Overwintering ability and habitat preference of Morimus asper: a two-year mark-recapture study with implications for conservation and forest management

Abstract

Morimus asper is a saproxylic longhorn beetle associated with mature forests. Its flightless condition makes its colonization of new trees in fragmented areas difficult. Our 2-year mark-recapture study revealed new information about the survival ability, population dynamics and habitat preference of M. asper in three beech forests of central Italy. Daily surveys were performed from May to July in 2013 and 2014, inspecting suitable trees for hosting the species. A low percentage of overwintered adults was observed for both sexes, with a very long lifespan: 282–409 days. Almost all individuals were recaptured on the tree of their first capture, and dispersal (20–451 m) was recorded only in thirteen individuals. Adult phenology showed two peaks of activity (middle of May and middle of June). Population estimates varied significantly according to site and year. Mean daily temperature affected recapture probability and total captures (optimal range of 15–26 °C). The species showed preference for huge lying trees, branches on the ground, a low percentage of debarked surface and high canopy closure. M. asper showed a high survival probability, but the few movements observed, combined with its flightless condition, suggest strongly that this species has a low dispersal ability, highly threatened by local fragmentation. Furthermore, almost all captures were made on the same tree, making this a “key tree” for population viability. Forest management techniques should retain many lying trees, abundant coarse woody debris and a dense canopy that ensures a ‘cooler’ temperature in the understory, favouring M. asper and its conservation.