| Professional | Research | Publications |

 

 

Pictures above: left - Arabian babbler (Turdoides squamiceps) female on sentinel duty (courtesy of Vladimir Khazin); center - mating in the bean beetle (Callosobruchus maculatus) (courtesy of Fleur de Crespigny); right - mating in the 'family' spider (Stegodyphus lineatus) (courtesy of Trine Bilde).

 

 

 

 

 

 

Diet affects both lifespan and reproduction leading to the prediction that the contrasting reproductive strategies of the sexes should result in sex-specific effects of nutrition on fitness and longevity and favour different patterns of nutrient intake in males and females. However, males and females share most of their genome and intralocus sexual conflict may prevent sex-specific diet optimization. In our recent paper (see Publications) we show thatboth male and female longevity were maximised on a high-carbohydrate low-protein diet in field crickets Teleogryllus commodus, but male and female lifetime reproductive performance were maximised in markedly different parts of the nutrient intake landscape.

 

Given a choice, crickets exhibited sex-specific dietary preference in the direction that increases reproductive performance but this sexual dimorphism in preference was incomplete with both sexes displaced from the optimum diet for lifetime reproduction. Sexes are, therefore, constrained in their ability to reach their sex-specific dietary optima by the shared biology of diet choice. Our data suggest that sex-specific selection has thus far failed fully to resolve intralocus sexual conflict over diet optimization. Such conflict may be an important factor linking nutrition and reproduction to lifespan and ageing.

 

 

 

 

The great body of my research includes the causes and consequences of conflicts of interest between the sexes. Such conflicts can generate "arms races" between the sexes, known as sexually antagonistic coevolution (SAC). SAC is now recognized as a central process in evolution with potential to shape various interactions between the sexes. I am interested in the role of SAC in the maintenance of genetic variation in populations, as well as the relative importance of direct versus indirect selection in male-female coevolution - the question that is at heart of the contemporary research on SAC.

 

Male adzuki bean beetle, Callosobruchus chinensis, makes use of this extremely long intromittent organ to transfer his ejaculate to female during mating. Courtesy of Johanna Ronn.

 

 

Understanding ageing is one of the major challenges in biology. The main theory for the evolution of aging holds that genes with beneficial effects early in life become established despite mildly deleterious effects later in life. It has very recently been suggested that sex-specific antagonistically pleiotropic genes may contribute to the evolution of senescence, and this idea integrates the classical models for the evolution of ageing with recent conceptual advances in evolutionary biology. Together with my collaborators, I am using an experimental evolutionary approach to address these questions in different species of bean beetles .

 

We used populations of bean beetle,Acanthoscelides obtectus, selected for reproduction at an early or late age, to show that males evolve to affect senescence in females in a manner consistent with the genetic interests of males. "Late" males evolved to decelerate senescence and increase the lifespan of control females, relative to "early" males. Our findings demonstrated that adaptive evolution in one sex may involve its effects on senescence in the other, showing that the evolution of optimal life-histories in one sex may be either facilitated or constrained by genes expressed in the other.

 

A. obtectus emerging from the seed. © Dennis Kunkel Microscopy, Inc. www.denniskunkel.com).

 

In a different study, we used experimental evolution, to test whether removal of sexual selection leads to the evolution of rapid senescence in the bean beetle Callosobruchus maculatus.

 

Males of C. maculatus, have spines on their intromittent organs that puncture female reproductive tract during the copulation. Courtesy of Johanna Ronn.

  

 

The mitochondrial genome was once considered as a silent bystander in the evolutionary processes. Yet there is increasing evidence that mtDNA mutations play an important role in the evolution of ageing. This can have a profound effect on individual fitness and population viability, which explains the contemporary increase of interest in variation in mtDNA among evolutionary ecologists. In my research, I asked whether the within-population variation in the cytoplasmic genome may contribute to the evolution of ageing by employing mitochondrial lines of Drosophila melanogaster, sampled from a single panmictic population and controlled for the nuclear genome by backcrossing. Our data supports the important role of mtDNA in the ageing process.

  

The evolution of female mating with multiple males (polyandry) is at heart of the current research on sexual selection. Polyandry is costly for females yet almost ubiquitous in nature, which is paradoxical. However, multiple mating provides females with the possibility to apply post-copulatory mechanisms of sperm choice. One way for polyandrous females to mitigate the costs of polyandry is to bias paternity towards preferred males. In collaboration with Dr. Trine Bilde (Aarhus University, Denmark), I investigate this possibility in a polyandrous 'family' spider Stegodyphus lineatus where large males are more successful in mating with already mated females.

 

Sex differences in lifespan are common in different taxa, including primates, but not well understood. Theory and comparative evidence suggest that differential costs of reproduction between the sexes may explain the differences in sex-biased mortality across large taxonomic groups. The level of sex-specific reproductive effort may thus affect the difference in lifespan across populations. Modern humans (Homo sapiens), generally show the typical mammalian pattern of male-biased mortality. I investigated whether the differences in female birth rates between countries affect the sex difference in lifespan. I used the data on male and female lifespan and female birth rate in different countries from publicly available databases, while controlling for geographic and economic factors. The analysis (to be published in Evolution and Human Behaviour) suggests that female birth rate explains 17% of the variation in relative sex differences in lifespan across countries. These data suggest that a simple biological factor - female birth rate - may explain a significant part of the variation in sex differences in lifespan across human populations.