UC San Diego

Thermal stress will become a more frequent occurrence as global temperatures continue to rise due to human induced climate change. Unlike many fortunate humans, animals do not have air conditioners to escape the harmful effects of higher temperatures. To persist organisms will move to suitable conditions increasing the likely hood of hybridization events or adapting by some sort of evolutionary mechanism. This dissertation contains research on the variation for thermal limit in the high intertidal copepod Tigriopus californicus. In Chapter 1, I investigated the genetic variation for thermal limit in a subtropical population from San Roque, Baja California, Mexico. In Chapter 2, I created interpopulation hybrids to explore the production of transgressive thermal phenotypes. In Chapter 3, I investigated the gene expression response to thermal stress in transgressive segregants of increased maximum thermal limit in crosses between Catalina Island and Abalone Cove, California, USA. In Chapter 4, I genotyped hybrids using the RNAseq data from Chapter 3 and population specific SNPs to determine the genetic composition of positive transgressive phenotypes