Journal of Zoology最新文献

Host–parasite systems, including social parasites that exploit resources of the host colonies, are fascinating objects for evolutionary biologists mainly due to the dynamic and often rapid host–parasite coevolution. Host-switching events are believed to induce rapid speciation of parasitic species. The socially parasitic ant lineage Myrmoxenus, which corresponds to the monophyletic Temnothorax corsicus group, counts in total a dozen species. Most Myrmoxenus species utilize a single host species, but a few others, like Myrmoxenus ravouxi (André, 1896) and M. gordiagini Ruzsky, 1902, are known to use multiple host taxa. Myrmoxenus zaleskyi (Sadil, 1953) was described as a putative congener of M. ravouxi based on its distinct host selection. In this paper, we investigate the diversity of the widely distributed European lineages M. ravouxi and M. zaleskyi from multiple and complementary perspectives to understand whether the host preference exhibited by these two forms implies speciation. We integrated evidence from molecular genetics using mitochondrial CO I/CO II genes, including the tLeu-region, and multivariate analyses of morphometric data collected from workers and female sexuals (gynes). Although there is substantial regional host species specificity, results suggest that host switching did not result in phylogenetic or morphological divergence and that the central European M. zaleskyi can be considered the junior synonym of M. ravouxi. As the lineage Myrmoxenus has been the subject of considerable evolutionary research, these results are essential to achieve a more accurate picture of host–parasite systems in the future and further strengthen the justification of an integrative approach in studying similarly complex systems. We advise against describing new parasitic species based on host preference unless coupled with marked heritable phenotypic adaptations.

Bird wings vary in size and morphology in terms of both size and number of feathers and the underlying skeletal anatomy. The number of primary remiges does not seem to vary much between bird species but, by contrast, the number of secondary remiges is reported to range between 6 and 40 depending on bird size. Given that the primaries are attached to the manus, and the secondaries are attached to the ulna, it was predicted that as bone lengths increased with increasing size of the bird, then feather count would increase. Data were collected for 268 species from 25 different orders, and phylogenetically controlled analysis explored the allometry between feather count and bone size. The number of primaries was typically 10 or 11 and did not vary with manus size. By contrast, the number of secondaries increased with ulna length, but only in some orders. For example, in Gruiformes, the number of secondary feathers increased concomitantly with ulna length but despite a two orders of magnitude range in body mass, almost all species in the Passeriformes had nine secondary remiges. It is unclear why, for instance, species with an ulna length of 70 mm can have between 9 and 24 secondaries depending on their order. This variation in secondary feather number can be added to variation in relative wing bone lengths, flight feather lengths, flight feather mechanical properties, and flight feather vane densities as another potential mechanism of adaptation to flight requirements. The apparent constraint of wingspan is scaling as approximately body mass^1/3. Further research is needed to explore whether changes in secondary feather number relative to ulna length are accompanied by changes in feather vane width or the overlap of adjacent feathers and how this relates to wing aerodynamics.

Climate warming combined with intensive human activities are modifying ecosystems globally, and the Arctic biota is shifting substantially faster than the global average, allowing many new species to expand their range poleward. One such species, is the American beaver (Castor canadensis), a highly specialized rodent capable of greatly modifying ecosystems by altering forest composition through selective foraging and by flooding the landscape through dam and channel building. As rodent cranial morphology is highly related to its functional requirements for foraging and feeding, the beaver provides an opportunity to evaluate the phenotypic response of species to changing environmental conditions. Here, we test the hypothesis that beaver skull morphology is optimized for its local environmental and habitat conditions across Canadian ecosystems. We found that temperature, precipitations, biomass, and local average tree hardness significantly affect the morphology of key masticatory functional traits of the skull, but not its size. Our results suggest that the beaver's phenotype is locally adapted to environmental conditions as a result of its selective foraging behavior. This work provides insight into the adaptive potential of newly established beaver populations in the sub-Arctic to inform management strategies for this keystone species. More generally, our work emphasizes the need to consider traits other than body size in research seeking to better understand the response of species to current global change.

Variation in thermal conditions during embryogenesis can have far-reaching impact throughout ontogeny and may give rise to behavioural variation. Many animals, such as salmonids, exhibit behavioural trade-offs related to foraging and predator avoidance. How embryonic temperature affects these behaviours has remained unexplored. Not only abiotic conditions during embryogenesis but also biotic factors such as predator conditioning may affect fish behaviour, especially anti-predator responses. We examined how elevated temperatures and predator odours throughout embryogenesis affect the behaviour of 28–37 mm young-of-the-year brown trout (Salmo trutta) in encounters with predators, namely Atlantic salmon (Salmo salar; 20 cm) and burbot (Lota lota; 40 cm). Juvenile brown trout were more active and aggressive if they were incubated in warmer water as eggs than if they were incubated in colder water, and trout remained inactive longer when encountering predators if they were cold incubated. Brown trout were less active and aggressive when an Atlantic salmon was present than when a burbot or no predator was present. Behavioural responses did not differ between trout that had been subjected to water with versus without predator odours during embryogenesis, possibly because brown trout were not subjected to conspecific alarm cues during egg incubation. This study shows that thermal conditions during embryogenesis can influence fish behaviour early in life and thus contribute to behavioural variation, with potential effects on life history. Considering the rapid warming of northern regions, elevated embryonic temperatures may contribute substantially to variation in salmonid behaviour in the near future.

