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Understanding the adaptive significance of variation in female mating behaviour is important because variation may often be favored by selection instead of a change in mean mating behaviour, particularly in variable environments. Females are known to adjust their mating behaviour to a variety of intrinsic and extrinsic factors including nutrition. There are multiple reasons why female behaviours might vary with nutrition; we tested two of these hypotheses: the search cost hypothesis and the direct benefits hypothesis. These hypotheses are not mutually exclusive, but they make contrasting predictions under some conditions. Low nutrition females may have less available energy to support the costs of searching for and sampling males. If sampling males is energetically costly, the search cost hypothesis predicts that low nutrition females will sample fewer males, and because they invest less in sampling, will show less biased mate choices. Alternatively, in species with male provided direct benefits, low nutrition females often benefit more from mating with preferred males. When this is the case, the direct benefits hypothesis predicts that low nutrition females will show stronger preferences for traits correlated with benefit quality and thus show more biased mate choices. The direct benefits hypothesis does not make an obvious prediction about female sampling behaviour, although greater sampling might be required to identify high benefit males. We tested these hypotheses using the variable field cricket, Gryllus lineaticeps. In this species, females receive fecundity benefits from mating with high chirp rate males but only in low nutrition females. We manipulated either diet quantity or quality (protein to carbohydrate ratio) and measured female mate preference. In the diet quality experiment, we also measured sampling behaviour. Diet quality influenced female sampling behaviour: females provided a high quality diet sampled more extensively. However, neither diet quantity nor diet quality influenced female preference. These results partially support the search cost hypothesis. Possible explanations for why diet treatments did not influence female chirp rate preference are discussed.
Advisor: William E. Wagner, Jr.