Variance in female quality, operational sex ratio and male mate choice in a bushcricket

Male bushcrickets, Kawanaphila nartee, exercise mate choice when nutrients are limited. Male mate choice is associated with a female-biased operationa l sex ratio (OSR) that arises from an increased relative paternal investmen t under nutrient limitation. However, increased male choosiness could be at tributable to the fact that females vary more in fecundity, and consequentl y in mate quality, when nutrient limited. Our objective was to experimental ly partition the influences of OSR (male or female bias) and variance in ma te quality (high or low) and to assess their relative influence on the inte nsity of mate choice by male bushcrickets. Female quality was manipulated b y controlled feeding regimes that directly affected female fecundity. We fo und that males and females engaged in sexual interactions sooner under a ma le-biased than a female-biased OSR. Males were more likely to reject female s on their first encounter when variance in female quality was high. Howeve r, the effect of quality variance on the total number of rejections during a 4-h observation period was dependent on the perceived OSR. A male's prior experience of variance in female quality did not influence male choosiness . Our observed rates of mate rejection conformed well with those predicted from recent theoretical models of sexual differences in choosiness. In conc lusion, our results show that the opportunity for selection via male mate c hoice is influenced by an interaction between OSR and the variance in mate quality that arises within nutrient-limited populations of females.