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1.
The patchy distribution of rocky intertidal communities in the tropical eastern Pacific (TEP) may impose severe constraints
on the genetic connectivity among populations of marine invertebrates associated with this habitat. In this study, we analyzed
a portion of the mitochondrial cytochrome c oxidase subunit I (COI) gene in two sympatric species of marine snails, Nerita scabricosta and Nerita funiculata, common inhabitants of the rocky intertidal from the Gulf of California (Sea of Cortez) and outer Pacific coast of the southern
Baja California (Baja) peninsula to northern South America, to assess genetic connectivity among populations of each species.
One of our aims was to determine whether the morphological, behavioral, and ecological differences observed among populations
of both species throughout their range in the TEP corresponded to population genetic differences. In addition, we were interested
in elucidating the demographic history of both species. We found no evidence of genetic structure throughout the Gulf of California
and outer coast of the Baja peninsula region for either species. Comparisons between Gulf of California/Baja and Panama populations,
however, showed significant genetic differentiation for N. scabricosta, but not for N. funiculata. The genetic differences between Mexican and Panamanian populations of N. scabricosta were consistent with previously reported ecological and behavioral differences for this species between these two distant
regions. However, previously reported size differences between northern and central/southern Gulf of California individuals
of N. scabricosta do not correspond with our findings of genetic connectivity among these populations. Results from neutrality tests (Tajima’s
D and Fu’s F
S), the mismatch distribution, and Bayesian skyline analyses suggested that both species have experienced dramatic population
expansions dating to the Pleistocene. 相似文献
2.
Understanding the evolutionary processes from recent demographic history is especially difficult for interstitial organisms
due to their poorly known natural history. In this study, the genetic variation and population history of the four Ototyphlonemertes (Diesing in Sitz ber Math Nat Kl Akad Wiss Wien 46:413–416, 1863) species were evaluated from samples collected along the Brazilian coast (between 27°31′S and 13°00′W) in 2006. The mitochondrial
region cytochrome c oxidase subunit 3 (COX3) is analyzed to assess the genetic variation of these dioecious species. Although these species have
a sympatric distribution along the coast, our data suggest that their levels of differentiation and their demographic histories
differ sharply. There is strong evidence of gene flow among demes in O. erneba and O. evelinae, and their level of structuring is much lower than for the other two species. Indeed, the COX3 fragment reveals cryptic lineages
in O. lactea and O. parmula. The results seem to contradict the high genetic structuring and low intrapopulational variability expected with the ecological
constriction and habitat discontinuity faced by these organisms, meaning that there might be gene flow among populations or
their dispersal capability has been underestimated. 相似文献
3.
Sympatric populations of two forms of the common dolphin, currently recognized collectively as Delphinus delphis Linnaeus, occur in several areas of the world's oceans. A molecular genetic study was initiated to determine whether these forms are genetically distinct in the Northeast Pacific. We compared mitochondrial DNA sequences from the control region and cytochrome b gene between specimens of the long-beaked and the short-beaked morphotypes collected between 1986 and 1989 off the coast of southern California. Additional short-beaked specimens collected from the eastern tropical Pacific (in 1978 and 1982) and the Black Sea (in 1989) were also compared. There were no shared mitochondrial DNA haplotypes between the two morphotypes, and both gene regions exhibited frequency and fixed nucleotide substitutions between the two morphotypes. This genetic differentiation, coupled with unique morphological characters of the short-beaked and long-beaked morphotypes determined in a parallel study, indicate that although sympatric, these populations of common dolphin are reproductively isolated from one another and may represent separate species. 相似文献
4.
Lingcod, Ophiodon elongatus Girard, have a 3-month pelagic larval stage and are an important recreational and commercial species on the west coast of
North America. Cytochrome-c oxidase I sequences from tissue samples were used to characterize population structure and infer
patterns of gene flow from California to Alaska. No significant genetic structure was found when estimates of Wright’s F
ST (i.e., ΦST) were generated among all populations sampled. Nesting populations within regions, however, indicated that the inner coast
of Washington State is distinct, a result corroborating previous allozyme work. Coalescent-based estimates of gene flow indicate
that although migration can be high from an evolutionary perspective, nearly half of all comparisons among populations showed
no gene flow in at least one direction. From an ecological perspective, moderate migration rates (Nm < 10) among most populations provide surprisingly limited connectivity at large (∼ 1,000 km) and small (∼100 km) spatial
scales. Coalescent-based estimates also show that gene flow between the inner and the outer coasts is asymmetric, a result
consistent with prevailing surface currents. Because the expected inter-locus variances for coalescent-based estimates of
gene flow are likely large, future work will benefit from analyses of nuclear DNA markers. However, limited demographic connectivity
on large spatial scales may help explain why stock recovery has been uneven, with greater recovery in the northern (87% rebuilt)
than in the southern (24% rebuilt) fishery region, supporting a regional management strategy. These results suggest that despite
a 3-month pelagic larval stage, some areas may be effectively closed with respect to both population dynamics and fishery
management issues. 相似文献
5.
