Because of their lack of mobility, flowering plants are sometimes thought to be passive mates, accepting all pollen indiscriminately. Yet the process of pollination offers plants a wealth of opportunity to breed selectively. Plants exhibit a stunning variety of floral and phenological mechanisms to selectively attract and bind pollen. Once bound, pollen embark on an elaborate journey through the pistil to deliver their sperm to the unfertilized ovules of the ovary. The pistil provides everything the pollen needs for success during this journey, including guidance cues and nutrients. Although the pistil is a great facilitator of pollen function, it also acts as a competitive arena, where pollen gather resources and race to gain access to unfertilized ovules. And since this race determines whose genes make it to the next generation, it isn’t surprising that the winners are not chosen at random. In other words, some pollen have greater mating success—a phenomenon called nonrandom mating.
While there has been intense theoretical work on the evolutionary pressures that lead to nonrandom mating, we understand much less of the genetics and physiology of process. In our lab, we are using the model organism Arabidopsis thaliana to map the genes and define the pollen and pistil behaviors that direct nonrandom mating.