the relatively short period of time elapsed since the end of whaling, which has been observed in other heavily‐exploited whale populations. The genetic variability of blue whales on their southern Chile feeding grounds was similar to that found in other Southern Hemisphere blue whale feeding grounds. Our phylogenetic analysis of mtDNA haplotypes does not show extensive differentiation of populations among Southern Hemisphere blue whale feeding grounds. The present study suggests that although levels of genetic diversity are frequently used as estimators of population health, these parameters depend on the biology of the species and should be taken into account in a monitoring framework study to obtain a more complete picture of the conservation status of a population.  相似文献   

5.
    
Glacial phases during the Pleistocene caused remarkable changes in species range distributions, with inevitable genetic consequences. Specifically, during interglacial phases, when the ice melted and new habitats became suitable again, species could recolonize regions that were previously covered by ice, such as high latitudes and elevations. Based on theoretical models and empirical data, a decrease in genetic variation is predicted along recolonization routes as a result of the consecutive founder effects that characterize the recolonization process. In the present study, we assessed the relative importance of historical and contemporary processes in shaping genetic diversity and differentiation of bank vole (Myodes glareolus) populations at different elevations in the Swiss Alps. By contrast to expectations, we found that genetic variation increased with elevation. Estimates of recent migration rates and a contrasting pattern of genetic differentiation observed at the mitochondrial cytochrome b gene and nuclear microsatellites support the hypothesis that higher genetic diversity at high elevation results from contemporary gene flow. Although historical recolonization processes can have marked effects on the genetic structure of populations, the present study provides an example where contemporary processes along an environmental gradient can reverse predicted patterns of genetic variation.  相似文献   

6.
Simple sequence repeat (SSR) markers were developed from expressed sequence tags (ESTs) for Rhododendron section Brachycalyx in order to elucidate its evolutionary processes and reproductive ecology. Nineteen polymorphic EST‐SSR markers were developed from EST libraries of R. amagianum and R. hyugaense. Polymorphisms for these markers were assessed using four species of section Brachycalyx. The number of alleles ranged from 1 to 14, and the observed and expected heterozygosity ranged from 0.000 to 0.931 and 0.000 to 0.904, respectively. The EST‐SSR markers developed in this study will be useful for elucidating population genetic structure and breeding systems in section Brachycalyx.  相似文献   

7.
    
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8.
    
Connectivity underpins the persistence and recovery of marine ecosystems. The Great Barrier Reef (GBR) is the world's largest coral reef ecosystem and managed by an extensive network of no‐take zones; however, information about connectivity was not available to optimize the network's configuration. We use multivariate analyses, Bayesian clustering algorithms and assignment tests of the largest population genetic data set for any organism on the GBR to date (Acropora tenuis, >2500 colonies; >50 reefs, genotyped for ten microsatellite loci) to demonstrate highly congruent patterns of connectivity between this common broadcast spawning reef‐building coral and its congener Acropora millepora (~950 colonies; 20 reefs, genotyped for 12 microsatellite loci). For both species, there is a genetic divide at around 19°S latitude, most probably reflecting allopatric differentiation during the Pleistocene. GBR reefs north of 19°S are essentially panmictic whereas southern reefs are genetically distinct with higher levels of genetic diversity and population structure, most notably genetic subdivision between inshore and offshore reefs south of 19°S. These broadly congruent patterns of higher genetic diversities found on southern GBR reefs most likely represent the accumulation of alleles via the southward flowing East Australia Current. In addition, signatures of genetic admixture between the Coral Sea and outer‐shelf reefs in the northern, central and southern GBR provide evidence of recent gene flow. Our connectivity results are consistent with predictions from recently published larval dispersal models for broadcast spawning corals on the GBR, thereby providing robust connectivity information about the dominant reef‐building genus Acropora for coral reef managers.  相似文献   

9.
    