We used microsatellite genetic markers to investigate adult population structure and the formation of a new year-class in
Sebastes mystinus (blue rockfish). Since S. mystinus may live as long as 45 years and reach reproductive age at approximately 5 years, the adult population may contain as many
as eight generations of reproductive adults. We investigated whether the juveniles of the 2000 year-class and the adult population
were genetically homogeneous along the California coast. We sampled approximately 100 juveniles from three sites, two sites
along the Monterey Peninsula (Carmel and Monterey) in central California and one at Fort Ross in northern California, and
approximately 50 adult S. mystinus from five sites throughout the population center. The adult sampling spanned approximately 700 km from the northern Channel
Islands to Fort Bragg. The juveniles showed significant heterogeneity in allele frequencies among distant locations and genetic
homogeneity among adjacent locations. In contrast, the adults showed genetic homogeneity over large distances (San Miguel
Island to Fort Bragg), indicating little limitation of gene flow in this region. Allele frequencies of juveniles differed
from adult samples and in some cases reduced genetic diversity indicative of sweepstakes recruitment (small sample of the
adult reproductive potential). The genetic structure of the 2000 year-class suggests that despite a genetically homogenous
adult population, settled juveniles can be genetically heterogeneous along the California coast. The results also suggest
that the adults, with several year-classes, are capable of maintaining a panmictic population despite the genetic distinctiveness
of individual year-classes. 相似文献
6.
We conducted a phylogeographic study of the meiofaunal nemertean Ototyphlonemertes parmula, an apparent species complex from the littoral zone of coarse-grained beaches, using a 494-bp fragment of the mitochondrial
cytochrome oxidase 3 gene (cox3). Six populations from the Gulf and Atlantic coasts of Florida, two from New England, and one from the Caribbean were sampled
in March and August 2005. Three major lineages were identified, separated by cox3 sequence divergence of 16–18%, with partially overlapping ranges. Tests for hybridization using ISSR markers detected nuclear
gene exchange within but not between the major mitochondrial lineages, indicating the presence of cryptic species. One lineage
dominating the Atlantic coast of Florida shows no evidence of geographic structuring. Another lineage shows a phylogenetic
break between the Atlantic and Gulf coasts, suggesting that unsuitable habitat may act as a barrier to dispersal. Long-distance
migration is evidenced by shared haplotypes between Florida and the eastern Caribbean. Overall, the widespread distribution
of individual haplotypes and lack of structuring within geographic regions contrast with O. parmula’s strongly sediment-bound lifestyle. We speculate that dispersal of adults by storms and/or sediment transport may be more
important than few and potentially short-lived planktonic larvae to explain geographic diversity in O. parmula and may be important for meiofauna in general. 相似文献
7.
Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida,
were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment
of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite
allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular
variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites
and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and
northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida
Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant
for both microsatellites (Φ
CT = 0.016, P = 0.009) and mtDNA (Φ
CT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic
heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly
less (P < 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly
less in the Western Group (P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective
population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability
between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality
of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups
have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood
analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups,
with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and
the order-of-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic
events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity
among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically
distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf. 相似文献
8.
The tellinid bivalve Macoma balthica (L.) has an extensive geographic range that reaches from temperate to arctic coastal waters in the North Atlantic and North Pacific oceans. Recent studies have indicated that eastern and western North Atlantic populations are morphologically and genetically different from one another, and that they may have diverged as sibling species. To determine the genetic relationship between M. balthica from the Pacific and Atlantic coasts of North America, populations from each coast were examined at 11 enzyme loci using standard starch gel electrophoresis. Allele frequency data indicate that M. balthica populations from San Francisco Bay, California appear more closely related to western North Atlantic populations than to populations from Oregon. We suggest that San Francisco Bay populations were introduced relatively recently from western North Atlantic populations. The Oregon populations are probably a natural extension of northern populations that occur along Northern Asia and in the eastern North Atlantic. 相似文献
9.
