Which coexistence mechanisms should biogeographers quantify? A reply to Alexander et al.

Abstract

An important challenge is the integration of biogeography and community ecology. This challenge is exemplified by controversies over the role of biotic interactions in shaping species’ range limits. In a recent paper [1], we argued that a key avenue for this integration is the explicit focus on the ability of a species to increase when rare, which is central to the use of ecological niche models in single-species biogeography (e.g., [2]) as well as coexistence theory in community ecology 3, 4, 5, 6. Alexander et al.[7] suggest that additional insights may come from distinguishing species’ ‘average fitness differences’ and ‘niche differences’. When studying the presence of a single species (the problem we discuss in [1]), it may typically be unnecessary to characterize fitness differences and niche differences, but for other biogeographic problems focusing on multiple species simultaneously, we see promise in Alexander et al.’s suggestion, although, as we note below, implementing it will be challenging.