Dimitris Kaltsas

Ground beetles respond to grazing at assemblage level, rather than species-specifically: the case of Cretan shrublands

Phrygana, maquis and subalpine shrublands are the most typical ecosystem types on the island of Crete. However, these formations are mostly mismanaged and poorly studied in terms of their fauna and the effect of long term land-use. We studied the impact of goat and sheep grazing on the diversity patterns of carabid beetles at 40 sites in relation to possible habitat uniqueness and geographic zonation. In total, 19,322 individuals belonging to 42 Carabidae species were identified. The composition of site assemblages was mainly determined by altitude. The six Cretan endemic species collected were widely distributed on the island and most of them were dominant. Species richness and equitability were significantly lower at overgrazed sites compared to areas with low grazing intensity. The diversity patterns of carabids were influenced by the level of grazing in each study area. As species richness and diversity were maximal under moderate/relatively high levels of grazing (hump-shaped pattern), our results support the intermediate disturbance hypothesis. Low tolerance of carabid taxa to intensive grazing was also ascertained through the significantly high values of temporal beta diversity at overgrazed sites, independent of local species richness. We conclude that Carabidae are good indicators of grazing pressure in Crete at assemblage level, rather than species-specifically. To maintain diversity and enhance niche space of invertebrate fauna, the spatiotemporal discontinuity of grazing is essential.

The foraging activity of Mesobuthus gibbosus (Scorpiones: Buthidae) in central and south Aegean archipelago

The foraging activity of Mesobuthus gibbosus was studied and analysed over 290 field samplings in Koufonisi island (central Aegean) and Crete (south Aegean) during the period of maximal activity of the species. The results showed that on both islands males and juveniles searched for prey mainly relatively near or far from their burrows (“sit‐and‐wait” strategy), whereas females foraged comparatively more than males and juveniles at the entrances of their burrows (“doorkeeping” strategy). Throughout the study, there was no evidence of two or more individuals foraging together. Re‐emergence time after digestion lasts probably more than one month, because no individual was observed foraging twice in the 30 consecutive days of the study period. The individuals that followed the sit‐and‐wait strategy were larger in size compared to those of the same sex or age‐class that used the doorkeeping strategy. The diet of the species was wide, including representatives of eight arthropod orders on Koufonisi and seven on Crete. Stinging was selective and prey selection was based on the age‐class of the predator and the size of the prey compared to the size of the predator. The success of sit‐and‐wait foraging individuals was much more dependent on abiotic factors compared to scorpions using the doorkeeping strategy. Moon phase, air and soil temperature and air relative humidity were the abiotic factors which mainly influenced the foraging activity of these generally non‐cannibalistic opportunistic ambush predators on both islands.

Temporal organization patterns of epigean beetle communities (Coleoptera: Carabidae, Tenebrionidae) in different successional stages of eastern Mediterranean maquis

This two-year study explores the community structure and temporal dynamics of carabid and tenebrionid beetles in five eastern Mediterranean juniper maquis formations in relation to successional stage. Based on vegetation cover, density and soil pH, the successional stage in two of the sites (Crete, Cyprus) was an earlier state compared with the other three (Attiki, Naxos, Samos), as a result of intense goat grazing. Diversity indices and abundance distributions were compared using morphoecological surrogates of the taxa. Temporal dynamics were regulated more by cumulative species richness than by sharp phenological patterns. The higher values of niche pre-emption parameter and species turnover imply better adaptation of endemic tenebrionids to the rapid change of environmental conditions, compared with carabids. Significantly lower abundance and biomass, and higher evenness and temporal turnover for both families in Crete and Cyprus are ascribed to the reversed course of succession caused by overgrazing.

Locomotory activity and orientation of Mesobuthus gibbosus (Scorpiones: Buthidae) in central Aegean Archipelago

This study explores the locomotory activity of Mesobuthus gibbosus on Koufonisi Island (central Aegean). We measured orientation of movement, shelter selection and abiotic factors that influence locomotive activity throughout the circadian and lunar cycles. Our results show M. gibbosus is a highly active and negatively phototactic species with sexually dimorphic patterns of movements that are related to maternal protective behaviour. Male scorpions disperse more widely, apparently as a function of mate search, and exhibit much more opportunistic locomotive behaviour. The locomotory activity of the population was influenced by moon phase (negative phototropic) and air temperature, did not differ intersexually, and was directed towards a dry stone-wall where shelter was readily available.

Intraspecific differentiation of social behavior and shelter selection in Mesobuthus gibbosus (Brullé, 1832) (Scorpiones: Buthidae)

We compared seasonal shelter selection and social behavior of Mesobuthus gibbosus from autumn to mid-summer in two similar phryganic ecosystems, in continental Greece (near Volos city) and in insular Greece (eastern Crete), and in the laboratory under simulated abiotic conditions. Our results showed that shelter selection is a critical indicator of the seasonal social behavior of the species. The abrupt climatic changes in spring caused a differentiation in shelter selection between the cold period (November–February) and the warm period (March–June) at both sites. Sociality was exhibited only during winter in the field and was more extensive under cold conditions in the laboratory. Co-occurrence of scorpions proved to be age-specific, facilitated by population density and by harsh abiotic conditions during winter, and negatively influenced by intraspecific competition, which was higher in continental Greece. The response of scorpions to changes of abiotic factors reveals synchronization of seasonal shelter selection with climatic changes.