RELATIONSHIP BETWEEN SHELL-PATTERN FREQUENCY AND MICROHABITAT VARIATION IN THE INTERTIDAL PROSOBRANCH, CLITHON OUALANIENSIS (LESSON)

A number of studies undertaken on the highly polymorphic intertidal mo llusc Clithon oualaniensis reported that colour-morph frequencies vari ed on a regional basis in the Indo-Pacific region (Gruneberg, 1976, 19 78, 1979). Our study examined colour-morph variation on a local scale in the same species and demonstrated that a level of variation similar to the regional variation described by Gruneberg was present in Clith on populations collected from different microhabitats at a single loca lity in northeastern Queensland. An examination of genetic differentia tion (using allozyme electrophoresis) of the same populations failed t o identify an association between genotype and microhabitat and confir med that Clithon populations at least on a local scale belong to a sin gle gene pool. Factors that influence the distribution of morphs at pa rticular sites are most likely to be such ecological factors as differ ential predation. The results of this study indicate that relationship s between environmental variables on a regional scale and colour-morph frequencies in Clithon need to be reassessed and the extent of local variation studied intensively.