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

Abstract

Abstract. An electrophoretic survey of allozyme variation revealed substantial genetic differentiation within the eastern Australian population of Actinia 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 (Fsr), 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.

Asexual reproduction and genetic determination of colour patterns within populations of the subtidal sea anemone Anthothoe albocincta

“…This population structure is similar to that reported for several intertidal sea anemones (e.g. Shick et al 1979, Hoffmann 1986) including the sympatric intertidal species Actinia tenebrosa (Ayre et al 1991).…”

EVIDENCE FOR RESTRICTED GENE FLOW IN THE VIVIPAROUS CORALSERIATOPORA HYSTRIX ONAUSTRALIA'S GREAT BARRIER REEF

“…Large F ST values have been reported in two earlier studies of clonal coelenterates. These were temperate populations ofthe coral P. damicornis (mean = 0.21, Stoddart 1984) and the sea anemone Actinia tenebrosa (mean = 0.38, Ayre et al 1991). However, in both cases variation apparently was inflated by the effects of clonal replication.…”

“…Reduced effective population sizes (N e ) , which must result when particular clonal genotypes become locally abundant or make skewed contributions to reproductive effort, should accelerate evolutionary change within, and divergence among, local populations (Wright 1978). Divergence may be further accentuated by effects of the restricted dispersal of 1183 clonal propagules and consequent effects of repeated episodes of site-specific selection (Williams 1975;Ayre 1985;Jackson 1986;Ayre et al 1991). However, other characteristics such as the occurrence of potentially long and overlapping generations should act to retard the rate of evolutionary change (Hughes et al 1992).…”

The role of sexual and asexual reproduction in structuring high latitude populations of the reef coral Pocillopora damicornis

“…For example, the levels of sexual and asexual reproduction in plants may vary with biotic and abiotic factors including latitude (Dorken and Eckert, 2001) and population density (van Kleunen et al, 2001). In marine environments, populations of sea anemones on relatively homogeneous, stable platforms or rock walls may be highly clonal (Hoffmann, 1986;Ayre et al, 1991) and dominated by locally adapted clones (Ayre, 1995). On less stable and more heterogeneous boulder shores, sexual recruits are more successful and subsequently levels of genotypic diversity are higher and match expectations for random mating (Ayre, 1984).…”