Genetic structure of a scleractinian coral, Mycedium elephantotus, in Taiwan

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     

Allozyme and mitochondrial DNA variation in Cuban populations of the shrimp Farfantepenaeus notialis (Crustacea: Decapoda)

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     

Evidence of limited gene flow in three species of coral reef fishes in the lagoon of New Caledonia

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     

Genetic structure and allozyme variation of sea bass (Dicentrarchus labrax and D. punctatus) in the Mediterranean Sea

This paper reports data on 28 allozyme loci in wild and artificially reared sea bass (Dicentrarchus labrax) samples, originating from either coastal lagoon or marine sites in the Mediterranean Sea. F _ST analysis (θ estimator) indicated strong genetic structuring among populations; around 34% of the overall genetic variation is due to interpopulation variation. Pairwise θ estimates showed that, on average, the degree of genetic structuring was much higher between marine populations than between samples from lagoons. Six polymorphic loci showed differences in allele frequencies between marine and lagoon samples. Multivariate analyses of individual allozymic profiles and of allele frequencies suggested that different arrays of genotypes prevail in lagoons compared to marine samples, particularly at those loci that, on the basis of previous acclimation experiments, had been implicated in adaptation to freshwater. On the other hand, variation at “neutral” allozyme loci reflects to a greater extent the geographic location of populations. Allozyme differentiation was also studied in a D. labrax population from the Portuguese coast. Average genetic distance between this population and the Mediterranean populations was quite high (Nei's D = 0.236) and calls into question the taxonomic status of the Portuguese population. Finally, genetic relationships between D. labrax and D. punctatus were evaluated. Average Nei's D was 0.648, revealing high genetic differentiation between the two species, even for two sympatric populations of these species in Egypt; thus gene flow was not indicated between species. Received: 24 October 1996 / Accepted: 27 November 1996     

Population genetics of the Antarctic heteronemertean Parbolasia corrugatus from the South Orkney Islands

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     

Effects of contrasting modes of larval development on the genetic structures of populations of three species of prosobranch gastropods

 In south-eastern Australia, the prosobranch gastropods Morula marginalba (Blainville), Cominella lineolata (Lamarck) and Bedeva hanleyi (Angas) have similar fine-scale distributions, but appear to possess very different dispersal capabilities due to contrasting modes of larval development. M.marginalba produce planktonic larvae, whereas C. lineolata and B. hanleyi undergo direct development in benthic egg capsules and emerge as crawling juveniles. To test for possible effects of contrasting life histories on levels of genetic variation within and among populations, a survey was conducted of allozyme variation at six polymorphic loci in 8 to 9 local populations of each species. Collections of snails were made between June 1992 and November 1993. Sampling ranges spanned between 162 and 180 km of coast. Regardless of larval type, proportions of single-locus genotypes in each collection were consistent with the recruitment of offspring which had been generated through random mating. However, genotypic diversity was lower in those species that undergo direct development. Loci surveyed in C. lineolata and B. hanleyi were polymorphic (i.e. frequency of most common allele <95%) in fewer populations than those examined for M.␣marginalba (P <0.001) and, where polymorphisms occurred, also possessed significantly fewer alleles (P <0.001). Consequently, average levels of expected heterozygosity were greater in populations of M. marginalba than in those of either of the other species (P <0.001). Genetic variation among populations, expressed as the standardised variance in allele frequencies (F _ST ), was inversely related to expected larval dispersal capability. The nine collections of M. marginalba showed little overall differentiation (F _ST  = 0.017; P <0.001), reflecting the ability of planktonic larvae to interconnect local populations, and so limit divergence due to drift and natural selection. In contrast, there were high levels of allelic heterogeneity among the nine collections of C. lineolata (F _ST  = 0.523; P <0.001) and eight collections of B. hanleyi (F _ST  = 0.140; P <0.001). These data imply that for species which undergo direct development, local populations are effectively closed and evolve largely independent of one another. Received: 3 May 1996 / Accepted: 12 July 1996     

Population structure of the giant tiger prawn Penaeus monodon in Australian waters, determined using microsatellite markers

 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     

Genetic protein variation in red mullet (Mullus barbatus) and striped red mullet (M. surmuletus) populations from the Mediterranean Sea

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     

Microsatellite variation, effective population size, and population genetic structure of vermilion snapper, Rhomboplites aurorubens, off the southeastern USA

