Evolutionary consequences of polyploidy and sexual system variation in mosses

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Many plants, fungi and animals are unisexual and have separate male and female individuals. Yet in each of these groups, many species have hermaphroditic individuals. What conditions favour which strategy? My research focusses on mosses to test questions about the factors selecting for the evolution and maintenance of different sexual strategies. This is because mosses have features that make them conducive to experimentation, such as a short time to reproduction in many, and established techniques to genetically manipulate the sexes. In addition, the cause of evolutionary changes between combined and separate sexes is likely to be different in mosses as the genetic control of sex is very different, and research in mosses can serve as a test of the generality of theoretical work developed for animals and flowering plants. Mosses have haploid sex chromosomes: females have one X and males one Y (contrast this with humans, where males are XY). Genome doubling in mosses is predicted to result in individuals with both X and Y chromosomes, which could be hermaphrodite. My research will experimentally test this proposed evolutionary pathway to hermaphroditism and examine the evolutionary stability of unisexuals and hermaphrodites following genome doubling. This research has implications that extend beyond mosses. While X and Y chromosomes have regions that do not recombine in separate sexes, recombination can now occur following genome duplication. This will allow mutations on the X or Y chromosomes to be exposed to selection. Examining the effect of this will allow us to understand the interplay between recombination and genetic mutations in all sexual organisms.