The Biogeography of Queensland's Shallow-water Echinoderm Fauna (excluding Crinoidea), with a Rearrangement of the Faunistic Provinces of Tropical Australia

Abstract

Analysis of Queensland's shallow-water echinoderm fauna reveals that approximately 44 per cent. of the 267 species recorded are confined to Queensland mainland waters and approximately 35 per cent, to Barrier Reef waters; the remainder are common to both environments.

Marked faunistic attenuation with increasing latitude is exhibited by echinoderms occurring on the mainland north of lat. 25ºS, and also by those found on the Great Barrier Reef. In both cases there are few substitutions. South of lat. 25ºS Peronian species occur, but an apparently isolated population of tropical species is found in the Moreton Bay-Caloundra area.

Queensland mainland echinoderms have strong affinities with those of the East Indies. The principal exchange route utilized by mainland species common to both areas seems to be via Torres Strait and the Arafura Sea. The Coral Sea appears to present a barrier to the spread of mainland species to the West Pacific area.

On the other hand Barrier Reef echinoderms have strong ties with those of the latter region. Gene flow between populations of species common to the Barrier Reef and the West Pacific area probably occurs by way of the Coral Sea as a result of the transport of the pelagic larval stages of West Pacific populations by the Pacific south equatorial current. A dearth of coral structures immediately to the west of Torres Strait seems to have prevented the spread of Barrier Reef species to northern Australian waters. However, a few reef echinoderms appear to have entered north-western Australian waters from the East Indies, probably by way of atolls and reef platforms found on the Sahul and Rowley Shelfs.

The echinoderm fauna of north-western Australia contains a large number of endemic species but has marked affinities with those of East Indian and Queensland mainland waters.

The origin of the echinoderm fauna of tropical Australia is discussed in the light of palaeogeographic and zoogeographic findings. It is concluded that the present fauna of the area is derived predominantly from recent East Indian and West Pacific stocks. Also it is postulated that barriers between echinoderm populations present in tropical Australian waters were set up during the Pleistocene falls of sea-level and that this has resulted in the formation of closely allied sympatric and allopatric species.

Available evidence indicates that the Solanderian Province should be restricted to the Great Barrier Reef area and, since Torres Strait does not present a barrier to the dispersal of echinoderms typically found in habitats in which terrigenous sediments predominate, the fauna of Queensland mainland waters and that of the Dampierian Province are grouped together tentatively in a single Tropical Australian Province.