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Della Rocca F.,University of Pavia | Stefanelli S.,University of Pavia | Pasquaretta C.,University of Strasbourg | Pasquaretta C.,French National Center for Scientific Research | And 3 more authors.
Journal of Insect Conservation | Year: 2014

Saproxylic beetles may act as bio-indicators of high-quality mature woodlands, and their conservation is strongly linked to the quality and quantity of deadwood in a biotope. We tested the effect of deadwood accumulation and habitat variables on saproxylic species richness by investigating six sampling sites under different deadwood management practices that belong to both alluvial and riparian mixed forests of the Po plain, Italy. We sampled 43 obligate saproxylic species. The main factor predicting saproxylic species richness was the amount of deadwood measured by both log diameter and volume. We found a threshold of 0.22 m diameter (confidence interval CI 0.18-0.37 m) and 32.04 m3/ha volume (CI 16.09-64.09 m3/ha) below which saproxylic beetle richness would be significantly reduced and a threshold of 35 m3/ha dead wood volume (CI 33-40 m3/ha) over which species richness increases by <5 %. The other deadwood and environmental components influenced saproxylic beetle richness to a lesser extent; some of them, however, should still be considered for proper management. Forest structure variables describing forest density such as large trees and basal areas have a negative effect on species richness. According to the results of our study, stumps and advanced decaying class are positively correlated, while small logs are negatively correlated to species richness. Thus, in extensively managed forests, the regular cutting of trees should be implemented to create artificial stumps, in order to assure a continuity of deadwood and, in the meantime, increase the number and width of openings in the forest. Moreover, prolonging rotation times can assure the presence of deadwood at intermediate/later stages of decay. © 2014 Springer International Publishing Switzerland.

Hybosorus hopei A. Costa, 1844 from Naples environs (Italy), described in the Lamellicornia, was later moved by Costa himself to the genus Trachyscelis Latreille, 1809 (Tenebrionidae) but was overlooked by almost all subsequent authors. Its history is summarized and the following new synonymy is established: Trachyscelis aphodioides Latreille, 1809 = Hybosorus hopei A. Costa, 1844 syn. nov. Up-to-date global and Italian distributions of T. aphodioides are provided. Copyright © 2010 Magnolia Press.

Hardersen S.,Centro Nazionale per lo Studio | Macagno A.L.M.,Centro Nazionale per lo Studio | Macagno A.L.M.,University of Rome La Sapienza | Sacchi R.,University of Pavia | Toni I.,Centro Nazionale per lo Studio
European Journal of Entomology | Year: 2011

In insects, allometries of exaggerated traits such as horns or mandibles are often considered species specific and constant during a season. However, given that constraints imposed by the advancing season affect the developmental processes of organisms, these allometries may not be fixed, and the switch point between morphs may vary between populations and within populations during a season. The hypothesis of such a seasonal variation in exaggerated traits was tested using the dimorphic males of the beetle Lucanus cervus. The remains of specimens killed by predators were collected along forest tracks from mid May to late August 2008 in a protected lowland forest in northern Italy. The largest beetles were collected in mid May and average size thereafter decreased. Males collected early in the season mostly had large mandibles (i.e. they belonged to the major morph). In contrast, late in the season the probability of finding males with large mandibles was very low. The threshold body size determining morph expression also shifted during the season. Early in the season, the threshold pronotum width for a 50% chance of developing into the major morph was 1.74 cm, whereas later in the season it was 1.90 cm. This shift in the threshold body size was interpreted as the effect of phenotypic plasticity in a population exposed to constraints imposed by the advancing season.

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