Habitat saturation and the spatial evolutionary ecology of altruism

• Published in: Journal of evolutionary biology Vol. 22; no. 7; pp. 1487 - 1502
• Main Authors: LION, S, GANDON, S
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.07.2009; Blackwell Publishing Ltd; Wiley
• Subjects: Altruism; Animals; Biodiversity; Biodiversity and Ecology; Biological Evolution; demography; Ecology; Ecosystem; empty sites; Environmental Sciences; Evolutionary biology; Habitats; inclusive fitness; kin selection; Life Sciences; Models, Genetic; Population genetics; population viscosity; Populations and Evolution; spatial moment equations; spatial structure; space; evolution of social traits
• ISSN: 1010-061X; 1420-9101
• DOI: 10.1111/j.1420-9101.2009.01769.x

Under which ecological conditions should individuals help their neighbours? We investigate the effect of habitat saturation on the evolution of helping behaviours in a spatially structured population. We combine the formalisms of population genetics and spatial moment equations to tease out the effects of various physiological (direct benefits and costs of helping) and ecological parameters (such as the density of empty sites) on the selection gradient on helping. Our analysis highlights the crucial importance of demography for the evolution of helping behaviours. It shows that habitat saturation can have contrasting effects, depending on the form of competition (direct vs. indirect competition) and on the conditionality of helping. In our attempt to bridge the gap between spatial ecology and population genetics, we derive an expression for relatedness that takes into account both habitat saturation and the spatial structure of genetic variation. This analysis helps clarify discrepancies in the results obtained by previous theoretical studies. It also provides a theoretical framework taking into account the interplay between demography and kin selection, in which new biological questions can be explored.