M. Albrecht K. M. Kneeland E. Lindroth J. E. Foster 《Journal of Coastal Conservation》2013,17(3):483-491
Rhizophora mangle L. is a widespread mangrove species in the Western Hemisphere. Mangrove habitat loss and their importance to coastal and reef ecosystems make greater understanding of their genetic structure useful for conservation and management. An amplified fragment polymorphism (AFLP) analysis was performed on samples from Florida and the Caribbean to discover the genetic structure present. R. mangle had variable genetic diversity not related to latitude; P ranged 7 %–92 %. Some other factor, perhaps human impact, has caused low genetic diversity in some populations. Across Florida R. mangle populations varied in genetic diversity with less diversity (Gst?=?0.195) and greater gene flow on the Atlantic coast (Nm =2.07) than on the Gulf coast (Gst?=?0.717, Nm?=?0.197). Gene flow between Caribbean islands was low (Nm?=?0.386) compared to continental populations (Nm?=?1.40), indicating that long distance dispersal is not common between islands. Analysis of molecular variance (AMOVA) analysis showed significant deviations from Hardy-Weinberg expectations at the level of region among subpopulations and overall genetic difference among subpopulations for R. mangle. One implication for management is that small continental populations and island populations may be genetically isolated and distinct from each other. 相似文献
10.
Six of the nine described species of the mole crab genus Emerita are distributed in the Americas, two [E. analoga (Stimpson, 1857) and E. rathbunae Schmitt, 1935] on the west coast, and four [E. benedicti Schmitt, 1935, E. brasiliensis Schmitt, 1935, E. portoricensis Schmitt, 1935 and E. talpoida (Say, 1817)] on the east. The presence of an extended planktonic larval stage in all Emerita species suggests high dispersal potential and the possibility of extensive gene flow among conspecific populations. Two taxa were sampled to study the extent of gene flow between widely separated conspecific populations: E. analoga (California and Chile) and E. talpoida (Massachusetts, South Carolina, and the west coast of Florida), while all other taxa were characterized from a single location. Portions of two mitochondrial genes, cytochrome oxidase I (COI) and 16S ribosomal RNA (16S rRNA) were sequenced. For data analysis, approximately 500 bp (COI) and 400 bp (16S rRNA) were examined. Estimated genetic divergence of 5.41% in COI between E. talpoida populations sampled from the Gulf of Mexico and the Atlantic coast, and 3.47% between E. analoga sampled in Chile and California, indicates that in both cases there has been no recent gene flow between disjunct populations. Additional molecular and morphological studies are necessary to decide whether disjunct populations should be accorded specific status. We predict that many marine invertebrates with antitropical distributions similar to E. analoga may consist of sibling species. In contrast to relationships inferred earlier from distribution patterns, parsimony analyses of both COI and 16S rRNA data yield similar phylogenetic trees in which E. analoga is separated from a clade composed of other species in the Americas; a bootstrap value (67%) in the COI inferred tree marginally supports the separation, but the same tree topology with a higher bootstrap value (84%) is obtained with 16S rRNA sequence data. Genetic divergence among the taxa indicates that the Emerita species constitute an old group and that distribution of species has been modified by past climatic and geological events. 相似文献
11.
Coelomactra antiquata is a commercially important bivalve species, but has been suffering from severe population decline due to over-exploitation
and the deterioration of environmental conditions. Previous genetic survey of C. antiquata conducted with allozymes combined with morphology revealed high levels of genetic differentiation between northern and southern
populations which suggests a cryptic species might exist in C. antiquata. To test this hypothesis, amplified fragment length polymorphisms (AFLPs) and 16S rRNA gene sequence were used to re-evaluate
the spatial genetic structure of six populations of C. antiquata along the coast of China. Both genetic markers display a sharp genetic break between the four northern populations (northern
lineage) and two southern population (southern lineage). Large numbers of private alleles (AFLP) were found within the northern
or southern populations and a deep divergence of about 6.5% in 16S rRNA gene sequence between the northern and southern lineages
suggests the occurrence of potential cryptic or sibling species of C. antiquata. Applying previously published rates of mutation, divergence between the two lineages is estimated to have occurred approximately
3 million years ago and may be due to allopatric isolation during the middle Pliocene times. While no genetic differentiation
was found within the northern or southern populations in both AFLP and 16S mtDNA markers, the results indicate that the northern
and southern lineage should be managed separately and any translocation between the two areas should be avoided. 相似文献
12.
