Background

 

Taricha granulosa, or the rough skin newt, is a common species of small newt that is abundant in the Pacific Northwest, frequently found in shallow ponds and damp rainforests. Its natural distribution lies along the Western coast of North America, from Northern BC down to California, with the majority of the distribution being centered on the stretch from Oregon to Haida Gwaii (Marks and Doyle, 2020). As amphibians, newts are extremely sensitive to environmental changes, making them excellent bio-indicators of ecosystem health and functionality. As such, modelling newt habitat niche response to various environmental impacts provides key insight into ecosystem resilience as a whole.

​

Species distribution modelling (SDM) is the practice of using machine-learning algorithms and geographic data to predict the likelihood of a given species appearing in a location based on observed sample data and environmental variables (Fitzpatrick et al., 2013). This is done for the purpose of analyzing species range size and extent, as well as species habitat response to various environmental changes over space and time by creating presence probability prediction maps. By far the most popular SDM modelling software, Maxent operates on the principle of maximum entropy to create presence-based species range maps using observed samples and environmental rasters (Phillips et al., 2006). Maximum entropy models assume that without the presence of ecological constraints, a species will have a distribution as widespread and uniform as possible (Duan et al., 2014).

​

In our study, we use Maxent to model the distribution of the rough skin newt in BC, Washington, and Oregon. To do this, we ran Maxent models using decades of citizen science newt observations and several bioclimatic environmental variable layers to model newt range in present day conditions and over the course of various climate change schemes. Results are also overlaid with land cover use to identify habitat constraints caused by human development or inappropriate land usage. This study was done with the goal of identifying whether warmer climates would benefit or disadvantage rough skin newts with regards to habitat niche extents in order to determine whether or not the species may require special conservation in the face of anthropogenic climate change.