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1.
F. Maltagliati A. P. Peru M. Casu F. Rossi C. Lardicci M. Curini-Galletti A. Castelli 《Marine Biology》2000,136(5):871-879
The genetic relationships between morphologically indistinguishable marine and brackish populations of Syllis gracilis Grube, 1840 (Polychaeta: Syllidae) were studied by means of allozyme electrophoresis. Samples of S. gracilis from marine coastal and brackish-water habitats were examined for variation at 13 presumptive loci. In addition, a sample
of the closely related species S. prolifera (Krohn, 1852) was analysed. Five loci were multiallelic in at least one population of S. gracilis and eight loci in S. prolifera. Low to moderate levels of within-population genetic variability were found, with average expected heterozygosity values
ranging from H = 0.068 (±0.043 SE) to 0.187 (±0.069 SE) in the populations of S. gracilis; higher values were found in S. prolifera (H = 0.325 ± 0.076). The presence of various private alleles indicated a marked genetic divergence among populations of S. gracilis, with Nei's genetic distances ranging from D = 0.000 to 0.833 and a highly significant F
ST value. Furthermore, evidence for strong genetic heterogeneity between two sympatric marine populations was found. UPGMA cluster
analysis and multidimensional scaling pointed out a clear genetic divergence between brackish and marine populations. At least
two genetically divergent entities occurred in marine and brackish habitats. This could be due to local adaptation of individuals
coming from marine populations to brackish habitats, but more presumably to the occurrence of a species complex within S. gracilis.
Received: 6 June 1999 / Accepted: 7 February 2000 相似文献
2.
Starch-gel electrophoresis of allozymes was used to differentiate the two red mullet species (Mullus barbatus L. and M. surmuletus L.) in the Mediterranean Sea and, further, to investigate the genetic stock structure of M. barbatus in the eastern Mediterranean area. Twenty putative enzyme-coding loci were examined in eight M. barbatus samples caught in the Aegean and Ionian Seas (Greece) and in the Gulf of Lion (France), and two M. surmuletus samples caught in the Aegean and Gulf of Lion. A high degree of genetic polymorphism was found in both species. Species-specific
electrophoretic patterns were found in PGI* and PGM*. Estimates of variance of allele frequencies among samples (F
ST) and 2 analyses both revealed significant differences (P < 0.05) among the M. barbatus samples. Most of the genetic variation was among samples regardless of region. The mean value of Nei's genetic distance between
the two species was 0.329. Genetic distance among M. barbatus samples was low (maximum Nei's D = 0.012), with the sample from Platania differing most from other M. barbatus samples. This is probably be due to founder effects existing at this area. These results suggest that allozyme analysis may
provide important information on the genetic structure of the red mullet to ensure sustainable management of this species.
Received: 7 May 1997 / Accepted: 13 October 1997 相似文献
3.
Allozyme variation in global populations of striped mullet, Mugil cephalus (Pisces: Mugilidae) 总被引:5,自引:0,他引:5
The striped mullet, Mugil cephalus Linnaeus, 1758, is one of the few species of marine shore fish with a worldwide circumtropical distribution. Because of this
distribution and the dependency of M. cephalus on coastal waters during various phases of its life cycle, as well as nearshore living habits, questions have been raised
regarding levels of genetic divergence and gene flow among transoceanic populations. To cast more light on this, allozyme
variation at 27 presumptive gene loci was investigated in ten globally diverse populations. The observed heterozygosity ranged
from 0.018 (Hawaii) to 0.081 (Florida), averaging 0.050. The proportion of polymorphic loci showed a similar trend. Several
populations were characterised by fixed allelic differences. Estimated gene diversities were very high, the allele frequency
variation among populations was found to be 68%; genetic distances reached 0.242, with an average of 0.117. Estimated rates
of gene flow were high among Mediterranean populations (Nm = 7.26), and between Mediterranean and East Atlantic populations (Nm= 2.86), but extremely low between non-contiguous populations within the Indian, Pacific and Atlantic Oceans, where Nm ranged from 0.03 to 0.05.
