The adaptive challenge of extreme conditions shapes evolutionary diversity of plant assemblages at continental scales

Danilo M. Neves, Andrew J. Kerkhoff, Susy Echeverría-Londoño, Cory Merow, Naia Morueta-Holme, Robert K. Peet, Brody Sandel, Jens Christian Svenning, Susan K. Wiser, Brian J. Enquist

Research output: Contribution to journalArticlepeer-review

Abstract

The tropical conservatism hypothesis (TCH) posits that the latitudinal gradient in biological diversity arises because most extant clades of animals and plants originated when tropical environments were more widespread and because the colonization of colder and more seasonal temperate environments is limited by the phylogenetically conserved environmental tolerances of these tropical clades. Recent studies have claimed support of the TCH, indicating that temperate plant diversity stems from a fewmore recently derived lineages that are nested within tropical clades, with the colonization of the temperate zone being associated with key adaptations to survive colder temperatures and regular freezing. Drought, however, is an additional physiological stress that could shape diversity gradients. Here, we evaluate patterns of evolutionary diversity in plant assemblages spanning the full extent of climatic gradients in North and South America. We find that in both hemispheres, extratropical dry biomes house the lowest evolutionary diversity, while tropical moist forests and many temperatemixed forests harbor the highest. Together, our results support a more nuanced view of the TCH, with environments that are radically different from the ancestral niche of angiosperms having limited, phylogenetically clustered diversity relative to environments that show lower levels of deviation from this niche. Thus, we argue that ongoing expansion of arid environments is likely to entail higher loss of evolutionary diversity not just in the wet tropics but in many extratropical moist regions as well.

Original languageEnglish (US)
Article numbere2021132118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number37
DOIs
StatePublished - Sep 14 2021

Keywords

  • Angiosperms
  • Drought
  • Evolutionary diversity
  • Latitudinal diversity gradient
  • Phylogenetic clustering

ASJC Scopus subject areas

  • General

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