Capturing the distribution as it shifts: chile pepper (Capsicum annuumL.) domestication gradient meets geography

Abstract

Aim: Domestication is an ongoing well-described process. However, while many have studied the changes domestication causes in the genetic landscape, few have explored the way domestication changes the geographic landscape in which the plants exist. Therefore, the goal of this study was to understand how the domestication status changed the suitable geographic space of chile pepper in its center of origin. Methods: Capsicum annuum is a major crop species globally whose domestication center, Mexico, has been well studied. This provides a unique opportunity to explore the degree to which ranges of different domestication classes diverged and how these ranges might be altered by climate change. To this end, we created ecological niche models for four domestication classes (wild, semiwild, landrace, modern cultivar) based on present climate and future climate scenarios for 2050, 2070, and 2090. Results: Considering present environment, we found substantial overlap in the geographic niches of all the domestication gradient categories. Yet, there were also clear unique environmental and geographic aspects to the current ranges. Wild and commercial varieties were at ease in desert conditions as opposed to landraces. With projections into the future, habitat was lost asymmetrically, with wild, semiwild and landraces at far greater risk than modern cultivars. Further, we identified areas where future suitability overlap between landraces and wilds is expected to decouple. Main conclusions: While range expansion is widely associated with domestication, there is little support of a constant niche expansion (either in environmental or geographical space) throughout the domestication gradient. However, a shift to higher altitudes with cooler climate was identified for landraces. The clear differences in environmental adaptation, such as higher mean diurnal range and precipitation seasonality along the domestication gradient classes and their future potential range shifts show the need to increase conservation efforts, particularly to preserve landraces and semiwild genotypes.