New Guinea is a topographically and biogeographically complex region that supports unique endemic fauna. Studies describing the population connectivity of species through this region are scarce. We present a population and landscape genetic study on the endemic malaria‐transmitting mosquito, Anopheles koliensis (Owen). Using mitochondrial and nuclear sequence data, as well as microsatellites, we show the evidence of geographically discrete population structure within Papua New Guinea (PNG). We also confirm the existence of three rDNA ITS2 genotypes within this mosquito and assess reproductive isolation between individuals carrying different genotypes. Microsatellites reveal the clearest population structure and show four clear population units. Microsatellite markers also reveal probable reproductive isolation between sympatric populations in northern PNG with different ITS2 genotypes, suggesting that these populations may represent distinct cryptic species. Excluding individuals belonging to the newly identified putative cryptic species (ITS2 genotype 3), we modeled the genetic differences between A. koliensis populations through PNG as a function of terrain and find that dispersal is most likely along routes with low topographic relief. Overall, these results show that A. koliensis is made up of geographically and genetically discrete populations in Papua New Guinea with landscape topography being important in restricting dispersal.  相似文献   

10.
    
Conservation biologists have increasingly used translocations to mitigate population declines and restore locally extirpated populations. Genetic data can guide the selection of source populations for translocations and help evaluate restoration success. Bighorn sheep (Ovis canadensis) are a managed big game species that suffered widespread population extirpations across western North America throughout the early 1900s. Subsequent translocation programs have successfully re‐established many formally extirpated bighorn herds, but most of these programs pre‐date genetically informed management practices. The state of Nevada presents a particularly well‐documented case of decline followed by restoration of extirpated herds. Desert bighorn sheep (O. c. nelsoni) populations declined to less than 3,000 individuals restricted to remnant herds in the Mojave Desert and a few locations in the Great Basin Desert. Beginning in 1968, the Nevada Department of Wildlife translocated ~2,000 individuals from remnant populations to restore previously extirpated areas, possibly establishing herds with mixed ancestries. Here, we examined genetic diversity and structure among remnant herds and the genetic consequences of translocation from these herds using a genotyping‐by‐sequencing approach to genotype 17,095 loci in 303 desert bighorn sheep. We found a signal of population genetic structure among remnant Mojave Desert populations, even across geographically proximate mountain ranges. Further, we found evidence of a genetically distinct, potential relict herd from a previously hypothesized Great Basin lineage of desert bighorn sheep. The genetic structure of source herds was clearly reflected in translocated populations. In most cases, herds retained genetic evidence of multiple translocation events and subsequent admixture when founded from multiple remnant source herds. Our results add to a growing literature on how population genomic data can be used to guide and monitor restoration programs.  相似文献   

11.
    
Biological invasions comprise accidental evolutionary experiments, whose genetic compositions underlie relative success, spread and persistence in new habitats. However, little is known about whether, or how, their population genetic patterns change temporally and/or spatially across the invasion's history. Theory predicts that most would undergo founder effect, exhibit low genetic divergence across the new range and gain variation over time via new arriving propagules. To test these predictions, we analyse population genetic diversity and divergence patterns of the Eurasian round goby Neogobius melanostomus across the two decades of its North American invasion in the Laurentian Great Lakes, comparing results from 13 nuclear DNA microsatellite loci and mitochondrial DNA cytochrome b sequences. We test whether ‘genetic stasis’, ‘genetic replacement’ and/or ‘genetic supplement’ scenarios have occurred at the invasion's core and expansion sites, in comparison with its primary native source population in the Dnieper River, Black Sea. Results reveal pronounced genetic divergence across the exotic range, with population areas remaining genetically distinct and statistically consistent across two decades, supporting ‘genetic stasis’ and ‘founder takes most’. The original genotypes continue to predominate, whose high population growth likely outpaced the relative success of later arrivals. The original invasion core has stayed the most similar to the native source. Secondary expansion sites indicate slight allelic composition convergence towards the core population over time, attributable to some early ‘genetic supplementation’. The geographic and temporal coverage of this investigation offers a rare opportunity to discern population dynamics over time and space in context of invasion genetic theory vs. reality.  相似文献   

12.
    