Received: 7 April 1997 / Accepted: 4 February 1998 相似文献
4.
Genetic variation in 15 Holothuria (Microthele) nobilis (Selenka, 1867) populations on the Great Barrier Reef was studied at seven polymorphic allozyme loci. Although populations
were separated by distances up to 1300 km, there were no apparent restrictions to gene flow (F
ST
values were not significantly different from 0) and the maximum Nei's unbiased genetic distance was 0.003. Populations were
in Hardy–Weinberg equilibrium at all loci. The estimated maximum sexual input [this is the ratio of the number of sexually
produced individuals (N*) to the sample size (N
i
)] and the minimum sexual input [this is the ratio of the number of genotypes (N
go
) over the sample size (N
i
)] were used as estimators for the amount of asexual reproduction. Both parameters suggested that H. nobilis reproduces solely by sexual means (N*:N
i
: = 1; N
go
:N
i
= 0.74 to 1). The allozyme data indicated high gene flow between populations, but the possibility that allozyme frequencies
may not be at equilibrium means that it was not possible to distinguish whether the patterns reflect present-day dispersal
or dispersal that occurred in the past.
Received: 27 March 2000 / Accepted: 29 June 2000 相似文献
5.
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
6.
E. García-Machado A. Robainas G. Espinosa M. Oliva J. Páez N. Verdecia M. Monnerot 《Marine Biology》2001,138(4):701-707
We investigated the genetic diversity among populations of the shrimp Farfantepenaeus notialis, the most abundant penaeid species around Cuba. A total of 25 allozyme loci were analyzed in samples of shrimps from seven
localities at the south central platform of the island (Ana María Gulf). Samples from three of these localities and from Batabanó
Gulf and Guacanayabo Gulf at the south west and south east platforms of the island, respectively, were also characterized
at the mtDNA level through sequence variation of a 2027 bp segment including part of the COI and COIII genes. Of the 25 allozyme
loci studied 9 were polymorphic: Akp2, Akp3, AmyB, Est3, Gdh, GP7, and Per1, 2 and 3. In contrast to mtDNA, the pattern of allozyme variation among localities revealed strong population structuring
at Ana María Gulf, with significant F
st in all pairwise comparisons. The magnitude of F
st estimates as well as the grouping pattern obtained by a UPGMA analysis based on a distance matrix indicated that the level
of differentiation was concordant with the geographical position of the localities and the hydrographic regime. Homogeneity
of mtDNA suggested that differentiation of allozyme loci might be due to more recent events rather than historical isolation
of the sampled populations. Ana María and Guacanayabo Gulf populations were differentiated by mtDNA from Batabanó Gulf, at
the southwestern end of the island. The analysis showed three restriction site differences among them, suggesting genetic
isolation of the two regions. The present results also suggest that an artificial introduction of larvae from Tunas de Zaza
into Batabanó Gulf, in an effort to repopulate this fishing region, may have been ineffective.
Received: 13 December 1999 / Accepted: 2 October 2000 相似文献
7.
Genetic divergence and phylogenetic inferences in five species of Mugilidae (Pisces: Perciformes) 总被引:4,自引:0,他引:4
Allozyme electrophoresis was used to compare the genetic divergence of global populations of Mugil cephalus Linnaeus, 1758 and two congeneric [M.␣curema Cuvier & Valenciennes, 1836; M. gyrans (Jordan & Gilbert, 1885)] and two more distantly related [Liza ramada (Risso, 1826); Xenomugil thoburni (Jordan & Starks, 1896)] species on the basis of 18 enzyme loci. The amount of genetic divergence among the species examined
is in agreement with their present systematic status, the differences being larger among non-congeneric species than among
species of the same genus. Intraspecific genetic distances in M. cephalus (average Nei's D= 0.154), although higher than those reported for conspecific populations of fish, appear to be small when compared to the
interspecific values among mugilid species (0.821 ≤ Nei's D ≤ 1.744). Phylogenetic trees obtained by genetic distance methods and discrete character parsimony analysis were of similar
topology, except for the relationships within the genus Mugil and for the arrangement of M. cephalus populations.
