共查询到20条相似文献,搜索用时 31 毫秒
1.
Carol A. Stepien Richard H. Rosenblatt Brian A. Bargmeyer 《Evolution; international journal of organic evolution》2001,55(9):1852-1862
Abstract Have the warm tropical waters and currents of the southern Gulf of California, Mexico (also known as the Sea of Cortez), formed a barrier to gene flow, resulting in disjunct populations in the upper gulf that are isolated from the outer Pacific Coast? Phylogeographic and genetic divergences of the spotted sand bass, Paralabrax maculatofasciatus, from three Gulf of California and two outer Pacific coastal locations were tested using mitochondrial DNA (mtDNA) control region sequences. Sequence data from two congeners that are sympatrically distributed along the outer Pacific Coast, the barred sand bass, P. nebulifer, and the kelp bass, P. clathratus, were used to gauge the levels of genetic divergences. Differences among the three species and between the northern gulf and outer Pacific coastal populations of P. maculatofasciatus also were analyzed using 40 allozymic presumptive gene loci. Allozyme and mtDNA analyses each revealed many fixed differences among the species. Three significant allozymic frequency differences and two fixed mtDNA substitutions differentiated the gulf and outer Pacific coastal populations of P. maculatofasciatus. Three unique mtDNA haplotypes and three unique allozyme alleles were identified from the outer Pacific coastal population. The gulf sites contained four unique mtDNA haplotypes and six unique allozyme alleles. Partitioning of the mtDNA variation revealed that 72% of the variance occurred between the gulf and outer Pacific Coast, 20% between sampling sites in the two regions, and 8% within the sites. There appears to be little gene flow across the waters of the southern Baja Penninsula, producing divergence estimated as 120,000 to 600,000 years between the outer Pacific coastal and the Gulf of California populations. This separation level may date to a hypothesized seaway closure near La Paz, Mexico, during the mid‐Pleistocene, and characterizes other fish populations. A second pattern of deeper allopatric species‐level divergences in some other fishes may date to a Pliocene closure of a mid‐Baja Penninsular seaway. Significant differences also were discerned in P. maculatofasciatus between the San Diego and central Baja California coastal sites and between the upper/central and the lower gulf locations. Variation between locations in the two regions may be indicative of larval retention and low adult migration, which needs to be tested further. 相似文献
2.
M. GONZÁLEZ-SUÁREZ‡ R. FLATZ D. AURIOLES-GAMBOA† P. W. HEDRICK L. R. GERBER 《Molecular ecology》2009,18(6):1088-1099
Understanding the spatial structure of a population is critical for effective assessment and management. However, direct observation of spatial dynamics is generally difficult, particularly for marine mammals. California sea lions ( Zalophus californianus ) are polygynous pinnipeds distributed along the Pacific coast of North America. The species' range has been subdivided into three management stocks based on differences in mitochondrial DNA, but to date no studies have considered nuclear genetic variation, and thus we lack a comprehensive understanding of gene flow patterns among sea lion colonies. In light of recent population declines in the Gulf of California, Mexico, it is important to understand spatial structure to determine if declining sea lion colonies are genetically isolated from others. To define population subdivision and identify sex biases in gene flow, we analysed a 355-bp sequence of the mitochondrial DNA control region and 10 polymorphic microsatellite loci from 355 tissue samples collected from six colonies distributed along Mexican waters. Using a novel approach to estimate sex biases in gene flow, we found that male sea lions disperse on average 6.75 times more frequently than females. Analyses of population subdivision strongly suggest a pattern of isolation by distance among colonies and challenge current stock definitions. Based on these results, we propose an alternative classification that identifies three Mexican management units: Upper Gulf of California, Southern Baja Peninsula, and Upper Pacific Coast of Baja. This revised classification should be considered in future assessment and management of California sea lion populations in Mexican waters. 相似文献
3.
