Morphological Differences in Isolated Brook Trout Populations in the Desolation Wilderness of the Sierra Nevada

abstract Brook trout ( Salvelinus fontinalis ) is an invasive species in the Desolation Wilderness of California. But it is unknown to what extent this species is evolving to adapt to isolated high altitude lakes. We quantified morphological differences between three brook trout populations in Desolation Wilderness that are in isolation and of common origin. We took standardized photos of fish, created geometric nets of each specimen using points located at known morphological features, and performed a Procrustes superimposition and principal component analysis to examine and cluster morphological variation between individuals. Together, our results show morphological differences between three Salvelinus fontinalis populations in independent environments. Our results suggest that invasive species introduced from one source can show physical variation generations after introduction, and thus deserve attention for adapting to and perhaps becoming an increasingly complex part of their ecosystem.