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1.
Orchid bees (Hymenoptera, Apidae, Euglossini) are important pollinators of many plant families in Neotropical forests, habitats that have become increasingly degraded and fragmented by agricultural practices. To understand the extent to which loss of natural habitat and isolation has affected the genetic diversity and diploid male production (DMP) of two orchid bee species, Euglossa dilemma and Euglossa viridissima, we collected and genotyped 1686 males at five microsatellite loci and tested for differences in allelic richness, heterozygosity and DMP across three different types of land use (natural, agricultural and urban) and between mainland and island populations in the Yucatan Peninsula of Mexico. We also investigated the impact of land use and geographic isolation on gene flow. Euglossa dilemma and E. viridissima seemed to be particularly resilient to loss of natural habitat; in locations with human impact, we did not find reduced genetic diversity, and populations generally showed very little population genetic structure. Only on islands did E. dilemma show significantly reduced genetic diversity. Even after accounting for putative null alleles, DMP was very low (0.2–1.3%) across all sampling sites, including on islands. We therefore suggest that DMP is an insensitive measure of inbreeding and population decline in our two study species.  相似文献   

2.
Patterns of genetic structure for some bee species suggest that gene flow may be limited across natural and human-created barriers and that local dispersal or natal site fidelity may be common. Interestingly, this past work has primarily focused on female bees, despite the fact that males may differ substantially in their dispersal processes. By examining genetic structure and diploidy in males, it is possible to gain insight into potential barriers to gene flow and drivers of inbreeding. In this study, we examine diploidy as well as regional and local spatial genetic structure using males of Bombus vosnesenskii, a stable bumble bee species found across western North America. Specifically, we investigate patterns of genetic structure in both island and mainland populations, across spatial scales, and over a range of natural and human-altered habitats. We document high levels of male diploidy, with significantly higher levels in mainland populations compared to island populations and increasing diploidy in areas with poor nesting habitat. Interestingly, we also find evidence of significant spatial genetic structure from 0 to 10 km and 0 to 5 km on island and mainland populations, respectively. Finally, we document low but significant genetic differentiation across the region (ΦST = 0.049). Overall, this work reveals the unique potential for biogeographic context and local habitat composition to drive male diploidy patterns in bumble bees.  相似文献   

3.
Sex determination is ruled by haplodiploidy in Hymenoptera, with haploid males arising from unfertilized eggs and diploid females from fertilized eggs. However, diploid males with null fitness are produced under complementary sex determination (CSD), when individuals are homozygous for this locus. Diploid males are expected to be more frequent in genetically eroded populations (such as islands and captive populations), as genetic diversity at the csd locus should be low. However, only a few studies have focused on the relation between population size, genetic diversity, and the proportion of diploid males in the field. Here, we developed new microsatellite markers in order to assess and compare genetic diversity and diploid male proportion (DMP) in populations from three distinct habitat types – mainland, island, or captive –, in the parasitoid wasp Venturia canescens. Eroded genetic diversity and higher DMP were found in island and captive populations, and habitat type had large effect on genetic diversity. Therefore, DMP reflects the decreasing genetic diversity in small and isolated populations. Thus, Hymenopteran populations can be at high extinction risk due to habitat destruction or fragmentation.  相似文献   

