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1.
Salima Machkour-MRabet Yann Hénaut Pierre Charruau Muriel Gevrey Peter Winterton Luc Legal 《Marine Biology》2009,156(6):1321-1333
Habitat loss and degradation in the Mexican Caribbean, caused by the development of tourism, have decreased the potential
nesting area for the American crocodile (Crocodylus acutus) and have fragmented the populations of the Yucatan peninsula. Our study investigated five populations (three continental:
North, South, Sian Ka’an, and two insular: Cozumel, Banco Chinchorro) of C. acutus in the Mexican Caribbean using seven different inter simple sequence repeat (ISSR) markers as tools for genetic variability
and population differentiation. Three classification methods were tested and compared: distance analysis, self-organizing
map, and Bayesian methods, to evaluate the resolution of each method with ISSR markers. The 77 loci selected revealed a high
variability between populations (polymorphism from 17% for Sian Ka’an to 75% for Banco Chinchorro) with a total polymorphism
of 84% and a global coefficient of gene differentiation (G
ST
) of 0.296, but low values of Nei’s Gene diversity (from 0.065 for Sian Ka’an to 0.233 for Banco Chinchorro). Our results
suggest elevated inbreeding in all local populations with higher indices for Banco Chinchorro and lower indices for Sian Ka’an.
Three independent classification methods gave similar results, and suggested that most continental individuals are admixtures,
with different levels of introgression, with the sympatric species Crocodylus moreletii. We propose that the islands/atolls remain the sole areas with genetically “pure” American crocodiles and we discuss these
results for future conservation of this endangered crocodile species. 相似文献
2.
Allozyme electrophoresis demonstrates that the scleractinian coral Montipora digitata is two species
Allozyme electrophoresis at five loci was used to clarify the species status of two morphs of the scleractinian coral Montipora digitata (Dana, 1846), using specimens collected from three locations off the Queensland coast between October 1991 and April 1993. The two morphs, occurring sympatrically, were distinguished by one fixed gene difference at Locus LT-2 and frequency differences at three other loci, indicating reproductive isolation between them. Populations of both morphs were generally in Hardy-Weinberg equilibrium, suggesting that sexual reproduction does occur. Despite sampling designed to reduce the chance of collecting clonemates, the genetic diversity ratio (G
O:GE) indicated that asexual reproduction also occurs. This is in agreement with the known modes of reproduction for this species. There was significant genetic differentiation between populations of one of the morphs of M. digitata. This could have been influenced by greater degrees of asexual reproduction in this morph, selection within sites, or variation in larval survival and recruitment patterns. Relatively low F
st (differentiation among populations) values found for a broadcast spawning species during this study are in accordance with the hypothesis that brooded planulae are adapted for rapid settlement, whereas planulae produced by broadcast spawners are adapted for widespread dispersal. 相似文献
3.
Population genetic theory predicts that marine animal species with planktonic larvae will have less genetic structure than
those with direct development. We compared the genetic structure of four species of littorinid snails – two with planktonic
egg capsules that hatch as planktonic larvae and two with benthic egg masses that hatch as crawl-away juveniles. We used DNA
sequencing and single stranded conformational polymorphism (SSCP) to assess sequence variation in a 480 bp fragment of the
mitochondrial cytochrome b gene and then used an analysis of molecular variance (AMOVA) to estimate Φst for populations from the northeastern Pacific coast. One of the two direct-developing species, Littorina subrotundata, had a moderate amount of population structure (Φst=0.209) as expected but the other direct-developing species, L. sitkana, was nearly fixed for a single haplotype that made it impossible to precisely estimate Φst. One of the two planktonic-developing species, L. scutulata, did not show any significant population structure (Φst=0.004). In contrast to our expectations, the other planktonic-developing species, L. plena, showed some weak but statistically significant population structure (Φst=0.052). We discuss how differences in population genetic structure between species with the same type of development may
reflect differences in their historical demography.
Received: 22 December 1999 / Accepted: 24 July 2000 相似文献
4.
