Extensive upland areas of the
Australian Wet Tropics, such as the
Atherton Tableland, were cleared for farming, largely between 1940 and 1990, leaving many scattered pockets of rainforest surrounded by open pasture. The prickly skink is abundant throughout this area and has become a research subject for studies on the effect of
habitat fragmentation on
genetic diversity,
gene flow and
adaptation in a rainforest dependent species. A 1993
phylogeographic study by Moritz and co-authors using
allozyme electrophoresis and restriction mapping of
mitochondrial DNA (mtDNA) genomes found distinct genetic lineages in populations from the northern and southern wet tropics. These areas are currently connected by a ribbon of rainforest habitat, around wide, known as the
Black Mountain Corridor or BMC, but historical climate modeling suggest that rainforests in the northern and southern wet tropics were separated by around of dry habitats in this area during
Pleistocene glacial climate periods. The late-Pleistocene divergence between these lineages (>0.5% across the mtDNA genome) is an
order of magnitude less than that between the Northern and Southern Wet Tropics but is indicative of emergence from separate
glacial refugia. The larger Wooroonooran refugium maintained higher diversity through the glacial period than the southern Tableland refugium and this natural historical difference in genetic diversity is much greater than any more recent, human induced, effects of forest clearing and fragmentation. Also, Sumner found
relatedness among males within fragments was lower in isolated forest fragments than within continuous forests, possibly reflecting greater dispersal within fragments due to lower habitat quality. However, these relatively slight differences show the difficulty of detecting effects of recent habitat fragmentation in a species with relatively low local population size and limited dispersal. Sumner and co-authors did find other ecological effects of fragmentation; skink abundance was higher in continuous forest sites than in fragments, and was lower in small habitat patches than in large patches, and on average, skinks from fragments were smaller than those from continuous forests. Estimates of population density and dispersal distances from
capture-recapture methods and from genetic data are broadly consistent, with a density varying from 65 - 136 individuals per ha, and a dispersal distance of 404 – 843 m2, respectively. Genetic estimates of relatedness among individuals found under the same log revealed that juveniles tend to stay with their parents for 1–2 years and subsequently disperse to other logs, with marked individuals observed away from their initial capture site over three years. ==References==