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1.
The distribution and diet of juvenile (<750 mm) Patagonian toothfish are described from four annual trawl surveys (2003–2006)
around the island of South Georgia in the Atlantic sector of the Southern Ocean. Recruitment of toothfish varies inter-annually,
and a single large cohort dominated during the four years surveyed. Most juveniles were caught on the Shag Rocks shelf to
the NW of South Georgia, with fish subsequently dispersing to deeper water around both the South Georgia and Shag Rocks shelves.
Mean size of juvenile toothfish increased with depth of capture. Stomach contents analysis was conducted on 795 fish that
contained food remains and revealed that juvenile toothfish are essentially piscivorous, with the diet dominated by notothenid
fish. The yellow-finned notothen, Patagonotothen guntheri, was the dominant prey at Shag Rocks whilst at South Georgia, where P. guntheri is absent, the dominant prey were Antarctic krill and notothenid fish. The diet changed with size, with an increase in myctophid
fish and krill as toothfish grow and disperse. The size of prey also increased with fish size, with a greater range of prey
sizes consumed by larger fish. 相似文献
2.
Molecular genetic variation in tarpon (<Emphasis Type="Italic">Megalops atlanticus</Emphasis> Valenciennes) in the northern Atlantic Ocean 总被引:2,自引:0,他引:2
The tarpon (Megalops atlanticus) is a highly valued game fish and occasional food fish in the eastern and western Atlantic Ocean. Tarpon have a high capacity for dispersal, but some regional biological differences have been reported. In this study we used two molecular genetic techniques—protein electrophoresis of nuclear DNA loci, and restriction fragment length polymorphism analysis of the mitochondrial DNA (mtDNA)—to assess this species population genetic structure in the eastern (coastal waters off Gabon and Sierra Leone, Africa) and western (coastal waters off Florida, Caribbean Sea) Atlantic Ocean north of the equator. Genetic differentiation was observed between tarpon from Africa and tarpon from the western Atlantic Ocean. A unique allele and haplotype, significant differences in allozyme allele and mtDNA haplotype frequencies between the African and western Atlantic samples, and significant FST analyses suggest that levels of gene flow between tarpon from these two regions is low. Among the western Atlantic Ocean collections, genetic diversity values and allele and haplotype frequencies were similar. AMOVA analyses also showed a degree of genetic relatedness among most of the western Atlantic Ocean collections: however, some significant population structuring was detected in the allozyme data. A regional jackknifed FST analysis indicated the distinction of the Costa Rica population from the other western Atlantic populations and, in pairwise analyses, FST values tended to be higher (i.e., genetic relatedness was lower) when the Costa Rican sample was paired with any of the other western Atlantic samples. These data suggest that Costa Rican tarpon could be partially isolated from other western Atlantic tarpon populations. Ultimately, international cooperation will be essential in the management of this species in both the eastern and western Atlantic Ocean.Communicated by P.W. Sammarco, Chauvin 相似文献
3.
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
4.
Stock heterogeneity was investigated in albacore tuna (Thunnus alalunga, Bonnaterre 1788), a commercially important species in the North Atlantic Ocean and Mediterranean Sea. Twelve polymorphic
microsatellite loci were examined in 581 albacore tuna from nine locations, four in the north-east Atlantic Ocean (NEA), three
in the Mediterranean Sea (MED) and two in the south-western Pacific Ocean (SWP). Maximum numbers of alleles per locus ranged
from 9 to 38 (sample mean, 5.2–22.6 per locus; overall mean, 14.2 ± 0.47 SE), and observed heterozygosities per locus ranged
from 0.44 to 1.00 (overall mean: 0.79 ± 0.19 SE). Significant deficits of heterozygotes were observed in 20% of tests. Multilocus
F
ST values were observed ranging from 0.00 to Θ = 0.036 and Θ′ = 0.253, with a mean of Θ = 0.013 and Θ′ = 0.079. Pairwise F
ST values showed that the SWP, NEA and MED stocks were significantly distinct from one another, thus corroborating findings
in previous studies based on mitochondrial DNA, nuclear DNA (other than microsatellites) and allozyme analyses. Heterogeneity
was observed for the first time between samples within the Mediterranean Sea. GENELAND indicated the potential presence of
three populations across the NEA and two separate populations in the Mediterranean Sea. Observed genetic structure may be
related to migration patterns and timing of movements of subpopulations to the feeding grounds in either summer or autumn.
We suggest that a more intensive survey be conducted throughout the entire fishing season to ratify or refute the currently
accepted genetic homogeneity within the NEA albacore stock. 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.
