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1.
Genetic surveys of reef fishes have revealed high population connectivity within ocean basins, consistent with the assumption that pelagic larvae disperse long distances by oceanic currents. However, several recent studies have demonstrated that larval retention and self-recruitment may be higher than previously expected. To assess connectivity in tropical reef fishes, we contribute range-wide mtDNA surveys of two Atlantic squirrelfishes (family Holocentridae). The blackbar soldierfish, Myripristis jacobus, has a pelagic juvenile phase of about 58 days, compared to about 71 days (~22% longer) in the longjaw squirrelfish, Holocentrus ascensionis. If the pelagic duration is guiding dispersal ability, M. jacobus should have greater population genetic structure than H. ascensionis. In comparisons of mtDNA cytochrome b sequences from 69 M. jacobus (744 bp) and 101 H. ascensionis (769 bp), both species exhibited a large number of closely related haplotypes (h=0.781 and 0.974, π=0.003 and 0.006, respectively), indicating late Pleistocene coalescence of mtDNA lineages. Contrary to the prediction based on pelagic duration, M. jacobus has much less population structure (φST=0.008, P=0.228) than H. ascensionis (φST=0.091, P<0.001). Significant population partitions in H. ascensionis were observed between eastern, central and western Atlantic, and between Brazil and the Caribbean in the western Atlantic. These results, in combination with the findings from 13 codistributed species, indicate that pelagic larval duration is a poor predictor of population genetic structure in Atlantic reef fishes. A key to understanding this disparity may be the evolutionary depth among corresponding taxonomic groups of “reef fishes”, which extends back to the mid-Cretaceous and encompasses enormous diversity in ecology and life history. We should not expect a simple relationship between pelagic larval duration and genetic connectivity, among lineages that diverged 50–100 million years ago. 相似文献
2.
Phylogeography and Limited Genetic Connectivity in the Endangered Boring Giant Clam across the Coral Triangle 总被引:1,自引:0,他引:1
TIMERY S. DeBOER MATTHEW D. SUBIA MARK V. ERDMANN KATIE KOVITVONGSA PAUL H. BARBER 《Conservation biology》2008,22(5):1255-1266
Abstract: The Coral Triangle is the global center of marine biodiversity; however, its coral reefs are critically threatened. Because of the bipartite life history of many marine species with sedentary adults and dispersive pelagic larvae, designing effective marine protected areas requires an understanding of patterns of larval dispersal and connectivity among geographically discrete populations. We used mtDNA sequence data to examine patterns of genetic connectivity in the boring giant clam (Tridacna crocea) in an effort to guide conservation efforts within the Coral Triangle. We collected an approximately 485 base pair fragment of mtDNA cytochrome c oxidase 1 (CO1) from 414 individuals at 26 sites across Indonesia. Genetic structure was strong between regions (φST=0.549, p < 0.00001) with 3 strongly supported clades: one restricted to western Sumatra, another distributed across central Indonesia, and a third limited to eastern Indonesia and Papua. Even within the single largest clade, small but significant genetic structure was documented (φST=0.069, p < 0.00001), which indicates limited gene flow within and among phylogeographic regions. Significant patterns of isolation by distance indicated an average dispersal distance of only 25–50 km, which is far below dispersal predictions of 406–708 km derived from estimates of passive dispersal over 10 days via surface currents. The strong regional genetic structure we found indicates potent limits to genetic and demographic connectivity for this species throughout the Coral Triangle and provides a regional context for conservation planning. The recovery of 3 distinct evolutionarily significant units within a well‐studied taxonomic group suggests that biodiversity in this region may be significantly underestimated and that Tridacna taxa may be more endangered than currently recognized. 相似文献
3.
