Assessing reliable and minimal-invasive methods for the monitoring of the longhorn beetle Rosalia alpina and implications for forest management

Different monitoring methods and data analysis procedures have been compared for the assessment of populations size and conservation status of the longhorn beetle Rosalia alpina. We surveyed the species in forests using visual encounters in natural condition, through the inspection of suitable trees for the species, and examining artificial habitat trees. Population sizes were analyzed using models which consider mark-recapture data and models that rely on simple count data. In order to provide minimal-invasive methods, we investigated the possible substitution of the canonical mark-recapture procedure (marking individual with pigments) with a procedure which exploits the "natural markings" of adult R. alpina (photographing the spots on the elytra). The reliability of computer-aided photographic identification was tested and an efficient workflow procedure for image capture and processing was elaborated using the software I3SC. Moreover, we investigated the habitat preference and population dynamics of the species in order to deduce best management practices for conservation. Within the study areas we identified a number of “key trees” for population surveys that should be maintained as well as open areas and decaying trees, likely to favor further colonization by R. alpina. Data were collected from populations of two National Parks in central Italy in 2014 and 2015. The study is part of the project MIPP (LIFE11 NAT/IT/000252), which aims to develop standard methods for the monitoring of saproxylic beetles listed in the Habitats Directive.