Heterotrophic nitrogen-fixation (acetylene reduction) was measured during decomposition (under dark conditions) of Rhizophora mangle L. and Avicennia germinans (L.) Stearn leaf litter. Nitrogen-fixation rates in leaf litter increased following 24 d incubation, then decreased after
≃44 d for both species. Maximum rates of 66.2 and 64.6 nmol C2H4 g−1 dry wt h−1 were reached by R. mangle and A. germinans leaf litter, respectively. Higher fixation rates of leaf litter were associated with an increase in water content and sediment
particles on leaf surfaces of both species. Rates of nitrogen fixation by diazotrophs attached to sediment particles were
not significantly different from zero. With additions of d-glucose, ethylene production rates increased by factors of 625-, 34- and 7-fold for sediment, R. mangle and A.␣germinans leaf litter, respectively, compared to rates prior to enrichment. These organically enhanced rates of nitrogen fixation on
leaves could be accounted for by increased activity associated with attached sediment particles and not the leaf material.
Total phenolics [reported as tannic acid equivalent (TAE) units] decreased nitrogen-fixation rates when added to d-glucose-enriched sediment at >20 mg TAE l−1. Phenolic compounds could explain the initial lag in rates of nitrogen fixation during leaf-litter decomposition of R. mangle (initial content of 110.8 mg TAE g−1 dry wt), but not of A. germinans (initial content of 23.4 mg TAE g−1 dry wt). The higher phenolic content and reportedly lower carbon substrate of R. mangle did not result in species-specific differences in either the magnitude or temporal pattern of nitrogen fixation compared
to A. germinans leaf litter. We conclude that the availability of organic substrates leached from the leaf litter along with colonization
by the heterotrophic diazotrophs (as indicated by sediment accumulation) controls nitrogen-fixation rates in a similar manner
in the leaf litter of both species.
Received: 8 August 1997 / Accepted: 4 December 1997 相似文献
5.
The loliginid squids Loligo pealei LeSueur and L. plei Blaineville (both recently proposed for reclassification as Doryteuthis) are commercially important, similar in appearance, and sympatric throughout much of the northwestern Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea. To investigate possible cryptic speciation and population structure, we examined samples (collected from 1995 to 1997) of both species for restriction fragment length polymorphisms (RFLPs) in PCR products of the mitochondrial gene cytochrome c oxidase (subunit I). RFLP haplotypes were further characterized by direct sequencing. In North American waters, cryptic speciation was rejected by the far greater nucleotide sequence divergence between species (~14%) versus within species (<1%). Each species displayed about a dozen RFLP haplotypes, but only three of their respective haplotypes were found among 90% of L. pealei specimens (n=356) and 97% of L. plei specimens (n=431). For L. pealei, a genetic break existed between the northern Gulf of Mexico and the Atlantic Ocean; among sample units within each population, gene flow was consistent with panmixia. The phylogeography of L. pealei is likely a consequence of the eastward currents of the Florida Straits, the elevated temperatures of those surface waters, and the restriction of this species to the continental shelf. For L. plei, a genetic break existed between longitudes 88°W and 89°W, with the northwestern Gulf of Mexico and the northeastern Gulf-Atlantic Ocean comprising separate populations; among sample units within each population, gene flow fit an isolation-by-distance model. If the genetic break found for L. plei represents resident populations separated by nearshore physical parameters (e.g. effects of the Mississippi River and the sediment boundary at longitude 88°W), the lack of structure within the Gulf for L. pealei might be due to its distribution farther from shore. However, the two populations of L. plei probably represent annual recolonization from the southwestern Gulf of Mexico and from the eastern Caribbean Sea, whereas the populations of L. pealei probably are permanent residents within their respective regions. 相似文献
6.
