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1.
Monica Gagliano Mark I. McCormick James A. Moore Martial Depczynski 《Marine Biology》2010,157(8):1849-1856
Ocean acidification is one of the key threats facing coral reef ecosystems, but there are few estimates of spatial and temporal
variability in pH among reef habitats. The present study documents levels of spatial variability in pH among coral reef habitats
(9 to 10), among locations separated by 100’s km of latitude and between east (Great Barrier Reef, GBR) and west (Ningaloo
Reef) coasts of Australia. Differences were found in pH between inshore and offshore waters along Ningaloo Reef (means 8.45,
8.53, respectively). Replicate assessments here ranged from 8.22 to 8.64. On the GBR, the range of values over all habitats
and replicates was 0.39 pH units (7.98 to 8.37). There were minor but significant differences of 0.05 pH units between 5 consecutive
days for habitats on average. Highest pH was recorded in filamentous algal beds maintained by the damselfish Dischistodus perspicillatus. Lowest pH was found in water extracted from sand-dwelling goby holes. While there were marked changes in pH over a 48-h
sampling period among 4 habitats at Lizard Island (GBR), there was little evidence of a diel trend. Understanding how pH varies
at scales that are relevant to organisms that live on shallow coral reefs is crucial for the design and interpretation of
experiments that test the effects on organisms of the changes in water chemistry predicted to affect oceans in the future. 相似文献
2.
Dianne L. Watson Euan S. Harvey Ben M. Fitzpatrick Timothy J. Langlois George Shedrawi 《Marine Biology》2010,157(6):1237-1250
Measures of fish abundance, assemblage composition and length were compared when sampled by baited remote underwater stereo-video
(stereo BRUV) and diver-operated stereo-video transects (stereo DOV) at the Houtman Abrolhos Islands and Ningaloo Reef. Species
richness counts were 40% higher on stereo BRUV than stereo DOV. Stereo BRUVs also recorded a greater number of large-bodied
targeted species in higher abundance than stereo DOV (e.g. Lethrinus nebulosus, Plectropomus leopardus) at the Houtman Abrolhos and at Ningaloo Reef. Many non-targeted species were also recorded in greater abundances on stereo
BRUV than stereo DOV (e.g. Coris auricularis, Gymnothorax spp). Stereo DOV transects recorded a greater abundance of some small-bodied Pomacentridae, Labridae and Scaridae species
than did stereo BRUV, particularly at Ningaloo Reef. This study demonstrates that choice of sampling technique for surveys
of reef fish can lead to very different biological interpretations of fish assemblage structure. 相似文献
3.
Xiang Li Yingying Liu Athanasia C. Tzika Qian Zhu Karine Van Doninck Michel C. Milinkovitch 《Marine Biology》2011,158(8):1791-1804
The existence of three distinct populations is widely accepted for the finless porpoise (Neophocaena phocaenoides) in Chinese waters: the Yellow Sea, Yangtze River, and South China Sea populations. Here, we use nine species-specific microsatellite
loci, the complete mitochondrial DNA control region (912 bp), and the complete mitochondrial cytochrome b gene (1,140 bp)
to further investigate potential population stratification in the Yellow Sea using 147 finless porpoise samples from the Bohai
Sea and adjacent northern Yellow Sea, two regions that were largely underrepresented in previous genetic studies. Our F-statistics analyses confirm the previously described three populations, but further demonstrate significant genetic differentiation
between the [Bohai + northern Yellow] Sea and the southern Yellow Sea. On the other hand, median-joining network analyses
do not exhibit well-differentiated haplotype groups among different geographic populations, suggesting the existence of shared
ancestral haplotypes. Levels of microsatellite diversity are moderate to high (mean H
E = 0.794) among the 147 [Bohai + northern Yellow] Sea finless porpoises and no recent bottleneck was detected, whereas mtDNA
control region and cytochrome b gene diversity is low to moderate. The microsatellite genotypic and mtDNA haplotypic data
also confirm the presence of mother-calf pairs in single-net bycatch cases. The results presented here highlight the necessity
to treat the [Bohai + northern Yellow] Sea population (highly impacted by anthropogenic threats) as a separate Management
Unit. 相似文献
4.