The nematode Caenorhabditis elegans is a central laboratory model system in almost all biological disciplines, yet its natural life history and population biology are largely unexplored. Such information is essential for in‐depth understanding of the nematode's biology because its natural ecology provides the context, in which its traits and the underlying molecular mechanisms evolved. We characterized natural phenotypic and genetic variation among North German C. elegans isolates. We used the unique opportunity to compare samples collected 10 years apart from the same compost heap and additionally included recent samples for this and a second site, collected across a 1.5‐year period. Our analysis revealed significant population genetic differentiation between locations, across the 10‐year time period, but for only one location a trend across the shorter time frame. Significant variation was similarly found for phenotypic traits of likely importance in nature, such as choice behavior and population growth in the presence of pathogens or naturally associated bacteria. Phenotypic variation was significantly influenced by C. elegans genotype, time of isolation, and sampling site. The here studied C. elegans isolates may provide a valuable, genetically variable resource for future dissection of naturally relevant gene functions.  相似文献   

13.
    
Vulture populations worldwide have suffered precipitous declines in recent decades. The Cinereous Vulture Aegypius monachus, a highly philopatric scavenger distributed across southern Europe and the central Asian plateau, is threatened in many parts of its range. Turkey holds the second largest population of this species in the Western Palaearctic, but there has been no research on its genetic structure and the possible implications of this structure for the future of the species. Here we report nuclear diversity and relatedness determined by short tandem repeat genotyping of 81 individuals from the four largest colonies. Our results demonstrated no significant genetic structuring, suggesting a single panmictic metapopulation connected by frequent dispersal. Furthermore, we show that the study population has retained moderate levels of genetic diversity, despite passing through a recent demographic bottleneck. We estimated the effective population size to be 112 individuals (95% confidence interval 74–201). Our results imply that the observed lack of increase in population size since the 1990s has not been caused by lowered fitness due to genetic inbreeding but rather by increased mortality via demographic processes. In the short term, we suggest that conservation efforts should treat the Turkish subpopulations as a single management unit and aim to increase population size through effective protection, especially during the breeding season.  相似文献   

14.
    
Sex differences in skews of vertebrate lifetime reproductive success are difficult to measure directly. Evolutionary histories of differential skew should be detectable in the genome. For example, male‐biased skew should reduce variation in the biparentally inherited genome relative to the maternally inherited genome. We tested this approach in lek‐breeding ruff (Class Aves, Philomachus pugnax) by comparing genetic variation of nuclear microsatellites (θn; biparental) versus mitochondrial D‐loop sequences (θm; maternal), and conversion to comparable nuclear (Ne) and female (Nef) effective population size using published ranges of mutation rates for each marker (μ). We provide a Bayesian method to calculate Ne (θn = 4Neμn) and Nef (θm = 2Nefμm) using 95% credible intervals (CI) of θn and θm as informative priors, and accounting for uncertainty in μ. In 96 male ruffs from one population, Ne was 97% (79–100%) lower than expected under random mating in an ideal population, where Ne:Nef = 2. This substantially lower autosomal variation represents the first genomic support of strong male reproductive skew in a lekking species.  相似文献   

15.
    
Symbiodinium are a diverse group of unicellular dinoflagellates that are important nutritional symbionts of reef‐building corals. Symbiodinium putative species (‘types’) are commonly identified with genetic markers, mostly nuclear and chloroplast encoded ribosomal DNA regions. Population genetic analyses using microsatellite loci have provided insights into Symbiodinium biogeography, connectivity and phenotypic plasticity, but are complicated by: (i) a lack of consensus criteria used to delineate inter‐ vs. intragenomic variation within species; and (ii) the high density of Symbiodinium in host tissues, which results in single samples comprising thousands of individuals. To address this problem, Wham & LaJeunesse (2016) present a method for identifying cryptic Symbiodinium species from microsatellite data based on correlations between allele size distributions and nongeographic genetic structure. Multilocus genotypes that potentially do not recombine in sympatry are interpreted as secondary ‘species’ to be discarded from downstream population genetic analyses. However, Symbiodinium species delineations should ideally incorporate multiple physiological, ecological and molecular criteria. This is because recombination tests may be a poor indicator of species boundaries in Symbiodinium due to their predominantly asexual mode of reproduction. Furthermore, discontinuous microsatellite allele sizes in sympatry may be explained by secondary contact between previously isolated populations and by mutations that occur in a nonstepwise manner. Limitations of using microsatellites alone to delineate species are highlighted in earlier studies that demonstrate occasional bimodal distributions of allele sizes within Symbiodinium species and considerable allele size sharing among Symbiodinium species. We outline these issues and discuss the validity of reinterpretations of our previously published microsatellite data from Symbiodinium populations on the Great Barrier Reef (Howells et al. 2013).  相似文献   

