The importance of defining the geographic distribution of species for conservation: The case of the Bearded Wood-Partridge

Delimitation of the distribution areas of species has fundamental implications for the understanding of biodiversity and for decision-making in conservation. This is illustrated by the case of the Bearded Wood-Partridge (Dendrortyx barbatus), which is endemic to Mexico and was classified as threatened by the IUCN. Recently the discovery of this species in new locations caused an increase in the known distribution area whereupon it was reclassified in a lower risk category. In our study, delimitation and comparison of the Bearded Wood-Partridge distribution area is carried out utilising five different methods: minimum convex polygon; areographic; cartographic; ecological niche modeling; and, “free hand”. A number of locality records are also used to demonstrate the chronological order of appearance. The results show that the size and shape of the distribution area of this species vary depending on the number of records and on their spatial and environmental location, as well as on the particular delimitation method used. However, ecological niche modeling provides the best results in terms of spatial and numerical sensitivity as well as lower values of omission and a moderate extent of predicted areas. We suggest that decisions related to species conservation (categories of risk, areas of endemism, etc.), particularly those species of high geographical restriction, should be contingent on the formalised delimitation of distribution areas based on ecological niche modeling methods.