Aridity weakens population-level effects of multiple species interactions on Hibiscus meyeri

Allison M. Louthan, Robert Mitchell Pringle, Jacob R. Goheen, Todd M. Palmer, William F. Morris, Daniel F. Doak

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Predicting howspecies' abundances and rangeswill shift in response to climate change requires a mechanistic understanding of how multiple factors interact to limit population growth. Both abiotic stress and species interactions can limit populations and potentially set range boundaries, but we have a poor understanding of when and where each is most critical. A commonly cited hypothesis, first proposed by Darwin, posits that abiotic factors (e.g., temperature, precipitation) are stronger determinants of range boundaries in apparently abiotically stressful areas ("stress" indicates abiotic factors that reduce population growth), including desert, polar, or highelevation environments, whereas species interactions (e.g., herbivory, competition) play a stronger role in apparently less stressful environments. We tested a core tenet of this hypothesis-that population growth rate is more strongly affected by species interactions in less stressful areas-using experimental manipulations of species interactions affecting a common herbaceous plant, Hibiscus meyeri (Malvaceae), across an aridity gradient in a semiarid African savanna. Population growth was more strongly affected by four distinct species interactions (competition with herbaceous and shrubby neighbors, herbivory, and pollination) in less stressful mesic areas than in more stressful arid sites. However, contrary to common assumptions, this effect did not arise because of greater density or diversity of interacting species in less stressful areas, but rather because aridity reduced sensitivity of population growth to these interactions. Our work supports classic predictions about the relative strength of factors regulating population growth across stress gradients, but suggests that this pattern results from a previously unappreciated mechanism that may apply to many species worldwide.

Original languageEnglish (US)
Pages (from-to)543-548
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number3
DOIs
StatePublished - Jan 16 2018

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Abiotic stress
  • Climate change
  • Population growth
  • Range boundaries
  • Species interactions

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