Evolution of conditional male dimorphism

Currently, my main research interest is male dimorphism, a phenomenon that often reflects alternative reproductive tactics among males: the large male morphs typically guard females or reproductive territories and have more elaborate weaponry; the small male morphs sneak copulations and have reduced weaponry. Male dimorphism is particularly common among arthropods, and usually results from a polyphenism: the differential expression of alternative phenotypes from a single genotype depending upon environmental conditions. I have been investigating several questions about polyphenic male dimorphism with experiments using mites, harvestmen, and dung beetles.

A major male of the gonyleptid harvestman

Arthrodes xanthopygus

Phenotypic plasticity and polyphenisms

My interest in the evolution of alternative mating tactics and male dimorphism led me into the topic of phenotypic plasticity. Therefore, in the last 5 years, part of my research has focused on threshold traits (polyphenisms), usually from a quantitative genetics perspective. On the left, the environmental-threshold model: a hypothesis to explain threshold traits such as earwigs' forceps.

Behavioural ecology in insects and arachnids

Moreover, I am also interested in the behavioural ecology of insects and arachnids, especially their reproductive biology. My research includes the evolution of parental care, mating systems, sperm competition, and social behaviour. On the right, a female of the gonyleptid harvestman Serracutisoma proximum laying eggs.

A multiple-male amplexus of the quacking frog (Crinia georgiana) with four males competing for the fertilization of eggs from a single female

Pre and post-copulatory sexual selection

During the 2013-2014 period, I was employed under the ARC Discovery Project entitled "Testing new theoretical models of sperm allocation: does competition for mates compromise male fertility?", by professors Leigh Simmons and J. Dale Roberts. My main role in this project was to investigate the trade-off between pre and postcopulatory investment in Crinia georgiana, a frog with simultaneous polyandry in the form of multiple-male amplexus. Males of this species vary greatly in their investment in arm muscles, which are used in male-male fights and in the multiple-male amplexi. Interestingly, males also present alternative reproductive tactics (calling vs sneaking) associated with the girth of their arms.

Bulb mites and artificial selection

In 2015 I started a three year fellowship from the Australian Research Council, the competitive Discovery Early Career Researcher Award (DECRA). This fellowship funded my research project entitled “The development, ecology and evolution of alternative phenotypes”, which included experiments on conditional male dimorphism in dung beetles, bulb mites and harvestmen (arachnids from the order Opiliones). A large part of the project involved an artificial selection experiment in bulb mites, which showed that selection imposed in one male morph generates correlated evolutionary responses in the other morph (see my papers under "Publications"). My DECRA has ended in December 2017, but I still have my selection lines (now at Macquarie University) and I am using them in creative ways to study the effects of selection on weapons on other naturally and sexually selected traits.

A fighter (left) and a scrambler (right) male of the male dimorphic bulb mite Rhizoglyphus echinopus. Note the thickened third pair of legs (red arrow) of the fighter.

Sydney Funnel-web spiders

In 2019 I started a collaboration with Danilo Harms (University of Hamburg), Braxton Jones (now a PhD student at the University of Sydney), the Australian Museum and the Australian Reptile Park. This large team is tackling a range of interesting questions about the popular and feared Sydney funnel-web spider. We know surprisingly little about this species, and I specifically want to get a better understanding of males' movements during the breeding season — how far do they go? what affects their mobility? Answering these questions is relevant for keeping the public safer and better informed about the risks of having males walking into people's houses and causing accidents. Moreover, the project also aims to find out whether A. robustus is only one species, or a collection of 2 or more very similar cryptic species, as there is some evidence for the latter. The genetics will reveal that. This project is supported by both Australian Geographic and National Geographic — meaning that I'm living my dream of becoming an explorer for one of these societies!