Genetic differentiation among populations of a broadcast spawning soft coral, Sinularia flexibilis, on the Great Barrier Reef 总被引:2,自引:0,他引:2
The genetic structure of 12 reef populations of the soft coral Sinularia flexibilis (Octocorallia, Alcyoniidae) was studied along the Great Barrier Reef (GBR) at a maximum separation of 1,300 km to investigate
the relative importance of sexual and asexual reproduction, genetic differentiation and gene flow among these populations.
S. flexibilis is a widely distributed Indo-Pacific species and a gamete broadcaster that can form large aggregations of colonies on near-shore
reefs of the GBR. Up to 60 individuals per reef were collected at a minimum sampling scale of 5 m at two sites per reef, from
December 1998 to February 2000. Electrophoretic analyses of nine polymorphic allozymes indicated that genotypic frequencies
in most populations and loci did not differ significantly from those expected from Hardy–Weinberg predictions. Analysis of
multi-locus genotypes indicated a high number of unique genotypes (N
go) relative to the number of individuals sampled (N) in each reef population (range of 0.69–0.95). The maximum number of individuals likely to have been produced sexually (N*) was similar to the number of individuals sampled (i.e. N*:N ˜ 1), suggesting that even repeated genotypes may have been produced sexually. These results demonstrated a dominant role
of sexual reproduction in these populations at the scale sampled. Significant genetic differentiation between some populations
indicated that gene flow is restricted between some reefs (F
ST=0.026, 95% CI= 0.011 − 0.045) and even between sites within reefs (F
ST=0.041, 95% CI=0.027 − 0.055). Nevertheless, there was no relationship between geographic separation and genetic differentiation.
Analyses comparing groups of populations showed no significant differentiation on a north-south gradient in the GBR. The pattern
in the number of significant differences in gene frequencies in pairwise population comparisons, however, suggested that gene
flow may be more restricted among inner-shelf reef populations near to the coast than among mid/outer-shelf populations further
from the coast.
Received: 10 July 2000 / Accepted: 5 October 2000 相似文献
4.
Prevailing oceanographic processes, pelagic larvae, adult mobility, and large populations of many marine species often leads
to the assumption of wide-ranging populations. Applying this assumption to more localized populations can lead to inappropriate
conservation measures. The Pacific ocean perch (Sebastes alutus, POP) is economically and ecologically valuable, but little is known about its population structure and life history in Alaskan
waters. Fourteen microsatellite loci were used to characterize geographic structure and connectivity of POP collections (1999–2005)
sampled along the continental shelf break from Dixon Entrance to the Bering Sea. Despite opportunities for dispersal, there
was significant, geographically related genetic structure (F
ST = 0.0123, P < 10−5). Adults appear to belong to neighborhoods at geographic scales less than 400 km, and possibly as small as 70 km, which indicates
limited dispersal throughout their lives. The population structure observed has a finer geographic scale than current management,
which suggests that measures for POP fisheries conservation should be revisited. 相似文献
5.
