Commonly rare and rarely common: comparing population abundance of invasive and native aquatic species.

Marit Izzo,Peter B. McIntyre,Julian D. Olden,M. Jake Vander Zanden,Michael Somers,Gretchen J. A. Hansen,Matthew S. Kornis,Michael J. Blum,Alison Mikulyuk,Erika Nilsson,Murray K. Clayton,Ernie F. Hain,Jennifer Hauxwell,Sapna Sharma,Monica Papeş

doi:10.1371/journal.pone.0077415

Abstract

Invasive species are leading drivers of environmental change. Their impacts are often linked to their population size, but surprisingly little is known about how frequently they achieve high abundances. A nearly universal pattern in ecology is that species are rare in most locations and abundant in a few, generating right-skewed abundance distributions. Here, we use abundance data from over 24,000 populations of 17 invasive and 104 native aquatic species to test whether invasive species differ from native counterparts in statistical patterns of abundance across multiple sites. Invasive species on average reached significantly higher densities than native species and exhibited significantly higher variance. However, invasive and native species did not differ in terms of coefficient of variation, skewness, or kurtosis. Abundance distributions of all species were highly right skewed (skewness>0), meaning both invasive and native species occurred at low densities in most locations where they were present. The average abundance of invasive and native species was 6% and 2%, respectively, of the maximum abundance observed within a taxonomic group. The biological significance of the differences between invasive and native species depends on species-specific relationships between abundance and impact. Recognition of cross-site heterogeneity in population densities brings a new dimension to invasive species management, and may help to refine optimal prevention, containment, control, and eradication strategies.

Highlights

Invasive species are recognized as leading drivers of environmental change, and can produce significant economic and ecological impacts [1]
For data collected by the authors, all animals were captured following protocols approved by the relevant Institutional Animal Care and Use Committee (IACUC), and permits for sampling were obtained from the appropriate authorities
The average abundance of invasive and native species was 6% and 2%, respectively, of the maximum abundance observed within a taxonomic group

Summary

Introduction

Invasive species are recognized as leading drivers of environmental change, and can produce significant economic and ecological impacts [1]. It has long been recognized that only a small fraction of introduced species will establish, spread, and cause impacts [6]. As a result, identifying species likely to cause ecological or economic impacts and predicting locations that are likely to be most vulnerable are important goals of invasive species research and management [7,8,9]. In principle it is recognized that abundance (and impact) of invasive species varies among sites, few attempts to quantify relative impacts of invasive species incorporate spatial variability in abundance [8]. We may miss important insights by ignoring variability among sites in invasive species abundance

Methods

Results

Discussion

Conclusion