Landscape corridors can increase invasion by an exotic species and reduce diversity of native species

Background/Question/Methods

Although corridors are often used to mitigate negative effects of habitat fragmentation, concerns persist that they may facilitate the spread of invasive species. In a large-scale experiment (n = 8 blocks), we measured effects of corridors on the invasive fire ant, Solenopsis invicta, and on communities of native ants. Fire ants have distinct two social forms: polygyne, which disperse poorly but establish at high densities, and monogyne, which disperse well but establish at low densities.

Results/Conclusions

In experimental landscapes dominated by polygyne fire ants (n = 3), fire ant abundance was higher (36% higher pitfall trap incidence; P = 0.02) and native ant diversity was lower ( 23% lower species richness and 11% lower evenness; P < 0.05), in habitat patches connected by corridors, compared to unconnected patches. In contrast, in landscapes dominated by monogyne fire ants (n = 5), habitat connectivity had no influence on fire ant abundance or native ant diversity. Polygyne fire ants dominated recently created habitat patches, suggesting their responses to corridors may be transient. These results demonstrate that corridors can facilitate the invasion of some non-native species, and highlight the importance of considering species’ traits when assessing the utility of corridors in conservation.