Spatial and temporal genetic homogeneity in the Arctic surfclam (<Emphasis Type="Italic">Mactromeris polynyma</Emphasis>) 总被引:1,自引:0,他引:1
Commercially harvested marine bivalve populations show a broad range of population-genetic patterns that may be driven by
planktonic larval dispersal (gene flow) or by historical (genetic drift) and ecological processes (selection). We characterized
microsatellite genetic variation among populations and year classes of the commercially harvested Arctic surfclam, Mactromeris polynyma, in order to test the relative significance of gene flow and drift on three spatial scales: within commercially harvested
populations in the northwest Atlantic; among Atlantic populations; and between the Atlantic and Pacific oceans. We found small
nonsignificant genetic subdivision among eight populations from the northwest Atlantic (F
ST = 0.002). All of these Atlantic populations were highly significantly differentiated from a northeast Pacific population
(F
ST = 0.087); all populations showed high inbreeding coefficients (F
IS = 0.432). We tested one likely source of heterozygote deficits by aging individual clams and exploring genetic variation
among age classes within populations (a temporal Wahlund effect). Populations showed strikingly different patterns of age
structure, but we found little differentiation among age classes. In one case, we were able to analyze genetic diversity between
age classes older or younger than the advent of intensive commercial harvesting. The results generally suggest spatially broad
and temporally persistent genetic homogeneity of these bivalves. We discuss the implications of the results for the biology
and management of surfclam populations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
Genetic variability and structuring of rabbitfish populations with contrasting life histories, Siganus argenteus and Siganus fuscescens were determined using allozyme analysis. A total of 13–14 polymorphic loci were examined from samples collected in 2002 and
2003 from eight reefs representing 25 populations north (Kuroshio Current) and south (Mindanao Current) of the bifurcation
of the North Equatorial Current along the eastern Philippine coast. S. fuscescens populations (H
OBS = 0.085) showed higher heterozygosity than S. argenteus (H
OBS = 0.053), consistent with predictions of the neutral theory for demersal egg spawners compared to pelagic egg spawners. The
generally lower genetic variability of Kuroshio populations may be due to greater environmental disturbance affecting larval
mortality and recruitment success. There was no significant overall population genetic structuring for S. argenteus (F
ST = 0.01485, P > 0.05) compared to S. fuscescens (F
ST = 0.03275, P < 0.05). The latter species showed highly significant genetic structuring among Kuroshio and Mindanao Current populations
in both 2002 and 2003 (F
CT = 0.08120, P < 0.05; F
CT = 0.07500, P < 0.05, respectively), as well as among populations within regions. This conforms to expectations of correlations between
observed population genetic structure and life history features related to dispersal potential and gene flow. However, there
were significant temporal (i.e., 2002 vs. 2003 samples) genetic variations for both S. fuscescens (F
CT = 0.08542, P < 0.05) and S. argenteus (F
CT = 0.06330, P < 0.05), which may reflect interannual variability in recruitment success. Differences in population spatial genetic patterns
between the two reef fish species suggest that broad scale physical factors (e.g. NEC bifurcation) and regional environmental
perturbations (e.g. incidence of typhoons) affect population genetic structure of sympatric congeneric species with different
life histories differently. Finer scale ecological processes, which affect larval dispersal and recruitment (e.g., local hydrographic
features, distribution of habitats), particularly in the Mindanao Current region, exert more influence on structuring populations
of S. fuscescens. 相似文献
7.
Pelagic dispersal of larvae in sessile marine invertebrates could in principle lead to a homogeneous gene pool over vast distances,
yet there is increasing evidence of surprisingly high levels of genetic differentiation on small spatial scale. To evaluate
whether larval dispersal is spatially limited and correlated with distance, we conducted a study on the widely distributed,
viviparous reef coral Seriatopora hystrix from the Red Sea where we investigated ten populations separated between ~0.150 km and ~610 km. We addressed these questions
with newly developed, highly variable microsatellite markers. We detected moderate genetic differentiation among populations
based on both F
ST and R
ST (0.089 vs. 0.136, respectively) as well as considerable heterozygote deficits. Mantel tests revealed isolation by distance
effects on a small geographic scale (≤20 km), indicating limited dispersal of larvae. Our data did not reveal any evidence
against strictly sexual reproduction among the studied populations. 相似文献
8.
The orange roughy Hoplostethus atlanticus is a well-known commercial species with a global distribution. There is no consensus about levels of connectivity among populations
despite a range of techniques having been applied. We used cytochrome c oxidase subunit I (COI) and cytochrome b sequences to study genetic connectivity at a global scale. Pairwise ΦST analyses revealed a lack of significant differentiation among samples from New Zealand, Australia, Namibia, and Chile. However,
low but significant differentiation (ΦST = 0.02–0.13, P < 0.05) was found between two Northeast Atlantic sites and all the other sites with COI. AMOVA and the haplotype genealogy
confirmed these results. The prevalent lack of genetic differentiation is probably due to active adult dispersal under the
stepping-stone model. Demographic analyses suggested the occurrence of two expansion events during the Pleistocene period. 相似文献
9.
