Temperature and host species affect nuptial gift size in a seed‐feeding beetle

Abstract

1. In many insects species, males contribute large nutritional gifts to females during mating, generally as seminal fluids (ejaculates) or spermatophores. These nuptial gifts can affect both male and female fitness, and can mediate selection on male body size. However, it is unclear how environmental variables, such as temperature and diet, affect gift size and the consequences of gift size for male and female fitness. 2. We examine how temperature and rearing host affect male nuptial gift size (both total ejaculate size and the proportion of a male's mass allocated to his seminal fluids), and the relationship between gift size and female reproduction, in two populations of the seed-feeding beetle Callosobruchus maculatus . 3. Males reared at lower temperature (20 ° C) produced substantially larger ejaculates than males reared at higher temperatures (25, 30 and 35 ° C). However, males allocated a smaller proportion of their body mass to their ejaculate at the lowest temperature compared with other temperatures. This effect of temperature on male allocation to their ejaculates mirrored the effect of temperature on female body size -male ejaculate size remained a relatively constant proportion of their mate's body mass across temperatures. 4. Rearing host also affected male ejaculate size but the magnitude and direction of the host effect differed between populations. 5. Rearing temperature affected the relationship between male body mass and ejaculate size. Temperature also affected the relationship between female body mass and fecundity. The relationship between male body mass and ejaculate size was significantly lower when beetles were reared on cowpea than when beetles were reared on azuki or mung. 6. We found no evidence that male body size or nuptial gift size affected female fecundity in either population of C. maculatus . We thus propose that the effect of nuptial gift size on male fitness is through a reduction in female mating frequency and thus increased paternity for males producing larger nuptial gifts.

Sex Differences in Phenotypic Plasticity Affect Variation in Sexual Size Dimorphism in Insects: From Physiology to Evolution

“…Fecundity selection on females and sexual selection on males are likely the major sources of selection favoring larger size in insects. Larger males often have increased mating success due to male-male competition or female choice (3) and may increase female fecundity via larger nuptial gifts (61). Larger females generally have greater fecundity and often produce larger offspring (32, 60, 72, 95).…”

Diet affects male gonad maturation, female fecundity, and larval development in the granivorous ground beetleAnisodactylus punctatipennis

“…In some insect species, diet affects ejaculate size and quality (e.g. Simmons & Parker, 1992;Fox et al , 2006 ). Simmons & Parker, 1992;Blay & Yuval, 1997;Droney, 1998 ), which can have large effects on both male and female fitness in various ways ( Simmons, 2001 ).…”

Male inbreeding status affects female fitness in a seed‐feeding beetle

“…Male seed beetles produce large nuptial gifts (Fox et al. , 2006b), materials from which are incorporated into eggs (Huignard, 1983; Boucher & Huignard, 1987).…”

“…Inbred beetles have higher larval mortality and take longer to develop to maturity, and inbred females have shorter adult lifespan and reduced fecundity compared to outbred beetles. Female survival and reproduction are also affected by the biology of their mate; male genital spines (Edvardsson & Tregenza, 2005), nuptial gifts (Fox et al. , 2006b; Ronn et al.…”