Population genetic structure was studied in one nearshore (Great Palm Island) and two offshore (Rib Reef and Reef 18-026) populations of Stichopus chloronotus on the Great Barrier Reef. Two stations approximately 500m were sampled on each reef at depths between 1 and 2 m. At each station, 30-40 individuals were sampled within a radius of 30m, in early November 1996. The sampling time in November was chosen to increase the likelihood of finding mature gonads in the sampled animals.
Genetic variation at 5 polymorphic loci was examined using allozyme electrophoresis. The polymorphic enzymes examined were: hexokinase (E.C. 18.104.22.168; HK*), mannose- 6-phosphate isomerase (E.C. 22.214.171.124; MPI*), phosphoglucomutase (E.C. 126.96.36.199; PGM*), triose-phosphate isomerase (E.C. 188.8.131.52; ¹PI*) and peptidase using valylleucine as substrate (E.C. 3.4.11/13; <¸*).
Estimates of the level of asexual reproduction were made using the ratios of the number of sexually produced individuals to sample size, observed genotypic diversity (Go) to expected genotypic diversity (Ge), and number of genotypes (Ngo) to sample size. Values of Go/Ge much smaller than one indicate the occurrence of clonal reproduction.
F-statistics were used to partition genetic variation into that occurring within populations (FIS) and that occurring between populations (FST).