Correlation between male and female reproduction in the subdioecious herb Astilbe biternata (Saxifragaceae)

Genotypic trade-offs between male and female reproduction are commonly assumed in theoretical studies of the evolution of gender specialization. Although these trade-offs are supported by higher seed production of females than hermaphrodites in natural populations of gynodioecious species, comparisons between male and female reproductive allocation among hermaphrodite individuals under controlled conditions are rare. We assessed phenotypic and genotypic correlations between stamen and fruit production in fruiting males of the near-dioecious herb Astilbe biternata. In the field, we found a significant negative phenotypic correlation between stamen production and fruit production within individuals that produced both stamens and fruit as well as higher fruit set in females than fruiting males. The negative correlation between fruit and stamen production that was observed in the field was also apparent across clonally propagated genotypes. These results suggest that negative genetic correlations between male and female reproduction may limit the independent evolution of fruit and stamen production in A. biternata.