N. E. Buroker 《Marine Biology》1983,75(1):99-112
An examination by protein-gel electrophoresis of 19 different geographical populations of the American oyster Crassostrea virginica (Gmelin) was conducted along the Atlantic coast and the Gulf of Mexico. Estimates were made of levels of genetic variation and similarity among the populations based on 32 structural loci. The percentage of loci polymorphic ranged from 46.9 to 65.6% along the Atlantic coast while the estimate ranged from 54.8% to 68.8% on the Gulf of Mexico. The percentage of loci heterozygous ranged from 18.6 to 23.6% along the Atlantic coast and from 20.0 to 25.4% in the Gulf of Mexico. The genetic similarities between all contiguous populations from Cape Cod, Massachusetts to Corpus Christi, Texas were estimated as 99%, while the same estimate between Corpus Christi and Brownsville, Texas was computed as 93%, indicating a major transition in genetic structure for the Brownsville population of the Laguna Madre. The study revealed that the migration of planktonic oyster larvae is predominantly in a westerly direction along the Gulf of Mexico and that gene flow appears to be disrupted in the region of the Laguna Madre. Evidence has been presented for single gene selection at the Lap-2 and Pgi loci in the form of macrogeographical clines in allele frequencies with changing environmental conditions. 相似文献
13.
Phyllorhiza
punctata, commonly called the Australian white spotted jellyfish, invaded the Caribbean in the 1960s, becoming established there and
subsequently in the United States in the northern Gulf of Mexico (by 2000) and eastern Florida (2001). With the prevailing
Loop Current flowing clockwise around the Gulf of Mexico and joining the Gulf Stream along eastern Florida, potential transport
of P. punctata along the eastern seaboard of the USA could be facilitated. P. punctata medusae were collected in small numbers along the entire Georgia coast during May–November in 2007 and 2008. Medusa bell
diameters increased both years from ca. 10 cm in May to ca. 33 cm in autumn. Specimens lacked zooxanthellae, as reported for
medusae in the northern Gulf of Mexico and Florida. It is possible that the P. punctata medusae observed were transported from established populations to the south; however, whether or not this species is established
along the Georgia coast has yet to be determined. 相似文献
14.
To determine the genetic population structure of blue crabs (Callinectes sapidus Rathbun), electrophoretic allozyme analysis was performed on 750 individuals collected from 16 nearshore locations ranging from New York to Texas, USA. Twenty enzymes and non-enzymatic proteins coded by 31 presumptive loci were examined. Twenty-two loci were either monomorphic or polymorphic at less than theP
95 level; alleles for these polymorphic loci were geographically dispersed. Allele frequencies for three of the remaining polymorphic loci were homogeneous over all populations, as were levels of polymorphism and heterozygosity. Phenograms generated by the UPGMA (unweighted pair-group method using arithmetic averages) and distance Wagner methods exhibited no geographic pattern in the clustering of populations. Estimates ofN
em (effective number of migrants per generation between populations) indicated substantial gene flow, with aalues sufficiently high to infer panmixia between all blue crab populations from New York to Texas. However, despite this high level of gene flow, two striking patterns of geographic differentiation occurred: genetic patchiness and clinal variation. Allele frequencies atEST-2, GP-1, IDHP-2, DPEP-1, DPEP-2, andTPEP exhibited genetic patchiness on local and range-wide geographic scales, and allele frequencies atEST-2 varied temporally. Genetic patchiness in blue crabs is likely to be the result of the pre-settlement formation and subsequent settlement of genetically heterogeneous patches of larvae; allele frequencies of those larval patches may then be further modified through ontogeny by localized selection. In the Atlantic Ocean, a regional latitudinal cline ofEST-2 allele frequencies was superimposed on the range-wide genetic patchiness exhibited by that locus. This pattern against a background of high gene flow is highly likely to be maintained by selection. In estuaries along the Atlantic Ocean coast, a combination of low adult long-distance migration and a high retention rate of locally spawned larvae could serve to segregate populations and allow for the development of the geographic cline inEST-2. The Gulf of Mexico showed no apparent cline, perhaps due to long-distance migration of females in some regions of the Gulf, or to masking by genetic patchiness. These results emphasize the importance of both ecological and evolutionary time scales and structuring mechanisms in determining genetic population structure. 相似文献
15.
