Secondary sexual traits: Genetic correlations and trade-offs
I have most recently been working with Drosophila bipectinata. We have been investigating a genetic correlation between a secondary sexual trait (sex comb) and traits associated with competitive fertilisation success. We are also studying the sexual conflict over toxic seminal protein transfer from males to females during mating.
(In collaboration with M. Polak, J. Hurtado-Gonzales & J. Benoit. Funded by NSF)
Sexual selection and reproductive isolation in field crickets
My PhD focused on the hybridising field crickets Gryllus bimaculatus and G. campestris. These sister species have overlapping distributions through central Spain, potentially the site of a hybrid zone. I worked with both lab reared and wild caught animals to investigate the reproductive barriers that prevent these species from interbreeding. I have used a combination of approaches and laboratory techniques (e.g phonotactic trials, behavioural assays, CHC analysis, competitive microsatellite PCR, fluorescent staining) to find multiple barriers acting in this system.
(In collaboration with T. Tregenza, R. Rodriguez-Munoz, T. Veen, X. Harrison, A. Bretman, P. d'Ettorre & D. Fisher Funded by ESF)
Males produce a calling song to attract potential mates. These songs differ between species, however females only show weak preference for conspecific song. Read the paper.
Crickets, like many insects, produce pheromones on the surface of their bodies known as cuticular hydrocarbons, or CHCs. The relative amounts of these molecules differ between the sexes as well as between species. Female G. campestris seem to use these pheromonal cues to determine male species identity. Read the paper.
When polyandrous G. bimaculatus females are mated to combinations of conspecific and heterospecific males, they preferentially uptake and store sperm from the conspecific male. Subsequent paternity of offspring is further biased in favour of conspecifc males, such that almost all offspring are pure-bred rather than hybrid, evidence for multiple post-mating barriers to hybridisation in this system. Read the paper.
The number of nuclei present in an egg after a set time period can be used to assess the success of early development. Hybrid eggs are far less likely to start developing, indicating that either heterospecific sperm aren't reaching the eggs, or that fertlised eggs die very early on. Of the eggs that do start to develop, those fertilised by heterospecific males are more likely to die along the way. Read the paper
I have also searched a G. campestris transcriptome for genes for reproductive behaviour. I found around 30 candidate genes, which have been implicated in behaviours associated with courtship and copulation in Drosophila melanogaster.
Copulation failure in flour beetles
Copulations failing to result in the production of offspring are common in Tribolium castaneum, with failure rates of up to 55% reported. By weighing individuals before and after mating, I found that failures are associated with a lack of transfer of sperm to the female. Copulation failure is not affected by the relatedness of mating partners, or the inter-copulation interval experienced by females. Read the paper.
(In collaboration with T. Tregenza. Funded by ESF)