Topics: Sex Ratios of Offspring Are Typically Balanced, but They

Essay

Topics: Sex ratios of offspring are typically balanced, but they can be modified by natural selection; mating systems describe the pattern of mating between males and females.
You discover a new species of wasp with females that lay their eggs inside tree branches. Although the tree material is not a good source of nutrients, the offspring are well protected and are seldom consumed by predators. After the eggs hatch, only the females possess the mouthparts needed to chew through the wood and escape. All of the males die in the nest. However, because the wasps cannot digest and obtain nutrients from the wood, the young females must obtain the strength necessary for eating their way out of the branch by ingesting spermatophores (small packets containing sperm and nutrients) that each male releases in the nest. These spermatophores also fertilize the females. Once a male releases his spermatophore, he dies. Although the spermatophores contain nutrients, the likelihood that a female will escape the nest is highly positively correlated with the number of spermatophores that she ingests.
In this wasp species, would you predict a sex ratio bias? Explain why or why not. Would this mating system be classified as promiscuity, polygyny, polyandry, or monogamy?