Planktonic populations of the calanoid copepod Labidocera aestiva show significant biochemical genetic heterogeneity along the Atlantic coast of the USA. In summer, 1981, copepods were collected by surface tows at Beaufort Inlet, North Carolina; Fort Pierce Inlet, Florida; and Vineyard Sound, Massachusetts. Genetic variation within each population and genetic differentiation among the three populations were studied by micro-acrylamide gel electrophoresis of six loci encoding four enzymes. All six enzyme loci were polymorphic when all populations were considered together, but the North Carolina population was monomorphic at two loci. High genetic variability was indicated by the following: (1) the number of alleles per locus averaged over all loci was 2.57±0.26 SD; (2) the average proportion of loci for which the frequency of the most common allele was not greater than 0.95 was 0.78±0.10; (3) the frequency of heterozygous individuals was 0.25±0.07. Genetic differentiation among population samples in the three regions was demonstrated in several ways: allele frequencies at one aminopeptidase-I locus, Lap-1, differed significantly among samples of the three populations, and there were unique alleles of high frequency at this locus in two population samples. Values of the statistic of genetic distance (D) averaged 0.20±0.08 for pairwise comparisons between all samples. Compared to expected heterozygosity if individuals across the entire range sampled mated at random, there were highly significant heterozygote deficiencies at five of the six loci. Genetic differentiation of populations of L. aestiva may result from (1) differential selection on populations in the three regions, or (2) restricted gene flow between the populations. Gene flow may be limited by geographic separation or differences in life history, such as seasonal presence in the plankton and diapause egg production.Contribution No. 5810 of Woods Hole Oceanographic Institution 相似文献
16.
Variation at five microsatellite loci (Sal1, Sal2, Sal3, Sal4 and Sal5) was examined in approximately 1300 Pacific ocean perch (Sebastes alutus) sampled from 14 coastal sites in British Columbia, Canada. Mean observed heterozygosities by locus ranged from 71% to 88%, and by sample ranged from 75% to 84%. Theta values ranged from 0 to 0.04 over the five loci, and averaged 0.015. Among Pacific ocean perch samples, ranged from 0.001 to 0.056. Canonical discriminate analysis of multilocus genotypes and neighbour-joining analysis of pairwise genetic distances between samples both indicated the presence of three populations, one off the west coast of Vancouver Island (the Vancouver Island population) and two co-existing populations in Queen Charlotte Sound, Dixon Entrance and along the west coast of the Queen Charlotte Islands (the eastern and western QCI populations). Pacific ocean perch of the eastern and western QCI populations were caught in close proximity to each other, but individual samples showed little evidence of admixture. Fall and spring samples collected within geographic areas were genetically similar, indicating seasonally stable population structure. Restricted gene flow between the Vancouver Island and the two more northerly populations may result from limited adult dispersal and larval retention within the California Current and Alaska Gyre, respectively, but the presence of two populations within Queen Charlotte Sound cannot be explained entirely by larval retention hypotheses. The presence of two Pacific ocean perch populations in central British Columbia has implications for fisheries management. 相似文献
17.
The upwelling systems along the coast of Morocco support some of the largest populations of sardine (Sardina pilchardus) in the world. Although these populations provide a base for a substantial fishing industry, virtually nothing is known about
the genetic stock structure of this fish. Samples (n = 346), collected from seven sites along the Atlantic coast and in the Alboran Sea, were examined for exon-primed intron-crossing
PCR (EPIC-PCR) polymorphism. Two markers, CaM-4 and Ops-1, had 6 and 9 alleles, respectively, after the pooling of gel fragments
into 5 bp length classes, Correspondence analysis and the distribution of F
st among samples indicated that Moroccan populations were divided into two groups with F
st = 0.034 (P < 0.05) across the Gibraltar Strait. Populations along the Atlantic coast of Morocco comprise one genetic unit, except for
a weak genetic boundary south of Cape Ghir and the peculiar behavior of the Safi sample would indicate a genetic drift. Complex
ocean hydrodynamics around Gibraltar Strait and across Cape Ghir, likely, contributes to these genetic isolations. These results
point out the usefulness of population genetic studies in stock management for sardine populations that may be particularly
vulnerable to overexploitation especially during upwelling intensity shifts. 相似文献
18.
