Males of many species invest resources in their offspring. For paternal investment to evolve, it must exhibit heritable variation. Using a standard half-sibling quantitative genetic design, we investigated whether genetic variation in male ejaculate size, a trait that affects female fecundity and copulation duration, are present in the seed beetle Callosobruchus maculatus. Ejaculate size was estimated as the amount of weight lost by males during mating. Dams, but not sires, had significant effects on their sons' absolute ejaculate size (both replicates) and relative ejaculate size (proportion of body weight; one replicate only), explaining 21-25% of the variance in absolute ejaculate size and 8-16% of the variance in relative ejaculate size. These results suggest either a large maternal effect on ejaculate size or sex-linkage of loci that affect the variation in ejaculate size. The proportion of phenotypic variance explained by sex-linkage (assuming no maternal effects) was 42 and 49% (ejaculate size) and 17 and 31% (relative ejaculate size) in the two replicates. These results indicate that male paternal investment can respond to selection, and that it may be able to do so especially rapidly because sex-linked traits have the potential to evolve much more quickly than autosomal traits. There were only weak negative correlations between ejaculate size and mating duration, contrary to what we predicted. There was additive genetic variation in female copulation duration, but not in male copulation duration, suggesting that copulation duration is under female control.
|Number of pages||9|
|State||Published - Oct 1998|
Bibliographical noteFunding Information:
This is contribution No. 161 of the Louis Calder Center of Fordham University. This research was funded in part by Fordham University Research Funds. F. J. Messina provided the beetle populations. We thank John Wehr and Berish Rubin for providing space and support to U.M.S. We are grateful to Mary Ellen Czesak for assistance in weighing beetles. Three anonymous referees made helpful comments on this manuscript.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology