Costs of reproduction in flowering plants.

Costs of reproduction arise when investments into current reproduction reduce future reproductive fitness. Studies on reproductive costs use diverse approaches, including the analysis of gene expression, physiology, trade-offs between reproduction and growth/survival, and the impact of reproductive investments on population growth. These studies demonstrate that reproductive trade-offs have far-reaching effects on plants, affect their fitness, and are therefore important for shaping the evolution of life histories. However, not all studies have detected costs of reproduction, and c. 90% of these were conducted in natural populations, where controlling for variation in plant resource status is challenging. For dioecious plants, there is a common perception that fruit production should result in greater costs of reproduction for females than males, but divergent reproductive costs between the sexes are not supported by studies of reproductive trade-offs in dioecious plants. Other aspects of reproductive costs remain poorly understood, including ecological costs of reproduction, the fitness effects of reproductive trade-offs involving growth or physiological processes, and how the male sex role influences reproductive costs. Progress will be enabled by the use of measurements that allow for easier comparisons across studies and by more clearly distinguishing between the processes that contribute to current vs future reproductive fitness.