Habitat preferences, dispersal and demography of two saproxylic longhorn beetles (Cerambycidae: Rosalia alpina, Morimus asper funereus): A case study from the Julian Alps, Slovenia

Saproxylic beetles are a diverse and predominant functional group that depend on dead or dying wood. We studied a population of two saproxylic longhorn beetles Rosalia alpina and Morimus asper funereus in a system of 12 potentially suitable habitat patches in a forest reserve in Triglav National Park, Slovenia. For each species we determined demographic parameters, dispersal, and microhabitat preference. We marked 68 individuals of M. a. funereus , 27 individuals of R. alpina . The best-fitting MARK model for M. a. funereus suggested the presence of two groups with different capture probabilities, probably a larger group of non-territorial males and females with lower capture probability, and a smaller group (1–13% of the population) of territorial males with higher capture probability. The total population size was estimated to be about 208 individuals (95% confidence interval 118–462) of M. a. funereus . For R. alpina , estimation of population size was not possible due to scarce recaptures. We detected several short-distance movements (maximum 34 m) for M. a. funereus and rare but longer movements for R. alpina (maximum 457 m). A preference for dead (preferred by R. alpina ) or decaying (preferred by M. a. funereus ) beech trees ( Fagus sylvatica ) with large diameters was observed for both species. Implications for insect conservation: Forest reserves with negligible human impact and an abundance of old, intact trees are important for the successful life cycle of both species studied, even more so when both competing species occur together.