Vermilion snapper (Rhomboplites aurorubens) were collected from four sites off the Atlantic coast of the USA and one site in the Gulf of Mexico to evaluate effective population size and genetic stock structure. Previous studies had suggested geographic variation in the ratio of males to females, so this population characteristic was explored in conjunction with the genetic analysis. Sex ratio varied greatly among the five sample sites; males comprised 57% of samples in the Gulf of Mexico, while within the South Atlantic Bight they comprised between 36% (Morehead City, North Carolina) and 53% (Carolina Beach, North Carolina) of samples. No clear geographic trends in the sex ratio emerged; instead, it was found to vary with fish length, the percentage of males decreasing with increasing size. Allelic variation assessed at seven dinucleotide microsatellite loci was large; gene diversities ranged from 0.43 to 0.95 and allelic counts from 7 to 39. Estimates of the effective population size ranged from 24 500 (based on the infinite-alleles model) to 150 500 (based on the stepwise-mutation model). There was evidence for excess homozygosity within samples: estimates of F _IS (the correlation of alleles within individuals) ranged from 0.01 to 0.03 among the seven loci, and three estimates were significantly greater than zero. Differentiation among localities was very weak, as estimates of F _ST (the correlation of alleles within populations) were on the order of 0.001 to 0.002 and genetic distance estimates between localities were not related to geographic distances. This suggested that vermilion snapper in the South Atlantic Bight (Cape Hatteras, North Carolina to Cape Canaveral, Florida) and Gulf of Mexico are likely to consist of one genetic stock. Despite the overall homogeneity, there were indications of a temporally dynamic local structure that would bear further examination. Received: 6 July 1998 / Accepted: 9 February 1999     

Genetic evidence for contrasting patterns of dispersal in solitary and colonial ascidians

In situ and in vitro observations indicate that brooding colonial ascidians commonly display limited larval dispersal, whilst the larvae of most solitary species are assumed to be widely dispersed. We used allozyme data to determine the population genetic consequences of reproduction and dispersal in a broadcast-spawning solitary ascidian and two brooding colonial species along the central and southern coast of New South Wales, Australia. We surveyed genetic variation at 2 to 9 variable loci for samples collected from 6 to 8 local populations of each of the stalked solitary species Pyura gibbosa gibbosa Heller, 1878; the social Stolonica australis Michaelsen, 1927 and the compound Botrylloides magnicoecum Hartmeyer, 1912. Samples from each local population displayed levels and patterns of genotypic diversity that were consistent with expectations for sexually-derived recruitment of both solitary zooids and separate colonies. However, we found clear differences in the structure of the populations of solitary and colonial species. Genotype frequencies within all nine samples of P. gibbosa gibbosa conformed to expectations for random mating (i.e. Hardy–Weinberg equilibria). Moreover, allele frequencies showed little variation among samples [mean standardised genetic variance (F _{S T} ) =0.002], which implies that local populations are strongly connected by larval dispersal. We estimate (via Wright's “island model”) that gene flow (N _e m) within this set of local populations is 125 effective migrants per generation, which is very similar to estimates obtained for other broadcast-spawning taxa in this region. In contrast, genotype frequencies within samples of both colonial species were characterised by large and statistically significant deficits of heterozygotes, consistent with expectations for highly limited dispersal of larvae or sperm. Moreover, local populations were highly differentiated (F _{S T} =0.201 and 0.202 for S. australis and B. magnicoecum, respectively) and N _e m was estimated to be ∼1.0 in each case. These values of F _{S T} and subsequent estimates of N _e m lie within the range of values reported for other New South Wales taxa with direct larval development, and imply that local populations are effectively closed to immigration. Received: 13 February 1997 / Accepted 18 July 1997     

Genetic heterogeneity among adult and recruit red sea urchins, Strongylocentrotus franciscanus

Allozyme electrophoresis was used to characterize genetic variation within and among natural populations of the red sea urchin Strongylocentrotus franciscanus. In 1995 to 1996, adult urchins were sampled from twelve geographically separated populations, seven from northern California and five from southern California (including Santa Rosa Island). Significant population heterogeneity in allelic frequencies was observed at five of six polymorphic loci. No geographic pattern of differentiation was evident; neighboring populations were often more genetically differentiated than distant populations. Northern and southern populations were not consistently distinguishable at any of the six loci. In order to assess within-population genetic variation and patterns of recruitment, large samples were collected from several northern California populations in 1996 and 1997, and were divided into three size classes, roughly representing large adults (>60 mm), medium-sized individuals (31 to 60 mm, “subadults”) and individuals <2 yr of age (≤30 mm test diam, referred to as “recruits”). Comparisons of allelic counts revealed significant spatial and temporal differentiation among size-stratified population samples. Recruit samples differed significantly from adult samples collected at the same locale, and showed extensive between-year variation. Genetic differentiation among recruit samples was much higher in 1997 than in 1996. Between-year differences within populations were always greater for recruits than for adults. Potential explanations for the differentiation of recruit samples include pre- and post-settlement natural selection and high interfamily variance in reproductive success or “sweepstakes” recruitment. Unless recruit differentiation can be attributed to an improbable combination of strong and spatially diverse selection, such differentiation across northern California populations indicates that the larval pool is not well mixed geographically (even on spatial scales <20 km), despite long planktonic larval duration. Received: 6 July 1999 / Accepted: 25 January 2000     

