Water and energy availability mediate biodiversity patterns along an elevational gradient in the tropical Andes

Maria Laura Tolmos, Holger Kreft, Jorge Ramirez, Román Ospina, Dylan Craven

Research output: Contribution to journalArticlepeer-review

Abstract

Aim: How tree taxonomic and phylogenetic diversity vary with elevation at multiple spatial scales may provide new insights into the ecological and evolutionary processes influencing biogeographical patterns. The effect of water- and energy-related climatic variables on forests diversity across elevations, as well as how clades have evolved on and established across mountain regions lack consensus. Here, we tested whether changes in biodiversity with elevation are consistent with one of, or multiple, competing hypotheses: the water–energy dynamics (WED), species–energy relationship (SER), Tropical Niche Conservatism (TNC) and Out of The Tropics hypothesis (OTT). Location: Patia watershed, Colombia. Taxon: Seed plants (trees). Methods: We used a large dataset of 490 0.1 ha forest plots in nine elevational belts (545–3410 m a.s.l) that correspond to three different life zones, and quantified alpha and gamma scales using taxonomic and phylogenetic diversity indices. We fitted linear mixed-effects models to evaluate how taxonomic and phylogenetic alpha diversity changed with elevation, precipitation and aboveground biomass. We assessed taxonomic and phylogenetic beta diversity using the Sørensen index and its spatial turnover and nestedness components. Results: Taxonomic and phylogenetic alpha diversity decrease with elevation. Yet, at the gamma scale, taxonomic and phylogenetic diversity predominantly increased with elevation. Taxonomic and phylogenetic beta diversity were strongly influenced by species turnover, and followed a hump-shaped pattern with elevation. Main conclusions: Overall, diversity shows a decreasing trend at the local scale, while coarse-scale gamma diversity followed a pattern of nonlinear increases for both taxonomic and phylogenetic diversity. Evidence supports the influence of SER and WED on diversity patterns across elevations, yet neither evolutionary hypotheses had sufficient empirical support to be conclusive.

Original languageEnglish
JournalJournal of Biogeography
DOIs
StateAccepted/In press - 2022
Externally publishedYes

Bibliographical note

Funding Information:
Data collection was funded through an interinstitutional agreement between the University of Cauca and the Regional Autonomous Corporation of Cauca (CRC). No permits were required for this research. MLT acknowledges funding from the EPOS programme of the German Academic Exchange Service (DAAD), and the Studienstiftung des Deutschen Volkes. DC acknowledges funding from FONDECYT Project 1201347. We would like to thank Will Pearse, two anonymous reviewers and the handling editor for their insightful comments.

Publisher Copyright:
© 2022 The Authors. Journal of Biogeography published by John Wiley & Sons Ltd.

Keywords

  • elevational gradient
  • environmental filtering
  • evolutionary processes
  • phylogenetic diversity
  • spatial scales
  • taxonomic diversity
  • tree diversity
  • tropical Andes
  • water–energy dynamics

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