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1.
Repeated exposure and flooding of the Sunda and Sahul shelves during Pleistocene sea‐level fluctuations is thought to have contributed to the isolation and diversification of sea‐basin populations within the Coral Triangle. This hypothesis has been tested in numerous phylogeographical studies, recovering an assortment of genetic patterns that the authors have generally attributed to differences in larval dispersal capability or adult habitat specificity. This study compares phylogeographical patterns from mitochondrial COI sequences among two co‐distributed seastars that differ in their adult habitat and dispersal ability, and two seastar ectosymbionts that differ in their degree of host specificity. Of these, only the seastar Linckia laevigata displayed a classical pattern of Indian‐Pacific divergence, but with only moderate genetic structure (Φ CT = 0.067). In contrast, the seastar Protoreaster nodosus exhibited strong structure (Φ CT = 0.23) between Teluk Cenderawasih and the remainder of Indonesia, a pattern of regional structure that was echoed in L. laevigata (Φ CT = 0.03) as well as its obligate gastropod parasite Thyca crystallina (Φ CT = 0.04). The generalist commensal shrimp, Periclimenes soror showed little genetic structuring across the Coral Triangle. Despite species‐specific phylogeographical patterns, all four species showed departures from neutrality that are consistent with massive range expansions onto the continental shelves as the sea levels rose, and that date within the Pleistocene epoch. Our results suggest that habitat differences may affect the manner in which species responded to Pleistocene sea‐level fluctuations, shaping contemporary patterns of genetic structure and diversity. 相似文献
2.
We combine kinship estimates with traditional F‐statistics to explain contemporary drivers of population genetic differentiation despite high gene flow. We investigate range‐wide population genetic structure of the California spiny (or red rock) lobster ( Panulirus interruptus) and find slight, but significant global population differentiation in mtDNA (Φ ST = 0.006, P = 0.001; Dest_Chao = 0.025) and seven nuclear microsatellites ( FST = 0.004, P < 0.001; Dest_Chao = 0.03), despite the species’ 240‐ to 330‐day pelagic larval duration. Significant population structure does not correlate with distance between sampling locations, and pairwise FST between adjacent sites often exceeds that among geographically distant locations. This result would typically be interpreted as unexplainable, chaotic genetic patchiness. However, kinship levels differ significantly among sites (pseudo‐ F16,988 = 1.39, P = 0.001), and ten of 17 sample sites have significantly greater numbers of kin than expected by chance ( P < 0.05). Moreover, a higher proportion of kin within sites strongly correlates with greater genetic differentiation among sites ( Dest_Chao, R2 = 0.66, P < 0.005). Sites with elevated mean kinship were geographically proximate to regions of high upwelling intensity ( R2 = 0.41, P = 0.0009). These results indicate that P. interruptus does not maintain a single homogenous population, despite extreme dispersal potential. Instead, these lobsters appear to either have substantial localized recruitment or maintain planktonic larval cohesiveness whereby siblings more likely settle together than disperse across sites. More broadly, our results contribute to a growing number of studies showing that low FST and high family structure across populations can coexist, illuminating the foundations of cryptic genetic patterns and the nature of marine dispersal. 相似文献
3.
The multistep method here applied in studying the genetic structure of a low dispersal and philopatric species, such as the Fire Salamander Salamandra salamandra, was proved to be effective in identifying the hierarchical structure of populations living in broad‐leaved forest ecosystems in Northern Italy. In this study, 477 salamander larvae, collected in 28 sampling populations (SPs) in the Prealpine and in the foothill areas of Northern Italy, were genotyped at 16 specie‐specific microsatellites. SPs showed a significant overall genetic variation (Global FST = 0.032, P < 0.001). The genetic population structure was assessed by using STRUCTURE 2.3.4. We found two main genetic groups, one represented by SPs inhabiting the Prealpine belt, which maintain connections with those of the Eastern foothill lowland (PEF), and a second group with the SPs of the Western foothill lowland (WF). The two groups were significantly distinct with a Global FST of 0.010 ( P < 0.001). While the first group showed a moderate structure, with only one divergent SP (Global FST = 0.006, P < 0.001), the second group proved more structured being divided in four clusters (Global FST = 0.017, P = 0.058). This genetic population structure should be due to the large conurbations and main roads that separate the WF group from the Prealpine belt and the Eastern foothill lowland. The adopted methods allowed the analysis of the genetic population structure of Fire Salamander from wide to local scale, identifying different degrees of genetic divergence of their populations derived from forest fragmentation induced by urban and infrastructure sprawl. 相似文献
4.