Genetic differentiation among populations of a broadcast spawning soft coral, Sinularia flexibilis, on the Great Barrier Reef

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     

Genetic relationships between marine and marginal-marine populations of Cerithium species from the Mediterranean Sea

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     

Is Syllis gracilis (Polychaeta: Syllidae) a species complex? An allozyme perspective

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     

Allozyme variation in global populations of striped mullet, Mugil cephalus (Pisces: Mugilidae)

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     

Mitochondrial and nuclear DNA analysis of population subdivision among young-of-the-year Spanish mackerel (Scomberomorus maculatus) from the western Atlantic and Gulf of Mexico

The degree of population subdivision among collections of young-of-the-year (YOY) Spanish mackerel Scomberomorus maculatus sampled from along the Atlantic coast of the United States (Atlantic) and Gulf of Mexico (Gulf) was examined. Young-of-the-year were collected from spawning areas to minimize possible mixing among putative spawning stocks that may occur at later life history stages along migratory pathways or at over-wintering grounds. Restriction fragment length polymorphism (RFLP) analysis of the mitochondrial DNA (mtDNA) ND4 region and a nuclear actin intron was conducted. Collections in each of two years were analyzed to minimize bias associated with sampling at a single point in space or time. Substantial variation was detected at ND4 (haplotype diversity=0.81) and at the actin intron locus (gene diversity=0.21). Significant differences in gene diversity or allele frequencies were not detected among temporal samples at any of three locations. A homogeneous distribution of genetic variance among samples from widely spaced geographic regions was consistent with the hypothesis that Spanish mackerel comprise a single intermingling genetic stock. Power analysis showed that the mitochondrial analysis from this study was much more likely to detect population subdivision than analysis of the nuclear actin locus, despite lower mtDNA sample size. Received: 3 January 2000 / Accepted: 28 August 2000     

Photosynthesis and growth of red and green morphotypes of Kappaphycus alvarezii (Rhodophyta) from the Philippines

The effect of photosynthetic available radiation (PAR) levels, light quality, ultraviolet (UV) radiation, and temperature on photosynthesis, growth, and chlorophyll fluorescence was evaluated in red and green morphotypes of the rhodophyte Kappaphycus alvarezii (Doty) Doty under controlled conditions. Chlorophyll a and phycoerythrin (PE) levels were similar in the red and green morphotypes cultured under the same conditions, but phycocyanin (PC) and allophycocyanin (APC) levels were 2-fold greater in the green than in the red morphotype. Pigment characterization indicated that the overexpression of PC and APC masked the red pigmentation in the green morphotype. Maximum photosynthesis and photosynthetic efficiency were similar between the two morphotypes assayed at a wide temperature range, which was reflected in the similar growth rates observed in outdoor culture systems. In the green morphotype, photosynthetic efficiency increased 2-fold relative to the red morphotype when assayed with red light (λ > 600 nm), indicating that photosynthetic characteristics are modified as a result of pigment variation in these morphotypes. Such increase in photosynthetic efficiency in the green morphotype, however, did not result in greater growth rates when cultured under white light. Short exposure to high levels of solar radiation (UV-A + UV-B + PAR), and filtered solar radiation (UV-A + PAR or PAR) decreased effective quantum yield (ΔF/F _m′) in both morphotypes. The reduction of ΔF/F _m′ values in the red and green morphotypes was accounted for by high levels of PAR and not by the UV-A + UV-B + PAR and UV-A + PAR treatments. Photoinhibition caused by UV-A, UV-B, or PAR was completely reversed within 30 h after incubations. Recovery rates from photoinhibition, however, were significantly reduced in the green morphotype when incubated with UV-B radiation. The results here suggest that the overexpression of pigments do not necessarily increase photosynthesis and growth in these morphotypes. Received: 19 June 2000 / Accepted: 28 November 2000     

Genetic subdivision within the eastern Australian population of the sea anemoneActinia tenebrosa