The Baja California peninsula represents a biogeographical boundary contributing to regional differentiation among populations of marine animals. We investigated the genetic characteristics of perennial and annual populations of the marine angiosperm, Zostera marina, along the Pacific coast of Baja California and in the Gulf of California, respectively. Populations of Z. marina from five coastal lagoons along the Pacific coast and four sites in the Gulf of California were studied using nine microsatellite loci. Analyses of variance revealed significant interregional differentiation, but no subregional differentiation. Significant spatial differentiation, assessed using θST values, was observed among all populations within the two regions. Z. marina populations along the Pacific coast are separated by more than 220 km and had the greatest θST (0.13–0.28) values, suggesting restricted gene flow. In contrast, lower but still significant genetic differentiation was observed among populations within the Gulf of California (θST = 0.04–0.18), even though populations are separated by more than 250 km. This suggests higher levels of gene flow among Gulf of California populations relative to Pacific coast populations. Direction of gene flow was predominantly southward among Pacific coast populations, whereas no dominant polarity in the Gulf of California populations was observed. The test for isolation by distance (IBD) showed a significant correlation between genetic and geographical distances in Gulf of California populations, but not in Pacific coast populations, perhaps because of shifts in currents during El Niño Southern Oscillation (ENSO) events along the Pacific coast. 相似文献
4.
Chris H. Floyd José Juan Flores-Martínez L. Gerardo Herrera M. Omar Mejía Bernie May 《Conservation Genetics》2010,11(3):813-822
The endangered Mexican fishing bat, Myotis vivesi, appears to have suffered widespread extinction and population decline on islands throughout the Gulf of California, largely
due to predation by introduced cats and rats. To restore populations of fishing bats and other native species, conservation
efforts have focused on eradicating introduced vertebrates from several Gulf islands. These efforts assume that individuals
from existing populations will recolonize islands and that continued dispersal will help sustain vulnerable populations thereafter.
However, the extent of inter-island dispersal in fishing bats is unknown. In this study we analyzed patterns of genetic variation
to gauge the extent of gene flow and, thus, potential dispersal among islands. DNA was sampled from 257 fishing bats on 11
Gulf islands (separated by ca. 6–685 km of open water), and individuals were genotyped at six microsatellite loci and haplotyped
at a 282 bp fragment of the mtDNA control region. With microsatellites, we found weak population genetic structure and a pattern
of isolation by distance, while with mtDNA we found strong structure but no isolation by distance. Our results indicate that
island subpopulations separated by large expanses of open water are nonetheless capable of maintaining high genetic diversity
and high rates of gene flow. Unfortunately, little is known about the spatial patterns of dispersal or mating system of fishing
bats, and these behavioral factors, in particular female philopatry, might reduce the probability of the species recolonizing
Gulf islands. 相似文献
5.
Jesús E. Maldonado Flavio Orta Davila Brent S. Stewart Eli Geffen Robert K. Wayne 《Marine Mammal Science》1995,11(1):46-58
Intraspecific patterns of mitochondrial DNA sequence variation were determined among California sea lions ( Zalophus califomianus californianus ) from three colonies along the Pacific coast of southern and Baja California and one colony in the Gulf of California. We found no variation in 368 base pairs (bp) of cytochrome b sequence among 40 sea lions from these localities, but analysis of 360 base pairs of control region revealed eleven genotypes. The four genotypes found in the Gulf of California population were unique and phylogenetically distinct from those found in sea lions along the Pacific coast. The average sequence divergence between Gulf and Southern California genotypes was 4.3%, suggesting a relatively long period of isolation. However, colonies along the Pacific coast, which are less than 200 km apart, shared mtDNA genotypes, indicating that recent genetic exchange has occurred between them. Therefore, we suggest that regional female philopatry exists in California sea lions. Regional boundaries may be related to oceanic currents or patchiness in the distribution of resources. Further research is needed to better understand the underlying causes of genetic differentiation in the California sea lion. 相似文献
6.