4.
Reduced levels of genetic variability and a prominent differentiation in both neutral marker genes and phenotypic traits are typical for many island populations as compared to their mainland conspecifics. However, whether genetic diversity in neutral marker genes reflects genetic variability in quantitative traits, and thus, their evolutionary potential, remains typically unclear. Moreover, the phenotypic differentiation on islands could be attributable to phenotypic plasticity, selection or drift; something which seldom has been tested. Using eight polymorphic microsatellite loci and quantitative genetic breeding experiments we conducted a detailed comparison on genetic variability and differentiation between Nordic islands (viz. Gotland, Öland and Læsø) and neighbouring mainland populations of moor frogs (Rana arvalis). As expected, the neutral variation was generally lower in island than in mainland populations. But as opposed to this, higher levels of additive genetic variation (V A) in body size and tibia length were found on the island of Gotland as compared to the mainland population. When comparing the differentiation seen in neutral marker genes (F ST) with the differentiation in genes coding quantitative traits (Q ST) two different evolutionary scenarios were found: while selection might explain a smaller size of moor frogs on Gotland, the differentiation seen in tibia length could be explained by genetic drift. These results highlight the limited utility of microsatellite loci alone in inferring the causes behind an observed phenotypic differentiation, or in predicting the amount of genetic variation in ecologically important quantitative traits.  相似文献   

5.
The red squirrel (Sciurus vulgaris) population in the United Kingdom has declined over the last century and is now on the UK endangered species list. This is the result of competition from the eastern grey squirrel (S. carolinensis) which was introduced in the 19th century. However, recent evidence suggests that the rate of population decline is enhanced by squirrelpox disease, caused by a viral infection carried asymptomatically by grey squirrels but to which red squirrels are highly susceptible. Population genetic diversity provides some resilience to rapidly evolving or exotic pathogens. There is currently no data on genetic diversity of extant UK squirrel populations with respect to genes involved in disease resistance. Diversity is highest at loci involved in the immune response including genes clustered within the major histocompatibility complex (MHC). Using the class II DRB locus as a marker for diversity across the MHC region we genotyped 110 red squirrels from locations in the UK and continental Europe. Twenty-four Scvu-DRB alleles at two functional loci; Scvu-DRB1 and Scvu-DRB2, were identified. High levels of diversity were identified at both loci in the continental populations. In contrast, no diversity was observed at the Scvu-DRB2 locus in the mainland UK population while a high level of homozygosity was observed at the Scvu-DRB1 locus. The red squirrel population in the UK appears to lack the extensive MHC diversity associated with continental populations, a feature which may have contributed to their rapid decline.  相似文献   

6.
In the Azores Islands, two Euphrasia L. (Orobanchaceae) endemic species are recognized: Euphrasia azorica H.C.Watson, an annual herb, in Flores and Corvo, and Euphrasia grandiflora Hochst. ex Seub., a semi-shrub, in Pico, São Jorge and Terceira. Both species are highly endangered and protected by the Bern Convention and Habitats Directive. A population genetics study was conducted with new microsatellite primer pairs in 159 individuals of E. azorica and E. grandifolia, sampled from populations in Flores, Corvo, Pico and São Jorge. Allele sizing suggested that E. azorica is a diploid while E. grandiflora is a tetraploid. Euphrasia grandiflora revealed higher genetic diversity then E. azorica. The E. grandiflora population of Morro Pelado in São Jorge, displayed higher genetic diversity when compared with all others, while the E. azorica population of Madeira Seca in Corvo, showed the lowest. Private and less common bands were also overall higher in E. grandiflora populations. Population genetic structure analysis confirmed a distinctiveness between the two Azorean endemic Euphrasia, in addition to island-specific genetic patterns in E. azorica. The genetic structure obtained for E. grandiflora was complex with the populations of Cabeço do Mistério in Pico Island and of Pico da Esperança in São Jorge sharing the same genetic group, while a putative spatial barrier to gene flow was still retrieved between both islands. Although some populations of both species might benefit from propagation actions, studies are needed on plant host species and translocations between islands or between some populations of a same island should be avoided, due to the occurrence of putative ESUs. Eradication of invasive species and control of grazing will be fundamental to promote in situ restauration.  相似文献   

