Thursday, March 5 – 9:30 AM
Sergio Nigenda, UC Los Angeles
Phenotypic variation and differential gene expression between tropical and temperate opossum (Didelphis virginiana) populations
Marsupials are a large and evolutionary important group of mammals; however, few studies on phenotypic variation have been performed on this group. The Virginia opossum (Didelphis virginiana) is a widely distributed marsupial through Central and North America, inhabits different environments and shows phenotypic variation across its geographic range. Combining phenotypic data from museum and live specimens, environmental data from satellite databases and transcriptome data generated with RNA-Sequencing (RNA-Seq), we attempted to identify environmental variables and differentially expressed genes that may play an important role in driving the phenotypic differences and adaptation in this species. We found that temperature seasonality and low temperatures are the environmental variables explaining most of the variation in skin pigmentation and coat coloration. Drastic changes in these phenotypes occur around 27°-30° latitude North indicating that tropical and temperate populations have different phenotypes. The genes peroxisome proliferator-activated receptor gamma coactivator 1-alpha (ppargc1a) and tyrosinase related protein 1 (tyrp1) showed differential expression between these populations, and in placental mammals are important in regulating energy metabolism and pigmentation respectively. Carbohydrate metabolism and skeletal muscle contraction biological processes were enriched in temperate populations while melanocyte development and pigmentation processes in tropical populations. Our results suggest that selective pressures or phenotypic plasticity related to temperature stability could be causing differential expression of genes involved in biological processes affecting skin pigmentation, coat coloration and energy metabolism which explain the phenotypic variation observed. These results contribute to a better understanding on how evolutionary processes drive phenotypic variation in marsupial species.