Biological Invasions

, Volume 12, Issue 6, pp 1627–1640

The distribution of native and exotic plants in a naturally fragmented sagebrush-steppe landscape

Authors

  • Randy Bangert
    • Department of Biological Sciences and Center for Ecological Research and EducationIdaho State University
    • Department of Biological Sciences and Center for Ecological Research and EducationIdaho State University
    • National Science Foundation
Original Paper

DOI: 10.1007/s10530-009-9575-4

Cite this article as:
Bangert, R. & Huntly, N. Biol Invasions (2010) 12: 1627. doi:10.1007/s10530-009-9575-4

Abstract

We tested two general hypotheses for the diversity of native and exotic plants in an undisturbed, naturally fragmented sagebrush-steppe landscape in SE Idaho, USA, evaluating whether the MacArthur–Wilson hypothesis of island biogeography or a suite of environmental variables explained the distributions of native and exotic plants. We also tested a third hypothesis, which incorporated assumptions about the origin of exotic plants and their interaction with native plants. Of the three hypotheses we tested, the hypothesis that included exotic species best explained the diversity of the native plant community. The MacArthur–Wilson model of island biogeography did not explain the diversity of native (R 2 = 0.13) or exotic plants well (R 2 = 0.11), and the model fit the data poorly. A model of environmental variables better explained the diversity of native (R 2 = 0.48) and exotic plants (R 2 = 0.57), but it also fit the data poorly. Instead, proximity to a railroad explained the cover (R 2 = 0.59) and richness of exotic plants (R 2 = 0.63), which then explained the species richness of native plants (R 2 = 0.34), and the model fit was adequate and had the lowest AIC value. This suggests that the transportation corridor had a significant, though indirect, effect on the native plant community, even in this undisturbed area. Moreover, explained variance, model fit, and the AIC model selection criteria favored the model with the railroad and exotic species over the M–W and environmental models. Since the habitat patches we studied were largely undisturbed by people and their activities, our results further suggest that the transportation corridor influenced the distribution of exotic plants by serving as a vector for colonization, rather than as a source of disturbance. Additionally, the results suggest that exotic plant species have had a negative effect on the diversity of the native plant community and have changed its composition. The results also support the inference that the nascent exotic plant community is influenced by source-sink (Pulliam in Am Nat 132:652–661, 1988) and assembly dynamics. In contrast, the native plant community appears to be more strongly influenced by environmental conditions associated with an elevational gradient, but there is evidence that the native community also has undergone directional change in species composition, associated with the invasion by non-native species.

Keywords

Craters of the Moon National Monument and Preserve Environment Exotic plants Geomorphic fragmentation Insular habitat fragments Island biogeography theory Kipuka Native plants Structural equation models Transportation corridor

Abbreviations

CRMO

Craters of the Moon National Monument and Preserve

M–W

MacArthur–Wilson model of island biogeography

SR

Species richness

SEM

Structural equation model

PCoA

Principal coordinates analysis

Supplementary material

10530_2009_9575_MOESM1_ESM.docx (21 kb)
(DOCX 20 kb)

Copyright information

© Springer Science+Business Media B.V. 2009