Reinforcement with multiple mating: Response from Marshall, Arnold and Howard

Abstract

In our recent article in TREE [1xReinforcement: the road not taken. Marshall, J.L. et al. Trends Ecol. Evol. 2002; 17: 558–563Abstract | Full Text | Full Text PDF | Scopus (79)See all References[1], we suggested that the cost of mating with a heterospecific, and thus the strength of selection against hybridization acting upon the individual, is reduced for those individuals that mate multiply and with at least one conspecific relative to individuals that mate once and with a heterospecific. Given the above and assuming that, in multiple mating systems, individuals always mate with at least one conspecific, we inferred that reinforcement would be less likely to occur in promiscuous systems than in monogamous systems. Under this scenario, our inferences about the role of multiple mating, per se, are correct.However, if the above assumption is removed and heterospecific matings are allowed to occur at a given frequency, as in Kisdi's model [2xReinforcement with multiple mating. Kisdi, E. Trends Ecol. Evol. 2003; See all References[2], then there is no a priori reason to predict that reinforcement would be less likely to occur in promiscuous systems. Nevertheless, the individual cost of mating with a heterospecific is reduced if it is preceded, or followed by a conspecific mating. Kisdi's model helps resolve the apparent disconnect between costs at the individual level and the spread of a ‘reinforcement’ allele (e.g. a preference or assortative mating allele) through a population.Kisdi's model and letter [2xReinforcement with multiple mating. Kisdi, E. Trends Ecol. Evol. 2003; See all References[2] also serve to underscore a major inference of our paper; that the interaction between the mating system and pattern of gamete utilization will influence the potential for reinforcement when there is selection against hybridization [1xReinforcement: the road not taken. Marshall, J.L. et al. Trends Ecol. Evol. 2002; 17: 558–563Abstract | Full Text | Full Text PDF | Scopus (79)See all References[1]. In particular, any deviation, regardless of how small, from equal utilization of gametes will affect the possibility of reinforcement under a multiple mating system. If conspecific gamete preference exists (the possibility explored in our paper [1xReinforcement: the road not taken. Marshall, J.L. et al. Trends Ecol. Evol. 2002; 17: 558–563Abstract | Full Text | Full Text PDF | Scopus (79)See all References[1]), reinforcement is less likely to occur. However, if hetero-population sperm precedence occurs (a possibility supported by recent experimental evidence [3xHeteropopulation males have a fertilization advantage during sperm competition in the yellow dung fly (Scatophaga stercoraria). Hosken, D.J. et al. Proc. R. Soc. Lond. Ser. B. 2002; 269: 1701–1707Crossref | PubMed | Scopus (43)See all References[3]), then reinforcement is more likely to occur.