Agnese Zauli

Surveying an endangered saproxylic beetle, Osmoderma eremita, in Mediterranean woodlands: a comparison between different capture methods

Measuring population size is riddled with difficulties for wildlife biologists and managers, and in the case of rare species, it is sometimes practically impossible to estimate abundance, whereas estimation of occupancy is possible. Furthermore, obtaining reliable population size estimates is not straightforward, as different sampling techniques can give misleading results. A mark-recapture study of the endangered saproxylic beetle Osmoderma eremita was performed in central Italy by applying four independent capture methods within a study area where 116 hollow trees were randomly selected to set traps. Detection probability and population size estimates were drawn from each of these four capture methods. There were strong differences in detection probability among methods. Despite using pheromone and beetle manipulation, capture histories were not affected by trap-happiness or trap-shyness. Population size estimates varied considerably in both abundance and precision by capture method. A number of 0.5 and 0.2 adult beetles per tree was estimated using the whole data set by closed and open population models, respectively. Pitfall trap appeared the optimal method to detect the occurrence of this species. Since in the southern part of its distribution range, a single population of O. eremita is widespread in the landscape, and includes beetles from more than one hollow tree, conservation efforts should focus not only on preserving few and isolated monumental hollow trees, but should be extended to large stands.

Habitat of an endangered saproxylic beetle, Osmoderma eremita, in Mediterranean woodlands

Abstract: The habitat of Osmoderma eremita, a European endangered beetle species restricted to tree cavities, was examined in central Italy, at the southernmost limit of its distributional range. The occurrence of adults, larvae, and fragments was investigated in 170 and 151 living hollow trees by pitfall trapping and sampling of wood mould (i.e., loose material) in the hollow, respectively. Overall, O. eremita was present in 22% of the trees, which belonged to 4 different tree species (Ostrya carpinifolia, Quercus suber, Acer obtusatum, and Quercus pubescens). The frequency of presence was higher in cavities with more than 4 L of wood mould, in cavities with dry or half-moist wood mould rather than wet wood mould, and with wood mould with low soil contamination. A comparison with northern regions indicated that the warmer macro-climatic conditions in the south make the species independent of a warm microclimate. As most of the hollow trees contain only a small amount of wood mould (<4 L), the habitat quality is generally poorer than in oak pastures studied in northern Europe.

Interactions between larvae of the threatened saproxylic beetle Osmoderma eremita and other flower chafers in Mediterranean woodlands: implications for conservation

Interactions between larvae of one of the most charismatic and threatened saproxylic beetles, Osmoderma eremita (Scopoli, 1763), and other flower chafer species (Coleoptera: Scarabaeidae) were investigated by taking samples of wood mould, i.e. loose material inside the cavity, from 151 living hollow trees in two Mediterranean woodlands during August 2010. Multi‐species occupancy models estimate low occupancy probabilities for both O. eremita (ψ ± SE = 0.36 ± 0.13) and other flower chafer species (0.42 ± 0.06), which showed similar microhabitat requirements without competing. In cavities where larvae of both groups were present, the probability of detecting O. eremita during the sieving of 2 l of wood mould was not affected by whether larvae of other flower chafers occur in the same sample and vice versa. Unexpectedly, larvae of O. eremita were detected with a higher probability when larvae of other flower chafers occurred in the cavity. Model selection statistics strongly support that increasing the sampled volume of wood mould increases the probability of detecting larvae, especially for O. eremita. Wood mould sampling resulted in a reliable method for detecting the presence of O. eremita larvae, but further studies are needed to investigate the potential damage caused by this procedure in the fragile microhabitat of tree cavities. To preserve populations of O. eremita and other flower chafers, management actions should be focused on increasing the density of hollow trees and the volume of tree cavities by favouring the natural ageing of trees and by creating artificial habitats in living trees.