Received: 7 April 1997 / Accepted: 4 February 1998 相似文献
8.
Genetic divergence among ten populations of small- and large-egg forms of the brackish-water polychaete Hediste japonica complex was investigated on 14 isozyme loci by electrophoretic analysis. The two forms were distinguishable by complete allele
substitutions at five loci, resulting in high genetic differentiation (Nei's D: 0.533 to 0.662). No genetic evidence of hybridization between the two forms was detected in sympatric populations in three
rivers. These results indicate that the two forms are reproductively isolated, clearly showing that the two forms are distinct
species. The genetic differentiation among populations was higher in the large-egg form (D: 0.005 to 0.111, G
ST: 0.435) than that in the small-egg form (D: 0.000 to 0.001, G
ST: 0.020). This genetic difference between the two forms seems to be attributable to a difference in their life histories.
The average expected heterozygosity was low in populations of both the large-egg form (0.005 to 0.068) and the small-egg form
(0.014 to 0.038) in comparison with other marine invertebrates.
Received: 11 April 1997 / Accepted: 8 September 1997 相似文献
9.
Genetic differentiation between North Sea and Baltic Sea Hediste diversicolor (O.F. Müller, 1776) (Polychaeta: Nereididae) populations was studied by allozyme electrophoresis on starch gel. Thirteen
loci were analyzed in eight populations. The level of genetic variation was very low (mean H
o = 0.000 to 0.015). Differentiation between H. diversicolor populations is quite high (F
ST = 0.892) and reflected by three enzyme loci (MDH-I*, MDH-II*, IDH-I*). The reduced gene flow (N
m<1) may be explained by the limited dispersal capacity of the species. Regardless of whether found in the North Sea or Baltic
Sea, there appear to be two different genetic types which are parapatric or sympatric in some places. The two types hybridize
at three localities, but no signs of hybridization have been found at one (Tallinn).
Received: 26 June 1997 / Accepted: 10 September 1997 相似文献
10.
Allozyme variation was used to investigate the genetic structure of the coral reef fishes Stegastes nigricans, Epinephelus merra and Acanthurus triostegus around New Caledonia. Each species was sampled from each of three sites in the ≃1000 km circumference of the lagoon of New
Caledonia. Allelic variation was recorded for each species at 14, 13 and 17 loci, respectively, and heterozygosity diversity
(H
s) was 0.082, 0.065 and 0.116, respectively. Analysis of genetic differentiation between sites produced inconsistent results
between species, with spatial heterogeneity in two species (S. nigricans, F
st
= 0.038; A. triostegus, F
st = 0.049) and homogeneity in one species (E. merra, F
st = 0.000). Hydrological and climatic data from the lagoon suggest that the eastern and western sides of the lagoon are isolated,
since they lie in water masses of different origin. This may explain the genetic differentiation and restricted gene flow
found at a local scale for S. nigricans and A. triostegus. Homogeneity in populations of E. merra is discussed in relation to its low genetic diversity and its reproductive behaviour.
Received: 23 April 1997 / Accepted: 25 September 1997 相似文献
11.
An allozyme survey, using starch-gel electrophoresis, was carried out on eight populations of the Antarctic nemertean worm
Parborlasia corrugatus (McIntosh, 1876) collected from locations around the South Orkney Islands, Antarctica. These populations were separated by
distances in the order of tens of kilometres. Genetic variation was estimated over 22 enzyme loci for all populations examined,
giving an observed heterozygosity of 0.142. This was much lower than the expected heterozygosity (H
e
= 0.201), and it was found that there was a significant deficiency of het‐erozygotes across four enzyme loci ( p ≤ 0.01). A more detailed examination of this deficiency of heterozygotes was undertaken for the six populations and six variable
enzyme loci for which the most complete data sets existed. A significant deficiency of heterozygotes was found at the enzyme
locus Odh-1 for four of the six populations examined ( p ≤ 0.01). Mean F
is
(0.240) indicated a significant ( p ≤ 0.01) within-population component of the heterozygote deficiency estimated for the six populations sampled, and this was
mainly due to the␣Ap-1, Odh-1 and Pgm-1 loci. The mean F
st
value (0.036) was also significant ( p ≤ 0.01), indicating a degree of genetic differentiation between populations. The observed levels of genetic differentiation
between populations of P. corrugatus and the significant heterozygote deficiencies were unexpected, because this species has been reported to have a long-lived
planktotrophic larva. It is hypothesised that recruitment of P. corrugatus in the South Orkney Islands originates from genetically distinct populations located in the Weddell Sea and to the west of
the Antarctic Peninsula. Shifts in the relative position of the Weddell Sea Front, Weddell–Scotia Confluence and Scotia Front,
relative to the South Orkney Islands, provide a mechanism for variation in the origin of recruits over time.