16.
Eleven microsatellites were isolated from the vairone Leuciscus souffia (Risso 1826), an endangered fish that inhabits river systems in and around the Alps in Europe. The level of genetic diversity was assessed in 29 individuals of the subspecies L. s. souffia, and their variability was further estimated in seven individuals of a different subspecies, L. s. muticellus. Eight of these microsatellite loci were also applied to seven closely related cyprinid species. Availability of the reported microsatellite loci will facilitate the investigation of population genetic structure of these species with applications for the development of conservation strategies and phylogeographical approaches.  相似文献   

17.
    
The giant kangaroo rat, Dipodomys ingens (Heteromyidae), is an endangered rodent that inhabits approximately 3% of its estimated historic range. Its current distribution is centered in two geographic areas, situated about 150 km apart, in south-central California. We sequenced a 293 base-pair fragment at the 5' end of the control region in 95 giant kangaroo rats from nine localities to examine the genetic structure of extant populations. We determine that mutations in this section of the control region follow a negative binominal distribution, rather than a Poisson. However, the distance between haplotypes is small enough that the difference between a tree that corrects for the non-Poisson distribution of mutations and one that does not, is minimal. This implies that the use of methods that assume a Poisson distribution of mutations, such as those based on coalescent theory, are justified. We find that the correlation between levels of genetic diversity and estimated census size is poor. This suggests that population sizes have fluctuated over time or that populations have not been isolated from one another, or both. We also examine the hierarchical structure of populations and find that the southern populations are not genetically subdivided but that there is significant subdivision between northern and southern populations and between some northern subpopulations. The phylogeographic relationship between northern and southern populations can primarily be attributed to isolation by distance, although the time since divergence between them appears to be less than the age of either. To examine the phylogeographic relationships in more detail we construct a minimum spanning tree based on Tamura-Nei gamma-corrected distances and superimpose on it the geographic position of haplotypes. This reveals that there is more genetic distance between some northern haplotypes than between any northern and southern haplotypes, despite the geographic distance separating north from south and the larger size of the southern population. It also reveals that one northern population, in the Panoche Valley, contains old allelic lineages and shares ancestral polymorphism with several other populations. It also shows that two, small, geographically remote populations contain a surprising amount of genetic diversity, but that different population/geographic processes have affected the structure of that diversity. We estimate the average migration rate among all populations to be 7.5 per generation, and conclude that a disproportionate number of migration events involve gene flow with one northern population, the Panoche Valley. We find evidence for the hypothesis that there has been an increase in population size in the remaining populations in the north and suggest that the Panoche Valley could play a role in these expansions. Finally we discuss the probabilitiy that the genetic structure of the southern populations has been affected by fluctuations in size. These results are briefly compared to other studies on the genetic structure of rodent populations.  相似文献   

18.
    
