Potential Effects of Climate Change on the Geographic Distribution of the Endangered Plant Species Manihot walkerae

Abstract

Walker's Manihot,Manihot walkerae, is an endangered plant that is endemic to the Tamaulipan thornscrub ecoregion of extreme southern Texas and northeastern Mexico.M. walkeraepopulations are highly fragmented and are found on both protected public lands and private property. Habitat loss and competition by invasive species are the most detrimental threats forM. walkerae; however, the effect of climate change onM. walkerae'sgeographic distribution remains unexplored and could result in further range restrictions. Our objectives are to evaluate the potential effects of climate change on the distribution ofM. walkeraeand assess the usefulness of natural protected areas in future conservation. We predict current and future geographic distribution forM. walkerae(years 2050 and 2070) using three different general circulation models (CM3, CMIP5, and HADGEM) and two climate change scenarios (RCP 4.5 and 8.5). A total of nineteen spatially rarefied occurrences forM. walkeraeand ten non-highly correlated bioclimatic variables were inputted to the maximum entropy algorithm (MaxEnt) to produce twenty replicates per scenario. The area under the curve (AUC) value for the consensus model was higher than 0.90 and the partial ROC value was higher than 1.80, indicating a high predictive ability. The potential reduction in geographic distribution forM. walkeraeby the effect of climate change was variable throughout the models, but collectively they predict a restriction in distribution. The most severe reductions were 9\% for the year 2050 with the CM3 model at an 8.5 RCP, and 14\% for the year 2070 with the CMIP5 model at the 4.5 RCP. The future geographic distribution ofM. walkeraewas overlapped with protected lands in the U.S. and Mexico in order to identify areas that could be suitable for future conservation efforts. In the U.S. there are several protected areas that are potentially suitable forM. walkerae, whereas in Mexico no protected areas exist withinM. walkeraesuitable habitat.