The Latitudinal Diversity Gradient: Novel Understanding through Mechanistic Eco-evolutionary Models

• Published in: Trends in ecology & evolution (Amsterdam) 2019-03, Vol.34 (3), p.211-223
• Main Authors: Pontarp, Mikael, Bunnefeld, Lynsey, Cabral, Juliano Sarmento, Etienne, Rampal S., Fritz, Susanne A., Gillespie, Rosemary, Graham, Catherine H., Hagen, Oskar, Hartig, Florian, Huang, Shan, Jansson, Roland, Maliet, Odile, Münkemüller, Tamara, Pellissier, Loïc, Rangel, Thiago F., Storch, David, Wiegand, Thorsten, Hurlbert, Allen H.
• Format: Article
• Language: English
• Subjects: biogeography; diversity patterns; ecology; Ecology, environment; Ecosystems; evolution; Life Sciences; macroecology; mechanistic modeling; Symbiosis
• ISSN: 0169-5347; 1872-8383
• DOI: 10.1016/j.tree.2018.11.009

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. The latitudinal diversity gradient (LDG) is one of the most widely debated patterns in ecology and evolution, associated with hundreds of papers, dozens of hypotheses, and disagreements about its underlying processes. The lack of agreement stems from: (i) the verbal nature of existing hypotheses, (ii) the failure to mechanistically integrate all relevant ecological and evolutionary processes to the LDG, and (iii) the degree to which many empirical patterns are consistent with multiple LDG explanations. We show how mapping LDG hypotheses to a set of key ecological and evolutionary processes leads to a better understanding of the internal logic of those hypotheses. The codification of those processes within a mechanistic eco-evolutionary model is essential for contrasting support for hypotheses and for understanding the relative importance of the processes themselves.