Leigh W Simmons

Publications

My research uses both vertebrates and invertebrates to test the predictions and assumptions of theoretical models of sexual selection and life history evolution. I currently hold two ARC Discovery Project grants that fund research into sperm competition and the evolution of multiple mating by females using insects, mice, and frogs as model systems. I am also engaged in research on sexual selection on humans. Collectively, these research programs seek to determine the direction and strength of selection acting on male and female reproductive strategies, and on the morphological and life history traits that contribute to fitness, from the whole organism to its gametes. My lab currently hosts collaborative research programs involving 5 PhD students and 4 postdoctoral researchers, and has hosted research fellows from Sweden, Finland, Spain, Switzerland and the UK. Opportunities are available for researchers at all levels, and I encourage interested individuals to apply under the schemes outlined on the Opportunities page.

Summary of key research programs

	PATERNAL INVESTMENT AND SEXUAL SELECTION \| Typically males compete for access to females who choose among potential mates. Sexual selection thus favours the evolution of secondary sexual traits in males. It is thought that this direction of sexual selection arises because greater female investment in reproduction makes them a limited resource over which males must compete. I have used a species of bushcricket endemic to Western Australia to test parental investment theory. In this model system males invest in reproduction by feeding the female at mating. My work showed that male investment can often exceed female investment resulting in a reversal in the direction of sexual selection, offering the first empirical support for theories on the control of sexual selection.
	EVOLUTION OF SEXUAL SIGNALS \| Field crickets are excellent model organisms for examining the evolution of male sexual signals and female preferences. In collaboration with Marlene Zuk, I have found that female Teleogryllus oceanicus prefer males with songs that have a longer long chirp element. On the Hawaiian Islands, males are subject to predation by an acoustically orienting parasitoid fly, that also prefers songs with longer long chirp elements. Opposing selection pressures on these islands appears to be associated with greater phenotypic variation in male songs that remained after 5 generations of common-garden breeding, indicating that geographically isolated populations have diverged genetically for song traits. We are extending our research to an analysis of courtship song.
	SPERM COMPETITION \| We are using within species studies and comparative analyses to determine the effects of sperm competition on male investment into sperm production. We are exploring population variation in sperm competition risk and intensity, and how this variation effects testis size and ejaculate quality, using both frogs (Crinia georgiana), and feral house mice as model systems. Our work on dung beetles in the genus Onthophagus is examining how among species variation in the frequency of males adopting the alternative mating tactic of sneaking influences testis size, both within and between species. Finally, with Melissa Thomas I am exploring how male crickets adjust their ejaculate expenditure to current risk and intensity of sperm competition, and the cues they use in risk assessment.
	THE EVOLUTION OF GENITAL MORPHOLOGY \| Male dung beetles have a series of genital sclerites on the aedeagus, variation in the size and shape of which influences competitive fertilization success. Our quantitative genetic studies of size and shape variation suggest low levels of genetic variance in individual sclerites, but functional integration of the sclerites may provide enough variation in multivariate trait space on which selection can act. Together with Paco Garcia-Gonzalez and Clarissa House, I am examining how genital sclerites respond to the relaxation of sexual selection via enforced monogamy. And with Michael Werner how these sclerites interact with the female genital tract.
	SPERM EVOLUTION \| Comparative studies across Australian frogs support the hypothesis that sperm competition favours the evolution of elongated sperm tails. Work with Dale Roberts and Martin Dziminski aims to examine how sperm motility and longevity vary with sperm morphology within and among species. I am also exploring with Stuart Humphries and Jon Evans, on how variation in sperm morphology influences sperm performance and competitive fertilization success. Work with crickets suggest that the production of high quality sperm may be costly for males in that it appears to trade off against bacterial immunity. With Damian Dowling I am currently exploring the mechanisms underlying this potentially important life history trade off.
	THE EVOLUTION OF FEMALE MATING BEHAVIOUR \| My work with field crickets is testing intrinsic sire and genetic incompatibility models for the evolution of polyandry. This collaborative work with Paco Garcia-Gonzalez, suggests that females may well gain intrinsic benefits from sires, but that these benefits need not be transmitted via genes per se, but rather via heritable environments or indirect genetic paternal effects. Our current work is exploring the mechanisms by which paternal effects influence offspring viability in the cricket system, using a white eye morphological marker to track paternity.
	SEXUAL SELECTION ON HUMANS \| I have extensive research collaborations with Gillian Rhodes in the School of Psychology. Our research is examining the roles of facial traits, such as masculinity/ femininity and symmetry in perceptions of attractiveness. We are attempting to determine whether traits that are perceived as attractive are indicators of mate quality, and whether preferences and traits are coevolved. My research on sperm competition also extends to humans. We have shown that men show considerable phenotypic plasticity in semen quality, increasing sperm motility when presented with cues of sperm competition. Current research is exploring the mechanism by which semen quality is adjusted.

Current Funding

ARC Federation Fellowship (2004-2009). The evolution of female mating frequency and its consequences.

ARC Discovery Project (2005-2009). Sperm competition and the evolution of ejaculates (with Dale Roberts)

West Australian Centres of Excellence in Science and Innovation Program (2005-2009).

