Environmental context shapes sex-specific reproductive costs in a dioecious plant

- Organismal fitness depends on how resources are allocated to growth, survival, and reproduction. When females and males invest different types of resources into reproduction, the resulting trade-offs—and their fitness consequences—may differ between the sexes. Although some evidence supports this idea, comprehensive tests of sex-specific reproductive costs across environmental gradients and time periods remain rare.- We assessed the somatic costs of reproduction in female and male broadleaf arrowhead (Sagittaria latifolia) plants grown in a common garden over two growing seasons. Using experimental manipulations of nutrient availability and reproductive investment, we measured photosynthesis and leaf nitrogen content before, during, and after flowering, and tracked growth and nutrient status in the following year.- Reproductive costs were both sex- and environment-specific. Under nutrient-limited conditions, males experienced greater somatic costs than females, including reduced photosynthetic rates, lower leaf nitrogen content, and diminished growth in the subsequent year. In contrast, under nutrient-rich conditions, neither sex exhibited detectable costs for the traits measured.- These findings demonstrate that the expression of reproductive costs depends on both sex and resource availability. By showing that males and females pay for reproduction using different currencies—nitrogen and carbon, respectively our study highlights the potential for environmentally dependent, sex-specific trade-offs in dioecious plants.