Regional assessments of inland aquatic biota, determined from compilations of mostly descriptive and distributional data, can reveal information to justify local, regional or even global conservation priorities. In the present study, a regional assessment of the wetlands of the Swan Coastal Plain (SCP), Western Australia, was conducted to test the hypothesis that the relatively recent (in geological terms) formation of the wetlands has yielded relatively homogeneous aquatic assemblages. A compilation of aquatic invertebrate taxa from 18 studies of 66 wetlands has shown a surprisingly rich fauna (considering the comparatively small survey area and the degree of anthropogenic alteration of the SCP). Some of this richness is associated with increased sampling effort and proximity to other wetlands, and the habitat complexity and degree of permanence of the wetlands has contributed to richness, community assemblage composition, rarity and endemism patterns. Although taxonomically rich, local and regional endemism is relatively low compared with other regional assessments. The caves and the springs of the bioregion have a distinctive faunal assemblage; however, the assemblages of surface water wetlands do appear more homogeneous. Although iconic wetlands demand priorities for conservation action, management should be directed at the entire suite of wetlands to ensure wetland ecosystem integrity.