Exaggerated Allometric Structures in Relation to Demographic and Ecological Parameters in Lucanus cervus (Coleoptera: Lucanidae)

Enlarged weapons and ornamental traits under sexual selection often show a positive allometric relationship with the overall body size. The present study explores the allometry of mandibles and their supporting structure, the head, in males of the European stag beetle, Lucanus cervus. This species shows a remarkable dimorphism in mandible shape and size that are used by males in intraspecific combats. Stag beetles were captured, measured, weighed, and released in the framework of a capture‐mark‐recapture study. The relationship of mandible length (ML) and head width in respect to the overall body size was described by a segmented regression model. A linear relationship was detected between ML and head width. The scaling relationships for both ML and head width identified the same switchpoint, highlighting the advantages of using combined results of weapons and their supporting structures in such analysis. These results led to a more consistent distinction of males in two morphologies: minor and major. The survival probability of individuals was dependent on the morphological class and was higher for minor males than for major. Elytron length and body mass of the individuals did not show any significant variation during the season. Differences in predatory pressure were detected between morphs by the collection and analysis of body fragments due to the predatory activity of corvids. Morphological differences and shift in demographic and ecological parameters between the two classes suggested that selection continues to favor intrasexual dimorphism in this species throughout a trade‐off mechanism between costs and benefits of carrying exaggerated traits. J. Morphol. 276:1193–1204, 2015.

Antennal fine morphology of the threatened beetle Osmoderma eremita (Coleoptera: Scarabaeidae), revealed by scanning electron microscopy.

The aim of this study was to characterize the antennal morphology of Osmoderma eremita, a threatened scarab beetle inhabiting tree hollows. O. eremita males produce a sex pheromone, (R)‐(+)‐γ‐decalactone, responsible mainly for the attraction of females but also other males. Gross and fine morphology of microstructures including sensilla, microsculpture and pores were analyzed using Scanning Electron Microscopy. The antenna of O. eremita showed the typical lamellicorn shape of scarab beetles, with a basal scape, a pedicel, a funicle composed of five antennomeres and a club composed of three lamellae. Six different subtypes of sensilla chaetica (Ch.1 − 6), Böhm sensilla (Bo), one subtype of sensilla basiconica (Ba.1), two subtypes of sensilla coeloconica (Co.1 − 2), two subtypes of sensilla placodea (Pl.1 − 2), pores and peculiar folds were described. The two sexes did not show any significant differences in the occurrence and number of the sensilla placodea, known to be responsible for the pheromone reception. Instead, some sexual differences were found on the occurrence and topology of three different microstructures: (1) one subtype of sensillum chaeticum (Ch.2) occurring on the pedicel only in males; (2) a characteristic pore occurring on the funicle only in males; (3) a peculiar fold occurring on different antennomeres of the funicle in the two sexes, on the fourth in males and on the fifth in females. A comparison between sensilla of O. eremita and those of other Scarabaeoidea is provided. Microsc. Res. Tech. 79:178–191, 2016.

Scanning electron microscopy analysis of the antennal sensilla in the rare saproxylic beetle Elater ferrugineus (Coleoptera: Elateridae)

Abstract This work provides the first morphological analysis (both at gross and fine level) of the antennal structures in the genus Elater (Coleoptera, Elateridae). The typology, number and distribution patterns of the antennal sensilla in the rare saproxylic Elater ferrugineus (both male and female) were studied using scanning electron microscopy (SEM). The serrate antennae of E. ferrugineus consisted of a scape, a pedicel, and nine flattened flagellomeres. Overall, 10 types of sensilla were identified according to their morphological features: one type of sensilla chaetica (Ch), one type of Böhm sensilla (Bo), three types of sensilla trichodea (Tr.1–3), two types of sensilla basiconica (Ba.1–2), one type of sensilla styloconica (St), one type of grooved peg sensilla (Gp) and one type of sensilla campaniformia (Ca). A marked sexual dimorphism was found at both gross and fine scale. The male antenna was bigger (8.6 mm) than the female one (7.0 mm) and carried one type of sensilla trichodea (Tr.2) absent in female antennae possibly responsible for reception of the female-emitted sex pheromone. The female antenna carried a higher number of sensilla (~ 9800) than the male one did (~7,000), with more abundant sensilla chaetica (Ch) and basiconica (Ba.1 and Ba.2).