ASEXUAL REPRODUCTION AND GENETIC DETERMINATION OF COLOR PATTERNS WITHIN POPULATIONS OF THE SUBTIDAL SEA-ANEMONE ANTHOTHOE-ALBOCINCTA

Southeastern Australian populations of the dioecious, subtidal sea ane mone Anthothoe albocincta display considerable spatial variation in th e colour patterns of the constituent polyps, and the most visually str iking feature of local populations are sets of dense aggregations each comprised of polyps with a single colour pattern. We used a combinati on of genetic data, observations and manipu lative experiments to infe r that A. albocincta generates these monomorphic aggregations via asex ual reproduction and that asexual reproduction plays the major role in the maintenance of established populations. Allozyme electrophoresis of 2 to 5 polyps from each of 20 mapped aggregations (in 2 populations ) revealed that in 18 cases (90 %) all polyps were electrophoretically identical and always distinct from differently coloured polyps taken from each of 26 adjacent aggregations. Furthermore, the genetic struct ure of each of 13 populations separated by up to 930 km was consistent with the predicted effects of localised asexual recruitment. We detec ted 16 heterozygote excesses and 11 heterozygote deficits (p < 0.05) i n a total of 66 tests for departures from Hardy-Weinberg equilibria. M oreover, each population contained significantly less (p < 0.005) mult i-locus genotypic diversity (G(o)) than was expected for a randomly ma ting population (G(e)) (mean G(o):G(e) = 0.30) and contained relativel y few unique 7-locus genotypes. Some genotypes were found within many aggregations, suggesting successful clones may have extensive and disc ontinuous distributions within populations. In addition, we observed l ongitudinal fission of adult polyps in both field and laboratory condi tions, and found that over a 6 mo period 82% (i.e. 1469 of 1790) of ne w recruits into 30 experimentally cleared patches, within 3 population s, were morphologically identical to those within surrounding aggregat ions. These data, together with our earlier analysis of genetic variat ion among populations, and observations of gonad development, imply th at this species uses fission to maintain populations, consisting predo minantly of spatially restricted clones (each with an almost unique co lour pattern), but uses sexual reproduction to produce widely disperse d colonists.