Received: 24 July 1997 / Accepted: 31 October 1997 相似文献
12.
Genetic structure of the flounders Platichthys flesus and P. stellatus at different geographic scales 总被引:1,自引:0,他引:1
The genetic structure of the flounders Platichthys flesus L. and P. stellatus Pallas was investigated on different spatial scales through analysis of allozyme variation at 7 to 24 polymorphic loci in
samples collected from different regions (Baltic Sea, North Sea, Brittany, Portugal, western Mediterranean, Adriatic Sea,
Aegean Sea and Japan) in 1984 to 1987. No geographic variation was evident within a region. Some pattern of differentiation
by distance was inferred within the Atlantic, while the Mediterranean comprised three geographically isolated populations
and was itself geographically isolated from the Atlantic (fixed allele differences at up to three loci were found among P. flesus populations from the Atlantic, the western Mediterranean, the Adriatic Sea, the Aegean Sea and also P. stellatus from the coast of Japan). Sea temperature during the reproductive period probably acts as a barrier to gene flow between
populations. Genetic distances among European flounder populations (P. flesus) were higher than, or of the same magnitude as, the genetic distance between Pacific (P. stellatus) and European flounder populations, suggesting that P. flesus is paraphyletic and/or there is no phylogenetic basis to recognising P. stellatus as a different species. The divergence between P. flesus and P. stellatus was thus inferred to be more recent than the divergence between the present P. flesus populations from the NE Atlantic and eastern Mediterranean. The eastern Mediterranean populations are thought to originate
from the colonisation of the Mediterranean by a proto-P. flesus/P. stellatus ancestor, whereas the present western Mediterranean population has undergone a more recent colonisation event by P. flesus. Patterns of mitochondrial DNA variation, established on a smaller array of P. flesus samples, were in accordance with the geographic patterns inferred from the allozyme survey. In addition, they supported the
hypothesis of a two-step colonisation of the western Mediterranean. These results contribute to our understanding of the biogeography
of the Mediterranean marine fauna, especially the group of boreal remnants to which P. flesus belongs.
Received: 7 February 1997 / Accepted: 26 March 1997 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.
Two populations of Marenzelleria spp. from the North Sea and the Baltic Sea that had already been characterized by allozyme electrophoresis and found genetically
different in 1994 were again examined in 1997. The genetic identity (I = 1.0) examined in 1994 and 1997 shows that the structures of the populations of genetic Type I in the North Sea (Ringkobing
Fjord) and genetic Type II in the Baltic Sea (Darss–Zingst Bodden chain) are stable. Three diagnostic gene loci that were
determined additionally (citrate synthase, one locus; alanine aminotransferase, two loci) support the hypothesis of the existence
of two sibling species of the genus Marenzelleria in Europe. In addition, the activities of ten electrophoretically separated enzyme systems were measured in the worms immediately
after removal from their habitat and after they had been kept in the laboratory for 2 months. Under both conditions four enzymes
showed significant differences between genetic types. The higher activity of the alanine aminotransferase of the North Sea
worms (Type I) is discussed in the context of the different preferred salinities of the two Marenzelleria sibling species.
Received: 21 January 1999 / Accepted: 13 July 1999 相似文献
15.
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
16.