No genetic differentiation of giant clam (Tridacna gigas) populations in the Great Barrier Reef,Australia 总被引:2,自引:0,他引:2
Six Tridacna gigas populations were sampled in 1990 from locations throughout the central and northern Great Barrier Reef (GBR). Despite separations in excess of 1000 km, mean Nei's unbiased genetic distances among the populations was 0.0007. The complete lack of spatial variation observed among populations did not results from lack of genetic variability. Genetic variation within populations was high, with mean heterozygosities from 0.221 to 0.250. Gene frequencies were consistent with expectations under conditions of Hardy-Weinberg equilibrium. These data suggest panmixis, or random mating, throughout the highly connected reef system of the central and northern GBR. The large gene exchange among the giant clam populations has important implications for conservation management of one of the few large populations of T. gigas in the world. Small local effects are likely to be overcome in time by inputs from other sources. However, large genetic perturbations, particularly from up-current sources, may spread rapidly through the population.Contribution No. 561 from the Australian Institute of Marine Science 相似文献
5.
Symbiont specificity and bleaching susceptibility among soft corals in the 1998 Great Barrier Reef mass coral bleaching event 总被引:1,自引:0,他引:1
Considerable variability in bleaching was observed within and among soft coral taxa in the order Alcyonacea (Octocorallia:
Cnidaria) on the central Great Barrier Reef (GBR, latitude 18.2°–19.0°S, longitude 146.4°–147.3°E) during the 1998 mass coral
bleaching event. In April 1998, during a period of high sea surface temperatures, tissue samples were taken from bleached
and unbleached colonies representative of 17 soft coral genera. The genetic identities of intracellular dinoflagellates (Symbiodinium spp.) in these samples were analyzed using PCR-denaturing gradient gel electrophoresis fingerprinting analysis of the internal
transcribed spacer regions 1 and 2. Alcyonaceans from the GBR exhibited a high level of symbiont specificity for Symbiodinium types mostly in clade C. A rare clade D type (D3) was associated only with Clavularia koellikeri, while Nephthea sp. hosted symbionts in clade B (B1n and B36). Homogenous Symbiodinium clade populations were detected in all but one colony. Colonies that appeared bleached possessed symbiont types that were
genetically indistinguishable from those in nonbleached conspecifics. These data suggest that parameters other than the resident
endosymbionts such as host identity and colony acclimatization are important in determining bleaching susceptibility among
soft corals.
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 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
7.
Lane snappers (Lutjanus synagris), sampled from eight localities in the northern Gulf of Mexico (Gulf) and one locality along the Atlantic coast of Florida,
were assayed for allelic variation at 14 nuclear-encoded microsatellites and for sequence variation in a 590 base-pair fragment
of the mitochondrially encoded ND-4 gene (mtDNA). Significant heterogeneity among the nine localities in both microsatellite
allele and genotype distributions and mtDNA haplotype distributions was indicated by exact tests and by analysis of molecular
variance (AMOVA). Exact tests between pairs of localities and spatial analysis of molecular variance (SAMOVA) for both microsatellites
and mtDNA revealed two genetically distinct groups: a Western Group that included six localities from the northwestern and
northcentral Gulf and an Eastern Group that included three localities, one from the west coast of Florida, one from the Florida
Keys, and one from the east (Atlantic) coast of Florida. The between-groups component of molecular variance was significant
for both microsatellites (Φ
CT = 0.016, P = 0.009) and mtDNA (Φ
CT = 0.208, P = 0.010). Exact tests between pairs of localities within each group and spatial autocorrelation analysis did not reveal genetic
heterogeneity or an isolation-by-distance effect among localities within either group. MtDNA haplotype diversity was significantly
less (P < 0.0001) in the Western Group than in the Eastern Group; microsatellite allelic richness and gene diversity also were significantly
less in the Western Group (P = 0.015 and 0.013, respectively). The difference in genetic variability between the two groups may reflect reduced effective
population size in the Western Group and/or asymmetric rates of genetic migration. The relative difference in variability
between the two groups was substantially greater in mtDNA and may reflect one or more mtDNA selective sweeps; tests of neutrality
of the mtDNA data were consistent with this possibility. Bayesian analysis of genetic demography indicated that both groups
have experienced a historical decline in effective population size, with the decline being greater in the Western Group. Maximum-likelihood
analysis of microsatellite data indicated significant asymmetry in average, long-term migration rates between the two groups,
with roughly twofold greater migration from the Western Group to the Eastern Group. The difference in mtDNA variability and
the order-of-magnitude difference in genetic divergence between mtDNA and microsatellites may reflect different demographic
events affecting mtDNA disproportionately and/or a sexual and/or spatial bias in gene flow and dispersal. The spatial discontinuity
among lane snappers in the region corresponds to a known zone of vicariance in other marine species. The evidence of two genetically
distinct groupings (stocks) has implications for management of lane snapper resources in the northern Gulf. 相似文献
8.