In situ and in vitro observations indicate that brooding colonial ascidians commonly display limited larval dispersal, whilst
the larvae of most solitary species are assumed to be widely dispersed. We used allozyme data to determine the population
genetic consequences of reproduction and dispersal in a broadcast-spawning solitary ascidian and two brooding colonial species
along the central and southern coast of New South Wales, Australia. We surveyed genetic variation at 2 to 9 variable loci
for samples collected from 6 to 8 local populations of each of the stalked solitary species Pyura gibbosa gibbosa Heller, 1878; the social Stolonica australis Michaelsen, 1927 and the compound Botrylloides magnicoecum Hartmeyer, 1912. Samples from each local population displayed levels and patterns of genotypic diversity that were consistent
with expectations for sexually-derived recruitment of both solitary zooids and separate colonies. However, we found clear
differences in the structure of the populations of solitary and colonial species. Genotype frequencies within all nine samples
of P. gibbosa gibbosa conformed to expectations for random mating (i.e. Hardy–Weinberg equilibria). Moreover, allele frequencies showed little
variation among samples [mean standardised genetic variance (F
S
T
) =0.002], which implies that local populations are strongly connected by larval dispersal. We estimate (via Wright's “island
model”) that gene flow (N
e
m) within this set of local populations is 125 effective migrants per generation, which is very similar to estimates obtained
for other broadcast-spawning taxa in this region. In contrast, genotype frequencies within samples of both colonial species
were characterised by large and statistically significant deficits of heterozygotes, consistent with expectations for highly
limited dispersal of larvae or sperm. Moreover, local populations were highly differentiated (F
S
T
=0.201 and 0.202 for S. australis and B. magnicoecum, respectively) and N
e
m was estimated to be ∼1.0 in each case. These values of F
S
T
and subsequent estimates of N
e
m lie within the range of values reported for other New South Wales taxa with direct larval development, and imply that local
populations are effectively closed to immigration.
Received: 13 February 1997 / Accepted 18 July 1997 相似文献
10.
Effects of contrasting modes of larval development on the genetic structures of populations of three species of prosobranch gastropods 总被引:1,自引:0,他引:1
M. G. Hoskin 《Marine Biology》1997,127(4):647-656
In south-eastern Australia, the prosobranch gastropods Morula marginalba (Blainville), Cominella lineolata (Lamarck) and Bedeva hanleyi (Angas) have similar fine-scale distributions, but appear to possess very different dispersal capabilities due to contrasting
modes of larval development. M.marginalba produce planktonic larvae, whereas C. lineolata and B. hanleyi undergo direct development in benthic egg capsules and emerge as crawling juveniles. To test for possible effects of contrasting
life histories on levels of genetic variation within and among populations, a survey was conducted of allozyme variation at
six polymorphic loci in 8 to 9 local populations of each species. Collections of snails were made between June 1992 and November
1993. Sampling ranges spanned between 162 and 180 km of coast. Regardless of larval type, proportions of single-locus genotypes
in each collection were consistent with the recruitment of offspring which had been generated through random mating. However,
genotypic diversity was lower in those species that undergo direct development. Loci surveyed in C. lineolata and B. hanleyi were polymorphic (i.e. frequency of most common allele <95%) in fewer populations than those examined for M.␣marginalba (P <0.001) and, where polymorphisms occurred, also possessed significantly fewer alleles (P <0.001). Consequently, average levels of expected heterozygosity were greater in populations of M. marginalba than in those of either of the other species (P <0.001). Genetic variation among populations, expressed as the standardised variance in allele frequencies (F
ST
), was inversely related to expected larval dispersal capability. The nine collections of M. marginalba showed little overall differentiation (F
ST
= 0.017; P <0.001), reflecting the ability of planktonic larvae to interconnect local populations, and so limit divergence due to drift
and natural selection. In contrast, there were high levels of allelic heterogeneity among the nine collections of C. lineolata (F
ST
= 0.523; P <0.001) and eight collections of B. hanleyi (F
ST
= 0.140; P <0.001). These data imply that for species which undergo direct development, local populations are effectively closed and
evolve largely independent of one another.
