Comparative ecology of a biogeographically heterogeneous Conus assemblage

Abstract

A biogeographically heterogeneous assemblage of tropical Indo-Pacific (IP) and temperate Australian (TA) species of Conus (Mollusca: Gastropoda) on intertidal limestone platforms at Rottnest Island, Western Australia, partitions habitat and food resources very similarly to homogeneous Indo-Pacific congeneric assemblages in tropical regions. The sample of about 400 individuals included nine species. C. dorreensis (TA) was by far the most abundant, averaging 4.2 m⁻² in the densest population. C. sponsalis (IP) ranked 2nd (0.3 m⁻²), and only 3 other species, C. anemone (TA), C. klemae (TA) and C. lividus (IP), appeared in quantitative samples. The rarer species were predominately IP. This study also extends the ranges of 5 IP species southward to include Rottnest Island. The Rottnest Island Conus assemblage resembles those of similar tropical IP habitats with respect to 1, species diversity; 2, population density; 3, size-frequency distributions; 4, types of microhabitats used as daytime refuges; 5, diets primarily of polychaete worms, mainly of the family Eunicidae; 6, positive correlation between predator size and prey size; 7, feeding rates, and 8, resource partitioning, or differential specialization on microhabitat types and prey taxa. Previously demonstrated only within the IP region, these ecological patterns and relationships are more geographically widespread than was formerly known.