Disentangling the relative effects of environmental versus human factors on the abundance of native and alien plant species in Mediterranean sandy shores
Article first published online: 10 JUN 2010
© 2010 Blackwell Publishing Ltd
Diversity and Distributions
Volume 16, Issue 4, pages 537–546, July 2010
How to Cite
Carboni, M., Thuiller, W., Izzi, F. and Acosta, A. (2010), Disentangling the relative effects of environmental versus human factors on the abundance of native and alien plant species in Mediterranean sandy shores. Diversity and Distributions, 16: 537–546. doi: 10.1111/j.1472-4642.2010.00677.x
- Issue published online: 10 JUN 2010
- Article first published online: 10 JUN 2010
- Biological invasions;
- coastal dunes;
- diversity patterns;
- environmental and human determinants;
- exotic species;
- inference-based model
Aim Mediterranean coastal sand dunes are characterized by both very stressful environmental conditions and intense human pressure. This work aims to separate the relative contributions of environmental and human factors in determining the presence/abundance of native and alien plant species in such an extreme environment at a regional scale.
Location 250 km of the Italian Tyrrhenian coast (Region Lazio).
Methods We analysed alien and native plant richness and fitted generalized additive models in a multimodel-inference framework with comprehensive randomizations to evaluate the relative contribution of environmental and human correlates in explaining the observed patterns.
Results Native and alien richness are positively correlated, but different variables influence their spatial patterns. For natives, human population density is the most important factor and is negatively related to richness. Numbers of natives are unexpectedly lower in areas with a high proportion of natural land cover (probably attributable to local farming practices) and, to a lesser degree, affected by the movement of the coastline. On the other hand, alien species richness is strongly related to climatic factors, and more aliens are found in sectors with high rainfall. Secondarily, alien introductions appear to be related to recent urban sprawl and associated gardening.
Main conclusions Well-adapted native species in a fragile equilibrium with their natural environment are extremely sensitive to human-driven modifications. On the contrary, for more generalist alien species, the availability of limited resources plays a predominant role.