| The majority of female animals are polyandrous: offspring within a single reproductive event are sired by more than one male. However, we lack a clear understanding of the ultimate causes of polyandry, and of the male reproductive strategies which have evolved in response to selection occurring after insemination. I addressed these issues by conducting three studies of the Ocoee salamander, Desmognathus ocoee (Family Plethodontidae).; In the first study, I examined the nature of polyandry. I collected D. ocoee clutches from the field and assessed the number of males siring offspring in each clutch. The data suggest that polyandry is common in D. ocoee, but females do not appear to mate multiply in order to increase clutch size (via female benefits) or from pressure by males (sexual conflict).; In the second study, I staged a series of laboratory encounters between a female and two males to investigate the effects of male body size and sperm competition on male reproductive strategies. Paternity data, combined with data from sperm counts (Ch. 3), revealed that large males allocate more sperm per spermatophore, and experience greater insemination and fertilization success, as compared to smaller males. Thus, selection for greater insemination and fertilization success favors the evolution of large male body size in D. ocoee.; In the third study, I examined one aspect of male reproductive strategy, sperm allocation. I counted the number of sperm per spermatophore provided to mated and unmated females by males of differing body sizes. I found that males can assess female mating status and vary sperm number to provide more sperm to unmated females. On average, larger males produced spermatophores with more sperm than did smaller males. Thus, variable sperm allocation is an important male strategy resulting from competition for the fertilization of ova (polyandry).; Overall, factors other than increased or decreased clutch size have resulted in the evolution of polyandry in D. ocoee. In addition, polyandry clearly has shaped the evolution of both male traits and reproductive strategies in D. ocoee. |