Received: 3 May 1996 / Accepted: 12 July 1996 相似文献
11.
Samples of the scleractinian coral Pocillopora damicornis were collected from six sites located around four islands in the Ryukyu Archipelago, southern Japan, and subjected to allozyme
electrophoresis. Seven polymorphic loci were examined for their allelic patterns. The ratio of observed to expected genotypic
diversity (0.30 < G
o
:G
e
< 0.64), the ratio of the observed number of genotypes to the number of individuals (0.47 < N
g
:N
i
< 0.75), and deviations from Hardy–Weinberg equilibrium indicated that asexual reproduction plays a major role in the maintenance
of established populations. However, populations were not completely dominated by a single or a few clones, and most clones
were represented by only a few individual samples. The high frequency of typhoons in the region suggests that, in P. damicornis, fragmentation caused through occasional exposure to powerful waves is a major mode of asexual reproduction, but asexual
production of planulae may also be contributing to the maintenance of populations. A significant genetic differentiation (F
ST) was found between the six populations examined (0.027 < F
ST < 0.092, average F
ST = 0.056). The moderate gene flow is discussed according to characteristics of the larval stage of the species, and to circulation
patterns in the region.
Received: 7 August 1998 / Accepted: 18 May 1999 相似文献
12.
Phylogeographic patterns in Uca annulipes sampled from 30 locations across an East African latitudinal gradient were investigated using mitochondrial DNA cytochrome
oxidase I sequences and analysed together with patterns of morphometric differentiation. Four hundred and four specimens along
the east African coast were sampled, and 18 haplotypes were encountered. Haplotype and nucleotide diversity values were very
low and the phylogenetic analysis did not reveal any clear phylogeographic structure. Furthermore, the analysis of molecular
variance and pairwise Φ
ST values showed no significant spatial population differentiation. Mismatch analyses and tests of neutrality supported the
hypothesis that this species has undergone a fairly recent demographic expansion. Our results, therefore, failed to demonstrate
significant geographical structure in the pattern of genetic variation, indicating that populations of U. annulipes are capable of extensive gene flow among mangroves along the coast. The genetic structure of this species could be panmictic
due to a high amount of gene flow along the geographical gradient in study during the planktonic larval phase, when larvae
are carried along stream by the dominant currents. Moreover, the morphometric analysis performed did not reveal differences
of shape differentiation according to a geographical pattern, although significant differences among the sampling areas were
found. 相似文献
13.
Coupled bio-physical models of larval dispersal predict that the Costa Rica–Panama (CR–PAN) reefs should constitute a demographically
isolated region in the western Caribbean. We tested the hypothesis that CR–PAN coral reef fish populations would be isolated
from Mesoamerican Barrier Reef System (MBRS) populations. To test that, we assessed population genetic structure in bicolor
damselfish (Stegastes partitus) from both regions. Adult fish were genotyped from five reefs in CR–PAN and from four reefs along the MBRS at 12 microsatellite
loci. Between-region F
ST (F
ST = 0.0030, P < 0.005) and exact test (x
2 = 74.34, df = 18, P < 0.0001) results indicated that there is weak but significant genetic differentiation between regions, suggesting some restriction
in connectivity along the Central American coastline, as predicted by bio-oceanographic models. Additionally, there is among-site
genetic structure in the CR–PAN region, relative to the MBRS and between regions, suggesting higher self-recruitment within
CR–PAN. This finding may be explained by differences in habitat characteristics. 相似文献
14.