Verónica Mendoza-Portillo Carolina Galván-Tirado David S. Portnoy Fausto Valenzuela-Quiñonez Omar Domínguez-Domínguez Jean-Dominique Durand Juan Carlos Pérez-Urbiola Francisco J. García-De León 《Journal of fish biology》2020,97(3):882-894
The almaco jack, Seriola rivoliana, is a circumtropical pelagic fish of importance both in commercial fisheries and in aquaculture. To understand levels of genetic diversity within and among populations in the wild, population genetic structure and the relative magnitude of migration were assessed using mtDNA sequence data and single nucleotide polymorphisms (SNPs) from individuals sampled from locations in the Pacific and Atlantic Oceans. A total of 25 variable sites of cytochrome c oxidase subunit 1 and 3678 neutral SNPs were recovered. Three genetic groups were identified, with both marker types distributed in different oceanic regions: Pacific-1 in central Pacific, Pacific-2 in eastern Pacific and Atlantic in western Atlantic. Nonetheless, the analysis of SNP identified a fourth population in the Pacific coast of Baja California Sur, Mexico (Pacific-3), whereas that of mtDNA did not. This mito-nuclear discordance is likely explained by a recently diverged Pacific-3 population. In addition, two mtDNA haplogroups were found within the western Atlantic, likely indicating that the species came into the Atlantic from the Indian Ocean with historical gene flow from the eastern Pacific. Relative gene flow among ocean basins was low with rm < 0.2, whereas in the eastern Pacific it was asymmetric and higher from south to north (rm > 0.79). The results reflect the importance of assessing genetic structure and gene flow of natural populations for the purposes of sustainable management. 相似文献
7.
Pacific halibut collected in the Aleutian Islands, Bering Sea and Gulf of Alaska were used to test the hypothesis of genetic
panmixia for this species in Alaskan marine waters. Nine microsatellite loci and sequence data from the mitochondrial (mtDNA)
control region were analyzed. Eighteen unique mtDNA haplotypes were found with no evidence of geographic population structure.
Using nine microsatellite loci, significant heterogeneity was detected between Aleutian Island Pacific halibut and fish from
the other two regions (F
ST range = 0.007–0.008). Significant F
ST values represent the first genetic evidence of divergent groups of halibut in the central and western Aleutian Archipelago.
No significant genetic differences were found between Pacific halibut in the Gulf of Alaska and the Bering Sea leading to
questions about factors contributing to separation of Aleutian halibut. Previous studies have reported Aleutian oceanographic
conditions at deep inter-island passes leading to ecological discontinuity and unique community structure east and west of
Aleutian passes. Aleutian Pacific halibut genetic structure may result from oceanographic transport mechanisms acting as partial
barriers to gene flow with fish from other Alaskan waters. 相似文献
8.
Nicole Reguera-Rouzaud Noé Díaz-Viloria Ricardo Pérez-Enríquez Elaine Espino-Barr Mailin Isabel Rivera-Lucero Adrián Munguía-Vega 《Journal of fish biology》2021,98(5):1267-1280
The tropical eastern Pacific (TEP) is a highly dynamic region and a model system to study how habitat discontinuities affect the distribution of shorefishes, particularly for species that display ontogenetic habitat shifts, including snappers (Lutjanidae). To evaluate the genetic structure of the Pacific red snapper (Lutjanus peru) and the yellow snapper (Lutjanus argentiventris) throughout their distribution range along the TEP, 13 and 11 microsatellite loci were analysed, respectively. The genetic diversity of L. peru (N = 446) and L. argentiventris (N = 170) was evaluated in 10 and 5 localities, respectively, showing slightly higher but non-significant values in the Gulf of California for both species. The genetic structure analysis identified the presence of significant genetic structure in both species, but the locations of the identified barriers for the gene flow differed between species. The principal driver for the genetic structure at large scales >2500 km was isolation by distance. At smaller scales (<250 km), the habitat discontinuity for juveniles and adults and the environmental differences throughout the distribution range represented potential barriers to gene flow between populations for both species. 相似文献
9.
Naohisa Kanda Mutsuo Goto Hidehiro Kato Megan V. McPhee Luis A. Pastene 《Conservation Genetics》2007,8(4):853-864
Bryde’s whales (Balaenoptera brydei) differ from other typical baleen whale species because they are restricted to tropical and warm temperate waters in major
oceans, and frequent trans-equatorial movement has been suggested for the species. We tested this hypothesis by analyzing
genetic variation at 17 microsatellite loci (N = 508) and 299 bp of mitochondrial DNA (mtDNA) control region sequences (N = 472) in individuals obtained from the western North Pacific, South Pacific, and eastern Indian Ocean. Combined use of microsatellite
and mtDNA markers allowed us to distinguish between contemporary gene flow and ancestral polymorphism and to describe sex-specific
philopatry. A high level of genetic diversity was found within the samples. Both nuclear and mtDNA markers displayed similar
population structure, indicating a lack of sex-specific philopatry. Spatial structuring was detected using both frequency-based
population parameters and individual-based Bayesian approaches. Whales in the samples from different oceanic regions came
from genetically distinct populations with evidence of limited gene flow. We observed low mtDNA sequence divergence among
populations and a lack of concordance between geographic and phylogenetic position of mtDNA haplotypes, suggesting recent
separation of populations rather than frequent trans-equatorial and inter-oceanic movement. We conclude that current gene
flow between Bryde’s whale populations is low and that effective management actions should treat them as separate entities
to ensure continued existence of the species. 相似文献
10.