Aim To elucidate the historical phylogeography of the dusky pipefish ( Syngnathus floridae) in the North American Atlantic and Gulf of Mexico ocean basins. Location Southern Atlantic Ocean and northern Gulf of Mexico within the continental United States. Methods A 394‐bp fragment of the mitochondrial cytochrome b gene and a 235‐bp fragment of the mitochondrial control region were analysed from individuals from 10 locations. Phylogenetic reconstruction, haplotype network, mismatch distributions and analysis of molecular variance were used to infer population structure between ocean basins and time from population expansion within ocean basins. Six microsatellite loci were also analysed to estimate population structure and gene flow among five populations using genetic distance methods ( FST, Nei’s genetic distance), isolation by distance (Mantel’s test), coalescent‐based estimates of genetic diversity and migration patterns, Bayesian cluster analysis and bottleneck simulations. Results Mitochondrial analyses revealed significant structuring between ocean basins in both cytochrome b ( ΦST = 0.361, P < 0.0001; ΦCT = 0.312, P < 0.02) and control region ( ΦST = 0.166, P < 0.0001; ΦCT = 0.128, P < 0.03) sequences. However, phylogenetic reconstructions failed to show reciprocal monophyly in populations between ocean basins. Microsatellite analyses revealed significant population substructuring between all locations sampled except for the two locations that were in closest proximity to each other (global FST value = 0.026). Bayesian analysis of microsatellite data also revealed significant population structuring between ocean basins. Coalescent‐based analyses of microsatellite data revealed low migration rates among all sites. Mismatch distribution analysis of mitochondrial loci supports a sudden population expansion in both ocean basins in the late Pleistocene, with the expansion of Atlantic populations occurring more recently. Main conclusions Present‐day populations of S. floridae do not bear the mitochondrial DNA signature of the strong phylogenetic discontinuity between the Atlantic and Gulf coasts of North America commonly observed in other species. Rather, our results suggest that Atlantic and Gulf of Mexico populations of S. floridae are closely related but nevertheless exhibit local and regional population structure. We conclude that the present‐day phylogeographic pattern is the result of a recent population expansion into the Atlantic in the late Pleistocene, and that life‐history traits and ecology may play a pivotal role in shaping the realized geographical distribution pattern of this species. 相似文献
5.
Biogeographic barriers potentially restrict gene flow but variation in dispersal or vagility can influence the effectiveness of these barriers among different species and produce characteristic patterns of population genetic structure. The objective of this study was to investigate interspecific and intraspecific genetic structure in two closely related species that differ in several life‐history characteristics. The grey teal Anas gracilis is geographically widespread throughout Australia with a distribution that crosses several recognized biogeographic barriers. This species has high vagility as its extensive movements track broad‐scale patterns in rainfall. In contrast, the closely related chestnut teal A. castanea is endemic to the mesic southeastern and southwestern regions of Australia and is more sedentary. We hypothesized that these differences in life‐history characteristics would result in more pronounced population structuring in the chestnut teal. We sequenced five nuclear loci (nuDNA) for 49 grey teal and 23 chestnut teal and compared results to published mitochondrial DNA (mtDNA) sequences. We used analysis of molecular variance to examine population structure, and applied coalescent based approaches to estimate demographic parameters. As predicted, chestnut teal were more strongly structured at both mtDNA and nuDNA (Φ ST= 0.163 and 0.054, respectively) than were grey teal (Φ ST < 0.0001 for both sets of loci). Surprisingly, a greater proportion of the total genetic variation was partitioned among populations within species (Φ SC= 0.014 and 0.047 for nuDNA and mtDNA, respectively) than between the two species (Φ CT < 0.0001 for both loci). The ‘Isolation with Migration’ coalescent model suggested a late Pleistocene divergence between the taxa, but remarkably, a deeper divergence between the southeastern and southwestern populations of chestnut teal. We conclude that dispersal potential played a prominent role in the structuring of populations within these species and that divergent selection associated with ecology and life history traits likely contributed to rapid and recent speciation in this pair. 相似文献
6.