Although New Caledonia is surrounded by one of the 3 largest coral reef systems of the world, the published generic records indicate abnormally low coral diversity. Exploration of the reefs in the south-eastern part of the island, largely by means of SCUBA, has yielded specimens which increase the known genera and sub-genera by 50%. New Caledonia now ranks sixth among the coral provinces of the world, with at least 53 genera and sub-genera of reef-building corals. Many of the new records were made in a type of coral environment unlike any previously described. Comparison of the New Caledonia fauna with those of Fiji, the Grett Barrier Reef of Australia, and the Ryukyu Islands reaffirms the remarkable homogeneity of the Indo-Pacific coral faunas. 相似文献
9.
Philip L. Munday Morgan S. Pratchett Danielle L. Dixson Jennifer M. Donelson Geoff G. K. Endo Adam D. Reynolds Richard Knuckey 《Marine Biology》2013,160(8):2137-2144
We tested the effect of near-future CO2 levels (≈490, 570, 700, and 960 μatm CO2) on the olfactory responses and activity levels of juvenile coral trout, Plectropomus leopardus, a piscivorous reef fish that is also one of the most important fisheries species on the Great Barrier Reef, Australia. Juvenile coral trout reared for 4 weeks at 570 μatm CO2 exhibited similar sensory responses and behaviors to juveniles reared at 490 μatm CO2 (control). In contrast, juveniles reared at 700 and 960 μatm CO2 exhibited dramatically altered sensory function and behaviors. At these higher CO2 concentrations, juveniles became attracted to the odor of potential predators, as has been observed in other reef fishes. They were more active, spent less time in shelter, ventured further from shelter, and were bolder than fish reared at 490 or 570 μatm CO2. These results demonstrate that behavioral impairment of coral trout is unlikely if pCO2 remains below 600 μatm; however, at higher levels, there are significant impacts on juvenile performance that are likely to affect survival and energy budgets, with consequences for predator–prey interactions and commercial fisheries. 相似文献
10.
Coral spawning in Western Australia (WA) occurs predominantly in the austral autumn in contrast to the Great Barrier Reef
(GBR) on Australia’s east coast where most spawning occurs in spring. Recent work, however, suggests a second spawning period
in northern WA with at least 16 Acropora spp spawning in spring or early summer. This discovery has initiated a re-examination of reproductive seasonality in northern
WA, particularly on inshore reefs adjacent to large development projects, such as the site of this study in Mermaid Sound,
in the Dampier Archipelago. Three locally abundant taxa, Porites spp, Pavona decussata and Turbinaria mesenterina were sampled monthly from September 2006 to May 2007 to determine sexuality, the mode of reproduction and the time of gamete
maturity. All three taxa were gonochoric broadcast spawners. Porites spp. colonies were mature in November and December, P. decussata in March and April. In contrast, most colonies of T. mesenterina contained mature gametes for up to 5 months beginning in November, suggesting either individuals are releasing gametes on
multiple occasions, or they retain mature gametes for more than 1 month. Field surveys to determine the reproductive status
of the remaining coral assemblage were conducted prior to the full moon in October 2006 and March 2007. Only four species
contained mature gametes in October 2006. In contrast, 55 species contained mature gametes in March 2007. We conclude that
the major spawning season of corals on shallow-inshore reefs in the Dampier Archipelago is autumn, although taxa that spawn
in spring and summer include Porites spp., Acropora spp. and possibly T. mesenterina that are numerically dominant at many of these sites. Consequently, management initiatives to limit the exposure of coral
spawn to stressors associated with coastal development may be required in up to five months per year. 相似文献
11.
