Phylogeography of two Australian species of funnel web spider (Araneae: Mygalomorphae: Hexathelidae) in Tallaganda State Forest, New South WalesThis article is part of a larger document. View the larger document here.
Decomposing logs are habitat for invertebrate species occupying a range of ecological niches. A collaborative research project is examining patterns of genetic endemism among saproxylic (dependent on decaying wood) invertebrates across the Tallaganda region of New South Wales, Australia. An earlier study of an unnamed species of 'giant' Collembolon revealed strong population structuring suggesting that the saproxylic habitat has been a major factor influencing the evolution and speciation of some invertebrates. Two species of funnel web spiders, one in each of the genera Hadronyche and Atrax, are found throughout Tallaganda. Although ecologically similar, the Hadronyche species is log-dwelling whereas the Atrax species is ground burrowing. The niche partitioning of these species allows the separation of species and habitat as contributing factors to the patterns of local endemism found in this system. Hence, the addition of funnel web spiders to this study of log-dwelling invertebrates is central to determining whether the saproxylic habitat induces consistent and predictable outcomes in the population structuring of diverse taxa. The resolution of this issue will permit the establishment of informed conservation priorities for invertebrates in Tallaganda State Forest. The phylogeography of the Hadronyche and Atrax species was investigated using mitochondrial sequence data. We found high levels of sequence divergence (average = 0.088) in Atrax accompanied by spatial structuring of haplotypes, whilst Hadronyche displayed low sequence divergence (0.014) and an absence of any spatial structuring of haplotypes. These findings indicate differential responses of the two species to Quaternary (<0.4Mybp) glacial-interglacial cycling, namely, that Atrax persisted in gully refuges during glacial periods whilst Hadronyche became locally extinct during glacial periods and recolonised the region from outside Tallaganda during the most recent inter-glacial. The differential persistence of Atrax and Hadronyche will require the implementation of management interventions appropriate to each species.