Female animals generally are selective in choosing their mates. To understand how natural selection shapes this kind of behavior, it is important to find out how the mate preferences of females affect the viability of their offspring. The aim of this research is to reveal whether the mate-selection system of female sierra dome spiders functions to test the metabolic capacities of their mates and ultimately to improve the physiological quality of their offspring. The study will illuminate the functions of female preferences by relating physiological and behavioral correlates of male and offspring viability to male success in two modes of female-mediated mating competition. Integrated field and laboratory studies of the spider's mating system will examine the significance of female-incited male-male competition and direct female choice for the acquisition of sires and production of offspring of superior metabolic competence. The spider's sexual-selection system permits these three aspects to be studied independently. Every female's first mate is determined by combat between males, whereas the female herself directly assesses secondary mates. Thus, operation of these modes of selection are temporally separated in the reproductive life of all females. The fighting ability of individual males will be assessed in nature, during fights on female webs. The fighting ability of these individuals will then be related, in the laboratory, to behavioral and metabolic performance before insemination occurs. Data on metabolic performance will be gathered using carbon-dioxide respirometry. The viability implication of differences among individuals in metabolic competence can be deduced from bioenergetic principles, so the relevance of female preferences for male traits that reveal metabolic competence will be clear. The study will provide unusual data addressing "good genes" models of sexual selection, and will provide data needed to tell if it is feasible to study the heritability of physiolog ical competence in this species.
