Cyclic habitat displacements during Pleistocene glaciations have induced independent evolution of Tasimia palpata populations (Trichoptera: Tasimiidae) in isolated subtropical rain forest patches
Aim Mechanisms generating biodiversity and endemism are influenced by both historical and ecological patterns, and the relative roles of history vs. ecological interactions are still being debated. The phylogeography of one rain forest-restricted caddisfly species, Tasimia palpata, thought to have good dispersal abilities, is used to address questions about shifts of highland rain forest habitat during Pleistocene glaciations and about their consequences for haplotype composition and distribution. Location Tasimia palpata occurs in highland subtropical rain forest patches, which are separated from one another by lowland dry bush, in south-eastern Queensland, Australia. Methods We sequenced 375 base pairs of the mitochondrial cytochrome oxidase I gene from 169 individuals (20 populations) of T. palpata, mainly from three fragmented subtropical rain forest blocks, revealing 46 haplotypes. Analysis of molecular variance (AMOVA), genetic divergence between populations, nested clade analyses and tests based on coalescent theory were used to analyse phylogeographical relationships among T. palpata populations. Results AMOVA indicates spatial genetic structure between isolated subtropical rain forest patches, with an isolation-by-distance effect. Tests based on coalescent theory suggest a repeated process of population reductions and divergence between isolated rain forests during Pleistocene glaciations as a consequence of habitat constrictions followed by population expansions during interglacial periods when subtropical rain forest expanded. In addition, these results suggest that, prior to the Pleistocene, rain forest and T. palpata had more widespread distributions in this region. Main conclusions Historical rain forest expansion and contraction during the Pleistocene resulted in changes in demography and genetic diversity of T. palpata, as well as in an increase in genetic divergence between populations from different patches of subtropical rain forest. Despite the fact that this caddisfly species was isolated in separate highland rain forest patches at various times during the Pleistocene, there is no evidence of allopatric speciation during the Quaternary, which contrasts with other examples of endemism and high diversity in rain forest highlands.
Journal of Biogeography
Biogeography and Phylogeography