7.
Melampyrum sylvaticum is an endangered annual hemiparasitic plant that is found in only 19 small and isolated populations in the United Kingdom (UK). To evaluate the genetic consequences of this patchy distribution we compared levels of diversity, inbreeding and differentiation from ten populations from the UK with eight relatively large populations from Sweden and Norway where the species is more continuously distributed. We demonstrate that in both the UK and Scandinavia, the species is highly inbreeding (global F IS = 0.899). Levels of population differentiation were high (FST = 0.892) and significantly higher amongst UK populations (FST = 0.949) than Scandinavian populations (FST = 0.762; P < 0.01). The isolated populations in the UK have, on average, lower genetic diversity (allelic richness, proportion of loci that are polymorphic, gene diversity) than Scandinavian populations, and this diversity difference is associated with the smaller census size and population area of UK populations. From a conservation perspective, the naturally inbreeding nature of the species may buffer the species against immediate effects of inbreeding depression, but the markedly lower levels of genetic diversity in UK populations may represent a genetic constraint to evolutionary change. In addition, the high levels of population differentiation suggest that gene flow among populations will not be effective at replenishing lost variation. We thus recommend supporting in situ conservation management with ex situ populations and human-mediated seed dispersal among selected populations in the UK.  相似文献   

8.
Nucleotide sequences of the mitochondrial DNA cytochrome b (CytB) gene fragment and the control region (D-loop) of Dolly Varden (Salvelinus malma) from the Commander Islands and the Kol River of the Kamchatka Peninsula were examined. A high level of genetic variability of island populations comparable to that of the mainland population of western Kamchatka was demonstrated. The belonging of the Commander Islands chars to the genetic lineage of northern Dolly Varden Salvelinus malma malma was confirmed.  相似文献   

9.
Patterns of genetic structure and diversity are largely mediated by a species’ ecological niche and sensitivity to climate variation. Some species with narrow ecological niches have been found to exhibit increased population differentiation, limited gene flow across populations, and reduced population genetic diversity. In this study, we examine patterns of population genetic structure and diversity of four bumble bee species that are broadly sympatric, but do not necessarily inhabit the same ecological niche in the Pacific Northwest of the United States. Testing for the effect of isolation by geographic distance (IBD) with linearized F st and D est found that Bombus sylvicola and B. mixtus exhibited significant IBD across populations. In contrast, both B. melanopygus and B. flavifrons, two species that are distributed across a broad elevation gradient, exhibited no IBD, a result further corroborated by Bayesian a priori population assignment tests. Furthermore, we discovered that B. sylvicola populations distributed on the Olympic Peninsula have significantly less average allelic diversity than populations distributed in the Cascade Mountains. Our results suggest that populations distributed in the Olympic Mountains represent a distinct genetic cluster relative to the Cascade Mountains, with B. sylvicola and B. mixtus likely experiencing the greatest degree of population genetic differentiation relative to B. flavifrons and B. melanopygus. While bumble bees are known to co-exist across a diversity of habitats, our results demonstrate that underlying population genetic structure and diversity may not necessarily be similar across species, and are largely governed by their respective niches.  相似文献   

10.
Owing to habitat loss populations of many organisms have declined and become fragmented. Vertebrate conservation strategies routinely consider genetic factors, but their importance in invertebrate populations is poorly understood. Bumblebees are important pollinators, and many species have undergone dramatic declines. As monoandrous social hymenopterans they may be particularly susceptible to inbreeding due to low effective population sizes. We study fragmented populations of a bumblebee species, on a model island system, and on mainland Great Britain where it is rare and declining. We use microsatellites to study: population genetic structuring and gene flow; the relationships between genetic diversity, population size and isolation; and frequencies of (sterile) diploid males - an indicator of inbreeding. We find significant genetic structuring (theta = 0.12) and isolation by distance. Populations > 10 km apart are all significantly differentiated, both on oceanic islands and on the mainland. Genetic diversity is reduced relative to closely related common species, and isolated populations exhibit further reductions. Of 16 populations, 10 show recent bottlenecking, and 3 show diploid male production. These results suggest that surviving populations of this rare insect suffer from inbreeding as a result of geographical isolation. Implications for the conservation of social hymenopterans are discussed.  相似文献   

