Research

RESEARCH INTERESTS

My research interests are in the field of evolutionary ecology, especially in ageing and senescence, life-history trade-offs, why these trade-offs might be different between the sexes, and what this means for the evolution of optimal strategies within the sexes. By combining sexual selection theory with life-history theory I aim to better understand the complex relationship between the outcome of sex-specific forces of sexual and natural selection. I am using experimental approaches to study these questions on the phenotypic and genetic level.

UPPSALA

At the Evolutionary Biology Centre of the University of Uppsala, I work on diet effects on life-history and ageing in the fruit fly, Drosophila melanogaster. This includes experiments on the interaction between reproduction and low or high yeast diet, acting on age-dependent mortality and reproductive patterns. Evolutionary trajectories of mortality, including the late life phase, in response to restricted and ‘obese’ diets are my main experimental focus at the moment.

RESEARCH on LIZARDS

I work on the maintenance of the color polymorphism in European wall lizards, Podarcis muralis, and on dispersal strategies in the Common Lizard (Lacerta vivipara) at the Station d’Ecologie Expérimentale du CNRS à Moulis. In 2010, we started to use a new experimental facility, called the Metatron, which consists of 24 cages (10x10m) that are connected by 20 meter long corridors (link to an article in a French newspaper about it). Corridors can be opened and closed individually to create self contained systems of connected cages, and environmental temperature and humidity conditions within cages can be manipulated. These features allow us to test dispersal decisions and strategies of individual common lizards, and how these are affected by interactions with other population members, e.g. through population density, relatedness, or by individual personality traits.

A Methods paper describing this facility and its first experimental data on lizards and butterflies in detail will be out soon!

Metatron at Caumont, 12km from Moulis

RESEARCH on CRICKETS

In the Australian black field cricket, Teleogryllus commodus (Orthoptera: Gryllidae), I can accurately measure a suite of age-dependent behavioural traits. In males, one of these traits is calling effort, which was shown to be under strong positive sexual selection in the wild. Females can be allowed to mate at a given age, and one can measure fecundity or hatching success of their offspring as an estimate of their Darwinian fitness.

Freshly eclosed cricket in the field

Crickets kept in individual containers in a temperature controlled room

Life-history theory provides ultimate causes of why traits like development time, mortality before and after maturation, or fecundity should be shaped in a specific way, depending on what species or even population we look at. It is obvious that lifespan of an organism does affect its fitness. Maximum potential lifespan is not the same in organisms with similar metabolic rates, therefore a purely mechanistic explanation of senescence (‘wear and tear’) is not sufficient. Rates of ageing and senescence should depend on the genetic architecture and the evolutionary forces, mainly selection, that shaped them.

GENETICS

To investigate the genetic architecture underlying age-dependent fitness traits, I performed a quantitative genetic study, where I looked at the genetic correlations between the expression of fitness related traits early and late in life. These kinds of correlations are an important tenet in evolutionary theory of ageing, more exactly in the antagonistic pleiotropy theory. I tested not only for genetic relationships within the two separate sexes, but also between the sexes. This allowed me to evaluate whether sexual conflict is potentially important in constraining sex-specific independent evolution of increased fitness.
More estimates of the effect of intra-locus sexual conflict on ageing in various different taxa are needed to assess the importance and ubiquity of this mechanism for the evolution of sex-specific senescent phenotypes.

DIET

Caloric or, better, dietary restriction is another area I am interested in. Theory predicts that sexually selected traits should be costly, and that does not only mean in an immediate physiological way (e.g. ‘the more a cricket calls, the more energy it spends, the higher its immediate resource intake has to be’), rather with a life-history background of some kind of lifetime balance between acquisition and allocation of resources. So, by combining this assumption with the fact that dietary restriction has been shown to prolong lifespan in a wide range of organisms, I would like to further explore the interface between sexual selection and ageing. Especially in the last two years, evidence for the importance of other characteristics of diet, rather than simply caloric intake, has emerged. Accordingly, to tease out what component or composition of the diet is responsible for a potential increase in longevity, is of major interest.

NATURAL POPULATIONS

Ageing and senescence in animals in the wild has been neglected for a long time, because animals that show senescent signatures were thought not to occur in nature. After studies showed senescence in vertebrate, longer-lived animals, this belief was still held up for short-lived animals like insects. We know now from a handful of studies that invertebrate species can show senescence in their natural environment. In the field cricket, I used capture-mark-recapture methodology to show a senescent increase in mortality rate for males and females. To design and carry out good experiments on ageing in natural populations is very hard, because there are many confounding environmental variables, and because the sample sizes have to be substantial in order to estimate mortality rates or other age-dependent fitness correlates (especially in older age-groups). But most often, study species have evolved for hundreds and thousands of generations in a fluctuating environment where external mortality risk is high, compared to lab environments. This means that testing findings from the lab in the wild can tell us about their adaptive significance, and, vice versa, results from the wild can be used to design experiments in the lab, under more controlled circumstances, allowing to further disentangle the results from nature.

Female cricket in the field, marked with the number 0263

A spider with a cricket as its prey

LINKS to past and present COLLABORATORS

• Alexei Maklakov – Sexual conflict, dietary restriction and ageing
• Ruth Archer – Sexual conflict over ageing in decorated crickets
• Jean Clobert – Consequences of personality traits and dispersal variability on meta-population dynamics; sibling dispersal; maintenance of colour polymorphism
• Don Miles – Physiological performance in lizards
• Susanne Zajitschek – Population effects of inbreeding in guppies
• Rob Brooks- Genetic architecture underlying ageing, dietary restriction, ageing in the wild
• Simon Lailvaux – Sex-effects of mating and diet on performance and demography
• John Hunt – Maintenance of genetic variarion, dietary restriction, demography, ageing
• Urban Friberg – Dietary restriction and ageing
• Anna Lindholm – Ageing in a wild mouse population
• Russell Bondurianky – Ageing in natural insect populations
• Matt Hall- Statistics of non-normal longitudinal data
• Mike Jennions – Dietary restriction, genetic architecture underlying ageing
• Chad Brassil – Mathematical modelling of ageing in natural populations
• Steve Simpson’s lab – Geometric framework of feeding and nutrition