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Species with highly restricted distributions are vulnerable to extinction, and modification of natural habitats within their small ranges is a primary threat to their persistence. Expansion of urban development significantly impacts natural habitats and, therefore, threatens local diversity. The Mexican axolotl, Ambystoma mexicanum, is a strictly aquatic species that persists currently in two highly threatened and isolated populations. The current habitat remaining for these species are remnants of a historically extensive lacustrine system that occupied the entire Valley of Mexico, but has been destroyed by the growth of Mexico City. Unexpectedly, a third viable population of axolotls has been found in Chapultepec Park, a public recreational area in the heart of Mexico City. Phylogenetic and haplotype network analyses of mitochondrial DNA sequences confirmed low genetic differentiation and a recurrent lack of monophyly in many of the taxa belonging to the Ambystoma tigrinum species group, including A. mexicanum, but clustered the Chapultepec samples with other A. mexicanum samples. Our data revealed higher haplotypic diversity in A. mexicanum populations than previously recorded, due to new haplotypes from Chapultepec Park. We found high incidence of parasites and deformities among individuals in this population, which could negatively impact their viability. Our results emphasize the important role that artificial or semi-natural urban habitats can play in the conservation of highly threatened species.
Bechstein's bat (Myotis bechsteinii) is one of the rarest European bat species. In oceanic climates, they appear to be restricted to woodlands, with preference for mature deciduous forests in lowlands. We investigated habitat selection by 20 lactating females belonging to 13 maternity colonies in Mediterranean landscapes. Deciduous forests (particularly Quercus pyrenaica) were positively selected, and coniferous forests were opportunistically used, whereas no foraging bouts occurred in evergreen broadleaved woodlands or in non-forested areas. Bats preferred to forage inside the forest rather than in edges or clearings. Stands of high canopy cover were also preferred. The preference for deciduous over evergreen broadleaved woodlands suggests that other variables such as prey availability, rather than structural constraints, drive habitat selection. M. bechsteinii might be abundant in well preserved deciduous forests within its Mediterranean range, in which the species' distribution might be limited by habitat loss and degradation related to agricultural practices and deforestation.
During the first few weeks of life, chicks of the capercaillie (Tetrao urogallus) and black grouse (T. tetrix) subsist mainly on insects, of which lepidopteran and hymenopteran larvae are the main components. We studied the breeding phenology of these two species and examined how the timing of breeding was related to the temporal distribution of their larval food source. During a five-year survey, capercaillie mated and hatched consistently four to six days before black grouse. Depending on the vegetation type, the number of larvae (≥ 2 mm in length) increased between five and ten times within 10 days, and hatching coincided roughly with the peaks in larval numbers. Due to body growth, however, larval abundance in terms of volume was reached later and occurred 8–9 and 13–14 days after the mean hatching dates in the two species, respectively. Slightly later development of Hymenoptera as compared with that of Lepidoptera contributed in extending the period of high larval abundances for more than one week. The timing of breeding of the two species appears, therefore, to match the temporal distribution of insect food for the fast-growing chicks as they hatch several days before the peak in larval volumes. In one year, when mating was advanced, presumably due to exceptionally warm weather before mating (yet the temporal abundance of larvae was unchanged), breeding success was higher than in years when mating occurred later.
Teeth are essential in mammals for the capture, handling and processing of food and self-defense. The rate of deterioration may affect longevity and indicate certain environmental conditions. The goal of this study was to characterize tooth conditions of moose (Alces alces) from multiple regions and to make inferences of possible causes of variation. An assessment of > 5500 moose incisors, found that the frequency of breakage and rate of decline in incisor integrity, with age, was much higher in Cape Breton and Newfoundland (breakage from 6% to 47%) than in New Brunswick, Ontario, New Hampshire, Vermont, and Yukon (breakage from 1% to 6%). Incisai degradation, among jurisdictions, differed significantly though population age structures did not appear different. The two jurisdictions most affected by incisai deterioration, Cape Breton and Newfoundland, are inhabited by genetically distinct subspecies, at higher densities than other regions; therefore, breakage may be linked to local environmental conditions.
Infanticide, the killing of offspring by adult conspecifics, has been demonstrated in many insect, mammal and bird species. In contrast to selective pressures influencing infanticide in other species, egg destruction in birds is thought to primarily represent interference competition for food, nest sites or predator-free nesting space. In the case of the great reed warbler, two opposing hypotheses exist for the explanation of its egg destruction behaviour. Our study tested these hypotheses separately by manipulating the presence of real conspecific, familiar and unfamiliar eggs and nests inside polygynous and monogamous great reed warbler territories. Out of 147 experimental nests placed in the vicinity of 49 active great reed warbler nests, only conspecific eggs were preyed upon by great reed warblers. Furthermore, significantly more great reed warbler nests were destroyed in polygynous than monogamous territories. These results support the hypothesis that egg destruction behaviour in this species is motivated intraspecifically and most probably intrasexually.
Evolutionary and ecological effects of DNA and protein polymorphisms are controversially discussed, since the raising of molecular approaches. Functional differences among different genotypes of allozymes might strongly influence evolutionary processes and spatial distributions. Therefore, we analysed nine polymorphic allozyme loci for 127 individuals sampled from one population of the chalk-hill blue Polyommatus coridon during one flight season. We observed fluctuations in the genotype frequencies during this flight season, but only two enzyme loci showed significant changes. The percentage of observed heterozygosity was decreasing in more than three quarters of all loci over time (e.g. Mdh2 decreasing from 72.7% to 36.4%). These changes might be due to different adaptations of heterozygotic individuals if compared with homozygotic ones. In contrast to genotypes, no changes in allele frequencies were observed (e.g. low FST value for Mdh2). Therefore, allozyme data represent a suitable tool for studying ecological adaptation and biogeographical pattern.