Human food use increases plant geographical ranges in the Sonoran Desert

Abstract

Aim Climate is usually regarded as the main determinant of plant species distributions. However, past human use of species for food might also have influenced distributions. We hypothesized that human‐mediated dispersal has resulted in food plants occupying more of their potential geographical range. We also hypothesized that key ecological traits could predispose a species to occupy more of its potential climatic geographical range and be selected by humans for food. Location The Sonoran Desert of south‐western North America. Time period Present day. Major taxa studied Food plants. Methods We used ethnobotanical data and data from large botanical ecoinformatics databases to estimate realized (dispersal‐ and climate‐constrained) and potential (climate‐constrained) ranges for food plants and their used and unused congeners. Results We found that food plants fill more of their potential geographical ranges than their unused congeners. We also found that succulence and annual growth interacted with food usage to increase range filling. Main conclusions Human food use has expanded the distribution of many plant species in the Sonoran Desert.

Diversity in habit expands the environmental niche of Ziziphus (Rhamnaceae)

“…Both wild harvesting and deliberate propagation of plants for food significantly increase plants' distribution (Flower et al, 2021). We also found that cultivated species occupied significantly different environmental niches than a non-cultivated comparator.…”

“…The range sizes of these two species are almost 10 times larger than the median of the range sizes of non‐cultivated tree species. This relationship may well be reciprocal; the species selected for widespread cultivation are likely able to thrive in a variety of conditions as well as being useful (i.e., Z. mauritiana ; a tree found abundantly in arid/semi‐arid places; Singh et al, 2021; Singh & Meghwal, 2020; and also in humid forests; eFloras, 2008) and species used by humans fill more of their potential ranges than unused species (Flower et al, 2021). Flower et al (2021) found that unused plant species filled significantly less of their range compared to species used for food, but that the difference was less clear when comparing food plants with species used for other purposes (i.e., medicinally).…”

“…Further, although only Z. mauritiana and Z. jujuba are actively cultivated, many other species are harvested in situ, with some species such as Ziziphus abyssinica edible but eaten under famine conditions (Ruffo et al, 2002). Both wild harvesting and deliberate propagation of plants for food significantly increase plants' distribution (Flower et al, 2021). We also found that cultivated species occupied significantly different environmental niches than a non‐cultivated comparator.…”

“…Cultivated species and primary human uses were identified from peer-reviewed articles, floras, and gray literature such as the United States Department of Agriculture Handbook (Table S4). Following Flower et al (2021), we distinguished between species with no use or unknown uses, species which are widely used but not cultivated (harvested in situ), and species that are deliberately cultivated. Uses for non-cultivated species included spiritual, medicinal, edible, and wood for building or forage.…”

“…For Ziziphus , shrubs and geoxyles have the lowest stature and are likely to have the smallest ranges. Cultivated species are likely to have the largest ranges in the genus, as human use enables species to fulfill their potential ranges (Flower et al, 2021).…”