Although sexual dimorphism was the inspiration for Darwin’s theory of sexual selection, the fundamental cause of differences between the sexes is still poorly understood. For example, sexual size dimorphism, perhaps the most widespread sexual difference among animals, remains a subject of considerable interest. I am currently testing hypotheses of sexual dimorphism using tree weta and giant weta as model species.

Contrary to our traditional view, male animals can be sperm limited.  Consequently, males should optimally allocate sperm by assessing the strategy adopted by competitors in order to maximize their lifetime reproductive success.  Recent theoretical models of sperm competition predict that males adopting the opportunistic (e.g. sneak male), and apparently less profitable, role should invest more heavily in traits that promote success in sperm competition. More specifically, opportunistic males should compensate for low probability of fertilization by allocating more resources to sperm production (e.g. larger testes), ejaculating greater volumes of sperm during copulation and/or spending longer in copulation than guarder or paired males.

Immune defence and reproduction both play large roles in individual fitness; however, biologists have only begun to examine how these factors interact in an evolutionary context. Because of a limited pool of resources, reproductive effort and immunity should trade-off with an increased investment in reproduction inhibiting immune function. Moreover, given that the sexes possess different optimal reproductive phenotypes, trade-offs between reproduction and immunity should exhibit sexual differences.

Scientometrics is the science of measuring and analysing science, typically by using bibliometrics (measurement of scientific publications). Recently I have addressed the lack of study replication in behavioural ecology, why behavioural ecologists explain so little variation, in even well-studied relationships and, in collaboration with Michael Jennions (ANU), I have analyzed the variation in publication rate among sub-disciplines of evolutionary ecology and examined the utility of a bibliometric (h index) for career assessment.