Miscanthus lutarioriparius is an endemic species that grows along the middle and lower reaches of the Yangtze River and is a valuable source of germplasm for the development of second‐generation energy crops. The plant that propagates via seeds, stem nodes, and rhizomes shows high phenotypic variation and strong local adaptation. Here, we examined the magnitude and spatial distribution of genetic variation in M. lutarioriparius across its entire distributional range and tested underlying factors that shaped its genetic variation. Population genetic analyses were conducted on 644 individuals from 25 populations using 16 microsatellite markers. M. lutarioriparius exhibited a high level of genetic variation ( HE = 0.682–0.786; Ar = 4.74–8.06) and a low differentiation ( FST = 0.063; Dest = 0.153). Of the total genetic variation, 10% was attributed to the differences among populations (df = 24, P < 0.0001), whereas 90% was attributed to the differences among individuals (df = 619, P ≤ 0.0001). Genetic diversity did not differ significantly across longitudes and did not increase in the populations growing downstream of the Yangtze River. However, significant associations were found between genetic differentiation and spatial distance. Six genetic discontinuities were identified, which mostly distributed among downstream populations. We conclude that anthropogenic factors and landscape features both contributed to shaping the pattern of gene flow in M. lutarioriparius, including long‐distance bidirectional dispersal. Our results explain the genetic basis of the high degree of adaptability in M. lutarioriparius and identify potential sources of new germplasm for the domestication of this potential second‐generation energy crop. 相似文献
7.
Here, we explore the historical and contemporaneous patterns of connectivity among Encholirium horridum populations located on granitic inselbergs in an Ocbil landscape within the Brazilian Atlantic Forest, using both nuclear and chloroplast microsatellite markers. Beyond to assess the E. horridum population genetic structure, we built species distribution models across four periods (current conditions, mid‐Holocene, Last Glacial Maximum [LGM], and Last Interglacial) and inferred putative dispersal corridors using a least‐cost path analysis to elucidate biogeographic patterns. Overall, high and significant genetic divergence was estimated among populations for both nuclear and plastid DNA (Φ ST(n) = 0.463 and Φ ST(plastid) = 0.961, respectively, p < .001). For nuclear genome, almost total absence of genetic admixture among populations and very low migration rates were evident, corroborating with the very low estimates of immigration and emigration rates observed among E. horridum populations. Based on the cpDNA results, putative dispersal routes in Sugar Loaf Land across cycles of climatic fluctuations in the Quaternary period revealed that the populations’ connectivity changed little during those events. Genetic analyses highlighted the low genetic connectivity and long‐term persistence of populations, and the founder effect and genetic drift seemed to have been very important processes that shaped the current diversity and genetic structure observed in both genomes. The genetic singularity of each population clearly shows the need for in situ conservation of all of them. 相似文献
8.
Divergent selection at ecologically important traits is thought to be a major factor driving phenotypic differentiation between populations. To elucidate the role of different evolutionary processes shaping the variation in gill raker number of European whitefish ( Coregonus lavaretus sensu lato) in the Baltic Sea basin, we assessed the relationships between genetic and phenotypic variation among and within three whitefish ecotypes (sea spawners, river spawners and lake spawners). To generate expected neutral distribution of FST and to evaluate whether highly variable microsatellite loci resulted in deflated FST estimates compared to less variable markers, we performed population genetic simulations under finite island and hierarchical island models. The genetic divergence observed among ( FCT = 0.010) and within ( FST = 0.014–0.041) ecotypes was rather low. The divergence in gill raker number, however, was substantially higher between sea and river spawners compared to observed microsatellite data and simulated neutral baseline ( PCT > FCT). This suggests that the differences in gill raker number between sea and river spawners are likely driven by divergent natural selection. We also found strong support for divergent selection on gill raker number among different populations of sea spawners ( PST > FST), most likely caused by highly variable habitat use and diverse diet. The putative role of divergent selection within lake spawners initially inferred from empirical microsatellite data was not supported by simulated FST distributions. This work provides a first formal test of divergent selection on gill raker number in Baltic whitefish, and demonstrates the usefulness of population genetic simulations to generate informative neutral baselines for PST– FST analyses helping to disentangle the effects of stochastic evolutionary processes from natural selection. 相似文献
9.
