Mexican alpine plants in the face of global warming: potential extinction within a specialized assemblage of narrow endemics
Alpine ecosystems occur under extreme climatic conditions and, as a result, house a unique and vulnerable biota. They are very scarce at tropical latitudes; in Mexico occur mainly along the Trans-Mexican Volcanic Belt, where species richness is not high but narrow endemics stand out. We investigate the effects of climate change under hypothesized contrasting climate warming scenarios using ecological niche modeling of five microendemic alpine species. Occurrence data was obtained mainly from field trips, but herbaria were also examined. A total of 21 climatic and topographic variables, as well as individual selections of 12–16 variables were employed to construct models with Maxent and GARP. Depending on the number of occurrences, current models were validated with Partial-ROC or Jackknife procedures; and projections to 2050 and 2070 were made using two Representative Concentration Pathways and two Global Circulation Models. All species’ models showed a clear pattern of contraction under the explored scenarios; over 58 % of contemporary climatic distribution disappeared, suggesting that analyzed species face imminent extinction due to climatic habitat loss. The models are useful in representing the endemic component of Mexican alpine grassland by reciprocal correspondence in geographic distribution, and we consider it as a highly endangered ecosystem due to climate change, which is probably applicable to other tropical alpine ecosystems. The Pico de Orizaba volcano seems the best option to preserve due to its extension and elevation. However, further studies at finer scales are needed to improve in situ preservation and conservation strategies that include translocation, assisted migration and seed banking.