Abstract
Males contributing costly investments to offspring (i.e., paternal care or nuptial gifts) are expected to have high confidence of paternity and to avoid cuckoldry. While studies of parental care have provided support for this hypothesis, paternity may be more uncertain in systems where males feed each mate. In contrast to many male-care systems, where mating co-occurs with each oviposition giving males control over insemination, in nuptial gift systems (mostly arthropods that feed mates with prey or glandular secretions) mating is separated from egg-laying so that males typically compete more with rivals for fertilizations. Given the large investments these males contribute to offspring, and long refractory periods that limit their ability to gain fitness from frequent copulations, there should be strong selection to avoid cuckoldry, especially complete paternity failure. Further, because females evolve to mate frequently in systems with competition for male-supplied nutrition, males may be 1) unable to avoid sperm competition by mating with virgins and 2) less likely to benefit from behaviours that prevent female remating or depend on last male sperm precedence. Thus, paternity sharing, in which males are not excluded from siring offspring completely, is an expected outcome of sperm competition in these systems. Using wild-caught females in two species (an orthopteran and a dipteran), in which sexually selected females compete for important male nuptial gifts, we examined paternity patterns and compared them to findings in other insects. Using microsatellite analysis of offspring and sperm stores, we found evidence of shared paternity in both study species, and there were very few males failing to sire offspring. Although paternity was not equal among sires, our estimates of paternity bias were similar to other insect species with valuable nuptial gifts and contrasted with patterns in gryllid cricket species where males supply little more than sperm and are frequently excluded from siring offspring. Unlike many insects with strong paternity bias, further support for paternity-sharing is the lack of last-male sperm precedence in either of our study species.
Competing Interest Statement
The authors have declared no competing interest.