Previous studies of the olive ridley Lepidochelys olivacea population structure in the tropical eastern Pacific have indicated the existence of a single panmictic population ranging from Costa Rica to Mexico. This information has been used to design specific management measures to conserve primary nesting beaches in Mexico. However, little is known about olive ridleys in the Baja California Peninsula, their northernmost reproductive limit, where recent observations have shown differences in nesting female behaviour and size of hatchlings relative to other continental rookeries. We used mtDNA control region sequences from 137 turtles from five continental and four peninsular nesting sites to determine whether such differences correspond to a genetic distinction of Baja California olive ridleys or to phenotypic plasticity associated with the extreme environmental nesting conditions of this region. We found that genetic diversity in peninsular turtles was significantly lower than in continental nesting colonies. Analysis of molecular variance revealed a significant population structure (Phi ST = 0.048, P = 0.006) with the inclusion of peninsular samples. Our results: (i) suggest that the observed phenotypic variation may be associated with genetic differentiation and reproductive isolation; (ii) support the recent colonization of the eastern Pacific by Lepidochelys; (iii) reveal genetic signatures of historical expansion and colonization events; and (iv) significantly challenge the notion of a single genetic and conservation unit of olive ridleys in the eastern Pacific. We conclude that conservation measures for olive ridleys in Mexico should be revised to grant peninsular beaches special attention. 相似文献
11.
Information on genetic connectivity and structure of populations in the tropical Pacific is critical for making inferences
about the origins and maintenance of diversity in this region. Sequences of the mitochondrial COI gene from 92 individuals
of the trans-Pacific gastropod Conus ebraeus from eight localities spanning the tropical Pacific were analyzed to determine whether populations in the western, central,
and eastern Pacific exhibit genetic structure, to examine the demographic histories of populations, and to infer patterns
of gene flow. A total of 43 unique haplotypes were recovered, including a common haplotype that occurred in six of the eight
populations examined. AMOVA and pairwise F-statistics showed that populations in the western and central Pacific were significantly differentiated from populations
in the eastern Pacific, but no other evidence of structure. Bayesian isolation–migration (IM) analysis suggested that populations
in the western and central Pacific separated from those in eastern Pacific during the Pleistocene. Examination of mismatch
distributions and results from IM revealed that populations in the western and central Pacific expanded during the Pleistocene.
Gene flow across the East Pacific Barrier appears to occur predominantly westward. 相似文献
12.
M. A. Tripp‐Valdez F. J. García‐de‐León H. Espinosa‐Pérez G. Ruiz‐Campos 《Zeitschrift fur angewandte Ichthyologie》2012,28(4):516-523
Population structure of the sablefish (Anoplopoma fimbria) in the northeastern Pacific Ocean was determined using three approaches: geometric morphometrics (14 landmarks), mitochondrial DNA (fragment of COI gene), and nuclear DNA (four microsatellite loci). Samples came from the Bering Sea, Gulf of Alaska, offshore Oregon, and offshore the mid‐Baja California Peninsula (at San Quintin). Differences in body shape were grouped in the samples from the north (Bering Sea and Gulf of Alaska). A slight but significant population structure was also observed in allele frequencies of microsatellites, FST values, amova , and Bayesian individual assignment tests; however, analyses of population structure using mtDNA did not reveal any population differentiation. Differences in population structure detected by distinct approaches, in addition to the moderately high haplotype diversity and low nucleotide diversity of the COI fragment, suggest recent and developing population differentiation in the sablefish. 相似文献
13.