This paper reports data on 28 allozyme loci in wild and artificially reared sea bass (Dicentrarchus labrax) samples, originating from either coastal lagoon or marine sites in the Mediterranean Sea. F
ST analysis (θ estimator) indicated strong genetic structuring among populations; around 34% of the overall genetic variation
is due to interpopulation variation. Pairwise θ estimates showed that, on average, the degree of genetic structuring was much
higher between marine populations than between samples from lagoons. Six polymorphic loci showed differences in allele frequencies
between marine and lagoon samples. Multivariate analyses of individual allozymic profiles and of allele frequencies suggested
that different arrays of genotypes prevail in lagoons compared to marine samples, particularly at those loci that, on the
basis of previous acclimation experiments, had been implicated in adaptation to freshwater. On the other hand, variation at
“neutral” allozyme loci reflects to a greater extent the geographic location of populations. Allozyme differentiation was
also studied in a D. labrax population from the Portuguese coast. Average genetic distance between this population and the Mediterranean populations
was quite high (Nei's D = 0.236) and calls into question the taxonomic status of the Portuguese population. Finally, genetic relationships between
D. labrax and D. punctatus were evaluated. Average Nei's D was 0.648, revealing high genetic differentiation between the two species, even for two sympatric populations of these species
in Egypt; thus gene flow was not indicated between species.
Received: 24 October 1996 / Accepted: 27 November 1996 相似文献
15.
Christine H. Petersen 《Marine Biology》2007,150(6):1289-1300
Discrete estuary subpopulations of the mud crab Hemigrapsus oregonensis (Dana, 1851) are connected via larval dispersal. Sequence variation at the mtDNA COI locus was examined in eight populations
sampled in 2001–2002 from central California through northern Oregon in the northeast Pacific (36.6–45.8°N) to infer patterns
of dispersal and historical connectivity in the region. Strong evidence for persistence since the mid-Pleistocene, with no
range truncation resulting from southward shifting temperature isoclines, was provided by a phylogeographic pattern of haplotypes
of an older clade distributed throughout the sampled range. A recently derived clade became widespread only north of Cape
Blanco after the last glacial maximum. Its clear pattern of restriction to the northern area, in the absence of similarly
restricted southern clades, suggests that contemporary dispersal around Cape Blanco is rare (population F
ST = 0.192). Low pairwise differentiation within Oregon and within central California, as well as contrasts between northern
and southern groups in the shape of the pairwise mismatch distribution, nucleotide diversity, and Tajima’s D suggest that these regions reflect different demographic histories. Potential mechanisms explaining this latitudinal break
include contemporary coastal circulation patterns, selection, and ancient patterns of larval dispersal in the California Current. 相似文献
16.
Results of isozyme electrophoresis were used to explore the genetic relationships between several Mediterranean morphs of
Cerithium (Gastropoda: Prosobranchia), for which taxonomy is currently uncertain because of high intraspecific variability and low
interspecific differentiation. The large species, classically known as C. vulgatum Bruguière, 1789 was identified at four sites (two in the French Mediterranean and two in southern Spain). Two different larval
types were found in the French sites, but poecilogony could not be demonstrated. Individuals collected from harbours were
not genetically distinct from open-sea populations of classic C. vulgatum. However, a population in the Embiez lagoon (French Mediterranean) which morphologically resembles C. vulgatum did display distinct genetic traits, supporting its status as a separate species. Of the small Cerithium species usually known as C. rupestre, two sympatric species (C.“rupestre” Risso, 1826 and C. lividulum Risso, 1826) were distinguished. Genotype frequencies within the analysed populations revealed much heterozygote deficiency.
F
ST
values (fixation index measuring the effects of population subdivision) suggest a higher genetic differentiation for C. lividulum populations than for C. vulgatum populations. We assume that a high larval dispersal capability (via planktotrophy) allows a high gene flow between populations
of C. vulgatum.
Received: 24 November 1998 / Accepted: 24 September 1999 相似文献
17.
