The latitudinal diversity gradient: novel understanding through mechanistic eco-evolutionary models
Abstract
The latitudinal diversity gradient (LDG) is one of the most widely studied patterns in ecology, yet no consensus has been reached about its underlying causes. We argue that the reasons for this are the verbal nature of existing hypotheses, the failure to mechanistically link interacting ecological and evolutionary processes to the LDG, and the fact that empirical patterns are often consistent with multiple explanations. To address this issue, we synthesize current LDG hypotheses, uncovering their eco-evolutionary mechanisms, hidden assumptions, and commonalities. Furthermore, we propose mechanistic eco-evolutionary modeling and an inferential approach that makes use of geographic, phylogenetic, and trait-based patterns to assess the relative importance of different processes for generating the LDG.
What the paper shows and why it matters (AI-generated)
The latitudinal diversity gradient has been studied for over a century without consensus, and this review argues that's partly a methodological failure: existing hypotheses are stated verbally, rarely linked mechanistically to underlying eco-evolutionary processes, and often equally consistent with the same empirical pattern. The proposed fix — mechanistic eco-evolutionary models tested against geographic, phylogenetic and trait data jointly, rather than gradient-fitting alone — set an agenda the field has visibly followed since, with nearly 250 citing papers spanning tetrapod diversity dynamics, cricket assemblages and sparrow biogeography.