Eduardo Sandoval-Castro Richard S. Dodd Rafael Riosmena-Rodríguez Luis Manuel Enríquez-Paredes Cristian Tovilla-Hernández Juan Manuel López-Vivas Bily Aguilar-May Raquel Mu?iz-Salazar 《PloS one》2014,9(4)
Mangrove forests in the Gulf of California, Mexico represent the northernmost populations along the Pacific coast and thus they are likely to be source populations for colonization at higher latitudes as climate becomes more favorable. Today, these populations are relatively small and fragmented and prior research has indicated that they are poor in genetic diversity. Here we set out to investigate whether the low diversity in this region was a result of recent colonization, or fragmentation and genetic drift of once more extensive mangroves due to climatic changes in the recent past. By sampling the two major mangrove species, Rhizophora mangle and Avicennia germinans, along the Pacific and Atlantic coasts of Mexico, we set out to test whether concordant genetic signals could elucidate recent evolution of the ecosystem. Genetic diversity of both mangrove species showed a decreasing trend toward northern latitudes along the Pacific coast. The lowest levels of genetic diversity were found at the range limits around the Gulf of California and the outer Baja California peninsula. Lack of a strong spatial genetic structure in this area and recent northern gene flow in A. germinans suggest recent colonization by this species. On the other hand, lack of a signal of recent northern dispersal in R. mangle, despite the higher dispersal capability of this species, indicates a longer presence of populations, at least in the southern Gulf of California. We suggest that the longer history, together with higher genetic diversity of R. mangle at the range limits, likely provides a gene pool better able to colonize northwards under climate change than A. germinans. 相似文献
14.
Hierarchical structure of mitochondrial DNA gene flow among humpback whales Megaptera novaeangliae, world-wide 总被引:3,自引:1,他引:2
C. S. BAKER R. W. SLADE J. L. BANNISTER R. B. ABERNETHY M. T. WEINRICH J. LIEN J. URBAN P. CORKERON J. CALMABOKIDIS O. VASQUEZ S. R. PALUMBI 《Molecular ecology》1994,3(4):313-327
The genetic structure of humpback whale populations and subpopulation divisions is described by restriction fragment length analysis of the mitochondrial (mt) DNA from samples of 230 whales collected by biopsy darting in 11 seasonal habitats representing six subpopulations, or 'stocks', world-wide. The hierarchical structure of mtDNA haplotype diversity among population subdivisions is described using the analysis of molecular variance (AMOVA) procedure, the analysis of gene identity, and the genealogical relationship of haplotypes as constructed by parsimony analysis and distance clustering. These analyses revealed: (i) significant partitioning of world-wide genetic variation among oceanic populations, among subpopulations or 'stocks' within oceanic populations and among seasonal habitats within stocks; (ii) fixed categorical segregation of haplotypes on the south-eastern Alaska and central California feeding grounds of the North Pacific; (iii) support for the division of the North Pacific population into a central stock which feeds in Alaska and winters in Hawaii, and an eastern or 'American' stock which feeds along the coast of California and winters near Mexico; (iv) evidence of genetic heterogeneity within the Gulf of Maine feeding grounds and among the sampled feeding and breeding grounds of the western North Atlantic; and (v) support for the historical division between the Group IV (Western Australia) and Group V (eastern Australia, New Zealand and Tonga) stocks in the Southern Oceans. Overall, our results demonstrate a striking degree of genetic structure both within and between oceanic populations of humpback whales, despite the nearly unlimited migratory potential of this species. We suggest that the humpback whale is a suitable demographic and genetic model for the management of less tractable species of baleen whales and for the general study of gene flow among long-lived, mobile vertebrates in the marine ecosystem. 相似文献
15.