Environmental factors, such as temperature, precipitation, and elevation, explain most of the variation in species richness at the global scale. Nevertheless, richness patterns may have different drivers across taxa and regions. To date, a comprehensive global examination of how various factors such as climate or topography drive patterns of species richness across all terrestrial vertebrates, using the same methods and predictors, has been lacking. Recent advances in species-distribution data allowed us to model and examine the richness pattern of all terrestrial tetrapods comprehensively. We tested the relationship between environmental and biogeographical variables and richness of amphibians (5983 species), birds (9630), mammals (5004), reptiles (8939), and tetrapods as a whole, globally, and across biogeographical realms. We studied the effects of climatic, ecological, and biogeographic drivers using generalized additive models. Richness patterns and their environmental associations varied among taxa and realms. Overall precipitation was the predominant richness predictor. However, temperature was more important in realms where both cold and warm conditions exist. In the Indomalayan realm, elevational range was very important. Richness patterns of mammals, birds, and amphibians were strongly related to precipitation whereas reptile richness was mostly associated with temperature. Our results support the universal importance of precipitation but also suggest that future global-scaled research should incorporate other relevant variables other than climate, such as elevational range, to gain a better understanding of the richness–environment relationship. By doing so, we can further advance our knowledge of the complex relationships between biodiversity and the environment.

Broad geographical distributions that include marked climatic variation may expose populations to distinct selective pressures. Local adaptation to differences in developmental conditions may lead to divergence in embryonic and hatchling traits for populations of oviparous reptiles. Among-population differences in hatchling size and the duration of development are often observed in lizards with wide and climatically diverse distributions. Variation in hatchling phenotypes can arise from variation in maternal allocation, developmental plasticity or selection acting on embryonic traits. We studied variation in hatchlings of the Australian water dragon (Intellagama lesueurii), comparing traits related to growth and patterns of developmental plasticity. We recorded marked differences in hatchling sizes among populations from different climate types, which did not result from differences in maternal investment or from a plastic response to incubation temperatures. Embryos from southern, temperate populations exhibited shorter incubation times when incubated at cold temperatures but utilized less yolk during development and hatched smaller, with more residual yolk, regardless of incubation treatment. We suggest that these findings represent the first example of among-population variation in patterns of embryonic resource allocation and a novel mechanism mediating offspring size in reptiles. We further suggest that variation in embryonic resource allocation in I. lesueurii, together with evolutionary changes in reaction norms for developmental rate, evolved as adaptations to seasonal length and conditions associated with a tropical-temperate gradient.

Understanding animals' selection of microhabitats is important in both ecology and biodiversity conservation. However, there is no generally accepted methodology for the characterization of microhabitats, especially for vegetation structure. We studied microhabitat selection of three Vipera snakes by comparing grassland vegetation structure between viper occurrence points and random points in three grassland ecosystems: V. graeca in mountain meadows of Albania, V. renardi in loess steppes of Ukraine and V. ursinii in sand grasslands in Hungary. We quantified vegetation structure in an objective manner by automated processing of images taken of the vegetation against a vegetation profile board under standardized conditions. We developed an R script for automatic calculation of four vegetation structure variables derived from raster data obtained in the images: leaf area (LA), height of closed vegetation (HCV), maximum height of vegetation (MHV) and foliage height diversity (FHD). Generalized linear mixed models revealed that snake occurrence was positively related to HCV in V. graeca, to LA in V. renardi and to LA and MHV in V. ursinii, and negatively to HCV in V. ursinii. Our results demonstrate that vegetation structure variables derived from automated image processing significantly relate to viper microhabitat selection. Our method minimizes the risk of subjectivity in measuring vegetation structure, enables the aggregation of adjacent pixel data and is suitable for comparison of or extrapolation across different vegetation types or ecosystems.

Gliding has evolved independently as an isolated adaptive event within many vertebrate taxa. Yet, the underlying selection forces that led to these innovative adaptations remain ambiguous, especially in species that preclude direct observation. Our study utilized accelerometry and machine learning algorithms to compare the behavioural repertoires of two sympatric species, the Mahogany glider (Petaurus gracilis) and brushtail possum (Trichosaurus vulpecula), as to explore previously proposed selection pressures such as energy expenditure (VeBA), canopy use and ground avoidance measured by activity budgets. We found that mahogany gliders on average expend more activity-related energy than brushtail possums but at different stages throughout the day. Canopy use was observed to be greater amongst mahogany gliders than brushtail possums, and we observed frequent ground use in brushtail possums yet none in mahogany gliders. The study found strong evidence to support ground avoidance as a potential driver for gliding evolution. The implications of these findings are important when considering the lack of knowledge surrounding evolved gliding behaviours in marsupials. Furthermore, the use of accelerometers and machine learning algorithms in behavioural studies has proven to be a robust and informative method and should be incorporated into future studies to understand the evolution of gliding behaviour.

The coexistence of multiple discrete color phenotypes (i.e. color polymorphism) has been studied in many diurnal species where environmental light allows most visual systems to chromatically discriminate color morphs. However, there is a large gap in our understanding of the discrimination thresholds and the function color polymorphisms play at night. We collected spectral data from the throats of red- and yellow-morph males in a polymorphic population of the nocturnal amphibian Salamandra salamandra gallaica. We estimated the discriminability between morphs and their conspicuousness at night by fitting visual models of conspecifics and predators. We also collected morphological, behavioral and physiological data and assessed the abundance and activity patterns of each morph to explore their potential function. Visual models indicated that both conspecifics and predators can visually discriminate salamander color morphs under night-light conditions. Assuming the potential role of yellow and red color patches as visual signals, putatively related to social signaling, we could suspect that these colors represent different adaptive optima. Red-morph individuals had shorter bodies and lower body condition, but both morphs showed similar space use. In addition, both color morphs exhibited similar metabolic physiology, suggesting that the observed similarity in these traits may be better explained by the shared environmental conditions, rather than color. Finally, differences in the conspicuousness of red and yellow morphs could result in differential predation pressure.