To examine population genetic diversity and variation of the red stingray Dasyatis akajei, samples from 1 freshwater region and 6 coastal localities within its distribution range were analyzed by using amplified fragment length polymorphism (AFLP) technology. A total of 207 loci were identified by 4 primer combinations from 87 individuals, 174 of which were polymorphic (84.1%). A high level of Nei's gene diversity was observed with the overall value of 0.230 ± 0.179. No significant genealogical clusters associated with sampling sites were revealed on the UPGMA tree. Both analysis of molecular variance (AMOVA, ΦST = 0.085, P = 0.00) and pairwise FST indicated significant genetic differentiation among four marine samples. However, no particular genetic differentiation was detected between marine and the limited sampling freshwater populations (AMOVA, ΦCT = 0.056, P > 0.05). Except for the TZ vs. WZ (5.193), the gene flow estimates ( Nm) demonstrated the effective immigrants were 1.918-2.976, suggesting low level dispersal between pairwise marine populations. Species-specific habits (demersal and sluggish habits) are probably responsible for the population structuring. 相似文献
10.
Knowledge of the degree to which populations are connected through larval dispersal is imperative to effective management,
yet little is known about larval dispersal ability or population connectivity in Lophelia pertusa, the dominant framework-forming coral on the continental slope in the North Atlantic Ocean. Using nine microsatellite DNA
markers, we assessed the spatial scale and pattern of genetic connectivity across a large portion of the range of L. pertusa in the North Atlantic Ocean. A Bayesian modeling approach found four distinct genetic groupings corresponding to ocean regions:
Gulf of Mexico, coastal southeastern U.S., New England Seamounts, and eastern North Atlantic Ocean. An isolation-by-distance
pattern was supported across the study area. Estimates of pairwise population differentiation were greatest with the deepest
populations, the New England Seamounts (average F
ST = 0.156). Differentiation was intermediate with the eastern North Atlantic populations ( F
ST = 0.085), and smallest between southeastern U.S. and Gulf of Mexico populations ( F
ST = 0.019), with evidence of admixture off the southeastern Florida peninsula. Connectivity across larger geographic distances
within regions suggests that some larvae are broadly dispersed. Heterozygote deficiencies were detected within the majority
of localities suggesting deviation from random mating. Gene flow between ocean regions appears restricted, thus, the most
effective management scheme for L. pertusa involves regional reserve networks. 相似文献
11.
Understanding patterns of connectivity in marine species is vital for the management and conservation of marine biodiversity.
Here, the population genetic structure of a common and abundant tropical reef damselfish, Pomacentrus amboinensis, is reported. Using nine polymorphic microsatellite loci, the genetic structure at both small (i.e., around Lizard Island,
Great Barrier Reef [GBR]) and large (GBR and Papua New Guinea [PNG]) spatial and temporal scales (2–1,600 km; 28 days– 6 years;
n = 1,119) was analyzed. Temporal analyses found no evidence of genetic differentiation within or between Lizard Island recruitment
pulses ( R
ST = −0.001, P = 0.788), or corresponding established adult populations separated by 6 years of sampling ( R
ST = 0.003, P = 0.116). The spatial analysis revealed that P. amboinensis populations are largely panmictic on the GBR and eastern PNG ( R
ST = 0.001, P = 0.913), the only genetic discontinuity being between Kimbe Bay to the north of PNG and all populations south of PNG ( R
ST = 0.077, P < 0.0001). Despite assumed high levels of self-recruitment based on previous tagging studies (15–60%), data presented here
indicate that enough recruits are dispersing to impede the evolution of genetic structure over distances as great as 1,600 kms
in this species. Data therefore indicate that the temporal genetic stability recorded here is maintained by high levels of
gene flow. 相似文献
12.
