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A major goal in evolutionary biology is to determine the mechanisms responsible for maintaining phenotypic variation. Species that have evolved intersexual differences provide an opportunity to increase our understanding of trait evolution. We hypothesize that phenotypic diversity is related to reproductive strategies of female lizards and therefore, to their reproductive potential. Consequently, we evaluated sexual dimorphism in several morphological traits and assessed phenotypic variability and selection on body traits of female lizards in a model species (Tupinambis merianae). The results support our hypothesis that certain phenotypic traits of body shape are sexually dimorphic and that females present large continuous variation in these traits. Moreover, some morphological traits in females favor the increment of energetic reserves and reproductive output. These results contribute to the identification of characters upon which selection may have acted and suggest that phenotypic variation in female lizards are related to a diversity of reproductive strategies. Therefore, we fill part of the knowledge gap on the proximate mechanisms that link maternal morphology and reproductive potential in female lizards.
We examined changes in genetic diversity in populations of two small mammal species inhabiting islands on a lake. We hypothesized that a less mobile species, such as the bank vole, would lose genetic diversity quicker than the yellow-necked mouse, which can more easily cross habitat barriers. In contrast to this we found that the effects of isolation were much more prominent in the case of the mouse than the vole. In the vole population, on the larger island, genetic diversity remained constant over subsequent years in spite of marked isolation. On the smaller island, we noted an increase in genetic diversity which was probably caused by immigration of a small group of individuals. Genetic diversity in the mouse population decreased markedly over the course of the study. In the bank vole, the preservation of genetic diversity, especially on the larger island, may have been possible due to the specific spatial and social organization of this species, which allows the maintenance of a relatively stable number of individuals. In contrast to the bank vole, the lack of territorial behavior in adult females of yellow-necked mice may lead to frequent dramatic seasonal ’booms and busts' in population size and genetic diversity. This can lead to extremely low numbers of mice, which are likely to lead to the extinction of some island populations.
In situ ecological studies on obligate cave-dwelling aquatic animals are scarce at best. This is particularly true for capture-mark-recapture (CMR) studies that form the basis of understanding population structure and dynamics. Here, we report on the in situ underwater application of the Visible Implant Elastomer (VIE) tagging system on the olm, Proteus anguinus, an obligate cave-dwelling aquatic amphibian. We tagged seven adult individuals and monitored the population during 31 dive transects during four years. We found that VIE tagging is applicable underwater. Based on our recaptures, the tags were recognisable after four years and the recaptured three individuals exhibited extreme site-fidelity. Our results indicate that CMR studies are feasible in underwater cave ecosystems without even temporarily removing individuals. In situ underwater tagging also holds great potential for studies of other aquatic ecosystems, where removing animals from water, their habitat or territory is problematic for ethical, logistic or scientific reasons.
Monitoring wild cervid populations have become a priority for management. However, accurate and reliable estimates of densities are difficult to achieve since they may be affected by environmental variation, species behaviour or observational issues. Therefore, to obtain unbiased estimates of densities it is necessary to adopt sampling methods that quantify the probability to detect the target species. In this study, we compare the results of roe deer sampling based on distance detection performed by two techniques: surveys on foot in the evening and nocturnal surveys by car. Estimates of roe deer population densities were conducted in Sierra de Guadarrama (Madrid, Spain). Distance sampling was conducted along tracks in 10 pine forests in October. Observations from the surveys done on foot were better fitted with detection functions, although this technique required more days and more observers for its realization, hence increasing field effort. Nocturnal surveys by car were also a proper technique and decreased distance sampling costs, since only three people were needed for 6 days to carry them out. However, observations obtained with this technique showed an imbalance in the detection function in the first few metres. This model was limited by the small number of roe deer observed in or near the line of progression. This is a handicap because functions used by the Distance software assume that the highest probability of detecting specimens is in the line of progression, causing an imbalance in the detection function at zero distance. To compensate for this, data were lefttruncated at 20 m. Therefore, when it is necessary to estimate absolute densities of roe deer populations, nocturnal distance sampling by car seems to be the most appropriate method due to its low cost, yet the influence of the vehicle on the distribution of roe deer and, therefore, on the estimated density, must be taken into account when carrying out such studies.
Studies on species distribution models evaluate the reliability and discrimination capacity of the models, while the accuracy of the spatial component of the data is often disregarded. The objective of our work was to design and validate an index, the Georeferencing Reliability Index (GRI), to measure and compare quality of different databases containing presence data of Aotus species. The database of A. lemurinus showed the highest georeferencing accuracy (GRI = 0.608) and that of A. zonalis the lowest (GRI = 0.167). Results indicated that there is poor-quality spatial information data for Aotus spp. Therefore, the distribution areas of all species should be more accurately established to evaluate whether they are at conservation risk. In addition, the index can be used to select the most accurate spatial data for constructing a species distribution model. Finally, we strongly believe that the GRI may provide accurate, up-to-date information essential for wildlife management programs.
There is a lack of documentation on the consumption of toxic fruits by carnivores. To quantify the importance of toxic fruits in the diets of badgers (Meles meles), foxes (Vulpes vulpes) and martens (Martes sp.), we collected faeces of these animals along nine transects (total 30.4 km long, 2 m wide) during the fruiting seasons (June–November) in 2010 and 2011. From 619 faecal samples we found seeds of 16 fleshy-fruited plant species, including four species with toxic fruits. Surprisingly, the fruit of Convallaria majalis having a high content of toxic substances was also eaten by these animals. Fruits of C. majalis were found in faeces in late summer/autumn after early frost when maturing processes had reduced the content of toxic substances in the mesocarp. Toxic fruits were detected in 6.3% of all faeces sampled (n = 619). The proportion of toxic fruits in the diet was the highest (up to 10.5%) in martens as compared with that in badgers and foxes (2.2% and 0.7%, respectively).