The nurse shark, Ginglymostoma cirratum, inhabits shallow, tropical, and subtropical waters in the Atlantic and the eastern Pacific. Unlike many other species of
sharks, nurse sharks are remarkably sedentary. We assayed the mitochondrial control region and eight microsatellite loci from
individuals collected primarily in the western Atlantic to estimate the degree of population subdivision. Two individuals
from the eastern Atlantic and one from the Pacific coast of Panama also were genotyped. Overall, the mtDNA haplotype (h = 48 ± 5%) and nucleotide (π = 0.08 ± 0.06%) diversities were low. The microsatellite data mirror the mitochondrial results
with the average number of alleles ([`(N)]A \bar{N}_{A} = 9) and observed heterozygosity ([`(H)]O \bar{H}_{O} = 0.58) both low. The low levels of diversity seen in both the mtDNA and the microsatellite may be due to historical sea
level fluctuations and concomitant loss of shallow water habitat. Eight of the 10 pair-wise western Atlantic F
ST estimates for mtDNA indicated significant genetic subdivision. Pair-wise F
ST values for the microsatellite loci indicated a similar pattern as the mtDNA. The western Atlantic population of nurse sharks
is genetically subdivided with the strongest separation seen between the offshore islands and mainland Brazil, likely due
to deep water acting as a barrier to dispersal. The eastern and western Atlantic populations were closely related. The eastern
Pacific individual is quite different from Atlantic individuals and may be a cryptic, sister species. 相似文献
7.
Population structure of the black tiger prawn, Penaeus monodon, among western Indian Ocean and western Pacific populations 总被引:4,自引:0,他引:4
We examined the population structure of the black tiger prawn, Penaeus monodon Fabricius, 1798, in the Indo-West Pacific by analyzing the geographic distribution of elongation factor 1-alpha intron sequences from specimens collected during the winter and spring of 1997. Both the molecular phylogeny of alleles and
F-statistics indicated very strong differentiation between populations from the western Indian Ocean and western Pacific. This
pattern is concordant with other recent studies of marine species in this region, implying that the Indo-Australian Archipelago
represents a biogeographic break between populations in the Indo-West Pacific. F
ST-values among populations in the western Indian Ocean also indicate structure within this region, whereas no structure was
found among western Pacific populations. Nucleotide diversity was significantly lower in the western Indian Ocean populations
than in the western Pacific, implying that the populations have regional differences in demographic history.
Received: 16 November 1998 / Accepted: 26 May 1999 相似文献
8.
The red porgy, Pagrus pagrus (L.), is a protogynous sparid associated with reefs and hard bottom habitat throughout the warm-temperate Atlantic Ocean.
In this study, the degree of geographic population differentiation in Atlantic populations was examined with microsatellite
and mitochondrial DNA markers (mtDNA). Six microsatellite loci were amplified and scored in 690 individuals from the eastern
North Atlantic (Crete, Madeira, and Azores), western North Atlantic (North Carolina to Florida, and the eastern Gulf of Mexico),
and Brazil. At two loci, fixed allelic differences were found among the three major geographic areas, while frequency differences
were observed at three other loci. The DNA of 371 individuals was amplified at the mtDNA control region, and 526 bp were sequenced.
Tamura–Nei’s D was used as a measure of nucleotide diversity and divergence: diversity averaged 0.011 within samples, while the corrected
divergence averaged 0 between samples within the same area and 0.061 between samples from different areas. Transversion haplotype
minimum spanning networks, nucleotide divergence, and F
ST values all show that the western Atlantic samples were more closely related to each other than any was to samples from the
eastern North Atlantic. Within the western North Atlantic, no significant population differentiation was observed, and within
the eastern North Atlantic, only the Azores sample showed detectable differences from Crete and Madeira. These data indicate
general homogeneity within large areas, and deep divisions between these areas.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
9.
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
10.
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
11.
Megrim, Lepidorhombus whiffiagonis, and four spot megrim, Lepidorhombus boscii, are two marine fish species of high commercial interest. Despite their quite heavy exploitation little is known on the genetic
structure of their populations. The present work aimed at characterizing the first seven microsatellites markers available
for the two megrim species. These new markers were in a second step employed to describe the population structure of the two
species among their almost entire habitat range (Atlantic and Mediterranean samples). Our study confirmed the existence of
a strong genetic difference between Atlantic and Mediterranean megrim species already described in the literature for L. whiffiagonis on the basis of variations at ribosomal genes. Additionally our analysis gave the first evidences of a strong genetic differentiation
among Atlantic populations in both megrim species (within Atlantic global FST in L. whiffiagonis and L. boscii were respectively 0.158 and 0.145). When describing megrim population structure, the comparison between allele-frequency-based
tests (FST comparisons) and genotype-based inferences (Bayesian approach) gave evidences of a hierarchical structure of the populations.
