Patterns of exotic species richness of different taxonomic groups in a fragmented landscape of central Chile

Abstract

Despite many studies have documented that fragmentation facilitates biological invasions, studies performed in different taxonomic groups have observed contrasting patterns. Unfortunately, the use of different ecosystems and fragmentation metrics among studies does not allow assessing the generality of the effect of fragmentation on invasion among different taxa. Studies evaluating the simultaneous responses of exotic species from different taxonomic groups to the same fragmentation patterns may help to assess generality of this relationship. Temperate forests in coastal central Chile are largely a suite of fragments of different sizes surrounded mainly (but not exclusively) by Pinus radiata plantations. Here, we evaluated exotic species richness of vascular plants, insects, mammals and birds in the coastal Maulino forest in a continuous native forest, fragments of native forest and Pinus radiata plantations. Species richness of exotic species of all taxa varied similarly across landscape units. Plantations presented the highest number of exotic species, followed by fragments and finally the continuous forest. In addition, regarding all exotic species, landscape units showed a nested pattern in which most exotic species present in the continuous forest were also present in fragments; and most species present in fragments were present in the pine plantation as well. Our results suggest that fragmentation may affect invasion of different taxa in a similar way, and that continuous forests may efficiently resist invasion. Our results also suggest that given that most of the native forest of south-central Chile is distributed in small fragments, it seems urgent to start an exotic species control to maintain their conservation value.