Documenting the scale of movement among populations is an important challenge for marine ecology. Using nine microsatellite markers, evidence of genetic structure in a marine kelp, the sea palm Postelsia palmaeformis Ruprecht, was examined in the vicinity of Cape Flattery, Washington state, USA (48° 24′ N, 124°44′ W). Genetic clustering analysis implemented without reference to geographic structure strongly suggested that a number of distinct genetic clusters existed among the 245 plants sampled in August in the years 1997–2001. Subsequent analysis showed that clustering was associated with geographically defined populations both among (km scale) and within (m scale) sampling sites. F
st analysis of geographically defined populations revealed significant genetic differentiation among populations of plants as little as 5 m apart, evidence of genetic structuring at even smaller scales, and a sharp increase in F
st across populations separated by up to 23 m. F
st values were also high and approximately unchanging (F
st=0.470) for populations separated by greater distances (up to 11 km), consistent with a scenario of rare dispersal by detached, floating plants carried by variable currents. The results corroborate natural history observations suggesting that P. palmaeformis has extremely short (1–3 m) spore dispersal distances, and indicate that the dynamics of sea palm populations are more affected by local processes than recruitment from distant populations. 相似文献
7.
Genetic diversity and genetic structure in a population of the brown seaweed Halidrys dioica Gardner were evaluated in five sites in southern California, USA, in 1991, using isozyme electrophoresis. H. dioica is relatively long-lived and has an outcrossing mating system and floating reproductive fronds with the potential for longdistance gamete dispersal. Because these characteristics are hypothetically important in determining genetic diversity and structure, we predicted that genetic diversity would be high and genetic structure would be exhibited only at relatively large geographic scales in H. dioica populations. The data were consistent with the prediction: genetic diversity (% polymorphic loci, no. of alleles/locus, average expected heterozygosity) was high compared to that of other seaweed species. Genetic structure (Wright's F statistics, Nei's genetic distance, point-pattern analysis of alleles) was low within and among distinct rocky reefs over 4 km of coast but high in subpopulations separated by 90 km. Life-history characteristics may be useful predictors of genetic diversity and structure in seaweed populations, but information on selection regimes, long-distance dispersal, and the extent of clonal propagation, for example, are critically lacking. 相似文献
8.
Venera Ferrito Anna Maria Pappalardo Adriana Canapa Marco Barucca Ignacio Doadrio Ettore Olmo Concetta Tigano 《Marine Biology》2013,160(12):3193-3208
We studied the genetic structure of the Mediterranean killifish Aphanius fasciatus. Analysis of the sequence variation in a 372-bp portion of the mitochondrial control region in 623 fish from 27 sampling sites along the species’ distributional range (Tyrrhenian coast, Sardinia, Sicily, Adriatic coast, Malta, Tunisia, and Greece) yielded 120 distinct haplotypes. Most of the haplotypes are unique, and only 15 % are shared among different populations. The high F ST value (=0.80) suggests a strong population genetic structuring. The phylogenetic analysis based on Bayesian inference, maximum likelihood and maximum parsimony, and the median-joining network show a sharp separation of the Southeastern Sicilian populations (belonging to the Hyblean region) and of the fluvial Tunisian population of Rio Melah from the others. The Adriatic, the Eastern Sicilian, and the Greek populations are well differentiated, while the group of populations from the Central-Western Mediterranean does not show a clear pattern of differentiation. Our findings indicate that the current genetic structuring of A. fasciatus reflects historical geographical patterns occurring within the Mediterranean basin from the Late Miocene to the Pleistocene. The presence of divergent evolutionary entities in the Hyblean region and the Tunisian Rio Melah supports their inclusion as target areas for the conservation of A. fasciatus. 相似文献
9.
