GENETIC CONSEQUENCES OF RESTRICTED DISPERSAL AND INCEST AVOIDANCE IN A COOPERATIVELY BREEDING WREN

Can restricted dispersal in a family-structured population produce con ditions that favor the evolution of helping behavior by kin selection? To address this question a numerical model of a population of coopera tively breeding stripe-backed wrens (Campylorhynchus nuchalis) was dev eloped. The model incorporated the demography and social dynamics of a natural population under long-term study in Venezuela. Replicated sim ulations followed uniquely labelled copies of alleles for 100 annual c ycles, in order to estimate coefficients of kinship between mates and between helpers and the young they raised in relation to overall level s of inbreeding in the population. The consequences of restricted disp ersal and incest avoidance were investigated, under different rates of migration. The results indicated that close incest occurred too infre quently to influence genetic structure significantly. Restricted dispe rsal, on the other hand, even in combination with relatively high rate s of immigration (10-20%), like those observed in the natural populati on, tended to produce genetically viscous populations. Relatedness bet ween mates was significantly greater than 0, and relatedness among mem bers of different groups decreased with distance. The relatedness betw een mates tended to increase both the relatedness of individuals to th eir own progeny and the relatedness of helpers to the young they raise d. The latter effect predominated, so the genetic consequences of rest ricted dispersal, in relation to the overall level of inbreeding, tend ed to favor the evolution of helping by kin selection. Mutually reinfo rcing consequences of short-range dispersal, on the one hand, and dela yed dispersal, on the other, could thus result in accelerating evoluti on of cooperative breeding. (C) 1995 Academic Press Limited