Is functional connectivity in common grasshopper species affected by fragmentation in an agricultural landscape?

Abstract

This study assessed the effects of a fragmented and intensively used agricultural landscape in Switzerland (study area: 95km2) on functional habitat connectivity of three common grasshopper species with different levels of habitat specialisation, Chorthippus albomarginatus, C. biguttulus and Gomphocerippus rufus. A combination of habitat suitability analysis (ecological niche factor analysis) with landscape genetic methods (clustering and least-cost transect analysis) was applied. This enabled the identification of population genetic structure, the habitats where species reproduce and the habitats through which species disperse. For all three study species, there was no distinct population genetic structure detected, and mean pairwise genetic differentiation was generally low (FST≤0.05), although highest for the least mobile species G. rufus. Habitat suitability analysis largely confirmed expectations from literature, finding a large area of suitable habitat for both C. albomarginatus and C. biguttulus in the study area. In contrast, the reproductive habitat of the more specialised species G. rufus was more distinct and less widespread. Furthermore, a most likely dispersal habitat could not be clearly identified for C. albomarginatus and C. biguttulus, but G. rufus seemed to disperse through forests. None of the three species showed a preference for dispersal paths through the mapped reproductive habitat. In conclusion, this study detected only a minor effect of a fragmented agricultural landscape on functional habitat connectivity in three common grasshopper species. The effects were more pronounced for G. rufus, which was the most specialised and least mobile of the three study species. These results exhibit an overall positive perspective for the long-term persistence of common grasshopper species in intensively managed agricultural landscapes.