Open Collections

Protein content of spermatophores and male investment strategies in nectar-feeding butterflies

University of British Columbia

The objective of this thesis was to investigate how male investment in ejaculates, both in terms of nutritional quality and sperm content, varies with the mating system in nectar-feeding butterflies. Protein content was determined using a dye-binding protein assay (Bio-Rad), and used as a measure of ejaculate quality. A comparative study on 11 species of butterflies from 2 genera was conducted to examine how male nutrient investment varied with female mating frequency (polyandry). Male ability to produce more than one large nutritious ejaculate was evaluated using three species of pierid that varied in the degree of polyandry. The cost of ejaculate production, in terms of recuperation time, was investigated in Pieris napi and Pieris rapae, two polyandrous species of pierid. Lastly, the effect of male body size on sperm precedence was examined using P. napi. I found that relative to males in monandrous systems, males in polyandrous systems transferred larger first ejaculates that contained proportionally more protein. Furthermore, the degree of polyandry had a substantial effect on the reproductive performance of males. My results suggest that male capacity to produce large, nutritious ejaculates is limited in monandrous species, and that males in polyandrous systems are better adapted to mating more than once. The interval between first and second matings by P. napi and P. rapae males had a strong effect on the size and protein content of second ejaculates. Copulation durations were longer and ejaculates smallest in matings involving recently mated males, suggesting that ejaculates are costly for males to produce. In virgin matings by Pieris napi males, ejaculate mass was positively correlated with male body mass but protein content was not. The effect of male body size was investigated in doubly mated P. napi females using normal and irradiated males. Relative male size had a significant effect on paternity. Larger males obtained the majority of fertilizations regardless of female mating status (virgin or nonvirgin). The effect of male body size on the proportion of offspring sired supports the hypothesis that sperm competition has played a major role in the evolution of ejaculate size.

Thesis/Dissertation

application/pdf

2009-03-17

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

http://hdl.handle.net/2429/6122

Zoology

University of British Columbia

UBCV

DSpace