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1.
The genetic structure of Patagonian toothfish populations in the Atlantic and western Indian Ocean Sectors of the Southern Ocean (SO) were analysed using partial sequences of the mitochondrial 12S rRNA gene and seven microsatellite loci. Both haplotype frequency data (F
ST>0.906, P<0.01) and microsatellite genotype frequency data (F
ST=0.0141–0.0338, P<0.05) indicated that populations of toothfish from around the Falkland Islands were genetically distinct from those at South Georgia (eastern Atlantic Sector SO), around Bouvet Island (western Atlantic Sector SO) and the Ob Seamount (western Indian Ocean Sector of the SO). Genetic differentiation between these populations is thought to result from hydrographic isolation, as the sites are separated by two, full-depth, ocean-fronts and topographic isolation, as samples are separated by deep water. The South Georgia, Bouvet and Ob Seamount samples were characterised by an identical haplotype. However, microsatellite genotype frequencies showed genetic differentiation between South Georgia samples and those obtained from around Bouvet Island and nearby seamounts (F
ST=0.0037, P<0.05). These areas are separated by large geographic distance and water in excess of 3,000 m deep, below the distributional range of toothfish (<2,200 m). No significant genetic differentiation was detected between samples around Bouvet Island and the Ob Seamount although comparisons may have been influenced by low sample size. These localities are linked by topographic features, including both ridges and seamounts, that may act as oceanic “stepping stones” for migration between these populations. As for other species of deep-sea fish, Patagonian toothfish populations are genetically structured at the regional and sub-regional scales. 相似文献
2.
Frequencies of electromorphs encoded by 14 polymorphic loci were used to estimate genetic distances among samples of the rabbitfishes Siganus argenteus, S. doliatus, S. fuscescens, S. guttatus, S. javus, S. punctatus, S. randalli, S. spinus, S. vermiculatus, and S. (Lo) vulpinus. Samples of the surgeonfish Naso lituratus (Acanthuridae) were included in the electrophoretic survey for the purpose of outgroup comparison. A matrix of genetic-distance estimates was used for construction of dendrograms by neighbor-joining, complete-linkage and single-linkage procedures, and the unweighted pair-group method of arithmetic averages (UPGMA). Cluster analysis revealed interspecific relationships that are concordant with several predictions intimated in the most recent taxonomic revision of this assemblage of fishes. S. randalli and S. vermiculatus, the pair postulated to be sibling species on the basis of strikingly similar external morphology, were found to exhibit the lowest levels of genetic divergence relative to all other pairs of study species. S. randalli, S. guttatus, and S. vermiculatus comprised one of three clusters discerned in all resultant topologies (i.e., ball clusters). S. argenteus, S. fuscescens, and S. spinus, three fusiform-bodied species, formed a second ball cluster that was clearly separable from the remainder of the siganids studied (which are all relatively deep-bodied). A third ball cluster contained S. punctatus and S. vulpinus: S. doliatus was depicted as being allied with S. punctatus and S. vulpinus in the neighbor-joining and complete-linkage topologies but not in topologies generated by UPGMA and single linkage. It is noteworthy that S. punctatus, S. vulpinus, and S. doliatus are the only three species included in the present study which purportedly school when young but form pair-bonds as adults. In all topologies, S. javus occupied branches stemming from furcation points between fusiform-bodied and deep-bodied species. Of all the siganids studied, S. argenteus was found to be least divergent genetically from N. lituratus. S. argenteus is the only siganid known to spawn pelagic eggs and undergo a specialized pelagic stage (features typical within the Acanthuridae). Hence, genetic relationships within the Siganidae and among the Siganidae and a representative acanthurid coincide with a host of predictions stemming from morphologic and life-history studies of the Acanthuroidei. 相似文献
3.
