Spatial arrangement overrules environmental factors to structure native and non-native assemblages of synanthropic harvestmen

PLoS One. 2014 Mar 4;9(3):e90474. doi: 10.1371/journal.pone.0090474. eCollection 2014.

Abstract

Understanding how space affects the occurrence of native and non-native species is essential for inferring processes that shape communities. However, studies considering spatial and environmental variables for the entire community - as well as for the native and non-native assemblages in a single study - are scarce for animals. Harvestmen communities in central Europe have undergone drastic turnovers during the past decades, with several newly immigrated species, and thus provide a unique system to study such questions. We studied the wall-dwelling harvestmen communities from 52 human settlements in Luxembourg and found the assemblages to be largely dominated by non-native species (64% of specimens). Community structure was analysed using Moran's eigenvector maps as spatial variables, and landcover variables at different radii (500 m, 1000 m, 2000 m) in combination with climatic parameters as environmental variables. A surprisingly high portion of pure spatial variation (15.7% of total variance) exceeded the environmental (10.6%) and shared (4%) components of variation, but we found only minor differences between native and non-native assemblages. This could result from the ecological flexibility of both, native and non-native harvestmen that are not restricted to urban habitats but also inhabit surrounding semi-natural landscapes. Nevertheless, urban landcover variables explained more variation in the non-native community, whereas coverage of semi-natural habitats (forests, rivers) at broader radii better explained the native assemblage. This indicates that some urban characteristics apparently facilitate the establishment of non-native species. We found no evidence for competitive replacement of native by invasive species, but a community with novel combination of native and non-native species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ecosystem*
  • Geography
  • Humans
  • Luxembourg
  • Species Specificity
  • Spiders / physiology*

Grants and funding

Field work of CM in Luxembourg was funded by the Fonds National de la Recherche Luxembourg through an AMC2 – Mobility Mobility of researchers grant (FNR/09/AM2c/03)(http://www.fnr.lu/). The salary of TS was funded by the Federal Office for the Environment Switzerland (http://www.bafu.admin.ch/index.html?lang=en) and the Swiss National Science Foundation (http://www.snf.ch/E/Pages/default.aspx). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.