11.
This paper presents data on the polymorphism of inter simple sequence repeats of DNA in the silver crucian carp Carassius auratus gibelio in water bodies in the southern part of Western Siberia. The share of polymorphic ISSR-PCR bands in silver crucian carp populations from different lakes varied from 40 to 70%, and Nei’s gene diversity index varied from 0.16 to 0.25. The genetic diversity indices were lower in the populations that were largely represented by females than in bisexual ones. The highest levels of genetic polymorphism were revealed in populations with diploid–triploid complexes. The gene diversity index of the silver crucian carp population is positively correlated with the reservoir size (r = 0.90, p = 0.015; Rs = 0.74, p = 0.036).  相似文献   

12.
Three Azorean endemic Ammi species were initially described: Ammi trifoliatum (Wats.) Trel., Ammi seubertianum (Wats.) Trel. and Ammi huntii (Wats.) Trel. Many taxonomic changes have been conducted, and one to three species have been considered. Two species are currently accepted: A. trifoliatum, which occurs in almost every island, and A. seubertianum, with a narrower distribution. In this research, the population genetic diversity and structure of the Azorean Ammi species were assessed using eight specifically designed SSR markers. A wide sampling of A. seubertianum and A. trifoliatum was conducted in seven Azorean islands, and four A. huntii herbarium samples were also included to further contribute to the taxonomy of this genus in Azores. Flores populations showed the highest genetic diversity, while North of Topo, in São Jorge, showed the lowest. None of the populations analysed displayed signs of putative inbreeding. The population genetic structure analyses conducted partially provided support for the two currently accepted species, but other possible cryptic taxa may also be present. The complex clustering obtained seems to result from a combined action of geography, geology and ecology, and although island-specific genetic patterns were found, environmental conditions connected to different altitudes and the existence of micro-niches may also play an important role. A thorough morphological revision and ecophysiological studies should be conducted to clarify the number of endemic taxonomic entities present in the Azores archipelago.  相似文献   

13.
Species endemic to sky island systems are isolated to mountain peaks and high elevation plateaux both geographically and ecologically, making them particularly vulnerable to the effects of climate change. Pressures associated with climate change have already been linked to local extinctions of montane species, emphasizing the importance of understanding the genetic diversity and population connectivity within sky islands systems for the conservation management of remaining populations. Our study focuses on the endangered alpine skink Pseudemoia cryodroma, which is endemic to the Victorian Alps in south-eastern Australia, and has a disjunct distribution in montane habitats above 1100 m a.s.l. Using mitochondrial DNA (mtDNA) and microsatellite loci, we investigated species delimitation, genetic connectivity and population genetic structure across the geographic range of this species. We found discordance between genetic markers, indicating historical mtDNA introgression at one of the study sites between P. cryodroma and the closely related, syntopic P. entrecasteauxii. Molecular diversity was positively associated with site elevation and extent of suitable habitat, with inbreeding detected in three of the five populations. These results demonstrate the complex interaction between geography and habitat in shaping the population structure and genetic diversity of P. cryodroma, and highlight the importance of minimising future habitat loss and fragmentation for the long-term persistence of this species.  相似文献   

14.
Honey bees are the most important managed pollinators as they provide key ecosystem services for crop production worldwide. Recent losses of honey bee colonies in North America and Europe have demonstrated a need to develop strategies to improve their health and conserve their populations. Previously, we showed that feral honey bees—colonies that live in the wild without human assistance—exhibit higher levels of immunocompetence than managed colonies in North Carolina (USA). In a first attempt to investigate the underlying mechanisms of this difference in immune response, here we characterize the genetic composition of feral and managed honey bees using microsatellite markers. Our results reveal significant but small genetic differentiation between feral and managed honey bee colonies (?CT = 0.047, P?=?0.03) indicating admixture between these two groups. Higher genetic diversity was correlated with higher immune response in feral (P MANOVA = 0.011) but not managed bees, despite the fact that the latter group showed significantly higher average genetic diversity (P ANCOVA < 0.001). These findings suggest that genetic diversity is positively associated with immunocompetence in feral honey bee colonies, and that the benefits of genetic diversity are obscured in managed bees, perhaps as a result of artificial selection. We hypothesize that high genetic variability provides the raw material upon which natural selection acts and generates adaptive genotypes in unmanaged populations. Feral populations could be useful sources of genetic variation to use in breeding programs that aim to improve honey bee health.  相似文献   