Zoë Anne Doubleday Jayson M. Semmens Adam J. Smolenski Paul W. Shaw 《Marine Biology》2009,156(6):1183-1192
Five polymorphic microsatellite loci were developed and then used to assess the population genetic structure of a commercially
harvested merobenthic octopus species (Octopus maorum) in south-east Australian and New Zealand (NZ) waters. Beak and stylet morphometrics were also used to assess population
differentiation in conjunction with the genetic data. Genetic variation across all loci and all sampled populations was very
high (mean number alleles = 15, mean expected heterozygosity = 0.85). Microsatellites revealed significant genetic structuring
(overall F
ST = 0.024, p < 0.001), which did not fit an isolation-by-distance model of population differentiation. Divergence was observed between
Australian and NZ populations, between South Australia and north-east Tasmania, and between two relatively proximate Tasmanian
sites. South Australian and southern Tasmanian populations were genetically homogeneous, indicating a level of connectivity
on a scale of 1,500 km. Morphometric data also indicated significant differences between Australian and NZ populations. The
patterns of population structuring identified can be explained largely in relation to regional oceanographic features. 相似文献
4.
Documenting the scale of movement among populations is an important challenge for marine ecology. Using nine microsatellite markers, evidence of genetic structure in a marine kelp, the sea palm Postelsia palmaeformis Ruprecht, was examined in the vicinity of Cape Flattery, Washington state, USA (48° 24′ N, 124°44′ W). Genetic clustering analysis implemented without reference to geographic structure strongly suggested that a number of distinct genetic clusters existed among the 245 plants sampled in August in the years 1997–2001. Subsequent analysis showed that clustering was associated with geographically defined populations both among (km scale) and within (m scale) sampling sites. F
st analysis of geographically defined populations revealed significant genetic differentiation among populations of plants as little as 5 m apart, evidence of genetic structuring at even smaller scales, and a sharp increase in F
st across populations separated by up to 23 m. F
st values were also high and approximately unchanging (F
st=0.470) for populations separated by greater distances (up to 11 km), consistent with a scenario of rare dispersal by detached, floating plants carried by variable currents. The results corroborate natural history observations suggesting that P. palmaeformis has extremely short (1–3 m) spore dispersal distances, and indicate that the dynamics of sea palm populations are more affected by local processes than recruitment from distant populations. 相似文献
5.
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
6.
The genetic structure of Mycedium elephantotus (Pallas, 1766) populations from three regions around Taiwan was examined using allozyme electrophoresis. Eight loci were
scored from seven enzyme systems. Seven loci were polymorphic under the 95% criterion. The high ratio of observed to expected
genotypic diversities at the collection sites (G
O:G
E=0.8 to 1.0) indicate that M. elephantotus propagates predominantly by sexual reproduction. Allele frequencies of M. elephantotus differed significantly among regions (D=0.024 to 0.256, F
ST=0.032 to 0.218, p < 0.001), while populations among collection sites within each region were homogeneous (D=0.000 to 0.015, F
ST=0.010 to 0.022, p > 0.05). Genetic differentiation between populations from southern Taiwan and the Penghu Islands is greater than that between
southern and northern Taiwan populations, although the former two regions are much closer geographically. The UPGMA dendrogram
based on Nei's unbiased genetic distance showed a clear subdivision of populations into two groupings, northern Taiwan/Penghu
Islands and southern Taiwan. A higher level of gene flow was found between M. elephantotus populations in northern Taiwan and the Penghu Islands (N
m=7.56) than that between populations in southern Taiwan and other regions (N
m=0.90 to 1.72). The pattern of genetic subdivision among regions is consistent with the pattern of ocean currents, indicating
that genetic differentiation is likely driven by surface circulation vicariance.
Received: 2 December 1997 / Accepted: 15 September 1998 相似文献
7.
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
8.
