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.
Most subterranean habitats, especially caves, are considered extreme environments, mainly because of the limited and erratic food supply and constant darkness. In temperate regions, many climatic ...conditions, such as temperature and air humidity, are periodically less adverse or even more favourable in caves than the harsh seasonal weather on the surface. Accordingly, many animal species search for hibernacula in caves. These overwintering, non-specialized subterranean species (non-troglobionts) show various modes of dormancy and ongoing development. Since they do not feed, they all undergo periodic starvation, a preadaptation, which might evolve in permanent starvation hardiness, such as found in most specialized subterranean species (troglobionts). To this end, we performed a comparative analysis of energy-supplying compounds in eleven most common terrestrial non-troglobiont species during winter in central European caves. We found highly heterogeneous responses to starvation, which are rather consistent with the degree of energetic adaptation to the habitat than to overwintering mode. The consumption of energy-supplying compounds was strongly higher taxa-dependant; glycogen is the main energy store in gastropods, lipids in insects, and arachnids rely on both reserve compounds. We assume that permanent starvation hardiness in specialized subterranean species might evolved in many different ways as shown in this study.
Protura is a small class of Hexapoda, generally poorly known, and rather scarce data on its occurrence in caves are scattered throughout literature on fauna in caves and in some papers on Protura. ...Although the cave-dwelling fauna is relatively well studied in Slovenia, published records on Protura are rare. In this paper, data on the occurrence and abundance of Protura in Slovenian caves are considered. Various statistical analyses were performed to compare caves with Protura to those without in 60 intensively monitored cavities to detect any differences in the selected environmental conditions. No significant difference was obtained. Samples collected from 15 caves yielded 286 specimens identified to genus or species level. Ten species were identified:
Acerentulus confinis
(Berlese, 1908), A. rafalskii Szeptycki, 1979*,
Acerentomon affine
Bagnall, 1912*,
A. balcanicum
Ionesco, 1933*,
A. italicum
Nosek, 1969,
A. maius
Berlese, 1908*,
A. meridionale
Nosek, 1960,
Acerella muscorum
(Ionesco, 1930)*,
Eosentomon armatum
Stach, 1926*, and
E. transitorium
Berlese, 1908*. The seven species marked with an asterisk are new records for Slovenia. Two specimens belonging to an unidentified species of the genus
Ionescuellum
Tuxen, 1960 were also found. As expected, Protura were most abundant at the cave entrance close to the surface, and none of the species were found exclusively in cavities. This suggests that proturans were introduced passively into the cavities via organic matter and surface soils.
Abstract
We explore the pattern of spatial variation in mandibular morphology in relation to subspecific taxonomy in the dwarf fat-tailed jerboa, Pygeretmus pumilio. The unguided k-means clustering ...on mandible shape scores, partitioned populations into two clusters, corresponding to western and eastern populations. These clusters nearly perfectly matched the two subspecies groups (pumilio and potanini groups) recognized in an independent study based on the morphology of the glans penis. The mandible, although under environmental pressure, has retained a sufficient amount of taxonomic information to retrieve grouping closely resembling the one derived from a sexually selective trait. We recommend morphometrics of the mandible as a routine step in addressing variations in mammals at species and subspecies levels. We also stress the advantage of unsupervised k-clustering in testing null expectation in subspecies taxonomies. However, the power of this approach has its limitations and in our analysis, the k-clustering failed to retrieve subspecies in the potanini group.
The herald moths,
Scoliopteryx libatrix
, overwinter in hypogean habitats. The ultrastructure of their fat body (FB) cells and Malpighian tubule (MT) epithelial cells was studied by light microscopy ...and transmission electron microscopy, and essential biometric and biochemical measurements were performed. The FB was composed of adipocytes and sparse urocytes. The ultrastructure of both cells did not change considerably during this natural starvation period, except for rough endoplasmic reticulum (rER) which became more abundant in March females. In the cells, the reserve material consisted of numerous lipid droplets, glycogen rosettes, and protein granula. During overwintering, the lipid droplets diminished, and protein granula became laminated. The MTs consisted of a monolayer epithelium and individual muscle cells. The epithelial cells were attached to the basal lamina by numerous hemidesmosomes. The apical plasma membrane was differentiated into numerous microvilli, many of them containing mitochondria. Nuclei were surrounded by an abundant rER. There were numerous spherites in the perinuclear part of the cells. The basal plasma membrane formed infoldings with mitochondria in between. Nuclei were located either in the basal or in the central part of the cells. During overwintering, spherites were gradually exploited, and autophagic structures appeared: autophagosomes, autolysosomes, and residual bodies. There were no statistical differences between the sexes in any measured biometric and biochemical variables in the same time frames. The energy-supplying lipids and glycogen, and spherite stores were gradually spent during overwintering. In March, the augmented rER signified the intensification of synthetic processes prior to the epigean ecophase.
During winter, cave cricket larvae undergo dormancy in subterranean habitats; this dormancy is termed diapause in second year Troglophilus cavicola larvae because they mature during this time, and ...termed quiescence in T. neglectus, because they mature after dormancy. Here we used electron microscopy to analyze ultrastructural changes in the epithelial cells in the Malpighian tubules (MTs) of T. cavicola during diapause, in order to compare them with previous findings on T. neglectus. Moreover, the autophagosomes were studied with immunofluorescence microscopy in both species. Although the basic ultrastructure of the cells was similar, specific differences appeared during overwintering. During this natural starvation period, the nucleus, rER, the Golgi apparatus and mitochondria did not show structural changes, and the spherites were exploited. The abundances of autophagic structures in both species increased during overwintering. At the beginning of overwintering, in both species and sexes, the rates of cells with autophagic structures (phagophores, autophagosomes, autolysosomes and residual bodies) were low, while their rates increased gradually towards the end of overwintering. Between sexes, in T. cavicola significant differences were found in the autophagosome abundances in the middle and at the end, and in T. neglectus at the end of overwintering. Females showed higher rates of autophagic cells than males, and these were more abundant in T. cavicola. Thus, autophagic processes in the MT epithelial cells induced by starvation are mostly parallel in diapausing T. cavicola and quiescent T. neglectus, but more intensive in diapausing females.