ARC Discovery project (2007-2009). Sperm competition and sexual selection in insects.

Postdoctoral Research Associates

Melissa Thomas | Marianne Peters | Renee Firman | Magdalena Nystrand | Michael Werner

Research Students

Michael Young | Nicola Watson | Janine Wojcieszek | Stephen Robinson | Bruno Buzatto

External collaborators

NINA WEDELL | Centre for Evolution and Conservation, University of Exeter, UK | Sexual conflict and the evolution of nuptial feeding

TOM TREGENZA | Centre for Evolution and Conservation, University of Exeter, UK | On the evolution of polyandry in crickets

DAMIAN DOWLING | Monash University | On the evolution of life-history trade-offs and the role of ROS in postcopulatory sexual selection

DOUGLAS EMLEN | University of Montana, USA | On the evolution and development of horns in Onthophagine dung beetles

MICHAEL POLAK | University of Cincinatti, USA | On the evolution of sex combs in Drosophila

	PATERNAL INVESTMENT AND SEXUAL SELECTION \| Typically males compete for access to females who choose among potential mates. Sexual selection thus favours the evolution of secondary sexual traits in males. It is thought that this direction of sexual selection arises because greater female investment in reproduction makes them a limited resource over which males must compete. I have used a species of bushcricket endemic to Western Australia to test parental investment theory. In this model system males invest in reproduction by feeding the female at mating. My work showed that male investment can often exceed female investment resulting in a reversal in the direction of sexual selection, offering the first empirical support for theories on the control of sexual selection.
	EVOLUTION OF SEXUAL SIGNALS \| Field crickets are excellent model organisms for examining the evolution of male sexual signals and female preferences. In collaboration with Marlene Zuk, I have found that female Teleogryllus oceanicus prefer males with songs that have a longer long chirp element. On the Hawaiian Islands, males are subject to predation by an acoustically orienting parasitoid fly, that also prefers songs with longer long chirp elements. Opposing selection pressures on these islands appears to be associated with greater phenotypic variation in male songs that remained after 5 generations of common-garden breeding, indicating that geographically isolated populations have diverged genetically for song traits. We are extending our research to an analysis of courtship song.
	SPERM COMPETITION \| We are using within species studies and comparative analyses to determine the effects of sperm competition on male investment into sperm production. We are exploring population variation in sperm competition risk and intensity, and how this variation effects testis size and ejaculate quality, using both frogs (Crinia georgiana), and feral house mice as model systems. Our work on dung beetles in the genus Onthophagus is examining how among species variation in the frequency of males adopting the alternative mating tactic of sneaking influences testis size, both within and between species. Finally, with Melissa Thomas I am exploring how male crickets adjust their ejaculate expenditure to current risk and intensity of sperm competition, and the cues they use in risk assessment.
	THE EVOLUTION OF GENITAL MORPHOLOGY \| Male dung beetles have a series of genital sclerites on the aedeagus, variation in the size and shape of which influences competitive fertilization success. Our quantitative genetic studies of size and shape variation suggest low levels of genetic variance in individual sclerites, but functional integration of the sclerites may provide enough variation in multivariate trait space on which selection can act. Together with Paco Garcia-Gonzalez and Clarissa House, I am examining how genital sclerites respond to the relaxation of sexual selection via enforced monogamy. And with Michael Werner how these sclerites interact with the female genital tract.
	SPERM EVOLUTION \| Comparative studies across Australian frogs support the hypothesis that sperm competition favours the evolution of elongated sperm tails. Work with Dale Roberts and Martin Dziminski aims to examine how sperm motility and longevity vary with sperm morphology within and among species. I am also exploring with Stuart Humphries and Jon Evans, on how variation in sperm morphology influences sperm performance and competitive fertilization success. Work with crickets suggest that the production of high quality sperm may be costly for males in that it appears to trade off against bacterial immunity. With Damian Dowling I am currently exploring the mechanisms underlying this potentially important life history trade off.
	THE EVOLUTION OF FEMALE MATING BEHAVIOUR \| My work with field crickets is testing intrinsic sire and genetic incompatibility models for the evolution of polyandry. This collaborative work with Paco Garcia-Gonzalez, suggests that females may well gain intrinsic benefits from sires, but that these benefits need not be transmitted via genes per se, but rather via heritable environments or indirect genetic paternal effects. Our current work is exploring the mechanisms by which paternal effects influence offspring viability in the cricket system, using a white eye morphological marker to track paternity.
	SEXUAL SELECTION ON HUMANS \| I have extensive research collaborations with Gillian Rhodes in the School of Psychology. Our research is examining the roles of facial traits, such as masculinity/ femininity and symmetry in perceptions of attractiveness. We are attempting to determine whether traits that are perceived as attractive are indicators of mate quality, and whether preferences and traits are coevolved. My research on sperm competition also extends to humans. We have shown that men show considerable phenotypic plasticity in semen quality, increasing sperm motility when presented with cues of sperm competition. Current research is exploring the mechanism by which semen quality is adjusted.

Centre for Evolutionary Biology

Leigh W Simmons