Genomic and Molecular Bases of Pollination Syndrome Evolution

The transition from one pollination syndrome to another should be difficult as it requires coordinated changes of multiple component traits, with each involving multiple genes, yet these transitions occur frequently in nature. Here, we explore the genetic and genomic properties that facilitate such rapid pollination syndrome switches. We begin this review by recognizing the important role of relaxed pollinator specificity and delayed selfing in providing adaptive continuity during pollinator shifts. We then compare theoretical predictions with empirical studies on the genetic architecture and molecular basis underlying pollination syndrome divergence. We find that dominance, pleiotropy, tight genetic linkage, and standing genetic variation are important contributors and highlight the novel insights provided by detailed molecular characterizations. We conclude by suggesting where future efforts can help us bridge the genetic basis of individual trait divergence, the fitness effect of each variant, and the genome-wide recombination landscape into a coherent, predictive framework.