James Davis Reimer Mamiko Hirose Yuka Irei Masami Obuchi Frederic Sinniger 《Marine Biology》2011,158(5):983-993
12.
Trochus niloticus L. and Tectus coerulescens Lmk., two coral reef trochid gastropods that have similar life-histories including a lecithotrophic larval stage, were sampled from reefs in the northern, central and southern sections of the Great Barrier Reef (GBR) in 1991. Significant sex-ratio biases were noted, and these varied among reefs, apparently with latitude. Demographic data suggested that highly discontinuous and localized recruitment occurs. Surveys of allozyme frequencies at 12 loci revealed no significant genetic differences among populations of Trochus niloticus at any geographical scale. High gene flow between zones of the GBR was inferred, with the number of migrants per generation (N
m
) of the order of 100. Directional selection was thought to occur at one locus (GDH
*). Genetic variability in T. niloticus (H=0.069 to 0.110, and only three loci polymorphic) was low compared with other trochids. This was thought to be due to smaller effective population size, resulting from an unbalanced sexratio, aggregative spatial distribution of adults, high variance in reproductive success, and/or the occurrence of population extinctions and recolonisations. In contrast, Tectus coerulescens exhibited significant genetic differences between zones, indicating a much lower rate of migration between populations (N
m
1 to 10), and displayed high genetic diversity (H=0.225 to 0.279). A trend for increasing genetic diversity from the northern to southern GBR was found in both species. It is not clear whether the occurrence of two contrasted population genetic structures in species with apparently similar life-histories is due to ecological or historical factors. 相似文献
13.
Late larvae of the serranid coral trout Plectropomus leopardus (Lacepède), captured in light traps, were released during the day both in open water and adjacent to two reefs, and their
behaviour was observed by divers at Lizard Island, northern Great Barrier Reef. Coral trout larvae (n = 110) were present in light-trap catches from 18 November to 3 December 1997, including new moon (30 November). The swimming
speed of larvae in open water or when swimming away from reefs was significantly greater (mean 17.9 cm s−1) than the speed of larvae swimming towards or over reefs (mean 7.2 cm s−1). Near reefs, larvae swam at average depths of 2.7 to 4.2 m, avoiding 0 to 2 m. In open water, swimming depth varied with
location: larvae >1 km east of Lizard Island swam steeply downward to >20 m in 2 to 4 min; larvae >1 km west oscillated between
2.6 and 13 m; larvae 100 to 200 m east of Lizard Island oscillated between 0.8 and 15 m. Nearly all larvae swam directionally
in open water and near reefs. In open water, the average swimming direction of all larvae was towards the island, and 80%
(4 of 5) swam directionally (p < 0.05, Rayleigh's test). Larvae swam directionally over the reef while looking for settlement sites. The frequency of behaviours
by larvae differed between two reefs of different exposure and morphology. Depending on site, 26 to 32% of larvae released
adjacent to reefs swam to open water: of these, some initially swam towards or over the reef before swimming offshore. In
some cases, offshore-swimming seemed to be due to the presence of predators, but usually no obvious cause was observed. Depending
on the reef, 49 to 64% of the larvae settled. Non-predatory reef residents aggressively approached 19% of settlers. Between
5 and 17% of the larvae were eaten while approaching the reef or attempting to settle, primarily by lizardfishes but also
by wrasses, groupers and snappers. A higher percentage of larvae settled in the second week of our study than in the first.
Average time to settlement was short (138 s ± 33 SE), but some larvae took up to 15 min to settle. Average settlement depth
was 7.5 to 9.9 m, and differed between locations. No settlement took place on reef flats or at depths <4.2 m. Larvae did not
appear to be selective about settlement substrate, but settled most frequently on live and dead hard coral. Late-stage larvae
of coral trout are capable swimmers with considerable control over speed, depth and direction. Habitat selection, avoidance
of predators and settlement seem to rely on vision.
Received: 7 July 1998 / Accepted: 26 January 1999 相似文献
14.
