Macrohabitat suitability model for the Trinity bristle snail in the Greater Trinity Basin of northern California

Abstract

Analytical methods used to identify species-specific suitability of habitat include statistical habitat distribution models. Habitat type is the most reliable predictor of species occurrence in a particular area. Here, I developed a spatially explicit landscape-level suitability framework using metrics derived from forest, climatic, and topographic criteria for the Trinity bristle snail (Monadenia setosa). I conducted surveys to document locations of Trinity bristle snails and then performed spatial analysis of ecological variables in a geographic information systems (GIS) framework using point density estimators to produce a spatially explicit habitat suitability model; a geographic map reflecting the total area of hypothesized suitable macrohabitat within the known geographic range of the species; and a set of density surfaces showing where point features were concentrated that defined habitat suitability ranging from low to critical. This model provides resource managers with a distributional framework and overlay useful in anticipating where suitable macrohabitat for the species may be found across the landscape and serves as a foundation for updating and expanding population-level surveys and site-specific microhabitat assessments.