As climate changes, ecosystems worldwide will face new conditions that challenge the growth and survival of species. Even in drought prone ecosystems, as in southwestern US, warmer temperatures (i.e. hot droughts) represent a more extreme challenge for piñon pine (Pinus edulis). Understanding the role of local adaptation to climate will be important for predicting future responses to extreme climate events. Piñon pine is a widespread conifer that is the dominant species in forests at mid-elevations across a large swath of southwestern North America. It is an excellent species within which to study genomic variation and local adaptation to climate change because its current distribution spans 10 degrees of latitude (~1100 km) and elevations ranging from 1500 m to 2500 m. In this study, we describe range-wide patterns of piñon pine genomic variation for the first time. To do this, we collected needles from 350 piñon pine individuals across the species range and sequenced DNA from large portions of the genome (>23, 714 genes). We used these data to 1) characterize genomic diversity and 2) describe the spatial distribution of genomic variation. We found that the increased number of loci allowed us a more accurate picture of population structure than past, mitochondrial studies did. We found modest population structure across the landscape, but without the refugial dichotomy the mitochondrial data showed. However, the most notable axis of genetic variation was from putatively admixed populations between edulis and fallax. Understanding the genomics of adaptation will be critical in predicting population responses to future conditions.