Dispersal shapes demographic processes and therefore is fundamental to understanding biological, ecological, and evolutionary processes acting within populations. However, assessing population connectivity in scoters ( Melanitta sp.) is challenging as these species have large spatial distributions that span remote landscapes, have varying nesting distributions (disjunct vs. continuous), exhibit unknown levels of dispersal, and vary in the timing of the formation of pair bonds (winter vs. fall/spring migration) that may influence the distribution of genetic diversity. Here, we used double‐digest restriction‐associated DNA sequence (ddRAD) and microsatellite genotype data to assess population structure within the three North American species of scoter (black scoter, M. americana; white‐winged scoter, M. deglandi; surf scoter, M. perspicillata), and between their European congeners (common scoter, M. nigra; velvet scoter, M. fusca). We uncovered no or weak genomic structure (ddRAD ΦST < 0.019; microsatellite FST < 0.004) within North America but high levels of structure among European congeners (ddRAD ΦST > 0.155, microsatellite FST > 0.086). The pattern of limited genomic structure within North America is shared with other sea duck species and is often attributed to male‐biased dispersal. Further, migratory tendencies (east vs. west) of female surf and white‐winged scoters in central Canada are known to vary across years, providing additional opportunities for intracontinental dispersal and a mechanism for the maintenance of genomic connectivity across North America. In contrast, the black scoter had relatively elevated levels of divergence between Alaska and Atlantic sites and a second genetic cluster found in Alaska at ddRAD loci was concordant with its disjunct breeding distribution suggestive of a dispersal barrier (behavioral or physical). Although scoter populations appear to be connected through a dispersal network, a small percentage (<4%) of ddRAD loci had elevated divergence which may be useful in linking areas (nesting, molting, staging, and wintering) throughout the annual cycle. 相似文献
13.
Southern smelts ( Retropinna spp.) in coastal rivers of Australia are facultatively diadromous, with populations potentially containing individuals with diadromous or wholly freshwater life histories. The presence of diadromous individuals is expected to reduce genetic structuring between river basins due to larval dispersal via the sea. We use otolith chemistry to distinguish between diadromous and nondiadromous life histories and population genetics to examine interbasin connectivity resulting from diadromy. Otolith strontium isotope ( 87Sr: 86Sr) transects identified three main life history patterns: amphidromy, freshwater residency and estuarine/marine residency. Despite the potential for interbasin connectivity via larval mixing in the marine environment, we found unprecedented levels of genetic structure for an amphidromous species. Strong hierarchical structure along putative taxonomic boundaries was detected, along with highly structured populations within groups using microsatellites ( FST = 0.046–0.181), and mtDNA (Φ ST = 0.498–0.816). The presence of strong genetic subdivision, despite the fact that many individuals reside in saline water during their early life history, appears incongruous. However, analysis of multielemental signatures in the otolith cores of diadromous fish revealed strong discrimination between river basins, suggesting that diadromous fish spend their early lives within chemically distinct estuaries rather than the more homogenous marine environment, thus avoiding dispersal and maintaining genetic structure. 相似文献
14.
The cereal stem borer Busseola fusca Fuller (Lepidoptera: Noctuidae) is a species endemic to sub‐Saharan Africa. It is a major pest of maize and cultivated sorghum, the main cereal crops on the African mainland. Previous studies using mitochondrial markers revealed the presence of three clades of haplotypes (W, KI, KII) among B. fusca populations. Previous preliminary studies based on a few B. fusca individuals collected from three localities within the Guineo‐Congolian rain forest in Cameroon demonstrated a matching with clade KII, a fairly surprising result because the putative centre of origin of that clade is located 3 000 km away in East Africa. To check this finding, 120 individuals of B. fusca covering several Cameroonian sites belonging to both Guineo‐Congolian rain forest and Afromontane vegetation mosaics were collected. Comparison of cytochrome b sequences using the same marker revealed low mitochondrial diversity (h = 0.483 ± 0.054, π = 0.073 ± 0.061%). Moreover, molecular diversity in the Guineo‐Congolian rain forest zone was lower than that in Afromontane vegetation, which is therefore thought to be the likely starting point for the colonization of other zones in Cameroon. The study showed a moderate but significant structuring between populations (Φ ST = 0.034, P<0.001) as well as within and among the two Cameroonian phytogeographical groups considered (Φ SC = 0.000 and Φ CT = 0.051, respectively, both P<0.001). Nested clade phylogeographic analysis indicated that all Cameroonian clades with significant geographical associations were interpreted as a phenomenon of contiguous range expansion. All results suggest that the Cameroonian population of B. fusca is relatively recent and originates from the recent geographical expansion of clade KII. 相似文献
15.