Jeffrey N. Schinske Giacomo Bernardi David K. Jacobs Eric J. Routman 《Marine Biology》2010,157(1):123-134
We compared morphology and sequenced nuclear and mitochondrial genes from 11 populations of a previously genetically unstudied
“Baja California disjunct” species, the diamond turbot (Hypsopsetta guttulata). This species exhibits very limited adult movement and restriction to soft-bottom habitats but has a moderately long pelagic
larval duration. Therefore, if pelagic larval duration is correlated with gene flow between Gulf of California and Pacific
populations, we expect a reduced level of genetic and morphological differentiation. However, if adult habitat and ecology
have more effect on gene flow, we expect the populations in the two bodies of water to be more highly differentiated. We used
logistic regression to compare morphological features and phylogenetic and population genetic analyses to compare nucleotide
sequence data. Gulf of California H. guttulata are different from Pacific populations in morphology and both mitochondrial and nuclear gene sequences. MtDNA shows reciprocal
monophyly, and nuclear sequences from the Gulf of California formed a monophyletic group. Population genetic analyses also
suggest further population subdivision within the Pacific and within the Gulf of California. We argue that adult ecology has
a significant effect on migration rates among populations in the Pacific Ocean and the Gulf of California. 相似文献
19.
Lauren M. Mathews 《Marine Biology》2007,152(3):645-655
Despite the apparent absence of geographic barriers, connectivity among marine populations may be restricted by, for example,
ecological or behavioral mechanisms. In such cases, populations may show genetic differentiation even over relatively small
spatial scales. Here, mitochondrial sequence data from the cytochrome oxidase I (COI) gene and seven polymorphic microsatellite
markers were used to investigate fine geographic scale population genetic structure in the snapping shrimp Alpheus angulosus, a member of the A. armillatus species complex, from collections in Florida, Jamaica, and Puerto Rico carried out from 1999 to 2005. The COI data showed
a deep divergence that separated these samples into two mitochondrial clades, but this divergence was not supported by the
microsatellite data. The COI data reflect past population divergence not reflected in extant population structure on the whole
genome level. The microsatellite data also revealed evidence for moderate population structure between populations as close
as ∼10 km, and no evidence for isolation by distance, as divergences between near populations were at least as strong as those
between more broadly separated populations. Overall, these data suggest a role for restricted gene flow between populations,
though the mechanisms that reduce gene flow in this taxon remain unknown. 相似文献
20.
Spatial and temporal patterns of gene-enzyme variation were estimated in the sibling species Gammarus zaddachi Sexton and G. salinus Spooner by starch gel electrophoresis. Twenty-one G. zaddachi and 18 G. salinus populations from coastal and estuarine areas in the Baltic Sea, North Sea and other localities of north-western Europe were surveyed. Both amphipods display similar electrophoresis patterns of the enzyme systems studied. Considerable interspecific and interpopulational differences were detected in allele frequencies at three highly polymorphic loci, phosphoglucose isomerase (PGI), glutamate oxalacetate transaminase (GOT) and arginine phosphokinase (APK). G. zaddachi exhibits a pronounced genetic heterogeneity in most areas of the sampled range. Populations from northern French and western English coasts differ significantly from the other samples in allele frequencies at the PGI or APK locus, respectively. Baltic populations are widely uniform in their genetic composition but can be distinguished from samples taken at North Sea sites in allele frequencies at the APK locus. The latter reveal a clinal variation, ranging from the Danish to the French coast. In contrast to G. zaddachi, a low degree of genetic differentiation was observed among the G. salinus populations examined. This indicates that migration and interregional mixing may be more important in maintaining the genetic structure than in G. zaddachi which, compared to G. salinus, prefers habitats of lower salinity levels. Evidently, less extensive dispersal capabilities owing to the confinement of G. zaddachi to brackish waters of dilute salt concentrations may account for a diminished gene flow and considerable genetic separation of local populations. This assumption is supported by the genetic homogeneity documented in Baltic G. zaddachi populations. In view of the low and constant salinities in wide areas of this brackish-water sea such barriers do not exist. Survey studies performed with selected populations over a 3-yr period demonstrated a general pattern of temporal constancy in the allozyme variation observed. 相似文献