Seabob shrimps of the genus Xiphopenaeus are important fishery resources along the Atlantic and Pacific coasts of Central and South America. The genus was considered to comprise two species: the Atlantic Xiphopenaeus kroyeri (Heller, Sitzungsber Math Naturwiss cl kaiserliche Akad Wiss Wien 45:389–426, 1862), and the Pacific Xiphopenaeus riveti (Bouvier, Bull Mus Hist Nat Paris 13:113–116, 1907). In a recent review, Xiphopenaeus was regarded as a monotypic genus, on the basis that no clear morphological differences could be found between Pacific and Atlantic specimens (Pérez Farfante and Kensley, Mem Mus Nat Hist Nat Paris 175:1–79, 1997). In the present work, nuclear (allozymes), and mitochondrial (Cytochrome Oxidase I) genes were used to demonstrate the validity of X. riveti and reveal the presence of two cryptic species of Xiphopenaeus within X. kroyeri in the Atlantic Ocean. The high levels of molecular divergence among these species contrast with their high morphological resemblance. Interspecific sequence divergences (Kimura 2-parameter distance) varied from 0.106 to 0.151, whereas intraspecific distances ranged from 0 to 0.008 in Xiphopenaeus sp. 1, from 0 to 0.003 in Xiphopenaeus sp. 2, and from 0.002 to 0.005 in X. riveti. In addition, five diagnostic allozyme loci were found between sympatric samples of Xiphopenaeus sp. 1 and 2 along the Brazilian coast. The results suggest that Xiphopenaeus sp. 2 from the Atlantic is more closely related to the Pacific X. riveti than to the Atlantic Xiphopenaeus sp. 1. Furthermore, a high level of genetic structuring (Xiphopenaeus sp. 1: F
ST
=0.026; P<0.05; Xiphopenaeus sp. 2: F
ST
=0.055; P<0.01) was found in the Brazilian Xiphopenaeus populations, indicating the presence of different genetic stocks in both Atlantic species. These findings have important commercial implications as they show that the fisheries of the two Atlantic species must be managed separately, and that each one is comprised of different populations.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
9.
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
10.
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
11.
Abstract: High‐latitude coral reefs (HLRs) are potentially vulnerable marine ecosystems facing well‐documented threats to tropical reefs and exposure to suboptimal temperatures and insolation. In addition, because of their geographic isolation, HLRs may have poor or erratic larval connections to tropical reefs and a reduced genetic diversity and capacity to respond to environmental change. On Australia's east coast, a system of marine protected areas (MPAs) has been established with the aim of conserving HLRs in part by providing sources of colonizing larvae. To examine the effectiveness of existing MPAs as networks for dispersal, we compared genetic diversity within and among the HLRs in MPAs and between these HLRs and tropical reefs on the southern Great Barrier Reef (GBR). The 2 coral species best represented on Australian HLRs (the brooding Pocillopora damicornis and the broadcast‐spawning Goniastrea australensis) exhibited sharply contrasting patterns of diversity and connectedness. For P. damicornis, the 8‐locus genetic and genotypic diversity declined dramatically with increasing latitude (Na= 3.6–1.2, He= 0.3–0.03, Ng:N = 0.87–0.06), although population structure was consistent with recruitment derived largely from sexual reproduction (Go:Ge= 1.28–0.55). Genetic differentiation was high among the HLRs (FST[SD]= 0.32 [0.08], p < 0.05) and between the GBR and the HLRs (FST= 0.24 [0.06], p < 0.05), which indicates these temperate populations are effectively closed. In contrast for G. australensis, 9‐locus genetic diversity was more consistent across reefs (Na= 4.2–3.9, He= 0.3–0.26, Ng:N = 1–0.61), and there was no differentiation among regions (FST= 0.00 [0.004], p > 0.05), which implies the HLRs and the southern GBR are strongly interconnected. Our results demonstrate that although the current MPAs appear to capture most of the genetic diversity present within the HLR systems for these 2 species, their sharply contrasting patterns of connectivity indicate some taxa, such as P. damicornis, will be more vulnerable than others, and this disparity will provide challenges for future management. 相似文献
12.
