Environmental Factors Associated With Triploid Aspen Occurrence in Intermountain West Landscapes

Polyploidy is common among plants and can contribute to physiological and morphological differences, altering how plants respond to environmental changes, promoting genetic diversification, and even species radiation. Quaking aspen (Populus tremuloides), a keystone species associated with high plant and animal diversity is frequently found in mixed diploid/triploid populations in the Intermountain West. High mortality rates and widespread population declines in aspen are of increasing concern in the Intermountain West, often ascribed to changing climates and drought stress events. The goal of this study was to better understand environmental factors influencing the distribution of triploid aspen population in the Intermountain West. Using restriction-site associated DNA sequencing (RAD-seq), we examined the occurrence of diploid and triploid aspen populations at various spatial scales in relation to environmental variables associated with soil moisture content. Our results suggest that triploidy in aspen on the landscape is associated with environmental variables related to soil moisture and may be influenced by specific local variations in topography, climate, and precipitation patterns. Overall, we found that conditions associated with low soil moisture were associated with lower frequencies of triploid aspen. Our results suggest that triploid aspen clones may be more susceptible to mortality than diploid clones in the warmer, drier climates expected with climate change. We acknowledge, however, that there are many knowledge gaps regarding the generation and persistence of triploid aspen clones. Understanding the causes and consequences of triploidy in aspen will be important in predicting and managing aspen persistence in landscapes of the western U. S. under changing climate conditions.