No apparent genetic basis to demographic differences in scarid fishes across continental shelf of the Great Barrier Reef 总被引:5,自引:2,他引:3
Two species of parrot fish, Scarus frenatus and Chlorurus sordidus, are known to exhibit demographic and life-history differences across the continental shelf of the northern Great Barrier
Reef (GBR). DNA sequences from the mitochondrial (mt) control region were analysed to determine whether there were genetic
differences between the populations from the mid- and outer-shelf reefs. Analysis of molecular variance (AMOVA) indicated
high levels of gene exchange for both species at a local scale between reefs on mid- and outer continental shelf positions
(20 km apart) and at a broader scale along the length of the GBR province (>1000 km apart). There was no evidence to suggest
that local differences in scarid life-history characteristics on the northern GBR have a genetic basis. Rather it appears
more likely that phenotypically plastic responses to prevailing social and environmental conditions explain differences in
the life-history characteristics of both taxa. However, analysis of genetic variation and historical demography revealed striking
differences between the two species. S. frenatus haplotypes differed from one another at relatively few nucleotide sites (mean = 3.30), and the pairwise mismatch distribution
suggested this species has undergone a population expansion within the limit of the resolution of the marker. C. sordidus haplotypes, however, differed from one another at a number of sites (mean = 7.67). Mismatch distribution analysis suggested
that the population size of this species has remained at equilibrium over time. These patterns could also reflect differences
in the metapopulation sizes or generation times between taxa. Some of the implications for fisheries management are discussed.
Received: 28 January 2000 / Accepted: 9 July 2000 相似文献
15.
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
16.
Population structure of the giant tiger prawn Penaeus monodon in Australian waters, determined using microsatellite markers 总被引:3,自引:0,他引:3
We describe three highly polymorphic microsatellite loci which have been isolated from the giant tiger prawn Penaeus monodon. The number of alleles present among 312 samples at the loci Pmo9, Pmo25 and Pmo27 were 84, 34 and 35, respectively, with
heterozygosities all >90%. Analyses of the distribution of length variation at three microsatellite loci among five Australian
P. monodon populations revealed strong differentiation between populations from the west and those from the northern and eastern coasts.
Tests for population differentiation (F
st) values and an analogous measure for microsatellite loci (R
st) all demonstrated that Western Australian P. monodon are a separate genetic stock which exhibits reduced genetic variation relative to the other populations. Reduced variability
is consistent with a recent population bottleneck or colonization by a small founding population from the east when sea links
between Indonesia, New Guinea and Australia were re-established following the last ice age. The results of this study are
in agreement with previous surveys of P. monodon conducted with allozymes and mtDNA.
Received: 18 December 1998 / Accepted: 27 August 1999 相似文献
17.
Latitudinal variation in abundance of herbivorous fishes: a comparison of temperate and tropical reefs 总被引:1,自引:0,他引:1
The aim of the study was to provide comparable estimates of abundance of herbivorous reef fishes at temperate and tropical
localities using a standardized methodology. Faunas of herbivorous fish were sampled on the rocky reefs of temperate northern
New Zealand and on the coral reefs of the northern Great Barrier Reef (GBR), Australia, and the San Blas Archipelago in the
Caribbean. A pilot study established the most appropriate habitat setting and the scale and magnitude of replication for the
sampling program in temperate waters. Herbivorous fishes, including members of families endemic to the southern hemisphere
(Odacidae and Aplodactylidae), were most abundant in turbulent, shallow water (0 to 6 m) and had patchy distributions within
this habitat. A hierarchical sampling program using 10-min transect counts within the 0 to 6 m depth stratum examined abundance
patterns at a range of spatial scales including mainland and island coasts, localities separated by up to 100 km and sites
separated by up to 10 km. This program identified a characteristic fauna of seven species of herbivorous fishes with mean
total abundances ranging from 23 to 30 individuals per 10-min transect. Species composition of the fauna varied between islands
and coasts. A similar methodology was used to sample the major families of herbivorous fish in a number of sites in each of
the tropical regions. These sampling programs revealed a fauna dominated by acanthurids and scarids in both the GBR and Caribbean
localities. Estimates of abundance from these regions were similar, with a mean of 108 individuals recorded on the GBR and
129 per 10-min transect in the Caribbean. Species richness varied between each region, with 44 taxa recorded from the GBR
and 11 from the Caribbean. Abundances of temperate water herbivores in New Zealand were found to be 75 to 80% lower than those
recorded from shallow water habitats sampled on coral reefs. This was not related to species richness, since both New Zealand
and the Caribbean locality had patterns of low richness. We suggest that the differences in abundance found by our study between
temperate and tropical regions are not restricted to herbivorous fishes, but are representative of general latitudinal trends
in reef fish faunas.