The population genetic structure of the neon damselfish (Pomacentrus coelestis) in the northwestern Pacific Ocean was revealed by the hypervariable control region of the mitochondrial gene (343 bp). In
total, 170 individuals were sampled from 8 localities distributed between Taiwan and Japan, and 71 haplotypes were obtained
through sequence alignment. High haplotype diversity (h = 0.956 ± 0.008) with low nucleotide diversity (π = 0.010 ± 0.006) was observed, and the results of the mismatch distribution test suggested that a historical population expansion
after a period of population bottleneck might have occurred among P. coelestis populations. Based on the results of the UPGMA tree and AMOVA (Φct = 0.193, P < 0.05) analyses, fish populations from eight localities could be divided into two groups: one includes populations from localities
around mainland Japan, and the other includes those from Okinawa and southern Taiwan. A genetic break was found between populations
from mainland Japan and Okinawa, and this break was congruent with the pattern of phenotypic variations documented in previous
studies. This evidence supports the latitudinal variation of reproductive traits among P. coelestis populations likely being genetically based. It is suggested that the changes in sea level and sea surface temperatures during
past glaciations might have resulted in population bottlenecks in P. coelestis and the modern populations in the northern West Pacific are likely the results of recolonization after such events. The Kuroshio
Current acts not only as a vehicle for larval transport along its pathway (between populations in southern Taiwan and Okinawa)
but also as a barrier for larval dispersal across the Kuroshio axis (between populations in mainland Japan and Okinawa).
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
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
14.
Mirimin Luca Westgate Andrew Rogan Emer Rosel Patricia Read Andrew Coughlan Jamie Cross Tom 《Marine Biology》2009,156(5):821-834
The understanding of population structure and gene flow of marine pelagic species is paramount to monitoring, management and
conservation studies. Such studies are often hampered by the potentially high dispersal behavior of the species, the lack
of obvious geographical barriers in the marine environment and the scarce sample availability. Short-beaked common dolphins
(Delphinus delphis) are widespread in coastal and open-ocean habitats of the North Atlantic Ocean, nevertheless population structure and migratory
patterns are poorly understood. Furthermore, concern has been raised about the status of the species because large numbers
of dolphins have been taken incidentally in several fisheries throughout the North Atlantic in the past decades. In the present
study, a large number of individual samples were obtained from seasonal and spatial aggregations of common dolphins from western
(wNA) and eastern North Atlantic (eNA) regions, mostly using opportunistic sampling (i.e. from incidental entanglement in
fishing gear or beach-cast carcasses). Genetic variability was investigated using nuclear (14 microsatellite loci) and mitochondrial
(360 bp of the control region) genetic markers. Levels of genetic diversity were relatively high in all sampled areas and
no evidence of recent reduction of effective population size (i.e. bottleneck) was detected at the nuclear loci. Significant
population structure was detected between the two main regions (wNA and eNA) where it appeared to be more pronounced at mitochondrial
(F
ST = 0.018, P < 0.001) than nuclear markers (F
ST = 0.005, P < 0.05), indicating the presence of at least two genetically distinct populations of common dolphins in the North Atlantic
Ocean. In contrast, no significant genetic structure was detected between temporal aggregations of dolphins from within the
same region, suggesting possible seasonal movement patterns at a regional scale. The observed levels of genetic differentiation
between classes of markers are discussed here as a possible consequence of migratory patterns or recent population subdivision.
An erratum to this article can be found at 相似文献
15.
H. von Westernhagen 《Marine Biology》1973,22(4):367-370
Specimens of juvenile and mature rabbitfish, Siganus oramin and S. striolata, were submitted to stomach analyses. Agarophytes of the genera Gracilaria, Hypnea and Laurencia proved to be the most preferred diet. Small invertebrates were ingested accidentally. 相似文献
16.
