Using biotic interactions in broad-scale estimates of species' distributions

Aim: To examine the combined effect of abiotic and biotic factors on species distributions in a marine environment. Specifically, we aim to account for the effects of trophic interactions at broad scales in ecological niche models (ENMs) of sea kraits (Laticauda: Reptilia) by including the potential distribution of food resources as predictor variables. Location: Oceania and Southeast Asia. Methods: First, we outline a simple method to generate biotic interaction variables for ENMs. We then test whether ENMs that include biotic interactions perform better than ENMs based on abiotic variables only. Results: The models based on biotic interactions (i.e. trophic interactions) and abiotic variables slightly outperformed the models informed only by abiotic variables. We found a strong relationship between prey species richness and probability of distribution of predator (sea kraits). The models that included potential distributions of prey species as predictor variables showed an increase in proportion of pixels predicted present and a decrease in omission error, compared with models based only on abiotic variables. Main conclusions: Distribution estimates of predator species at broad scales are more accurate if calibration of ENMs includes relevant biotic variables (prey species richness, in this study). Hence, when data are available, biotic variables should be included in ENMs.