AbstractThe Parastacidae is a family of freshwater crayfish restricted to the southern hemisphere, reaching its highest diversity in Australia, specifically the southeastern mainland and Tasmania. There are major knowledge gaps in relation to the diversity and phylogenetic relationships of burrowing species in southeastern Australia including the speciose genus Engaeus. This study examines aspects of the phylogeography and evolutionary history of burrowing crayfish species in southeastern Australia at a range of evolutionary scales.
The first research chapter focuses at the intraspecific phylogeographic level by examining patterns of genealogical variations in the widespread Engaeus sericatus using mt16S rDNA sequences to investigate the influence of historical sea level changes on the diversification of this species. This study presents a novel integration of GIS and phylogeography within an NCPA framework by reconstructing ancient shorelines and river drainages and discovers that palaeodrainages and local geomorphological effects have influenced geographical diversification of this species.
The second research chapter examines deeper intra- and inter-generic perspectives focusing on the genera Geocharax and Engaeus and tests existing biogeographic hypotheses using 16S sequences. Gramastacus and Tenuibranchiurus are included in the analyses. Geocharax and Gramastacus are monophyletic genera. Geocharax contains two additional cryptic species and Gramastacus containing one additional species. Engaeus is non-monophyletic with E. lyelli most likely representing an undescribed genus.
The third research chapter adds nuGAPDH to the 16S alignment and increases the taxon sampling to test a priori phylogenetic hypotheses. The analysis strongly supports iv the inclusion of Engaewa in the lineage containing Engaeus, Geocharax, Gramastacus and Tenuibranchiurus and that generic-level diversification among these genera coincides with the mid Miocene aridification. Overall, the results of this thesis make a significant contribution to the understanding of parastacid diversity through the discovery of cryptic diversity at generic and species levels and by establishing new hypotheses of relationships and geographic diversification.
|Date of Award||2008|
|Supervisor||Christopher Austin (Supervisor) & Sarah Smith (Supervisor)|