Abstract
In some species where males make no direct contribution to a female’s lifetime reproductive success, females choose mates based on the indirect benefits manifested in their offspring. One trait that may be subject to this sexual selection is immunocompetence (the ability to mount an immune response following exposure to pathogens); however, the results of previous work on its link to male attractiveness have been ambiguous. Herein we examine the life history consequences of mating with males with a history of failure or success in reproductive competitions in Drosophila melanogaster. By examining egg-to-adult survival, body weights, and bacterial loads of offspring reared in either the absence or presence of a bacterial pathogen, we were able to examine whether sire reproductive success was associated with their offsprings’ ability to respond to an immunological challenge and other life history traits. Our results are partially consistent with the predictions of the “immunocompetence handicap hypothesis”: competitively successful males (“studs”) sire male offspring that are better able to handle an immunological challenge than those sired by competitively unsuccessful males (“duds”). However, our assay also revealed the opposite pattern in female offspring, suggestive of the complicating presence of alleles with sexually antagonistic effects on the expression of this important life history trait.
Highlights
In many species where males provide no parental care or other direct resources to their mates, females often exhibit preferences for mates that are “attractive” and of superior intra-sexual competitive ability
Ever since Darwin (1871) proposed the theory of sexual selection to explain the evolution of elaborate display traits in males, biologists have attempted to understand the extent to which the selective pressures produced from differential mating success complement, or conflict, with the pressures resulting from natural selection (Andersson 1994; Arnqvist and Rowe 2005)
By experimentally mating females with males that had been previously assayed as being of relatively high or low sexual attractiveness and competitiveness (i.e., “studs” or “duds”), we were able to measure the cross-generational effects associated with sexual selection
Summary
In many species where males provide no parental care or other direct resources to their mates, females often exhibit preferences for mates that are “attractive” and (or) of superior intra-sexual competitive ability (see Andersson 1994, pp. 124–142). If there is relatively more genetic variation for resource allocation, trade-offs and negative correlations between these life history traits will be revealed (van Noordwijk and de Jong 1986; Houle 1991; Westneat and Birkhead 1998). Genetic variation for allocation may be especially important if the sexes have different optimal levels of investment into immune function and other life history traits (due to sex-specific fitness-maximizing strategies). In cases of sexual conflict, alleles that may be beneficial when expressed in one sex may be maladaptive when expressed in members of the opposite sex (Holland and Rice 1998; Chippindale et al 2001; Pischedda and Chippindale 2006)
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