Interactions between body size and mating history influence the reproductive success of males of a tortricid moth, Zeiraphera canadensis

Abstract

The independent and interacting effects of male body size, age, and previous number of matings on (i) spermatophore size and (ii) female reproductive performance were examined in the laboratory using Zeiraphera canadensis Mut. &Free. (Lepidoptera: Tortricidae). Spermatophore size was not influenced by male age, but large males produced larger spermatophores and their size decreased with the number of consecutive matings. The capacity of males to produce spermatophores on successive days was size dependent. Large males produced well-defined spermatophores over five consecutive copulations, whereas small males were no longer able to produce a discernible spermatophore by the fourth mating. Male body size and mating history, independently or in combination, did not affect female fecundity or longevity despite their influence on spermatophore size, suggesting that potential spermatophore-derived nutrients were not utilized for reproduction or somatic maintenance. However, the number of previous matings on consecutive days influenced successful insemination as well as the receptivity of successfully inseminated females to additional matings. Moreover, the influence of multiple male matings on insemination success and mating receptivity was also size dependent. After several consecutive copulations, small males were less likely to successfully inseminate females and "switch off" the females' mating receptivity than large males. The size-dependent decline in ability to inseminate and switch off females, independent of spermatophore size, suggests that small males were more limited than large ones in their capacity to produce accessory gland secretions other than those required for spermatophore construction. Large Z. canadensis males may experience higher reproductive success than small ones by inseminating more females over consecutive evenings and leaving fewer females receptive to remating.