Sperm choice and sperm competition: suggestions for field and laboratory studies

The recent explosion of research on sperm competition, and the emerging idea that females may control paternity of their offspring via 'sperm choice', raise many methodological questions. One central issue is the role of inbreeding-induced mortality of offspring. We present a theoretical model which makes the relationship between parental relatedness and offspring mortality explicit, and discuss its applicability as a null model of offspring mortality in studies of sperm competition/sperm choice. We also discuss the extent to which partner relatedness may be overlooked in studies of behavioural ecology in natural populations, and the extent to which a failure to mimic crucial aspects of sperm competition scenarios in the wild may limit our ability to make evolutionary inferences from laboratory experiments.