Reproductive allocation and the long-term costs of reproduction in Siparuna grandiflora, a dioecious neotropical shrub

1 Using a combination of observational and experimental approaches, both al location of resources to reproduction (often called the direct cost of repr oduction) and the subsequent long-term costs (the indirect, delayed or demo graphic cost) associated with reproductive allocation to male and female fu nction in Siparuna grandiflora (Siparunaceae), a tropical dioecious shrub, were examined. 2 The objectives were to determine whether females allocate more biomass or nitrogen per reproductive episode than males, and whether there is a long- term cost of reproduction in terms of subsequent growth or reproduction for either sex. If there is no long-term cost of reproduction, then reproducti on may be viewed as free in an evolutionary sense. 3 As is generally the case in dioecious species, females allocated more bio mass and nitrogen to reproduction than males. Females also showed delayed c osts of reproduction in terms of decreased growth and subsequent reproducti on, whereas males did not. 4 The lack of measurable delayed costs in males suggests that with the evol ution of dioecy, selection has reduced delayed costs of reproduction in S. grandiflora males. In contrast, females that were prevented from reproducin g were able to re-allocate resources to growth, and produced more stem leng th on average than males. This reallocation response may have evolved to re duce delayed costs of reproduction in females over time frames longer than that considered in the present study.