15.
A successful control or eradication programme using biological control or genetically-mediated methods requires knowledge of the origin and the extent of wasp genetic diversity. Mitochondrial DNA variation in the native and invaded range of the social wasp Vespula germanica was used to examine intra-specific genetic variation and invasive source populations. We also examined wasps for the presence of four viruses found in honey bees: Acute bee paralysis virus, Deformed wing virus, Israeli acute paralysis virus and Kashmir bee virus. German wasps showed reduced genetic diversity in the invaded range compared to that of their native range. Populations in the introduced range are likely to have arrived from different source populations. All four viral honey bee pathogens were found in V. germanica, although they varied in their distribution and strain. Multiple introductions of German wasps have occurred for most invaded regions, though some populations are genetically homogenous. The differing locations of origin will guide researchers searching for biocontrol agents and the reduced genetic diversity may make these wasps a potentially viable target for control via gene drives.  相似文献   

16.
The island of Borneo is the diversity center of the Dipterocarpaceae, the most important family of tropical rainforest trees in Southeast Asia. However, changes in land use and climate have affected dipterocarp distributions on the island, raising concerns about the vulnerability (inter alia) of the endemic riparian species Shorea macrophylla. Thus, to aid conservation efforts, we have investigated the genetic diversity, structure, and demographic history of S. macrophylla. The species’ genetic diversity and structure in Kalimantan (part of Indonesia, covering 75% of the island) were explored by examining genotypes of 377 individuals representing 13 populations in three regions (Northeast, Central, and West Kalimantan) using 14 newly developed microsatellite loci. Higher genetic diversity was found, at all loci, in samples from Northeast Kalimantan than in samples from the other regions. Moderate genetic differentiation between populations was detected (FST 0.093). Bayesian clustering, principal coordinate, and neighbor joining tree analyses of the population structure consistently identified two genetically distinct groups, one in the Northeast and the other in the Central and West regions. The higher diversity of the diverged populations in Northeast Kalimantan indicates that the region may have hosted rainforest refugia during the ice age. Accordingly, analysis using DIY ABC software indicated that the Northeast and Central-West Kalimantan groups diverged 194,000 years ago. We conclude that global climate change during the Pleistocene strongly influenced the genetic diversity and structure of S. macrophylla populations in Kalimantan.  相似文献   

17.
The island of St Helena in the South Atlantic Ocean has a rich endemic flora, with 10 endemic genera and 45 recognised endemic species. However, populations of most endemic species have undergone dramatic reductions or extinction due to over-exploitation, habitat destruction and competition from invasive species. Consequently, endemic species are likely to have lost genetic variation, in some cases to extreme degrees. Here, the entire extant wild populations and all planted trees in seed orchards, of two critically endangered species in the endemic genus Commidendrum (Asteraceae), C. rotundifolium and C. spurium, were sampled to assess levels of genetic variation and inbreeding. Six new microsatellite loci were developed from next-generation sequence data, and a total of 190 samples were genotyped. Some seed orchard trees contained alleles from both wild C. rotundifolium and C. spurium indicating they could be hybrids and that some backcrossing may have occurred. Some of these trees were more similar to C. rotundifolium than C. spurium both genetically and morphologically. Importantly, allelic variation was detected in the putative hybrids that was not present in wild material. C. rotundifolium is represented by just two individuals one wild and one planted and C. spurium by seven, therefore the seed orchard trees comprise an important part of the total remaining genetic diversity in the genus Commidendrum.  相似文献   

