The effect of landscape composition on colonization success, growth rate and dispersal in introduced bush-crickets Metrioptera roeseli

Abstract

1. Fragmentation and habitat loss affects both existing and introduced populations. Small habitat areas may have harsher biotic and abiotic conditions, as well as restricting population sizes. Loss of connectivity reduces the opportunities for individuals to move between patches to rescue populations or to re-colonize patches. Knowledge of how landscape composition affects the introduced populations is therefore essential for successful management and future re-introductions. 2. To study the effect of landscape composition and structure on the success of colonization, population growth and dispersal distances, we introduced Roesel's bush-crickets Metrioptera roeseli to 70 habitat islands in areas previously unoccupied by the species. The introduction sites differed in habitat area and connectivity. The population survival and dispersal were then studied for 5 years after initial introductions. 3. In addition to results showing the importance of suitable habitat for population persistence, connectivity in form of linear landscape elements and nodes was also crucial. Linear landscape elements and/or nodes were important for colonization success, growth and dispersal. Linear landscape elements and nodes also reduced the negative effects of unsuitable habitat (matrix) and isolation from suitable habitat and on the populations. 4. These results stress the importance of connectivity in the landscape for population survival and establishment. Consideration of this should be taken into account in both management and re-introductions of bush-crickets and other invertebrates with similar population characteristics and behaviour.