Predicting potential range shifts using climatic time series and niche models: A Neotropical montane shrew's case

Abstract

Ecological niche models (ENMs) can forecast species' potential range shifts by transferring a model to a future climatic scenario. However, this approximation does not identify whether range shifts have occurred in species' distributional limits in the last several decades. Given ongoing anthropogenic climate change, changes in distributional limits are expected to occur (poleward and upslope for several montane species). Here, I use a climatic time series to predict potential changes in distributional limits in response to climate change over the last four decades, using the Mexican small-eared shrew (Cryptotis mexicanus), a montane cloud-forest species, as an example. I transferred the ENM (tuned to optimize complexity) to a series of thirty-year bioclimatic periods between 1979 and 2019 created with monthly precipitation and temperature data. I detected trends in suitability and bioclimatic variables using a Mann-Kendall test and identified which variables could be driving the suitability changes in distributional limits. The detected extent and direction of suitability trends do not suggest the uniform pole-ward or upslope shifts expected under warming conditions. Comparisons between suitability and variable trends suggest that precipitation, not temperature, plays a stronger role in explaining changes in climatic suitability for C. mexicanus. Where precipitation decreased, there was suitability loss, while in areas where precipitation increased, suitability gain was observed. These analyses illustrate how incorporating time-series climatic data into ENMs can aid in understanding if species are already responding to changes in climate. Here, the potential response of C. mexicanus to climate change varies across its distribution and therefore the species' range shifts may not necessarily follow expected general patterns. These findings should be verified with field data. More generally, using the valuable climatic information of the last several decades should be incorporated into studies that determine potential range shifts under recent or future climatic conditions.