Understanding the population structure and evolutionary history of the eastern Pacific seahorse Hippocampus ingens is critical for the effective management of this threatened species. Life history characteristics of H. ingens (site fidelity and brooding of young) may limit gene flow and lead to population differentiation. A recent study analyzing
conserved fragments of the mitochondrial cyt b and control region found no population structure. We re-assess this conclusion with a phylogeographic analysis of relationships
among 115 individuals of H. ingens over a broader geographic range (San Diego Bay in California, Gulf of California, Central America, Ecuador, and Peru) based
on a more variable 428 base pair fragment of the control region. This expanded analysis affirms low overall nucleotide diversity
relative to other seahorses (θπ = 0.004), and shows evidence of a recent bottleneck and population expansion since the middle Pleistocene. AMOVA analysis
shows moderate overall population structure (ΦST = 0.10, P val = 0.00), and pairwise ΦST estimates indicate structure between the Gulf of California and all Pacific coast localities. Knowledge of population structure
in H. ingens may improve conservation efforts by identifying evolutionarily important management units, and could determine source regions
in the continuing trade of seahorses for traditional Chinese medicine. The level of genetic divergence observed between the
Gulf of California and all other localities sampled may distinguish the Gulf as a separate management unit. Additional phylogeographic
research with more quickly evolving genetic markers and targeted sampling at the mouth of the Gulf of California is warranted
to inform strategies for conservation of this threatened seahorse. 相似文献
16.
The global distribution of the reddish egret is characterized by disjunct colonies occurring from the Pacific side of Northwest
Mexico to the Caribbean. We examined distantly isolated colonies of reddish egret to determine global population genetic structure.
We used seven polymorphic microsatellites to accomplish five goals: (1) to assess range wide population differentiation among
reddish egret (Egretta rufescens) populations, (2) identify extent of gene flow, (3) determine any historical occurrence of bottlenecks, (4) assess genetic
differentiation between color morphs, (5) clarify subspecies status of E.
r. dickeyi, a completely dark morph population located in and around the Baja California peninsula, Mexico. Genetic differentiation was
dramatic (global Fst = 0.161) throughout the reddish egrets range extending from Baja California, Mexico to Great Inagua,
Bahamas. Differentiation occurred among three distinct regions (Fst = 0.238) but not among colonies/islands within regions
suggesting regional philopatry. Genetic diversity (alleles per locus, and heterozygosity) in Baja California Sur, Mexico and
Great Inagua, Bahamas populations is lower than in the Texas/Mexico population due to minimal dispersal between regions and
smaller population sizes. Dark and white color morphs when present within the same region showed no differentiation. Patterns
of recent population bottlenecks are not evident in each of the three regional populations. With evidence of limited gene
flow in addition to low genetic diversity and prospects of habitat loss we recommend that reddish egrets be managed as three
distinct or evolutionary significant units. 相似文献
17.
Tabib M Zolgharnein H Mohammadi M Salari-Aliabadi MA Qasemi A Roshani S Rajabi-Maham H Frootan F 《Genetics and molecular research : GMR》2011,10(3):1499-1503
Genetic diversity of sea turtles (hawksbill turtle) was studied using sequencing of mitochondrial DNA (mtDNA, D-loop region). Thirty dead embryos were collected from the Kish and Qeshm Islands in the Persian Gulf. Analysis of sequence variation over 890 bp of the mtDNA control region revealed five haplotypes among 30 individuals. This is the first time that Iranian haplotypes have been recorded. Nucleotide and haplotype diversity was 0.77 and 0.001 for Qeshm Island and 0.64 and 0.002 for Kish Island, respectively. Total haplotype diversity was calculated as 0.69, which demonstrates low genetic diversity in this area. The data also indicated very high rates of migration between the populations of these two islands. A comparison of our data with data from previous studies downloaded from a gene bank showed that turtles of the Persian Gulf migrated from the Pacific and the Sea of Oman into this area. On the other hand, evidence of migration from populations to the West was not found. 相似文献
18.
