Megan Higgie

Pheromones as a mating trait in cryptic skinks and geckos: Australia has a number of lizard groups in which genetics shows there is high cryptic diversity. Traditional morphology (body size, shape, and colour) cannot distinguish these groups, and we do not yet know their mating traits (e.g., male mating calls in frogs). The mating traits in these cryptic lizard groups are likely to be pheromones. We are focussing on two cryptic lizard groups in north-eastern Queensland: Lampropholis skinks and Heteronotia geckoes. In both these lizard groups genetics has revealed many highly divergent genetic lineages (often species level divergence). These lineages appear morphologically indistinguishable, but in the few cases where hybrid zones are known, there appears to be little interbreeding. Finding and characterizing these pheromones will help us understand the evolution of these groups and resolve their taxonomy.

Reproductive isolation in the Green-eyed Tree frog complex: Two deeply-divergent genetic lineages of Green-eyed tree frog meet in two places in the Wet Tropics behind Cairns. At one contact there has been rapid and strong evolution of prezygotic isolation between the two lineages. One question we are answering is - what were the genomic changes that allowed the rapid evolution of prezygotic isolation at this contact? On the other, at the other contact the two lineages still mate freely, with no hint of prezygotic isolation between the lineages. However, these hybrid matings leave almost no offspring - so why doesn't prezygotic isolation evolve? This is another of the questions we are working on in this system.

Evolution of female preference and male mating signals (pheromones) due to species interactions in a native rainforest Drosophila community: Along the east coast of Australia is a species of fly, Drosophila serrata, which overlaps over some of its geographic distribution with the closely-related species D. birchii and D. bunnanda. We have direct experimental evidence that co-existence with D. birchii causes the evolution of D. serrata male mating signals (pheromones). There is also some evidence that co-existence with D. birchii causes the evolution of female preferences. This makes the D. serrata species complex perfectly placed to study how male signals and female preferences are expressed and evolve in the presence of closely-related species. To do this, the following questions will be answered in the D. serrata system: Does co-existence with other species change the phenotypic expression and evolution of male mating pheromones? Does co-existence with other species cause evolution of female preferences for male pheromones? Are female preferences expressed differently depending on presence/absence of other species? To answer these questions we are using a combination of wild flies and lab-based experimental evolution to measure the evolution of male pheromones and female preferences for those pheromones in different combinations of Drosophila communities.

Species interactions between Frog-biting flies and their frog hosts: In humans and birds, the major vectors of disease-causing parasites are blood-feeding flies; therefore it stands to reason that these may also be a major vector of parasites in frogs. Australian frogs are known to host a diversity of blood parasites, including protozoans, nematodes, and trematodes. However, the diversity of species and habits of frog-biting flies in the tropical rainforest of north Queensland, which has had major declines in frog populations in the recent past, is poorly known. We have recently carried out surveys of stream frogs of the Wet Tropics and found a diverse community of at least 12 species of frog-biting flies. We are currently investigating the host specificity of these frog-biting flies, and whether they are vectors for protozoan (e.g., Trypanosomes), nematode, and trematode parasites in Wet Tropics frog communities.

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