UC Riverside

My dissertation focuses on the evolutionary effects of introgression on a complex group of paradise spiders that experience strong sexual selection. I use an integrative approach to evaluate morphological, genetic, and behavioral consequences of gene flow across species boundaries in the Habronattus americanus subgroup. In Chapter 1, I uncover extensive genomic homogenization between members of the americanus subgroup, such that evolutionary lineages reflect geography rather than species or morph type. Despite the genomic homogenization, selective forces maintain the very diverse male courtship ornamentation of different species and morphs. In Chapter 2, behavioral analyses of courtship display traits indicate a geographical pattern with a southeastern display group and a western+northern display group. Courtship displays in the southeastern distribution include more fling repetitions and longer introductory motif times compared to courtship displays from other geographical areas. Patterns of courtship display diversity are discordant with patterns of morphological diversity and seem to align more with geographical location than morph or species identity. In Chapter 3, population genetic and morphological analyses from a H. americanus x H. kubai hybrid zone near Mt. Shasta, CA uncover very little genomic diversity but substantial morphological diversity of male courtship ornamentation traits, which seem easily introgressed across species boundaries. Hybrid zone dynamics at Mt. Shasta appear to act as a microcosm for periodic processes of divergence and reticulation in the entire americanus subgroup. In its entirety, my dissertation offers an integrative analysis of the effects introgression may have on diverging lineages and highlights the importance of new perspectives on how we think about speciation and lineage diversification.