Biological anachronisms among trapdoor spiders reflect Australia's environmental changes since the Mesozoic

Abstract

Mygalomorph spiders have radiated within Australia in response to geoclimatic changes. Relicts are arbitrarily aged in relation to the geological history of the sites in which they occur and their affinity with microhabitats, which are postulated as mimicking lost Mesozoic and early Tertiary biological landscapes. Against the gee-historical background of the south-west Australian landscape, selected trapdoor spiders from the ten relictual genera are discussed in the context of five focal areas. It is suggested that the taxonomic relicts are biological anachronisms, some of which have persisted relatively unmodified beyond the decline of the landscapes in which they evolved. Some relicts are vulnerable to current hazards including fire while others appear to be able to withstand them through behavioural avoidance. The contrast in survival capabilities is presented between Moggridgea (a Jurassic relict with African affinity) and Neohomogona (a Cretaceous relict which has affinities with eastern Australian mesophytic forest representatives). Conservation of relict mygalomorph tars must (a) take note of the poor dispersal powers of most species (b) maximize retention of favourable microhabitats and (c) recognize their vulnerability to frequent fire.