Annual activity of two endemic beetles (Carabidae) at the edge between fell-field and moorland on a sub-Antarctic island

Abstract

At Ile de la Possession (Iles Crozet), an Indian Ocean sub-Antarctic island, the two typical habitats are the fell-field above 150 m in altitude and the moorland in low altitude zones. The boundary between fell-field and moorland is usually very sharp (less than 5 m). This paper presents the first full-year pitfall trapping study of insect activity on both sides of this boundary, with particular reference to the habitat distribution and annual distribution of surface activity of the two endemic carabids of Iles Crozet: Amblystogenium pacificum Putzeys and A. minimum Luff. A. pacificum was abundant in moorland (399 specimens) while A. minimum was vanishingly rare (three specimens). In fell-field in contrast, both species were taken in similar although small numbers (86 and 92, respectively). A. pacificum remained active in the moorland for the whole year, with no winter reduction in trap catches. Pitfall trapping results also showed no surface activity by A. pacificum in winter on fell-field, where both sexes here likely maintain the required level of both feeding and mate encounter in the inter-stone crevices of the multi-layered stony part of the fellfield.