Deborah R. Smith Yong‐Chao Su Reut Berger‐Tal Yael Lubin 《Ecology and evolution》2016,6(15):5479-5490
Dispersal in most group‐living species ensures gene flow among groups, but in cooperative social spiders, juvenile dispersal is suppressed and colonies are highly inbred. It has been suggested that such inbred sociality is advantageous in the short term, but likely to lead to extinction or reduced speciation rates in the long run. In this situation, very low levels of dispersal and gene flow among colonies may have unusually important impacts on fitness and persistence of social spiders. We investigated sex‐specific differences in dispersal and gene flow among colonies, as reflected in the genetic structure within colonies and populations of the African social spider Stegodyphus dumicola Pocock, 1898 (Eresidae). We used DNA fingerprinting and mtDNA sequence data along with spatial mapping of colonies to compare male and female patterns of relatedness within and among colonies at three study sites. Samples were collected during and shortly after the mating season to detect sex‐specific dispersal. Distribution of mtDNA haplotypes was consistent with proliferation of social nests by budding and medium‐ to long‐distance dispersal by ballooning females. Analysis of molecular variance and spatial autocorrelation analyses of AFLPs showed high levels of genetic similarity within colonies, and STRUCTURE analyses revealed that the number of source populations contributing to colonies ranged from one to three. We also showed significant evidence of male dispersal among colonies at one site. These results support the hypothesis that in social spiders, genetic cohesion among populations is maintained by long‐distance dispersal of female colony founders. Genetic diversity within colonies is maintained by colony initiation by multiple dispersing females, and adult male dispersal over short distances. Male dispersal may be particularly important in maintaining gene flow among colonies in local populations. 相似文献
19.
Stephen R. Palumbi Gail Grabowsky Thomas Duda Laura Geyer Nicholas Tachino 《Evolution; international journal of organic evolution》1997,51(5):1506-1517
Unlike populations of many terrestrial species, marine populations often are not separated by obvious, permanent barriers to gene flow. When species have high dispersal potential and few barriers to gene flow, allopatric divergence is slow. Nevertheless, many marine species are of recent origin, even in taxa with high dispersal potential. To understand the relationship between genetic structure and recent species formation in high dispersal taxa, we examined population genetic structure among four species of sea urchins in the tropical Indo-West Pacific that have speciated within the past one to three million years. Despite high potential for gene flow, mtDNA sequence variation among 200 individuals of four species in the urchin genus Echinometra shows a signal of strong geographic effects. These effects include (1) substantial population heterogeneity; (2) lower genetic variation in peripheral populations; and (3) isolation by distance. These geographic patterns are especially strong across scales of 5000-10,000 km, and are weaker over scales of 2500-5000 km. As a result, strong geographic patterns would not have been readily visible except over the wide expanse of the tropical Pacific. Surface currents in the Pacific do not explain patterns of gene flow any better than do patterns of simple spatial proximity. Finally, populations of each species tend to group into large mtDNA regions with similar mtDNA haplotypes, but these regional boundaries are not concordant in different species. These results show that all four species have accumulated mtDNA differences over similar spatial and temporal scales but that the precise geographic pattern of genetic differentiation varies for each species. These geographic patterns appear much less deterministic than in other well-known coastal marine systems and may be driven by chance and historical accident. 相似文献
20.
Analyses of mitochondrial DNA (mtDNA) control region polymorphism and of variation at 10 nuclear microsatellite loci were used to investigate the mechanisms and genetic consequences of postglacial expansion of Myotis myotis in Europe. Initial sampling consisted of 480 bats genotyped in 24 nursery colonies arranged along a transect of approximately 3000 km. The phylogeographical survey based on mtDNA sequences revealed the existence of major genetic subdivisions across this area, with several suture zones between haplogroups. Such zones of secondary contact were found in the Alps and Rhodopes, whereas other potential barriers to gene flow, like the Pyrenees, did not coincide with genetic discontinuities. Areas of population admixture increased locally the genetic diversity of colonies, which confounded the northward decrease in nucleotide diversity predicted using classical models of postglacial range expansion. However, when analyses were restricted to a subset of 15 nurseries originating from a single presumed glacial refugium, mtDNA polymorphism did indeed support a northwards decrease in diversity. Populations were also highly structured (PhiST = 0.384). Conversely, the same subset of colonies showed no significant latitudinal decrease in microsatellite diversity and much less population structure (FST = 0.010), but pairwise genetic differentiation at these nuclear markers was strongly correlated with increasing geographical distance. Together, this evidence suggests that alleles carried via male bats have maintained enough nuclear gene flow to counteract the effects of recurrent bottlenecks generally associated with recolonization processes. As females are highly philopatric, we argue that the maternally transmitted mtDNA marker better reflects the situation of past, historical gene flow, whereas current levels of gene flow are better reflected by microsatellite markers. 相似文献