The genetic relationships between morphologically indistinguishable marine and brackish-water populations of Monocelis lineata (O.F. Müller, 1774) (Proseriata: Monocelididae) were analysed by means of allozyme electrophoresis. Fifteen samples of M. lineata (13 from the Mediterranean and two from the Atlantic) from coastal marine and brackish-water habitats were examined for variation at 18 loci. Eleven loci were polymorphic in at least one population of M. lineata. Low levels of within-population genetic variability were found, with average observed and expected heterozygosity values ranging from Ho=0.015±0.015 to 0.113±0.044, and from
He=0.028±0.028 to 0.138±0.054, respectively. The occurrence of a number of private alleles indicated a marked genetic divergence among populations of M. lineata, with Rogers genetic distances ranging from
DR=0.003 to 0.676 and a highly significant FST value (0.918±0.012, P<0.001). UPGMA (unweighted pair-group method using arithmetic average) cluster analysis and multidimensional scaling showed a clear genetic divergence between marine and brackish-water populations. Moreover, Atlantic and Mediterranean populations were sharply separated. Our results suggest that M. lineata is a complex of sibling species.Communicated by R. Cattaneo-Vietti, Genova 相似文献
17.
The molecular diversity of symbiotic dinoflagellates associated with the widespread western Pacific coral Plesiastrea versipora was explored in order to examine if associations between reef-building corals and symbiotic dinoflagellates change with environment. Several ribosomal DNA genes with different evolutionary rates were used, including the large subunit (28S), the 5.8S region and the internal transcribed spacers (ITS). The phylogenetic analysis of the 28S and 5.8S rDNA regions indicated that a single endosymbiont species, highly related to one of the species of Symbiodinium in clade C (= Symbiodinium goreaui, Trench et Blank), associates with P. versipora along the Ryukyu Archipelago. The persistence of the same endosymbiont within P. versipora across this wide array of latitudes may be a result of such features as the Kuroshio Current, which brings tropical temperatures as far north as Honshu, Japan. Analysis of the faster evolving ITS rDNA region revealed significant genetic variability within endosymbionts from different populations. This variation was due to a high degree of interpopulation variability, based on the proportion of pairwise variation detected among the populations (0.95% approximately). By comparison with other studies, the results also indicate that some ITS1 haplotypes from P. versipora endosymbionts seem to be widely distributed within the western Pacific Ocean, ranging from the Great Barrier Reef to the northeast of the China Sea. 相似文献
18.
Mitochondrial control region (HVR-1) sequences were used to identify patterns of genetic structure and diversity in Naso vlamingii, a widespread coral reef fish with a long evolutionary history. We examined 113 individuals from eight locations across the Indo-Pacific Ocean. Our aims were to determine the spatial scale at which population partitioning occurred and then to evaluate the extent to which either vicariance and/or dispersal events have shaped the population structure of N. vlamingii. The analysis produced several unexpected findings. Firstly, the genetic structure of this species was temporal rather than spatial. Secondly, there was no evidence of a barrier to dispersal throughout the vast distribution range. Apparently larvae of this species traverse vicariance barriers that inhibit inter-oceanic migration of other widespread reef fish taxa. Thirdly, an unusual life history and long evolutionary history was associated with a population structure that was unique amongst coral reef fishes in terms of the magnitude and pattern of genetic diversity (haplotype diversity, h = 1.0 and nucleotide diversity π = 13.6%). In addition to these unique characteristics, there was no evidence of isolation by distance (r = 0.458, R
2 = 0.210, P = 0.078) as has also been shown for some other widespread reef species. However, some reductions in gene flow were observed among and within Ocean basins [Indian–Pacific analysis of molecular variance (AMOVA), Φ
st = 0.0766, P < 0.05; West Indian–East Indian–Pacific AMOVA Φ
st = 0.079, P < 0.05]. These findings are contrasted with recent studies of coral reef fishes that imply a greater degree of spatial structuring in coral reef fish populations than would be expected from the dispersive nature of their life cycles. We conclude that increased taxon sampling of coral reef fishes for phylogeographic analysis will provide an extended view of the ecological and evolutionary processes shaping coral reef fish diversity at both ends of the life history spectrum. 相似文献
19.
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
20.
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