The evolution of novel traits can change the way that organisms interact with their environments to survive, grow and reproduce. Deep knowledge of the underlying genes and developmental changes that underly most evolutionary innovations is sparse, as is the understanding of the ecological consequences for both the organisms in which novel traits emerged and the organisms with which they interact in communities. A particular gap in understanding is how the evolution of novel traits influences the biodiversity of their associated microbial communities. This project will help fill this gap in our knowledge by studying a remarkable innovation of male pregnancy in seahorses, pipefish, and seadragons. This project will include the creation of new genome sequences and detailed studies of the developmental genetic underpinnings of the embryo brooding structures that make male pregnancy possible. The consequences of pouch evolution on the complexity and function of the community microbes in the pouch will also be studied, as well as how this unique host-associated microbiota can affect the fitness of embryos in the pouch.