Range extensions and population decline of the endemic desert perennial orocopia sage (salvia greatae [lamiaceae]) in the mecca hills and orocopia mountains, california

Orocopia Sage, Salvia greatae Brandegee (Lamiaceae), is an endemic shrub restricted to the Orocopia and Chocolate Mountains within the Colorado Desert of Riverside and Imperial Counties, California. Very little has been published on this species' demographics, distribution, range, ecology, or threats. Generally, habitat for S. greatae has been described as alluvial fans, slopes, and washes between 30–450 m elevation. Our study was designed to focus specifically on documenting threats and describing the demographic patterns of S. greatae populations, as well as establishing a set of baseline data for long-term monitoring. Our surveys, performed in fall and winter of 2019–2020, revealed patterns that differed from the previously documented distribution for this species; we found denser, more expansive populations, and lower mortality rates at even higher elevations, up to 1011 m on steep slopes and rugged terrain. Populations at mid-elevations, 200 to 500 m, had higher mortality rates than high elevation sites. For populations previously considered to be within ‘core habitat’ at elevations below 200 m and within bajadas and alluvial fans, we relocated very few of the populations recorded in the early 1900s, and observed high mortality within those that persisted. Over the gradient studied, we found that the condition of plants significantly increased with elevation, with the highest proportion of vigorous individuals found at higher elevations. Our data indicate that either this species is shifting to higher elevations, or the previously described habitat of S. greatae was biased toward the lower, easily accessible populations, and may have been composed of waifs, as opposed to stable upland populations. Declines noted in mid- and lower-elevation populations are consistent with the effects of drying due to anthropogenic climate change.