An electrophoretic survey of allozyme variation revealed substantial genetic differentiation within the eastern Australian population ofActinia tenebrosa. This differentiation appears to reflect the effects of both asexual reproduction and limited gene flow among local populations separated by up to 1050 km. Variation was assessed within groups of 27 to 55 adults sampled between September 1985 and December 1988 collected from small areas of shore within each of 24 local populations. All individuals were collected from stable rock platforms, with the exception of Boulder Bay, where some sea anemones were removed from small mobile boulders. High levels of variability were detected for each of seven enzyme-encoding loci. The patterns of genotypic variation detected imply that local populations are maintained by predominantly asexually generated recruitment. Levels of multi-locus genotypic diversity within samples were consistently less than 50% of the level expected for sexual reproduction with free recombination. This was reflected by the detection of relatively low numbers of multi-locus genotypes and significant departures from expectations for single-locus Hardy-Weinberg equilibria within 17 of the 24 local populations. Standardised genetic variances (F _ST ), calculated from the genotypes of all individual adults were typically much greater than those expected for marine organisms with widely dispersed larvae. The former values were reduced, but were still extremely large when clonal genotype frequencies were substituted into the calculation. These data imply that although widely dispersed larvae may be an important source of initial colonists, levels of gene flow among established local populations are low. Furthermore, cluster analysis revealed a clear subdivision of the population into northern and southern groups. However, this subdivision was largely explained by strong clinal variation at a GPI-encoding locus. For this locus, allele frequencies ranged from fixation of the A allele in samples from the 12 most northern sites to near fixation of the alternative B allele in southern samples. Subdivision of the eastern Australian population is consistent with the predicted off-shore movement of the Eastern Australian Current close to the border between Victoria and New South Wales. However, the split into northern and southern regions, as evidenced by the variation forGpi, could reflect patterns of gene flow and/or other factors such as natural selection or the recent patterns of colonisation.Contribution No. 78 from the Ecology and Genetics Group of the University of Wollongong     

Genetic evidence of the presence of two species of Crassostrea (Bivalvia: Ostreidae) on the coast of Brazil

 Although oysters are commercially very important in Brazil, there is still much dispute about the number of Crassostrea species occurring on the Brazilian coast. The dispute is centered around C. brasiliana, considered by some authors to be a junior synonym of C. rhizophorae. In this paper we compared, by allozyme electrophoresis, sympatric and allopatric populations of the two putative species. Of the 17 loci analysed, five were diagnostic for the two species in sympatry (gene identity = 0.46 to 0.47), clearly demonstrating that they are distinct biological species. Heterozygosity (h) levels were high for both species (h = 0.24 to 0.28), and no heterozygote deficiencies were observed in any population (local inbreeding, F _IS  = 0.141; P > 0.70). Levels of population structure in C. rhizophorae along 1300 km of coast were very low (population inbreeding, F _ST  = 0.026; P > 0.15), indicating that the planktonic, planktotrophic larvae of these species are capable of long-range dispersal. Received: 14 January 1999 / Accepted: 8 December 1999     

Genetic relationships within and between clonal and solitary forms of the sea anemone Anthopleura elegantissima revisited: evidence for the existence of two species

Along the temperate Pacific coast of North America, the actiniarian sea anemone Anthopleura elegantissima exhibits two discrete life-history phenotypes. Although both forms sexually produce planula larvae, the clonal morph can also asexually propagate by fission, whereas the solitary morph does not. Whether the two forms constitute one or two species has long been contested. Hand originally designated the two forms as conspecifics, whereas Francis – on the basis of differences in microhabitat, biogeographic range and phenotypic frequencies – argued that the two forms constituted a sibling-species pair. From the results of an electrophoretic survey in which they pooled allelic frequencies across several geographic locations, Smith and Potts subsequently argued that the two forms were not genetically differentiated, and therefore represented a single species. We re-examined the relationship between the forms electrophoretically, substantially extending the geographic range and doubling the sample sizes beyond those used by Smith and Potts, and not pooling allelic frequencies in our analyses. Our analysis of patterns of genetic variation at ten highly polymorphic allozyme loci shows that although no fixed genetic differences distinguish the two forms, there are significant differences in allele frequencies between clonal and solitary A.␣elegantissima at every site we sampled throughout their range of sympatry (over 1000 km); within each form, however, there is little detectable genetic differentiation among populations. We therefore conclude that the two forms represent recently reproductively isolated taxa, and propose that the clonal form retain the binomial A. elegantissima (Brandt, 1835), whereas the solitary form be described and named a new species, Anthopleura sp. Received: 28 August 1996 / Accepted: 25 September 1996