Aim: Following the classical MacArthur-Wilson island equilibrium model of species richness, we hypothesize that island size and isolation affect prey composition and diet diversity of predators on islands. We used the barn owl as a model predatory organism that is known for feeding and habitat flexibility and explored the patterns of its diet on Mediterranean islands in relation to the island biogeography and human population density. Location: Mediterranean Islands. Taxon: Barn owl (Tyto alba) and its prey. Methods: Data on taxonomic composition of the barn owl diet were obtained from pellets (Adriatic island of Korčula) and from published studies performed on 18 Mediterranean islands. For each island, diet diversity indices were calculated and correlated with island area, linear distance from the mainland, human population size and density, and geospatial trends. Results: Murinae mice and rats were the dominant prey. The proportion of birds and reptiles consumed was 5 and 18 times higher, respectively, than in Europe in general. Diet diversity correlated with island size, but not island isolation. Island size was also a good predicator of the proportions of the vertebrate prey. Human population density and longitude had no effect on diet diversity. Main conclusions: Diet diversity of the barn owl on Mediterranean islands only partly followed the island biogeography theory. Diet diversity was greater on the larger Mediterranean islands. However, a more diverse diet did not mean a higher number of taxa, but a wider range of abundant and evenly represented taxa. The smaller the islands, the more birds and reptiles were consumed, compared to higher proportions of mammals on the larger islands. These findings support the idea of barn owls' feeding flexibility and opportunistic predator behaviour. Despite the barn owl being a synanthropic bird, urbanization had no influence on its diet diversity. Also island isolation had no significant effect.

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Pit-building antlion larvae are predators that construct pitfall traps in fine sand. We used three-dimensional laser scanning and geometric morphometrics to reveal the shape of antlion pits of two antlion species, analysed the particle size composition of sands from the different natural habitats, and measured the slope angles of the pits of the two species. In most antlions, the pits are structured as a simple inverted cone, as in Myrmeleon hyalinus, studied here. The other antlion studied, Cueta lineosa, constructs a unique pit composed of two inverted truncated cones inserted into one another, which feature substantially steeper walls than the pits of any other antlion studied to date. Pit stability depends on the slope inclination, which oscillates between the maximum angle of stability and the angle of repose. The angles in C. linosa-substrates were larger than those in M. hyalinus. One reason for the steeper walls is the greater proportion of fine sand in the natural sand inhabited by C. lineosa. However, video-recording revealed that both the natural sand of C. lineosa and the finest sand tested had a higher maximum angle of stability than any of the other substrates studied here. Furthermore, experiments with pits built in different substrates revealed that the shape of the pit is variable and depends on the structure of the sand. M. hyalinus displayed a more flexible pit construction behaviour than C. lineosa. The present demonstration of such differences in pit characteristics contributes to understanding how these two species co-exist in the same habitat.

We explored modularity and morphological integration of the ventral cranium during postnatal ontogeny in Martino’s vole (Dinaromys bogdanovi). Two closely related phylogenetic groups, originating from the Central and Southeastern part of the species range in the western Balkans, were considered. As expected, both phylogroups had similar patterns of ontogenetic changes in cranial size and shape variation, modularity and integration. At the level of within individual variation, the hypothesis that the viscerocranial and neurocranial regions are separate modules was rejected, indicating that the hypothesized modules are not developmental, but rather functional. At the level of among individual variation, the viscerocranium and the neurocranium could not be recognized as separate modules at the juvenile stage. The strength of association between the hypothesized modules becomes lower with age which finally results in a clear 2-module organization of the ventral cranium at the adult stage. On the other hand, patterns of morphological integration for the cranium as a whole, the viscerocranium and the neurocranium stay consistent across ontogenetic stages. The developmental mechanism producing integration of the cranium as a whole, as well as integration of the neurocranium, varies throughout postnatal ontogeny. In contrast, we detected the ontogenetic stability of the mechanism responsible for covariation of viscerocranial traits which could provide ongoing flexibility of the viscerocranial covariance structure for high functional demands during lifetime. Findings from our study most likely support the idea of the ‘palimpsest-like’ model of covariance structure. Moreover, similarity or dissimilarity in the patterns of within and among individual variation in different sets of analyzed traits and comparisons across ontogenetic stages demonstrate how studies on small mammals other than mice can give new insights into postnatal cranial development.