Differences in relative fitness among alternative mating tactics might be more apparent than real

[ Males of the striped mouse can follow alternative reproductive tactics, the fitness consequences of which might differ greatly between generations. Image by Ivana Schoepf. ] Schradin, C. & Lindholm, A. (2011) Relative fitness of alternative male reproductive tactics in a mammal varies between years. Journal of Animal Ecology , 80 , 908–917. Two theoretical frameworks guide research on multiple male phenotypes within natural populations. Each scheme recognizes that male polymorphisms vary in the degree to which genotype and environment influence trait expression. Consensus remains elusive, however, on whether average fitnesses must be equivalent and whether genetic differences need exist for polymorphism to persist over time. Schradin and Lindholm address these hypotheses in African four‐striped mice with detailed parentage and body size data. Their results and interpretation call each framework’s predictions into question, but reveal a common truth. Debate might be resolved if researchers agreed on which parameters to measure and compare.