Quantitative Biology Colloquium
Hybridization, polyploidy, and adaptation to extreme environments in resurrection plants Selaginella [Selaginellaceae]
Hybridization and polyploidization (whole genome duplication) are common and important evolutionary processes in vascular plants. Despite the frequency of these processes most nascent polyploid species go extinct due to a combination of genetic and ecological obstacles, and little is known about the relative role of hybridization and whole genome duplication to allopolyploid establishment. Selaginella have some of the smallest nuclear genomes found in vascular plants as well as variable levels of desiccation tolerance, with many around the world known as resurrection plants. The southwestern U.S. and mainland mexico is a center of functional and taxonomic diversity for the genus. In the transition zone between the Lower Colorado River Valley and Arizona Upland subdivisions in the Sonoran Desert diploid hybrids and allopolyploids are found, formed between crosses of Selaginella arizonica and S. eremophila [Selaginellaceae]. Both hybrid populations occupy drier, warmer climatic niches than either of their parents and have different ecophysiological strategies associated with more variable precipitation. Using a combination of transcriptome, genome, and ddRADseq data we confirm the parentage and hybrid nature of these populations. Our results have broad implications for our understanding of the ecological and evolutionary genetic processes that occur in nascent diploid and polyploid hybrid populations in natural conditions.