Our research focuses on the evolutionary ecology of ageing in a broad sense and we employ experimental evolution, nutritional ecology, quantitative genetics, gene expression analyses, RNA interference and experimental pharmacology approaches in a number of classic laboratory model organisms (e.g. nematode worms, seed beetles, fruit flies), as well as field data from long-term studies in birds (the Collared Flycatcher, in collaboration with Lars Gustafsson) and historical human population registry (Utah, USA). Our main research questions are: i) why and how ageing evolves and ii) what determines the variation in longevity and ageing across species, populations and sexes.
Why and how ageing evolves
Ageing – a physiological deterioration leading to reduced fertility and increased probability of death with age – is a nearly universal feature of living organisms. As evolutionary biologists, we focus mostly on the fundamental questions, but many of our projects have strong potential to inform biogerontologists and some of our projects directly stem from the progress in biomedical sciences.
a) The role of condition-dependent mortality in the evolution of ageing
Novel theory suggests that our current understanding of ageing evolution could be incomplete because it does not account for condition-dependence of mortality. This is a long-term project involving experimental evolution in nematodes followed by gene expression analyses of the evolved lines.
b) Slow development as an evolutionary cost of long life
There is a growing appreciation in the field that by focusing on the trade-off between reproduction and adult longevity we unduly overlooked key trade-offs between growth, development and adult longevity. There are at least two major non-mutually exclusive possibilities for why accelerated development to maturity can result in accelerated ageing: 1) increased oxidative stress due to increased metabolism during growth and 2) developmental errors resulting from accelerated growth that impair survival.
c) Evolutionary ecology of ageing in a natural environment
In nature, animals face a highly variable environment that is difficult to fully recreate in the laboratory. In this project, in collaboration with Prof. L. Gustafsson, we are using a unique experimental database, which includes 31 years of data on experimental manipulation of brood size in the wild population of the collared flycatcher, Ficedula albicollis on the island of Gotland, Sweden. Experimental manipulation of early-life conditions followed by a life-long study of survival and reproduction in the wild provides us with the unique opportunity to study the evolutionary ecology of ageing.
d) Evolution of ageing under dietary restriction
We are running a long-term experimental evolution project in fruit flies, which utilises the most successful and cross-taxonomic lifespan-extending treatment ever known – dietary restriction (DR). Despite decades of extensive research, the evolutionary underpinnings of the DR effect on lifespan are still widely debated. Because lifespan extension under DR is accompanied by reduced reproduction, the leading theory – the “disposable soma” theory of aging – suggests that the DR effect is adaptive and results from reallocation of resources from reproduction to somatic maintenance in order to survive periods of famine in nature. We are evolving Drosophila melanogaster fruit flies on classic ‘DR’, ‘standard’ and ‘high’ adult diets in replicate population cages with overlapping generations for 3.5 years to test this theory.
Sex differences in lifespan and ageing
Another line of research involves the origin and evolutionary consequences of sex differences in ageing. Sex differences in lifespan and ageing are ubiquitous across the animal kingdom and represent a long-standing challenge in evolutionary biology. In most species, including humans, sexes differ not only in how long they live and when they start to senesce, but also in how they react to environmental interventions aimed at prolonging their lifespan or decelerating the onset of ageing.
a) Intra-locus sexual conflict over lifespan and ageing
Males and females often have different fitness optima for life-history traits. Because majority of the genes are shared between the sexes, sex-specific selection can be constrained by intersexual genetic correlation resulting in intra-locus sexual conflict (IaSC). We recently showed that multivariate IaSC maintains genetic variation for lifespan in C. maculatus and such genomic conflict reduces fitness of both sexes.
b) The origin of sex differences in ageing
Life-history and sexual selection theories maintain that sex differences in lifespan and ageing evolve as a result of sex-specific reproductive strategies. For example, in many taxa males are hypothesized to adopt a “live fast, die young” strategy by investing relatively more resources into reproduction and less into somatic maintenance than females, but the universality of this claim remains highly debated. We are developing this project in collaboration with laboratory of Dr. S. Immler at the Dept. of Evolutionary Biology, UU.
c) Sex differences in human lifespan
In humans, as in most other mammals, females commonly outlive males. Using unique longitudinal demographic records on 140,600 individuals from the Utah population database, we are studying how the population demography changed during the demographic transition.