The group of subspecies of Patella ulyssiponensis, described by Christiaens, was widely known as Patella aspera until recently. The group extends throughout the Mediterranean, on all Macaronesian islands, along the North African coast, and in Europe, as far north as southern Norway. Throughout its range it displays great variation in shell sculpture and colour. The aim of this work was to re-examine the various subspecies proposed by Christiaens and, genetically, to test the hypothesis that European continental populations belong to a different species than the one composed by Macaronesian (north-west African) populations. In the present work, this group was studied by allozyme electrophoresis of 21 loci and by six morphological variables. The monomorphic locus of malate dehydrogenase (Mdh-1) was found to be diagnostic for distinguishing European continental populations from those of north-west African archipelagos, confirming the specific status of both groups. The allele observed at this locus in the Macaronesian populations was novel, while European continental populations showed a plesiomorphic one, shared with all other north-west Atlantic patellids with the exception of Patina pellucida, suggesting a more recent origin of the Macaronesian species from the continental forms. Both species showed a genetic identity of 0.730±0.061, which allowed rough estimations of 6.5–3 Mya since speciation. The subspecies Patella ulyssiponensis deserta described by Christiaens was not confirmed by our genetic data. Other loci (glyceraldehyde-3-phosphate dehydrogenase and the second locus of lactate dehydrogenase) were partially diagnostic, in which both species showed different most common alleles. Morphologically, both species are easily recognised by shell characters and the results agree with previous findings, that continental populations are more homogeneous in shell morphology and radula characters than populations from the Macaronesia. This work supports retention of the earliest valid name, Patella ulyssiponensis Gmelin, with Lisbon, Portugal as type locality, for the European continental species, and Patella aspera Röding for the Macaronesian populations. Population subdivision within species was measured by theta, the estimator of Fst, showing in both P. aspera and P. ulyssiponensis a high degree of genetic structuring (=0.226 and 0.182, respectively) mostly explained by the large distances separating the populations within species.Communicated by J.P.Thorpe, Port Erin 相似文献
10.
Genetic structure of fissiparous populations of Holothuria (Halodeima) atra on the Great Barrier Reef 总被引:1,自引:0,他引:1
Allozyme variation at five polymorphic loci was surveyed in a total of 311 individuals of the sea cucumber Holothuria (Halodeima) atra (Jäger, 1833) collected from two nearshore and two midshelf populations in the Great Barrier Reef in November 1996. Strong deviations in genotype frequencies from those expected under Hardy–Weinberg equilibrium, particularly a large number of heterozygote excesses, confirmed the occurrence of asexual reproduction. Females and males differed significantly in genotype frequencies as a result of differences in either the amount of fission in each sex or in the mortality of asexually produced recruits. The estimated maximum sexual input (number of sexually produced individuals: sample size = N*:Ni) to the two nearshore reefs (38 to 67%) was low relative to that to the two midshelf reefs (74 to 87%). The three ratios and G o :G e , N go :N i , N*:N i , (where G o = observed genotypic diversity, G e = expected genotypic diversity, N go = number of genotypes) considered to be indicators of the extent of asexual reproduction, showed a consistent trend in the degree of asexual reproduction similar to that derived from the number of regenerating individuals observed in the populations for which data were available. F-statistic analyses of clonal gene frequencies demonstrated that all populations received sexual recruits from the same gene pool. There was evidence of restricted sexual recruitment to the Fantome population, suggesting that asexual reproduction was dominant only in areas where sexual recruitment was limited by other factors. 相似文献
11.
Twenty populatios of Littorina angulifera, inhabiting islands composed of the mangrove tree Rhizophora mangle, were assayed at an esterase locus to determine whether genetic differentiation was associated with distance between populations. It was predicted, on the basis of larval dispersal in this species, that genetic differentiation between populations on islands separated by long distances should be greater than those on islands located near each other. A chi0square test of homogeneity revealed significant differences in esterase gene frequencies among the 20 island populations. However, there was no association of distance between islands and genetic heterogeneity. In addition, a cline in gene frequency was found to be assiciated with latitude. Factors responsible for the observed pattern of heterogeneity at the esterase locus are discussed. 相似文献
12.