Samples of the Antarctic octopus Pareledone turqueti were taken from three locations on the Scotia Ridge in the Southern Ocean. The genetic homogeneity of these populations was
investigated using isozyme electrophoresis. Whilst panmixia appeared to be maintained around South Georgia (F
ST = 0) gene flow between this island and Shag Rocks, an island only 150 km away but separated by great depths, was extremely
limited (F
ST = 0.74). These results are examined with respect to the discontinuous distribution of P. turqueti throughout Antarctica. An estimate of effective population size was also calculated (N
e = 3600).
Received: 7 March 1997 / Accepted: 27 March 1997 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.
The pelagic copepod Calanus pacificus ranges nearly continuously across temperate-boreal regions of the North Pacific Ocean and is currently divided into three
subspecies—C. pacificus oceanicus, C. pacificus californicus, C. pacificus pacificus—based on subtle morphological differences and geographic location. The relation between geography and genetic differentiation
was examined for 398 C. pacificus individuals sampled from six widely distributed locations across the North Pacific, including an open ocean site and coastal
sites on both sides of the North Pacific basin. For each individual copepod, the DNA sequence was determined for a 421-bp
region of the mitochondrial coxI gene (mtCOI). A total of sixty-three different mtCOI sequences, or haplotypes, were detected,
with a sequence divergence between haplotypes of 0.2–3.1%. The number and distribution of haplotypes varied with sampling
location; 12 haplotypes were distributed across multiple sampling locations, and 51 occurred at only one location. Five genetically
distinct populations were detected based on F
ST values. Haplotype minimum spanning networks, nucleotide divergence and F
ST values indicated that individuals from coastal sites in the North Pacific Ocean were more closely related to each other than
to individuals from the open ocean site at Station P. These results provide genetic support for the designation of two subspecies—a
coastal subspecies that consists of what is currently referred to as C. p. pacificus and C. p. californicus and an open ocean subspecies C. p. oceanicus. This work also indicates that planktonic copepods with potentially high dispersal capacity can develop genetically structured
populations in the absence of obvious geographic barriers between proximate locales within an ocean basin. 相似文献
20.
Reef habitats of the tropical Atlantic are separated by river outflows and oceanic expanses that may preclude larval dispersal or other population connections in shorefishes. To examine the impact of these habitat discontinuities on the intraspecific phylogeography of reef-associated species we conducted range-wide surveys of two amphi-Atlantic reef fishes that have dispersive pelagic larval stages. Based on 593 bp of mtDNA cytochrome b from the rock hind Epinephelus adscensionis and 682 bp from the greater soapfish Rypticus saponaceous (n=109 and 86, respectively), we found evidence of relatively ancient separations as well as recent surmounting of biogeographic barriers by dispersal or colonization. Rock hind showed slight but significant population genetic differentiation across much of the tropical Atlantic Ocean (ST=0.056), but deep divergence between the southeastern United States and seven other localities from the Bahamas to the south, central and east Atlantic (mean pairwise d=0.040, overall ST=0.867). The geographic distribution of the two rock hind lineages is highly unusual in genetic studies of Caribbean Sea reef fishes, because those lineages are separated by less than 250 km of open water within a major biogeographic region. In contrast, highly significant population genetic structure was observed among greater soapfish from the SW Caribbean, Brazil, and mid-Atlantic ridge (ST=0.372), with a deep evolutionary separation distinguishing putative R. saponaceous from West Africa (mean pairwise d=0.044, overall ST=0.929). Both species show evidence for a potential connection between the Caribbean and Brazilian provinces. While widespread haplotype sharing in rock hind indicates that larvae of this species cross oceanic expanses of as much as 2000 km, such a situation is difficult to reconcile with the isolation of populations in Florida and the Bahamas separated by only 250 km. These findings indicate that populations of some species in disjunct biogeographic zones may be isolated for long periods, perhaps sufficient for allopatric speciation, but rare gene flow between zones may preclude such evolutionary divergence in other species.Communicated by P.W. Sammarco, Chauvin 相似文献