Speciation is a continuous and dynamic process, and studying organisms during the early stages of this process can aid in identifying speciation mechanisms. The mallard ( Anas platyrhynchos) and Mexican duck ( A. [ p.] diazi) are two recently diverged taxa with a history of hybridization and controversial taxonomy. To understand their evolutionary history, we conducted genomic scans to characterize patterns of genetic diversity and divergence across the mitochondrial DNA (mtDNA) control region, 3523 autosomal loci and 172 Z‐linked sex chromosome loci. Between the two taxa, Z‐linked loci (Φ ST = 0.088) were 5.2 times more differentiated than autosomal DNA (Φ ST = 0.017) but comparable to mtDNA (Φ ST = 0.092). This elevated Z differentiation deviated from neutral expectations inferred from simulated data that incorporated demographic history and differences in effective population sizes between marker types. Furthermore, 3% of Z‐linked loci, compared to <0.1% of autosomal loci, were detected as outlier loci under divergent selection with elevated relative (Φ ST) and absolute (d XY) estimates of divergence. In contrast, the ratio of Z‐linked and autosomal differentiation among the seven Mexican duck sampling locations was close to 1:1 (Φ ST = 0.018 for both markers). We conclude that between mallards and Mexican ducks, divergence at autosomal markers is largely neutral, whereas greater divergence on the Z chromosome (or some portions thereof) is likely the product of selection that has been important in speciation. Our results contribute to a growing body of literature indicating elevated divergence on the Z chromosome and its likely importance in avian speciation. 相似文献
16.
Connectivity, the exchange of individuals among locations, is a fundamental ecological process that explains how otherwise disparate populations interact. For most marine organisms, dispersal occurs primarily during a pelagic larval phase that connects populations. We paired population structure from comprehensive genetic sampling and biophysical larval transport modeling to describe how spiny lobster (Panulirus argus) population differentiation is related to biological oceanography. A total of 581 lobsters were genotyped with 11 microsatellites from ten locations around the greater Caribbean. The overall F
ST of 0.0016 (P = 0.005) suggested low yet significant levels of structuring among sites. An isolation by geographic distance model did not explain spatial patterns of genetic differentiation in P. argus (P = 0.19; Mantel r = 0.18), whereas a biophysical connectivity model provided a significant explanation of population differentiation (P = 0.04; Mantel r = 0.47). Thus, even for a widely dispersing species, dispersal occurs over a continuum where basin-wide larval retention creates genetic structure. Our study provides a framework for future explorations of wide-scale larval dispersal and marine connectivity by integrating empirical genetic research and probabilistic modeling. 相似文献
17.
Spinner dolphins ( Stenella longirostris) exhibit different social behaviours at two regions in the Hawaiian Archipelago: off the high volcanic islands in the SE archipelago they form dynamic groups with ever‐changing membership, but in the low carbonate atolls in the NW archipelago they form long‐term stable groups. To determine whether these environmental and social differences influence population genetic structure, we surveyed spinner dolphins throughout the Hawaiian Archipelago with mtDNA control region sequences and 10 microsatellite loci ( n = 505). F‐statistics, Bayesian cluster analyses, and assignment tests revealed population genetic separations between most islands, with less genetic structuring among the NW atolls than among the SE high islands. The populations with the most stable social structure (Midway and Kure Atolls) have the highest gene flow between populations (mtDNA ΦST < 0.001, P = 0.357; microsatellite FST = ?0.001; P = 0.597), and a population with dynamic groups and fluid social structure (the Kona Coast of the island of Hawai’i) has the lowest gene flow (mtDNA 0.042 < ΦST < 0.236, P < 0.05; microsatellite 0.016 < FST < 0.040, P < 0.001). We suggest that gene flow, dispersal, and social structure are influenced by the availability of habitat and resources at each island. Genetic comparisons to a South Pacific location ( n = 16) indicate that Hawaiian populations are genetically depauperate and isolated from other Pacific locations (mtDNA 0.216 < FST < 0.643, P < 0.001; microsatellite 0.058 < FST < 0.090, P < 0.001); this isolation may also influence social and genetic structure within Hawai’i. Our results illustrate that genetic and social structure are flexible traits that can vary between even closely‐related populations. 相似文献
18.