The European cave spider, Meta menardi, is among the most common troglophile species inhabiting the cave entrance zone in Europe, where prey is scarce in winter. Spiders feed only if prey is ...available; otherwise, they are subjected to long-term winter starvation. We carried out a four-month winter starvation of M. menardi under controlled conditions to analyze ultrastructural changes in the midgut diverticula epithelial cells at the beginning, in the middle and at the end of the starvation period. We used light microscopy, TEM and quantified reserve lipids and glycogen. The midgut diverticula epithelium consisted of secretory cells, digestive cells and adipocytes. During starvation, gradual vacuolization of some digestive cells, and some necrotic digestive cells and adipocytes appeared. Autophagic structures, autophagosomes, autolysosomes and residual bodies were found in all three cell types. Spherites and the energy-reserve compounds were gradually exploited, until in some spherites only the membrane remained. Comparison between spring, autumn and winter starvation reveals that, during the growth period, M. menardi accumulate reserve compounds in spherites and protein granules, and energy-supplying lipids and glycogen, like many epigean, overwintering arthropods. In M. menardi, otherwise active all over the year, this is an adaptive response to the potential absence of prey in winter.
Intraspecific variation in size along spatial and environmental gradients has been documented in many studies, and different hypotheses have been proposed to explain these patterns of geographic ...variation. We explored size variation in 4 island and 35 mainland samples of the Edible Dormouse (
Glis glis
Linnaeus, 1758) from the western Balkans in Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, and Serbia. Samples comprised 4 to 207 (mean ± SD=19.0±32.9; total n=740) adult skulls (age>1 year) of both sexes. To remove phylogenetic effects, all samples were from a widespread European lineage. Condylobasal length of skull was used as a proxy for overall size. Dormice were the smallest along the southern margin of the Pannonia Plain, the largest were from beech forests of the Dinaric Alps, and intermediate in hilly parts of Serbia and on the Adriatic islands. The largest skulls (from Mt. Zelengora, Bosnia and Herzegovina) were on average 25% longer than the smallest, from the population occurring near Belgrade in northern Serbia. Size correlated with longitude (R
2
=0.262; p=0.0009) and the 1
st
Climatic Principal Component (R
2
=0.687; p<0.0001) derived from ordination of 19 climatic variables (40% of variance explained). Dormice tended to be small in a warm and dry climate, and larger in cold and humid areas.
We address in this study the taxonomic status of the two major phylogenetic lineages of fat dormice, genus
. These lineages show unique mutations at 43 positions of the cytochrome
alignment and are ...classified as two distinct species, the European fat dormouse
(Linnaeus, C. 1766.
. Laurentii Salvii, Holmiae Stockholm) and the Iranian fat dormouse
(Erxleben, I.C.P. 1777. Systema regni animalis per classes, ordines, genera, species, varietates cum synonymia et historia animalium. Classis I. Mammalia. Impensis Weygandianis, Lipsia Leipzig). The European dormouse is widespread in Europe, Asia Minor and the Caucasus, while the Iranian dormouse occupies the southern Caspian coast in Iran. Ranges are presumably delimited in Azerbaijan by rivers Kura and Aras. The two species differ categorically in size of the glans penis, size and shape of the baculum and in width of the posterior extension of the premaxilla. The Iranian fat dormouse has on average a more blackish distal half of the tail, a higher count for abdominal nipples, and a longer maxillary tooth-row. Intraspecific structuring in
indicates a taxonomic complexity which is not yet understood and requires a comprehensive systematic revision. To define the nominal taxon objectively we designate voucher PMS 27369 (Slovenian Museum of Natural History) as the neotype for
therefore restricting the type locality for the species to Mt. Krim in Slovenia.
During the growth period, in surface habitats, spiders catch enough prey to feed normally. In contrast, in the cave entrance zone, prey may be relatively scarce.
Meta menardi
inhabits this cave ...section, resulting in temporary starvation. We studied structural changes in the midgut epithelial cells of
M. menardi
during a short-term and a medium-term controlled starvation to mimic the occasional starvation in caves, during spring and autumn. Digestive cells, secretory cells and adipocytes were examined before the experimental starvation, in the middle and at the end of starvation. We used light microscopy, transmission electron microscopy and specific histochemical methods for the detection of lipids, polysaccharides and proteins. Detection of lysosomes, autolysosomes and apoptosis was also carried out. The general structures of the cells did not change during the experimental starvation in either season, while some specific differences in the ultrastructure were observed. In both sexes, in both seasons, the amounts of lipids, glycogen and proteins decreased during starvation. Larger amounts of lipids were found in autumn, while there were no significant differences in the amounts of glycogen and proteins. In both sexes, in both seasons, autophagy and apoptosis intensified with starvation in progress, but more intensively in females. Thus, autumn individuals, in contrast to spring ones, compile energy-supplying stores to confront the subsequent winter deficiency of prey in caves, while the cellular ultrastructures undergo the same starvation-dependant changes at any time during the growth period.
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