Are exotic plants more abundant in the introduced versus native range?

PEARSON, DEAN E.; EREN, ÖZKAN; ORTEGA, YVETTE K.; VILLARREAL, DIEGO; SENTÜRK, MUHYETTIN; MIGUEL, M. FLORENCIA; WEINZETTEL, C. MIGUEL; PRINA, ANÍBAL; HIERRO, JOSÉ L.

JOURNAL OF ECOLOGY (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Año: 2018 vol. 106 p. 727 - 736

0022-0477

1. Many invasion hypotheses postulate that introducing species to novel environmentsallows some organisms to escape population controls within the native rangeto attain higher abundance in the introduced range. However, introductions mayalso allow inherently successful species access to new regions where they mayflourish without increasing in abundance.2. To examine these hypotheses, we randomly surveyed semi-arid grasslands in thenative and two introduced ranges (12,000?21,000 km2 per range) to quantify localabundance (mean cover per occupied plot) and occurrence (percentage of 1-m2plots occupied) for 20 plant introductions that included pest and non-pest species.For each of these metrics, we evaluated relationships between abundance in theintroduced vs. native range (1) across all species and (2) according to designatedpest status in the introduced range. We predicted that if escape from populationcontrols primarily explained invader success, then these species would be moreabundant in the introduced range; while if invader success was driven primarily byintrinsic species attributes, then their abundance would be correlated betweenranges.3. Across all 20 invaders, we found that neither cover nor occurrence metrics werecorrelated between ranges. While cover was significantly higher in the introducedrange, this result was driven by pest species. When the four pest species were excluded,cover but not occurrence was correlated between ranges. Interestingly,whereas cover of pest and non-pest species was comparably low in the nativerange, pest species cover increased sevenfold in the introduced range.4. Synthesis. Our results confirm previous findings that local abundance in the nativerange predicts local abundance in the introduced range for many introduced plants,suggesting that intrinsic species? attributes may determine most invasion outcomes.However, we also found that some species increased in local abundance in the introduced range, suggesting that changes in biogeographic context may also playan important role. While these latter species were pests, the small sample size precludedstrong inferences. Determining what underlies the success of invasive pestsremains elusive due to their low representation among introduced species.