Competition does not come at the expense of colonization in seed morphs with increased size and dispersal

M. Florencia Miguel, Christopher J. Lortie, Ragan M. Callaway, José L. Hierro

Research output: Contribution to journalArticlepeer-review

Abstract

PREMISE OF THE STUDY: Seed-level trade-offs of heterocarpic species remain poorly understood. We propose that seedlings emerging from seeds with a permanent pappus (dispersing seeds) are stronger competitors than those emerging from seeds without a pappus (nondispersing seeds) because dispersing seeds are larger and germinate faster than nondispersing seeds in Centaurea solstitialis. METHODS: We conducted a competition experiment with both seed morphs, in which we recorded emergence rate and proportion, estimated seed dispersal by wind (anemochory) and by mammals (exozoochory), and measured size and abundance of seed morphs. KEY RESULTS: We found that seedlings from pappus seeds had greater competitive abilities than those from non-pappus seeds. Similarly, pappus seedlings emerged at much faster rates and larger proportions than non-pappus seedlings. Pappus seeds were larger, were more numerous, and displayed improved exozoochory compared to non-pappus seeds. Anemochory was poor for both seed morphs. CONCLUSIONS: We found support for our hypothesis, raising in turn the possibility that competition and colonization are positively associated in seed morphs of heterocarpic species with enhanced exozoochory of larger seeds. These findings are not consistent with those from heterocarpic species with enhanced anemochory of smaller seeds or slower-germinating seeds. Our results additionally suggest that pappus and non-pappus seeds of C. solstitialis display a task-division strategy in which pappus morphs colonize and preempt unoccupied sites through improved dispersal and fast and large emergence of seedlings with increased competitive abilities, whereas non-pappus morphs promote site persistence through delayed germination and dormancy. This strategy may contribute to the success of C. solstitialis in highly variable environments.

Original languageEnglish
Pages (from-to)1323-1333
Number of pages11
JournalAmerican Journal of Botany
Volume104
Issue number9
DOIs
StatePublished - 2017

Keywords

  • Anemochory
  • Bet-hedging
  • Centaurea solstitialis
  • Competition
  • Dispersal
  • Dormancy
  • Exozoochory
  • Heterocarpy
  • Life history traits
  • Seed size

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