Spatial and temporal population genetic structures of the common sole, Solea solea, were studied in Northeastern Atlantic and Mediterranean Sea populations, using three polymorphic exon-primed intron-crossing
(EPIC) markers. Results demonstrated significant multilocus differentiation among Eastern Mediterranean and a group composed
by Western Mediterranean and Atlantic populations (θ = 0.150, P < 0.001), but also suggested unrecorded genetic differentiation of the Adriatic Sea population. No pattern of isolation-by-distance
was recorded across the range covered by sampling, from the Kattegat to the Aegean Sea. Conversely to genetically structured
Mediterranean populations, Atlantic populations ranging from Denmark to Portugal could be considered as representative of
the same panmictic unit (θ = 0.009, not significant). Results further demonstrated stability of multilocus genetic structure among temporarily replicated
cohort samples [0+, 1+, subadults] from several coastal and estuarine locations from Bay of Biscay, excepted for the amylase
locus Am2B3-2 at one location (Pertuis d’Antioche). Despite coherence of such observed patterns of multilocus differentiation with previous
allozymic surveys in sole, and with patterns generally obtained for other marine fish species, single-locus results from EPICs
indicated divergent coalescence schemes supporting a complex response to ecology and history of sole’s populations. Results
stress the use of nuclear genes such as EPIC markers to investigate population structure, but also historical, demographic,
and possibly selective processes in marine fishes. 相似文献
17.
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
18.
Variation in the genetic composition of coral (Pocillopora damicornis and Acropora palifera) populations from different reef habitats 总被引:6,自引:0,他引:6
The genetic structure of populations of the corals Pocillopora damicornis and Acropora palifera was examined in three habitats at One Tree Island during March and April 1993, using electrophoretically detectable variation at six allozyme loci. There were significant genetic differences among populations of P. damicornis within each of the reef crest, lagoon and microatoll habitats. The level of differentiation among populations was similar in each of the habitats. Differences between populations of P. damicornis from lagoon and microatolls were no greater than that within habitats, but genetic differentiation of these from crest populations was much higher. There was no difference in the genetic composition of A. palifera populations within or between the lagoon and microatolls, the only habitats where this species was found. Both coral species had observed:expected (G
O:GE) genotypic diversity rations >0.80, indicating predominantly sexual reproduction. These data, the high genotype diversity and general conformance of genotype frequencies to those expected under conditions of Hardy-Weinberg, suggested panmixis at each site. The high degree of sexual reproduction in the P. damicornis populations is unusual for a species where asexual reproduction has been the dominant mode of reproduction reported to date. Gene flow in both species was considerable between the lagoon and the closed microatolls. The genetic differences between populations of P. damicornis in these habitats and the reef crest may reflect the relative isolation of all populations within the closed One Tree Lagoon from those outside. However, local currents appear to offer effective means of dispersal between the habitats, suggesting that the genetic differences result from natural selection in the different environments within One Tree Lagoon and the reef crest. 相似文献
19.
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
20.
Microgeographic genetic differentiation in a colonial ascidian (Botryllus schlosseri) population 总被引:3,自引:0,他引:3
Limited gene flow via the restricted dispersal of larvae and gametes is expected to result in the genetic differentiation
of populations of clonal invertebrates on small spatial scales. However, occasional dispersal events over greater distances
may generate sufficient gene flow to maintain genetic homogeneity. We applied a spatial autocorrelation approach that does
not require a priori definitions of subdivision boundaries to examine genetic differentiation within a continuous population
of the colonial ascidian Botryllus schlosseri (Pallas) at two allozyme and five polychromatism loci. Colonies were sampled in July 1992, on a 12 by 18 m grid superimposed
on a shallow subtidal (1 to 3 m) population in the Damariscotta River estuary in Maine, USA. Low but significant levels of
positive autocorrelation were detected over very small spatial scales (<5 m), with negative autocorrelation occurring on larger
scales (>8 m). This pattern indicates significant genetic differentiation over distances of 8 to 21 m, and is consistent with
genetic drift and inbreeding creating small scale genetic structure.
Received: 18 October 1999 / Accepted: 11 July 2000 相似文献