Pollination and mating traits underlie diverse reproductive strategies in flowering plants

Abstract

Reproductive and floral traits present an enormous diversity in angiosperms (flowering plants) and are associated with differences in species diversity. These traits also interact in non-trivial ways but their interdependence in the influence of species' evolutionary success has only rarely been taken into account. Here we characterize the strategies plants have evolved to achieve pollination and reproduction using 21 floral and life-history traits from an original and representative set of 360 species sampled in 170 families across the angiosperms. We found that, while outcrossing rates per se are associated with a plant size / growth form axis, pollination-related traits such as flower gender and floral reward represent an almost equally important axis of variation. This correlation with pollination clearly sets unisexuality (monoecy and dioecy) apart as a separate outcrossing strategy that likely results from more ecological selective pressures than the avoidance of selfing and inbreeding alone. Species are not evenly distributed across trait space and we identified three main reproductive strategies corresponding to combinations of traits that repeatedly evolved together (herbaceous bisexual, woody bisexual and woody unisexual species). We argue that pollination-related traits, which have largely been overlooked in studies of plant functional ecology, allow the integration of ecological and evolutionary timescales and provide a new perspective in the study of mating and sexual system evolution and ecosystem functioning.