AI Insight
This study examined sexual selection in the hermaphroditic plant Brassica rapa by combining direct observations of bumblebee pollinator movements with genetic paternity analyses. The researchers found that pollen competition for ovules is the primary mechanism of sexual selection, while competition for mate access is secondary and stronger in the male sex function than female, consistent with evolutionary theory. Pollinator abundance significantly influenced the balance between pre- and post-pollination sexual selection, with reduced pollinator numbers increasing selection pressure on mate acquisition.
Why it matters
This research reveals that sexual selection in flowering plants operates through multiple sequential stages and is strongly shaped by ecological factors like pollinator availability. Understanding these dynamics has implications for predicting plant evolution in changing environments where pollinator populations are declining, and for optimizing crop breeding strategies that depend on pollination efficiency.
Understand the Science
by Estelle Barbot, Mathilde Dufaÿ, Tim Janicke, Benoit Lapeyre, Denis Orcel, François Rousset, Jeanne Tonnabel
Sexual selection is a central force in evolutionary biology that has been shown to shape phenotypes and population dynamics in animals. While this selective force is increasingly recognized in flowering plants, theory predicts that anisogamy generates sex differences in the fitness benefits of acquiring additional mates—a pattern well supported in animals but with limited tests in plants. Plant studies rely solely on genetic parentage analyses to estimate mate numbers, thereby conflating performance in accessing mates with success in gamete fertilization. Pollinators add an ecological layer, as their behavior and abundance can influence competition for access to mates and their gametes. Here, we disentangle consecutive episodes of sexual selection in the hermaphroditic plant Brassica rapa by combining direct observations of Bombus terrestris movements with genetic paternity analyses in experimental populations, thus providing independent estimates of the observational number of mates acquired and realized fertilization success. Our approach identifies pollen competition for ovules as the primary arena for sexual selection in B. rapa. Competition for access to mates constitutes a secondary force and was found to be stronger in the male compared to the female sex function, as predicted by classic theory. Experimentally reduced pollinator abundance modulated the balance between pre- and post-pollination sexual selection, increasing the opportunity for selection on mate acquisition. Ignoring pollinator movements led to biased estimates of pre-pollination sexual selection. Our findings demonstrate that sexual selection in plants unfolds across multiple, sequential episodes shaped by ecological context.
Source: Pollinator abundance shapes sexual selection in an angiosperm