Sexual dimorphism masks life history trade-offs in the dioecious plant Silene latifolia

Females of dioecious plant species are expected to show greater trade-offs with other life history traits than males because of their high investment in reproduction. We investigated life history traits and resource allocation patterns for both males and females of the dioecious plant Silene latifolia, to document allocation both prior to and after reproductive investment. In addition, the impact of fruit production on subsequent allocation to reproduction and growth was investigated by varying the number of flowers pollinated on females. The mean date of first reproduction was the same for males and females. Early-flowering plants of both sexes invested less in leaf biomass than plants that delayed flowering. The percentage of flowers pollinated had a significant effect on how resources were allocated, and on the amount and timing of further flower production. Sexual dimorphism was observed in resource allocation patterns after, but not prior to, investment in reproduction. Overall, pollinated females were found to have more leaf biomass and invest nearly twice as much in reproduction as males, in spite of an apparent trade-off between leaf production and reproduction within both females and males. We conclude that sexual dimorphism in life history traits that affects resource acquisition causes the resource pool that is allocated to be variable, rather than static, thereby masking the underlying tradeoffs. Key words: dioecious; life history traits; sexual dimorphism; Silene latifolia; trade-offs.
INTRODUCTION Traits affecting reproduction and survival will be bound together by physiological trade-offs, because allocation of limited resources to any one activity will occur at the expense of others (Cody [...]