Abstract
Multiple mating allows females to obtain material (more sperm and nutrient) and/or genetic benefits. The genetic benefit models require sperm from different males to fertilize eggs competitively or the offspring be fathered by multiple males. To maximize genetic benefits from multiple mating, females have evolved strategies to prefer novel versus previous mates in their subsequent matings. However, the reproductive behavior during mate encounter, mate choice and egg laying in relation to discrimination and preference between sexes has been largely neglected. In the present study, we used novel and previous mate treatments and studied male and female behavior and reproductive output in Spodoptera litura. The results of this study do not support the sperm and nutrient replenishment hypotheses because neither the number of mates nor the number of copulations achieved by females significantly increased female fecundity, fertility and longevity. However, females showed different oviposition patterns when facing new versus previous mates by slowing down oviposition, which allows the last male has opportunities to fertilize her eggs and the female to promote offspring diversity. Moreover, females that have novel males present called earlier and more than females that have their previous mates present, whereas no significant differences were found on male courtship between treatments. These results suggest that S. litura females can distinguish novel from previous mates and prefer the former, whereas males generally remate regardless of whether the female is a previous mate or not. In S. litura, eggs are laid in large clusters and offspring competition, inbreeding and disease transfer risks are thus increased. Therefore, offspring diversity should be valuable for S. litura, and genetic benefits should be the main force behind the evolution of female behavioral strategies found in the present study.
Highlights
Mating is very costly due to energy consumption, the risks of disease transmission and predation, and injury caused during mating [1,2]
A number of genetic benefits hypotheses have been suggested to explain the evolutionary significance of female multiple mating: 1) good genes – paternally derived genes enhanced the attractiveness of offspring or genes from their parents improved the survival of offspring [8,9]; 2) genetic incompatibility – females can bias paternity and give priority to males with good or more compatible genes to fertilize her eggs [10,11,12,13]; 3) genetic diversity – by increasing genetic diversity within progeny, females guard against future environmental uncertainty [14,15], offspring benefit from enhanced genetic diversity by disease resistance, niche separation [16,17] and inbreeding avoidance [4,18]
Behavioral data on the subsequent night after first mating revealed that females called at a higher rate when novel males were present (Novel) than that of females when previous mates were present (Paired) (ANOVA: F1,18 = 4.89, P = 0.040) (Fig. 1a)
Summary
Mating is very costly due to energy consumption, the risks of disease transmission and predation, and injury caused during mating [1,2]. Both theoretical [3] and empirical (e.g., [4,5]) studies have demonstrated that one copulation is adequate for females to obtain their maximum reproductive success in many insect species. Two categories of hypotheses have been developed to explain the evolutionary significance of female multiple mating: to obtain material benefits and to gain genetic benefits. A number of genetic benefits hypotheses have been suggested to explain the evolutionary significance of female multiple mating: 1) good genes – paternally derived genes enhanced the attractiveness of offspring or genes from their parents improved the survival of offspring [8,9]; 2) genetic incompatibility – females can bias paternity and give priority to males with good or more compatible genes to fertilize her eggs [10,11,12,13]; 3) genetic diversity – by increasing genetic diversity within progeny, females guard against future environmental uncertainty [14,15], offspring benefit from enhanced genetic diversity by disease resistance, niche separation [16,17] and inbreeding avoidance [4,18]
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