Present address: Département de Biologie, Université de Sherbrooke, Sherbrooke, J1K 2R1, Québec, Canada.
An experimental test of the causes of small-scale phenotypic differentiation in a population of great tits
Article first published online: 23 SEP 2005
Journal of Evolutionary Biology
Volume 19, Issue 1, pages 176–183, January 2006
How to Cite
SHAPIRO, B. J., GARANT, D., WILKIN, T. A. and SHELDON, B. C. (2006), An experimental test of the causes of small-scale phenotypic differentiation in a population of great tits. Journal of Evolutionary Biology, 19: 176–183. doi: 10.1111/j.1420-9101.2005.01004.x
- Issue published online: 23 SEP 2005
- Article first published online: 23 SEP 2005
- Received 28 February 2005; revised 14 May 2005; accepted 17 May 2005
- evolutionary differentiation;
- fledging mass;
- genotype–environment interaction;
- great tits
Phenotypic differentiation between populations is thought to occur mainly at spatial scales where gene-flow is restricted and selection regimes differ. However, if gene flow is nonrandom, dispersal may reinforce, rather than counteract, evolutionary differentiation, meaning that differences occurring over small scales might have a genetic basis. The purpose of this study was to determine the cause of differences in mean phenotype between two parts of a population of great tits Parus major, separated by <3 km. We conducted a partial cross-fostering experiment between two contrasting parts of this population to separate genetic and environmental sources of variation, and to test for gene–environment interaction. We found strong environmental effects on nestling size, mass and condition index, with nestlings reared in a low density part of the population being larger, heavier and in better condition, than those in a high density part, irrespective of their origin. In addition, we found smaller, but significant, differences in nestling condition and shape associated with the areas that birds originated from, suggesting the presence of genetic differences between parts of this population. There was no evidence of gene–environment interaction for any character. This experiment is thus consistent with previous analyses suggesting that differences between parts of this population had evolved recently, apparently due to phenotype-dependent dispersal, and indicates that population differentiation can be maintained over small spatial scales despite extensive dispersal.