The effect of nuptial gift number on fertilization success in a Hawaiian swordtail cricket

Abstract

In many insects, males transfer nuptial gifts to females prior to, during, or after copulation. Nuptial gifts comprise any form of non-gametic material transfer, such as glandular secretions, prey items, and spermatophores. These gifts can increase male fitness by facilitating copulation or sperm transfer or by promoting the female’s use of the focal male’s sperm. However, when a female mates with multiple males, the relationships between the relative size, number, or quality of nuptial gifts that each male donates and the proportion of offspring that each male sires are unknown in many cases. Here, we assessed these relationships in the Hawaiian swordtail cricket Laupala cerasina. We experimentally manipulated the number of gifts a female received from two male mating partners in sequence, with the first male giving either more, fewer, or an equal number of gifts relative to the second male. We found that there was a significant positive relationship between nuptial gift number and paternity share. In addition, we found considerable first-male sperm precedence, regardless of gift contribution. Finally, offspring from second males tended to be produced later and to be part of larger families. These results show that both nuptial gift number and mating order play important roles in sperm use patterns and fertilization success in this species. SIGNIFICANCE STATEMENT: In many insects, males transfer nuptial gifts (a token, often nutritional, gift) to females prior to, during, or after copulation. In the Hawaiian swordtail cricket Laupala cerasina, males transfer a series of nuptial gifts in the form of spermless spermatophores, to females during courtship. Moreover, males experience sperm competition as females of this species are known to mate multiply. By manipulating the number of gifts transferred, we tested the hypothesis that males who transfer more nuptial gifts achieve higher fitness by fathering more offspring. We found a significant positive relationship between gift number and the proportion of offspring a male sires. In addition, controlling for gift number, the first male to mate with a female achieves more paternity. These results show that both nuptial gift number and mating order affect sperm use patterns and fertilization success in this species.