rTPI: An R Package for Calculating Thermal and Aridity Position Indices for Terrestrial Vertebrates

Species environmental niche limits provide useful information for generating estimates of species niche position. Recent work investigating species' responses to climate change has shown that models that included metrics of species-specific thermal and aridity niche position improve in performance. However, availability to generate thermal and aridity niche limits as well as estimates of niche position has been lacking for large numbers of species. To address the lack of thermal and aridity niche limit data, the rTPI package provides access to a dataset of realized thermal and aridity niche tolerance limits for terrestrial birds, mammals, reptiles, and amphibians. Further, it provides users with the ability to generate thermal and aridity niche limit estimates for terrestrial species of interest. Additionally, the package contains functions for calculating Thermal Position Index (TPI) and Aridity Position Index (API) which provide information about species proximity to environmental niche limits. These values can then be utilized in downstream statistical or distribution models aimed at understanding species responses to environmental variables and climate change. rTPI provides easy-to-use functions and straightforward access to a wide range of realized thermal and aridity niche tolerance limits for a large number of terrestrial vertebrates to be used in addressing a multitude of ecological questions.