We conducted a phylogeographic study of the meiofaunal nemertean Ototyphlonemertes parmula, an apparent species complex from the littoral zone of coarse-grained beaches, using a 494-bp fragment of the mitochondrial
cytochrome oxidase 3 gene (cox3). Six populations from the Gulf and Atlantic coasts of Florida, two from New England, and one from the Caribbean were sampled
in March and August 2005. Three major lineages were identified, separated by cox3 sequence divergence of 16–18%, with partially overlapping ranges. Tests for hybridization using ISSR markers detected nuclear
gene exchange within but not between the major mitochondrial lineages, indicating the presence of cryptic species. One lineage
dominating the Atlantic coast of Florida shows no evidence of geographic structuring. Another lineage shows a phylogenetic
break between the Atlantic and Gulf coasts, suggesting that unsuitable habitat may act as a barrier to dispersal. Long-distance
migration is evidenced by shared haplotypes between Florida and the eastern Caribbean. Overall, the widespread distribution
of individual haplotypes and lack of structuring within geographic regions contrast with O. parmula’s strongly sediment-bound lifestyle. We speculate that dispersal of adults by storms and/or sediment transport may be more
important than few and potentially short-lived planktonic larvae to explain geographic diversity in O. parmula and may be important for meiofauna in general. 相似文献
13.
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
14.
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
15.
Phyllorhiza
punctata, commonly called the Australian white spotted jellyfish, invaded the Caribbean in the 1960s, becoming established there and
subsequently in the United States in the northern Gulf of Mexico (by 2000) and eastern Florida (2001). With the prevailing
Loop Current flowing clockwise around the Gulf of Mexico and joining the Gulf Stream along eastern Florida, potential transport
of P. punctata along the eastern seaboard of the USA could be facilitated. P. punctata medusae were collected in small numbers along the entire Georgia coast during May–November in 2007 and 2008. Medusa bell
diameters increased both years from ca. 10 cm in May to ca. 33 cm in autumn. Specimens lacked zooxanthellae, as reported for
medusae in the northern Gulf of Mexico and Florida. It is possible that the P. punctata medusae observed were transported from established populations to the south; however, whether or not this species is established
along the Georgia coast has yet to be determined. 相似文献
16.
Population differentiation of the Atlantic spotted dolphin (Stenella frontalis) in the western North Atlantic, including the Gulf of Mexico 总被引:4,自引:2,他引:2
Information about the genetic population structure of the Atlantic spotted dolphin [Stenella frontalis (G. Cuvier 1829)] in the western North Atlantic would greatly improve conservation and management of this species in USA
waters. To this end, mitochondrial control region sequences and five nuclear microsatellite loci were used to test for genetic
differentiation of Atlantic spotted dolphins in the western North Atlantic, including the Gulf of Mexico (n=199). Skin tissue samples were collected from 1994–2000. Significant heterozygote deficiencies in three microsatellite loci
within samples collected off the eastern USA coast prompted investigation of a possible Wahlund effect, resulting in evidence
for previously unsuspected population subdivision in this region. In subsequent analyses including three putative populations,
two in the western North Atlantic (n=38, n=85) and one in the Gulf of Mexico (n=76), significant genetic differentiation was detected for both nuclear DNA (R
ST=0.096, P≤0.0001) and mitochondrial DNA (Φ
ST=0.215, P≤0.0001), as well as for all pair-wise population comparisons for both markers. This genetic evidence for population differentiation
coupled to known biogeographic transition zones at Cape Hatteras, North Carolina and Cape Canaveral, Florida, USA, evidence
of female philopatry, and preliminary support for significant genetic differences between previously documented morphotypes
of Atlantic spotted dolphins in coastal and offshore waters all indicate that the biology and life history of this species
is more complex than previously assumed. Assumptions of large, panmictic populations might not be accurate in other areas
where S. frontalis is continuously distributed (e.g., eastern Atlantic), and could have a detrimental effect on long-term viability and maintenance
of genetic diversity in this species in regions where incidental human-induced mortality occurs.
相似文献
Lara D. AdamsEmail: |
17.
