Population genetics in Octopus pallidus

Dispersal is an important factor in population demographics, and therefore understanding dispersal is important for population management. In marine environments, the presence or absence of pelagic larvae is considered an important factor determining the dispersal capacity of an organism. Organisms with pelagic larvae that spend long periods in the plankton are considered to have high dispersal capacities, while organisms with no pelagic larval phase (direct development) are considered to have very low dispersal capabilities and therefore highly structured populations. Dispersal is often difficult to observe directly, however the use of natural chemical markers has enabled organisms to be traced back to their place of origin. The other primary method by which dispersal can be inferred is by population genetic analyses, which can provide information on the differentiation of populations and therefore how much dispersal has occurred between them. The most informative analyses use a combination of approaches to provide a more comprehensive assessment of dispersal. This study determines population genetic variation of the benthic cephalopod Octopus pallidus over spatial and temporal scales using microsatellite markers. Octopus pallidus populations were found to be spatially structured at larger (> 300km) scales and homogenous at smaller scales, consistent with isolation by distance. Allele frequencies of populations were temporally stable. Genetic analyses suggested greater levels of dispersal than a previous stylet microchemistry study on this species, which reflects the differing sensitivities of the two approaches. Isolation by distance is likely to be more important in determining population structure in organisms with direct development, as species with plallktonic stages are more strongly affected by oceanography and larval behaviour, as demonstrated by previous research on the sympatric Octopus maorum