AND

Abstract.—Estimation of the dimensions of fundamental ecological niches of species to predict their geographic distributions is increasingly being attempted in systematics, ecology, conservation, public health, etc. This technique is often (of necessity) based on data comprising records of presences only. In recent years, modeling approaches have been devised to estimate these interrelated expressions of a species’ ecology, distributional biology, and evolutionary history—nevertheless, a formal basis in ecological and evolutionary theory has largely been lacking. In this paper, we outline such a formal basis to clarify the use of techniques applied to the challenge of estimating ‘ecological niches; ’ we analyze example situations that can be modeled using these techniques, and clarify interpretation of results. Key words.—ecological niche, fundamental niche, realizad niche, geographic distribution The fact that, at certain scales, climatic and physical factors affect profoundly the distributions of species has been known for a very long time. In the last two decades, mathematical techniques designed to estimate the geographic extent of the “fundamental ecological niche ” (FN), or subsets o