Mr. Billingham et Dj. Ayre, ASEXUAL REPRODUCTION AND GENETIC DETERMINATION OF COLOR PATTERNS WITHIN POPULATIONS OF THE SUBTIDAL SEA-ANEMONE ANTHOTHOE-ALBOCINCTA, Marine ecology. Progress series, 156, 1997, pp. 121-130
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.