Received: 4 November 1996 / Accepted: 15 December 1996 相似文献
18.
Coelomactra antiquata is a commercially important bivalve species, but has been suffering from severe population decline due to over-exploitation
and the deterioration of environmental conditions. Previous genetic survey of C. antiquata conducted with allozymes combined with morphology revealed high levels of genetic differentiation between northern and southern
populations which suggests a cryptic species might exist in C. antiquata. To test this hypothesis, amplified fragment length polymorphisms (AFLPs) and 16S rRNA gene sequence were used to re-evaluate
the spatial genetic structure of six populations of C. antiquata along the coast of China. Both genetic markers display a sharp genetic break between the four northern populations (northern
lineage) and two southern population (southern lineage). Large numbers of private alleles (AFLP) were found within the northern
or southern populations and a deep divergence of about 6.5% in 16S rRNA gene sequence between the northern and southern lineages
suggests the occurrence of potential cryptic or sibling species of C. antiquata. Applying previously published rates of mutation, divergence between the two lineages is estimated to have occurred approximately
3 million years ago and may be due to allopatric isolation during the middle Pliocene times. While no genetic differentiation
was found within the northern or southern populations in both AFLP and 16S mtDNA markers, the results indicate that the northern
and southern lineage should be managed separately and any translocation between the two areas should be avoided. 相似文献
19.
Gene flow between populations of the asteroid Linckia laevigata (Linnaeus) was investigated by examining over 1000 individuals collected from ten reefs throughout the Great Barrier Reef (GBR), Australia, for genetic variation at seven polymorphic enzyme loci. Despite geographic separations in excess of 1000 km, Nei's unbiased genetic distance (0 to 0.003) and standardised genetic variation between populations (F
ST) values (mean 0.0011) were small and not significant. Genetic homogeneity among L. laevigata populations is consistent with the long-distance dispersal capability of its 28 d planktonic larval phase, and is greater than that observed for other asteroid species, including another high-dispersal species, Acanthaster planci, which has a 14 d larval phase. Variation within populations was also higher than previously recorded for asteroids (mean heterozygosity=0.384; number of alleles per locus ranged from 5.1 to 6.0 in each population). Among asteroids, dispersal ability is positively correlated with gene flow and levels of variation, and negatively correlated with levels of differentiation. 相似文献
20.
Sarcophyton elegans is a common symbiotic (zooxanthellate) octocoral species in the shallow waters of the Great Barrier Reef (GBR). Study of
a population at Lizard Island (14°40′S, 145°28′E) on the GBR from October 1991 to January 1994 revealed that, as is typical
of tropical alcyonarian corals, S. elegans is a gonochoric broadcast spawner with a 1:1 sex ratio. Sexual reproduction was closely correlated with colony size, with
first reproduction at 13-cm basal stalk circumference for females and 12 cm for males. Oogenesis took 19–24 months, with a
new cycle commencing every year, and spermatogenesis took 10–12 months. The majority of gametes were released during the annual
austral mass coral spawning event after the full moon in November, but gametes were also released after the full moon in each
month between August and February. All autozooid polyps participated in reproduction, but those at the outer edge of a colony
released their gametes first. During subsequent months, the polyps closer to the center of the colony released their gametes.
This is a novel strategy of gamete release, reported here for the first time, which accommodates the demands of feeding and
reproduction in a different way than other corals where individual polyps have separate feeding or reproductive roles. Colonies
upstream in the prevailing current spawned up to 1 month earlier than those downstream and ceased 1 month earlier. The mechanism
controlling this spatial differentiation in spawning time, repeatedly observed over three seasons, is unknown. Sarcophyton elegans appears to have a dual strategy of providing protection for its gametes by releasing most of them concurrently with the single,
annual mass spawning of a large number of cnidarians, while also hedging its bets by individual colonies spawning a fraction
of their gametes over an extended period of 6 months. 相似文献