Biological Invasions

, Volume 14, Issue 4, pp 901–913

Darwin’s naturalization hypothesis up-close: Intermountain grassland invaders differ morphologically and phenologically from native community dominants

  • Dean E. Pearson
  • Yvette K. Ortega
  • Samantha J. Sears
Original Paper

DOI: 10.1007/s10530-011-0126-4

Cite this article as:
Pearson, D.E., Ortega, Y.K. & Sears, S.J. Biol Invasions (2012) 14: 901. doi:10.1007/s10530-011-0126-4

Abstract

Darwin’s naturalization hypothesis predicts that successful invaders will tend to differ taxonomically from native species in recipient communities because less related species exhibit lower niche overlap and experience reduced biotic resistance. This hypothesis has garnered substantial support at coarse scales. However, at finer scales, the influence of traits and niche use on invasibility and invader impacts is poorly understood. Within grasslands of western Montana, USA, we compared morphological and phenological traits for five top exotic invasive forbs and five dominant native forbs using multivariate techniques to examine niche separation between exotics and natives. Exotic forbs differed from native forbs in multivariate space. Phenologically, native forbs synchronized vegetative growth with bolting and flowering early in spring. In contrast, exotics initiated vegetative growth concurrent with natives but bolted and flowered later. Morphologically, vegetative growth of exotics was three times shorter and narrower, but flowering stem growth was 35% taller and 65% wider than the natives. Collectively, these patterns suggest different strategies of resource uptake and allocation. Additionally, following wildfire, survival was four times higher for exotics compared to natives, and three times more of the surviving exotics flowered. The exotics we examined appeared to be exploiting an empty community-level niche. The resulting pattern of trait differences between exotics and natives suggests a predictable pattern of invasion and a predictable trajectory of community change. Our results illustrate how quantifying trait differences between invading exotics and natives at the within-community scale can improve understandings of community invasibility and invader impacts.

Keywords

Biotic resistanceFireInvasionLife history strategyMorphologyNichePhenology

Copyright information

© Springer Science+Business Media B.V. (outside the USA) 2011

Authors and Affiliations

  • Dean E. Pearson
    • 1
    • 2
  • Yvette K. Ortega
    • 1
  • Samantha J. Sears
    • 1
  1. 1.Rocky Mountain Research StationUSDA Forest ServiceMissoulaUSA
  2. 2.Division of Biological SciencesUniversity of MontanaMissoulaUSA