We estimated local and metapopulation effective sizes ( and meta‐) for three coexisting salmonid species (Salmo salar, Salvelinus fontinalis, Salvelinus alpinus) inhabiting a freshwater system comprising seven interconnected lakes. First, we hypothesized that might be inversely related to within‐species population divergence as reported in an earlier study (i.e., FST: S. salar> S. fontinalis> S. alpinus). Using the approximate Bayesian computation method implemented in ONeSAMP, we found significant differences in () between species, consistent with a hierarchy of adult population sizes (). Using another method based on a measure of linkage disequilibrium (LDNE: ), we found more finite values for S. salar than for the other two salmonids, in line with the results above that indicate that S. salar exhibits the lowest among the three species. Considering subpopulations as open to migration (i.e., removing putative immigrants) led to only marginal and non‐significant changes in , suggesting that migration may be at equilibrium between genetically similar sources. Second, we hypothesized that meta‐ might be significantly smaller than the sum of local s (null model) if gene flow is asymmetric, varies among subpopulations, and is driven by common landscape features such as waterfalls. One ‘bottom‐up’ or numerical approach that explicitly incorporates variable and asymmetric migration rates showed this very pattern, while a number of analytical models provided meta‐ estimates that were not significantly different from the null model or from each other. Our study of three species inhabiting a shared environment highlights the importance and utility of differentiating species‐specific and landscape effects, not only on dispersal but also in the demography of wild populations as assessed through local s and meta‐s and their relevance in ecology, evolution and conservation.  相似文献   

19.
    
Habitat loss and fragmentation negatively impact the size and diversity of many natural populations. Woodland amphibians require connected aquatic and terrestrial habitats to complete their life cycle, and often rely on metapopulation structure for long‐term persistence. Wetland loss and deforestation fragment amphibian populations, which may result in population isolation and its negative effects. The aim of this research was to analyze the population genetic structure of small‐mouthed salamanders (Ambystoma texanum) in western Ohio, where agriculture is now the dominant land use. Salamander tail tissue was collected from eight breeding pools. Three pools occur in the same forest; the other five are in forest patches at distances ranging from 250 m to 20 km from one another. Eight microsatellite loci were amplified by PCR and genotyped for allele size. Observed heterozygosities were lower than expected in all sampled populations; the two most isolated sites (Ha1, Ha2) had the highest inbreeding coefficients. Ha2 also had the lowest mean number of alleles and was found to be genetically differentiated from populations to which our data analysis indicates it was historically connected by gene flow. The most distant site (Ha1) had the highest number of private alleles and showed genetic differentiation from other populations both historically and currently. Geographic distance between pools was strongly correlated with the number of private alleles in a population. The results suggest that population isolation results in decreased genetic diversity and that a breakdown of metapopulation structure due to landscape change may contribute to differentiation between once‐connected populations.  相似文献   

20.
    
Fish migrations are energetically costly, especially when moving between freshwater and saltwater, but are a viable strategy for Pacific salmon and trout (Oncorhynchus spp.) due to the advantageous resources available at various life stages. Anadromous steelhead (O. mykiss) migrate vast distances and exhibit variation for adult migration phenotypes that have a genetic basis at candidate genes known as greb1L and rock1. We examined the distribution of genetic variation at 13 candidate markers spanning greb1L, intergenic, and rock1 regions versus 226 neutral markers for 113 populations (n = 9,471) of steelhead from inland and coastal lineages in the Columbia River. Patterns of population structure with neutral markers reflected genetic similarity by geographic region as demonstrated in previous studies, but candidate markers clustered populations by genetic variation associated with adult migration timing. Mature alleles for late migration had the highest frequency overall in steelhead populations throughout the Columbia River, with only 9 of 113 populations that had a higher frequency of premature alleles for early migration. While a single haplotype block was evident for the coastal lineage, we identified multiple haplotype blocks for the inland lineage. The inland lineage had one haplotype block that corresponded to candidate markers within the greb1L gene and immediately upstream in the intergenic region, and the second block only contained candidate markers from the intergenic region. Haplotype frequencies had similar patterns of geographic distribution as single markers, but there were distinct differences in frequency between the two haplotype blocks for the inland lineage. This may represent multiple recombination events that differed between lineages where phenotypic differences exist between freshwater entry versus arrival timing as indicated by Micheletti et al. (2018a). Redundancy analyses were used to model environmental effects on allelic frequencies of candidate markers, and significant variables were migration distance, temperature, isothermality, and annual precipitation. This study improves our understanding of the spatial distribution of genetic variation underlying adult migration timing in steelhead as well as associated environmental factors and has direct conservation and management implications.  相似文献   

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