Zooplanktonic taxa have a greater number of distinct populations and species than might be predicted based on their large population sizes and open‐ocean habitat, which lacks obvious physical barriers to dispersal and gene flow. To gain insight into the evolutionary mechanisms driving genetic diversification in zooplankton, we developed eight microsatellite markers to examine the population structure of an abundant, globally distributed mesopelagic copepod, Haloptilus longicornis, at 18 sample sites across the Atlantic and Pacific Oceans ( n = 761). When comparing our microsatellite results with those of a prior study that used a mtDNA marker (mtCOII, n = 1059, 43 sample sites), we unexpectedly found evidence for the presence of a cryptic species pair. These species were globally distributed and apparently sympatric, and were separated by relatively weak genetic divergence (reciprocally monophyletic mtCOII lineages 1.6% divergent; microsatellite FST ranging from 0.28 to 0.88 across loci, P < 0.00001). Using both mtDNA and microsatellite data for the most common of the two species ( n = 669 for microsatellites, n = 572 for mtDNA), we also found evidence for allopatric barriers to gene flow within species, with distinct populations separated by continental landmasses and equatorial waters in both the Atlantic and Pacific Ocean basins. Our study shows that oceanic barriers to gene flow can act as a mechanism promoting allopatric diversification in holoplanktonic taxa, despite the high potential dispersal abilities and pelagic habitat for these species. 相似文献
19.
Continental island systems harbour relict biota and populations that might have migrated during glacial periods due to the
formation of landbridges. Here we analysed the genetic structure of relict populations of the temperate plant Shortia rotundifolia on the subtropical island of Iriomotejima, Japan. This plant, which inhabits riparian environments, is designated “near threatened”.
Only five extant populations have been found on the island. Our analyses of 10 nuclear microsatellite loci detected genetic
diversity of H
E = 0.488 and H
O = 0.358 for all populations of S. rotundifolia on the island. A high inbreeding coefficient for all populations together ( F
IS = 0.316) and each population separately ( F
IS = 0.258–0.497) might be attributable to crossing among closely related descendants within a population, an idea that is supported
by the relatedness coefficient. These results and an examination of the populations’ demographic histories suggest that the
extant populations on Iriomotejima have not experienced a recent population bottleneck. The five extant populations were genetically
differentiated ( F
ST = 0.283; P < 0.001), suggesting low seed dispersal by gravity and/or low pollen flow via pollinators in the riparian environment. In
addition, population differentiation was not related to genetic distance, implying that at one time, ancestral populations
might have been distributed over a wider area of the island. However, population fragmentation and range contraction might
have occurred at random during the postglacial period. 相似文献
20.
Habitat loss and isolation is pervasive in the Midwest U.S. Wetlands are experiencing particularly dramatic declines, yet
there is a paucity of information on the genetic impacts of these losses to obligate wetland vertebrates. We quantified the
genetic variation of extant populations of a shallow wetland specialist and evaluated potential reductions in population size
(i.e. bottlenecks) using seven polymorphic microsatellite DNA markers. We analyzed 228 copperbelly water snakes ( Nerodia erythrogaster neglecta), representing populations from three states. Moderate genetic differentiation exists among all three regions ( F
ST = 0.12, P < 0.001), with evidence for low levels of differentiation within the federally protected Ohio region ( F
ST = 0.025, P = 0.007), and moderate to strong differentiation within the Indiana region ( F
ST = 0.23, P < 0.001). Furthermore, Bayesian clustering (i.e. STRUCTURE) supports the separation of the Indiana sites, both from each
other and from all other sampling sites. However, it does not support the separation of the Ohio sites from the Kentucky sites.
Differentiation among sampling sites did not appear to be related to geographic distance, but rather depended on the quality
of terrestrial corridors used for dispersal. Mode shifts in allele frequencies and excess heterozygosity tests were negative,
while M-ratio tests were nearly all positive, indicating the likelihood of historical rather than contemporary population bottlenecks.
However, potential subspecific intergradation in the Kentucky region may have artificially lowered the M-ratio, and we suggest caution when using the M-ratio approach if intergradation is suspected. Our results have conservation implications for wetland management and management
of the copperbelly populations, and emphasizes the importance of protecting wetland complexes. 相似文献
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