Biogeographic patterns on Kimberley islands, Western Australia

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – Australia’s islands play a significant role in the conservation of its biota. The near-pristine islands along the Kimberley coast of north-western Australia are important natural refuges that have been relatively isolated from many of the threatening processes affecting the adjacent mainland. Between 2007 and 2010, 24 of the largest of these islands were surveyed for non-volant mammals, reptiles, birds, frogs, bats, land snails and vascular plants. To facilitate the setting of conservation priorities, I examined congruence in the biogeographic patterns among these taxonomic groups and related those to island-wide attributes. A high level of congruence in both spatial patterns of species richness and community similarity across most of the taxonomic groups was found. Congruence in species richness was best explained by a strong relationship with island area; while congruence in community similarity was infl uenced by the dispersal ability of taxa. Average annual rainfall and the extent of rock scree (or ruggedness) on an island were also strong correlates of both spatial patterns in community similarity and richness of regional endemics. I also show that this pattern was not explained by richness differences of species between islands alone, but largely due to species replacement among islands. These patterns refl ect the greater diversity of regional endemic species and/or habitat specialists that are restricted to the relatively high rainfall and extensively rocky islands; whereas the drier islands typically support widespread generalists that have distributions that extend into the semi-arid and arid zones. In terms of conservation signifi cance, the largest islands in the most mesic section of the coast are important for their high species diversity, including regional endemics. However, the lower rainfall islands support unique assemblages, and some are also important for their threatened mammal species. The high level of island endemism of the camaenid land snails indicates that all the islands sampled are important in terms of representing their diversity. The results of the survey also support the hypothesis that these islands are microcosms of the adjacent Northern Kimberley mainland with 74% of mammal, 59% of reptile, 70% of frog, 69% of bird and 49% of plant species of the Northern Kimberley bioregion now known on the islands sampled. Future management of the islands requires strategies that minimise the risk of incursions by exotic species and appropriate fi re regimes to preserve habitat quality.

Author(s) L.A. Gibson
Volume
Supplement 81 : Biodiversity values on selected Kimberley islands, Australia
Article Published
2014
Page Number
245

DOI
10.18195/issn.0313-122x.81.2014.245-280