Evolution and Expression of Gene Families at the Interface of Predator-Prey Interactions.

Abstract

Species interactions represent fundamental ecological processes that drive the organismal evolution, but the genetic mechanism of predation traits at the interface of predator-prey interactions is still unclear. In this dissertation, I employed ecological and molecular approaches to determine patterns of evolution and expression of gene families involved in predator-prey interactions and roles of gene duplication in these processes.

Predatory marine snails of the genus Conus use venoms, cocktails of conotoxins, to paralyze prey, and conotoxins are encoded by many large gene families. Investigation of the evolution of A-superfamily genes revealed a dynamic of frequent expansion and contraction of this gene familiy. Extensive gene duplication facilitates rapid evolution of these genes, combinations of which lead to dramatic differences in genomic compositions of this gene family among species. Expression of this gene family is also highly variable among closely-related species. Patterns of phylogenetic distribution of expressed genes differ among species, which implies that Conus species differentially exploit their venome space. Intraspecific variation in allelic composition and expression of conotoxin genes are associated with changes in dietary breath rather than shifts to certain prey taxon. Patterns of geographic variation exhibited at conotoxin genes result from difference in selective forces that likely stem from geographic difference in prey compositions, because local diversity and geographic variation of conotoxin genes are positively correlated with local diversity and geographic heterogeneity of prey utilization. Similarly, ontogenetic variation of conotoxin gene expression is significantly positively correlated but out of phase with shifts of dietary diversity, which implies that conotoxin gene regulation is evoked by shifts of dietary breadth through development. Genes associated with species interactions undergo distinct evolutionary pathways and play different roles in these interactions.

In summary, gene duplication facilitates the extensive turnover, rapid evolution and expression divergence of gene families at the interface of predator-prey interactions. Evolution and expression of genes involved in predation are adaptive to changes of prey, and conotoxin gene evolution and expression are highly associated with dietary diversity.