Calochortus gunnisonii furthers evidence for the complex genetic legacy of historical climate change in the southern Rocky Mountains

Abstract

Premise of the Study Climate cycles of the Quaternary have impacted plants at a global scale, leaving behind a complex genetic legacy. Species of the northern Rocky Mountains of North America were exposed to more uniform glacial patterns than the central and southern ranges, where synergistic relationships between temperature and precipitation caused differences in the timing and extent of glacier onset. We examined the genetic impacts of climate oscillations on Calochortus gunnisonii (Liliaceae) in the central and southern Rocky Mountains. Methods Populations were sampled from disjunct mountain ranges across the basins of Wyoming and northern and central Colorado. Allelic data from nuclear microsatellites and plastid sequences (trnV‐ndhC, petA‐psbJ, and rpl16) were used to examine patterns of genetic structure between and among populations along the southern Rocky Mountain corridor. Key Results We infer considerable population structure concordant with mountain range of origin. Clustering analysis supports separate north and south genetic clusters on either side of major basins in Wyoming, suggesting that populations were maintained in two distinct refugia. Additionally, populations within the Sierra Madre Range of southern Wyoming show localized, divergent genetic signal indicative of a third potential glacial refugium. By contrast, recent genetic admixture is observed in the Laramie, Medicine Bow, and Front ranges, where population expansion from glacial refugia has likely occurred. Conclusions We conclude that during climate cycles of the Quaternary, C. gunnisonii experienced periods of population expansion and reduction, habitat fragmentation, isolation in three or more refugia, and admixture mirroring genetic impacts of other southern Rocky Mountains organisms.

Range shifts in butternut, a rare, endangered tree, in response to past climate and modern conditions

“…As glaciers expanded, species were pushed southward into glacial refugia, typically defined as small, distinct regions of suitable habitat near or surrounded by ice sheets during glacial cycles (Bennett & Provan, 2008). Subsequently, climate warming and glacial retreat allowed species to migrate north into their current ranges in a series of founder events, during which bottlenecks likely led to a reduction in genetic diversity with increasing latitude, while species maintained genetic structure indicative of shared glacial refugia during the LGM (Fuller & McGlaughlin, 2019;Hewitt, 2004). For example, Petit et al (2003) determined that several woody European species exhibit genetic signatures of being pushed into southern glacial refugia, as demonstrated by clines in genetic diversity (higher diversity in the south and less diversity in the north of ranges) and shared structure representative of shared refugia in the major peninsulas of Europe (in Italy, Iberia and the Balkans).…”