In conclusion, our work enlighten the existence of two different stocks within the Atlantic Ocean and one in the Mediterranean
Sea that will clearly need to be managed separately. As the present results do not fully support the current megrim stock
boundaries they will surely help to rethink megrim management policies in the future. 相似文献
12.
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
13.
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
14.
Variations at 22 enzyme coding loci were surveyed in 11 populations of the oyster Ostrea edulis L., which were sampled between 1988 and 1990 along the Atlantic and Mediterranean coasts of Europe. Atlantic oyster beds suffered a steady decline during the last century, and restocking of beds with oysters of foreign origin has probably resulted in a high degree of interbreeding of natural oyster stocks from all Atlantic Europe. Our study confirms the low levels of genetic variability previously reported for the oyster populations from the Atlantic coasts, and extends it to the Mediterranean coasts. The locus arginine-kinase (ARK
*) exhibited a high degree of interpopulation differentiation (F
ST=0.289), resulting from extensive variation in gene frequencies along a geographical cline. However, the overall genetic differentiation between populations was slight, and similar to that reported for other local populations of bivalves (mean genetic distance between populations is 0.010, mean F
ST=0.062). A general pattern of increasing differentiation along the coastline in an Atlantic-mediterranean direction emerged; but genetic differentiation among the Atlantic populations was not significantly lower than that observed among the Mediterranean populations. This and other results suggest that the effects of extensive transplantation of oysters among various areas in Europe are detectable only in some particular localities. The geographical distribution of low-frequency alleles suggests a restriction to gene flow outwards from the Mediterranean Sea, across the Straits of Gibraltar. 相似文献
15.
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
16.
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
17.
Multi-marker estimate of genetic connectivity of sole (Solea solea) in the North-East Atlantic Ocean
E. L. Cuveliers M. H. D. Larmuseau B. Hellemans S. L. N. A. Verherstraeten F. A. M. Volckaert G. E. Maes 《Marine Biology》2012,159(6):1239-1253
A thorough knowledge on the genetic connectivity of marine populations is important for fisheries management and conservation.
Using a dense population sampling design and two types of neutral molecular markers (10 nuclear microsatellite loci and a
mtDNA cytochrome b fragment), we inferred the genetic connectivity among the main known spawning grounds of sole (Solea solea L.) in the North-East Atlantic Ocean. The results revealed a clear genetic structure for sole in the North-East Atlantic
Ocean with at least three different populations, namely the Kattegat/Skagerrak region, the North Sea and the Bay of Biscay,
and with indications for a fourth population, namely the Irish/Celtic Sea. The lack of genetically meaningful differences
between biological populations within the southern North Sea is likely due to a large effective population size and sufficient
connection (gene flow) between populations. Nevertheless, an isolation-by-distance pattern was found based on microsatellite
genotyping, while no such pattern was observed with the cytochrome b marker, indicating an historical pattern prevailing in the latter marker. Our results demonstrate the importance of a combined
multi-marker approach to understand the connectivity among marine populations at region scales. 相似文献
18.
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
19.
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
20.
Genetic population structure of the blacktip shark, Carcharhinus limbatus, a commercially and recreationally important species in the southeast U.S. shark fishery, was investigated using mitochondrial DNA control region sequences. Neonate blacktip sharks were sampled from three nurseries, Pine Island Sound, Terra Ceia Bay, and Yankeetown, along the Gulf of Mexico coast of Florida (Gulf) and one nursery, Bulls Bay, on the Atlantic Ocean coast of South Carolina (Atlantic). Sequencing of the complete mitochondrial control region of 169 neonates revealed 10 polymorphic sites and 13 haplotypes. Overall haplotype diversity and percent nucleotide diversity were 0.710 and 0.106%, respectively. Haplotype frequencies were compared among nurseries to determine if the high mobility and seasonal migrations of adult blacktip sharks have maintained genetic homogeneity among nurseries in the Atlantic and Gulf. Chi-square analysis and AMOVA did not detect significant structuring of haplotypes among the three Gulf nurseries, P(2)=0.294, ST=–0.005 to –0.002. All pairwise AMOVA between Gulf nurseries and the Atlantic nursery detected significant partitioning of haplotypes between the Gulf and Atlantic (ST=0.087–0.129, P<0.008), as did comparison between grouped Florida Gulf nurseries and the Atlantic, CT=0.090, P<0.001. Based upon the dispersal abilities and seasonal migrations of blacktip sharks, these results support the presence of philopatry for nursery areas among female blacktip sharks. Our data also support the treatment of Atlantic and Gulf blacktip shark nursery areas as separate management units.Communicated by P.W.Sammarco, Chauvin 相似文献