18.
Oceanic archipelagos are typically rich in endemic taxa, because they offer ideal conditions for diversification and speciation in isolation. One of the most remarkable evolutionary radiations on the Canary Islands comprises the 16 species included in Limonium subsection Nobiles, all of which are subject to diverse threats, and legally protected. Since many of them are single-island endemics limited to one or a few populations, there exists a risk that a loss of genetic variation might limit their long-term survival. In this study, we used eight newly developed microsatellite markers to characterize the levels of genetic variation and inbreeding in L. macrophyllum, a species endemic to the North-east of Tenerife that belongs to Limonium subsection Nobiles. We detected generally low levels of genetic variation over all populations (H T = 0.363), and substantial differentiation among populations (F ST = 0.188; R ST = 0.186) coupled with a negligible degree of inbreeding (F?=?0.042). Obligate outcrossing may have maintained L. macrophyllum relatively unaffected by inbreeding despite the species’ limited dispersal ability and the genetic bottlenecks likely caused by a prolonged history of grazing. Although several factors still constitute a risk for the conservation of L. macrophyllum, the lack of inbreeding and the recent positive demographic trends observed in the populations of this species are factors that favour its future persistence.  相似文献   

19.
Many animal populations that are endangered in mainland areas exist in stable island populations, which have the potential to act as an “ark” in case of mainland population declines. Previous studies have found neutral genetic variation in such species to be up to an order of magnitude lower in island compared to mainland populations. If low genetic variation is prevalent across fitness-related loci, this would reduce the effectiveness of island populations as a source of individuals to supplement declining mainland populations or re-establish extinct mainland populations. One such species, the black-footed rock-wallaby (Petrogale lateralis lateralis), exists within fragmented mainland populations and small island populations off Western Australia. We examined sequence variation in this species within a fitness-related locus under positive selection, the MHC class II DAB β1 locus. The mainland populations displayed greater levels of allelic diversity (4–7 alleles) than the island population, despite being small and isolated, and contained at least two DAB gene copies. The island population displayed low allelic diversity (2 alleles) and fewer alleles per individual in comparison to mainland populations, and probably possesses only one DAB gene copy. The patterns of DAB diversity suggested that the island population has a markedly lower level of genetic variation than the mainland populations, in concordance with results from microsatellites (genotyped in a previous study), but preserved unique alleles which were not found in mainland populations. Where possible, conservation actions should pool individuals from multiple populations, not only island populations, for translocation programs, and focus on preventing further declines in mainland populations.  相似文献   

20.
Lepidospartum burgessii is a rare gypsophilic shrub with limited distribution in New Mexico and Texas. Most of the known plants are restricted to two large populations, with a few small, isolated populations scattered in the surrounding area. The low recruitment observed in the two largest populations may be due to low seed set resulting from high inbreeding and/or self-incompatibility. We used eight microsatellite loci to quantify diversity, relatedness, inbreeding, population structure, and frequency of clonal reproduction. Seed collections were made to quantify seed set and germination rates. Overall, there was a moderate level of clonal diversity within patches of L. burgessii indicating asexual growth is important for population persistence. Inbreeding coefficients were high both between and within populations. Most patches showed a significant level of relatedness between individuals. At a fine scale, patches within populations were significantly different from each other, however when all patches were combined, the two populations of L. burgessii were not genetically distinct. Compared to a population of its common congener, Lepidospartum latisquamum, L. burgessii populations had similar measures of diversity, more clonal reproduction, and lower germination rates. High relatedness and inbreeding may explain the low seed set and recruitment in L. burgessii, however factors such as insect herbivory and precipitation changes may further depress recruitment.  相似文献   

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