Historical Invasion Records Can Be Misleading: Genetic Evidence for Multiple Introductions of Invasive Raccoons (Procyon lotor) in Germany

PLoS One. 2015 May 6;10(5):e0125441. doi: 10.1371/journal.pone.0125441. eCollection 2015.

Abstract

Biological invasions provide excellent study systems to understand evolutionary, genetic and ecological processes during range expansions. There is strong evidence for positive effects of high propagule pressure and the associated higher genetic diversity on invasion success, but some species have become invasive despite small founder numbers. The raccoon (Procyon lotor) is often considered as a typical example for such a successful invasion resulting from a small number of founders. The species' largest non-native population in Germany is commonly assumed to stem from a small number of founders and two separate founding events in the 1930s and 1940s. In the present study we analyzed 407 raccoons at 20 microsatellite loci sampled from the invasive range in Western Europe to test if these assumptions are correct. Contrary to the expectations, different genetic clustering methods detected evidence for at least four independent introduction events that gave rise to genetically differentiated subpopulations. Further smaller clusters were either artifacts or resulted from founder events at the range margin and recent release of captive individuals. We also found genetic evidence for on-going introductions of individuals. Furthermore a novel randomization process was used to determine the potential range of founder population size that would suffice to capture all the alleles present in a cluster. Our results falsify the assumption that this species has become widespread and abundant despite being genetically depauperate and show that historical records of species introductions may be misleading.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ecosystem
  • Founder Effect
  • Genetic Variation / genetics*
  • Genetics, Population
  • Germany
  • Introduced Species*
  • Microsatellite Repeats / genetics*
  • Raccoons / genetics*
  • United States

Associated data

  • Dryad/10.5061/dryad.412H3

Grants and funding

MH and the laboratory work was funded by the German Science Foundation (www.dfg.de, GRK 1319) as part of the interdisciplinary graduate school ‘Cooperation of Science and Jurisprudence in Improving Development and Use of Standards for Environmental Protection – Strategies for Risk Assessment and Management’. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.