Effects of Selfing on Offspring Survival and Reproduction in a Colonial Simultaneous Hermaphrodite (Bugula stolonifera, Bryozoa)

Abstract

Understanding the consequences of selfing in simultaneous hermaphrodites requires investigating potential deleterious effects on fitness at all stages of life. In this study, I examined the effects of selfing throughout the life cycle of the marine bryozoan Bugula stolonifera, a colonial simultaneous hermaphrodite. In 2008, larvae from field-collected colonies were cultured through metamorphosis to reproductively mature colonies either in the presence of one other colony, the paired treatment, or alone, the solitary treatment. Results demonstrated that selfing in this species is possible, in that colonies in the solitary treatment produced viable larvae that successfully completed metamorphosis. On average, however, these colonies released significantly fewer larvae, which experienced reduced rates of metamorphic initiation and completion compared to the paired treatment. These experiments were extended in 2009, when metamorphs from colonies reared in the solitary (n = 58) and paired (n = 61) treatments were transferred to the field for growth to reproductive maturity and then brought back to the laboratory for larval collection. Results revealed additional deleterious effects associated with selfing, as no viable larvae were recovered from colonies deriving from the solitary treatment. In contrast, offspring from the paired treatment released 1030 larvae and 99% initiated metamorphosis, 97% of which completed metamorphosis. Overall, selfed larvae not only had significantly decreased chances of survival, but those that did survive did not successfully reproduce.