Gretchen Goodbody-Gringley Steven V. Vollmer Robert M. Woollacott Gonzalo Giribet 《Marine Biology》2010,157(12):2591-2602
Understanding population connectivity in corals is particularly important as these organisms are increasingly threatened by
abiotic and biotic factors. This study examined the population genetic structure of the brooding coral Favia fragum across four locations in the Caribbean and Western Atlantic using mitochondrial and nuclear markers. Morphological features
were also compared to test whether genetic diversity corresponds with skeletal morphology. When comparing across distantly
related Caribbean and Bermudian locations, F
ST values were high and significant, indicating strong genetic structure. At a local scale, significant genetic structure was
found among reefs in Panama, while no genetic structure was found among reefs within Barbados, Bermuda or Jamaica. Surprisingly,
a single haplotype for each of the three markers examined was found in Bermuda, where samples varied significantly from all
other locations in three out of four morphological features analyzed. These data indicate that gene flow of F. fragum may occur locally among reefs but is highly restricted at distant locations. Furthermore, isolated populations, such as that
of Bermuda, must be self-seeding to maintain the observed genetic uniformity. 相似文献
18.
Stable isotope ratios and fatty acid signature analyses were employed to examine the fine-scale population structure of a year-round resident population of 600–800 bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon (IRL), Florida. The IRL, a 250-km-long estuary running along the central east coast of Florida (28.0°N, 80.6°W), is comprised of the northern and southern IRL, Mosquito Lagoon (ML), Banana River (BR), and St. Lucie Estuary. Samples of skin and blubber were collected from dead stranded (n = 61, 1994–2004) and live dolphins (n = 153, 2002–2007, 2010, 2011) from throughout the IRL and surrounding environs. Using stable isotopes (SI), dolphins could be assigned to a ML subpopulation, a St. Lucie Estuary subpopulation, and an IRL subpopulation. Fatty acid signature analysis (FASA) allowed for finer resolution, detecting ML and BR subpopulations, a separation of northern and southern IRL subpopulations, and a St. Lucie Estuary subpopulation. Differences between sexes were detectable within subpopulations using FASA, but not using SI. This may indicate that males and females are foraging in similar locations at a similar trophic level (detected using SI), but are varying in the types or proportions of specific prey (indicated by FASA). The combination of these complementary analyses results in a powerful tool for assessing fine-scale population substructure. 相似文献
19.
Genetic differentiation and genetic variability of sporophytic and gametophytic populations of Gelidium arbuscula (Bory) from three localities sampled in 1989 and 1990 in the Canary Islands (Spain) were examined by isozyme electrophoresis. Twenty-three to 29 putative alleles corresponding to 22 gene loci, were compared. High deviations in Hardy-Weinberg equilibrium, and significant differences between allelic frequencies of sporophytic and gametophytic subpopulations at the same locality were found, suggesting a predominant asexual reproduction of G. arbuscula. The genetic variability (percentage of polymorphic loci, mean number of alleles per locus and average gene diversity) of haploid subpopulations was lower than that of diploid subpopulations at all three localities, being the lowest described for seaweeds. No correlation between genetic and geographical distance was found. The high genetic differentiation coefficient between all subpopulations suggests a very reduced genetic flow between subpopulations of the same and of different localities. These results suggest that the genetic structure of the populations of G. arbuscula from the Canary Islands is due to a founder-effect combined with a predominance of asexual reproduction. This is the first report comparing allelic frequencies between sporophytic and gametophytic subpopulations of seaweeds. 相似文献
20.
Measurements in situ were made of oxygen exchange and 14C fixation in calcareous sediments off the coast of Florida, USA, and at various sites in the Caribbean Sea at depths to 60 m. Sediment samples were analyzed for total organic carbon, nitrogen and photosynthetic pigments. In some cases, measurements were made of the pH of sediment interstitial water and its concentration of total CO2. In the Caribbean Sea, routine hydrological sampiing was undertaken and in situ plankton productivity determined.Contribution No. 1522 from the University of Miami, Rosenstiel School of Marine and Atmospheric Science, 10 Rickenbacker Causeway, Miami, Florida 33149, USA. 相似文献