Spatial, dietary and temporal niche dimensions in ecological segregation of two sympatric, congeneric marsupial species

Didelphis aurita and D. albiventris are widely distributed in South America, with a range of sympatry in the limit of their distribution, particularly in Araucaria mixed ombrophilous forest in the southern Atlantic Forest. We investigated the spatial, feeding, and time use between these morphologically similar species in a remnant of Araucaria forest in southern Brazil for one year. We tested the hypothesis that these species when in sympatry segregate each other in space use, diet, and/or activity time. We expect that they segregate between each other primarily in the dimension of space use, as occurs for Australian congeneric marsupials. We used a mark-capture-release protocol for obtaining data. We analysed the spatial segregation by measuring the distance of captures in relation to the remnant centre, stream and edges. There were significant differences in the use of space, as adult females of D. aurita used mainly the remnant interior and stream sides, and D. albiventris females its edges or open areas. The consumption of feeding resources, particularly fruits, was different mainly between females and during the breeding season. However, there was no difference in the activity time between species. We believe that the territorial behaviour of D. aurita females had a crucial role in this spatial segregation with D. albiventris females, leading to a diet differentiation, particularly for fruits which were highly available inside the remnant. Interspecific competition between females is thought to be the main reason maintaining D. albiventris females far from the richest parts of the remnant. The mechanism behind this ecological segregation is discussed, and an ecological niche shift when both species are in sympatry is suggested, rather than the ghost of competition past. © Cáceres and Machado; Licensee Bentham Open

Factors affecting the home range size of felids (Mammalia, Carnivora) with emphasis on three American species

El objetivo de este estudio fue evaluar los factores que influyen en el tamaño del ámbito hogareño de felinos en los niveles inter- e intraespecífico. En nivel interespecífico, evaluamos la influencia de la masa corporal en el ámbito hogareño de 19 especies de felinos, controlando la filogenia. A nivel de especies, evaluamos el efecto del sexo y el hábitat (abierto vs. cerrado) sobre el ámbito hogareño de tres especies de felinos americanos, Panthera onca, Leopardus pardalis y Puma concolor, para los cuales existe una buena cantidad de información. Los datos de masa corporal, sexo y ámbito hogareño fueron extraídos de la base de datos Pantheria (para 19 especies, para comparación interespecífica) y 48 estudios para la variación intraespecífica. Evaluamos la influencia de la masa corporal en el tamaño del ámbito hogareño de felinos utilizando un análisis filogenético de los mínimos cuadrados generalizados. Evaluamos la existencia de dimorfismo sexual en el ámbito hogareño y la masa corporal usando una prueba t pareada. Finalmente, investigamos la influencia del hábitat en el ámbito hogareño utilizando un modelo ANOVA. Nuestros resultados mostraron que el tamaño del ámbito hogareño está asociado positivamente con la masa corporal en felinos. A nivel intraespecífico, confirmamos que la masa corporal y el ámbito hogareño de los machos son mayores que los de las hembras en P. onca y L. pardalis y P. concolor. Además, el ámbito hogareño de P. onca aumenta en hábitats abiertos (i.e., pastizales, desiertos y matorrales), tal como se esperaba. En general, nuestros resultados confirman que los mayores ámbitos hogareños están asociados con un tamaño corporal más grande en los animales que necesitan más recursos alimentarios o recursos específicos (como presas para felinos) para satisfacer las tasas metabólicas. Además, el ámbito hogareño de los tres felinos parece estar muy influenciado por los atributos de reproducción, así como por la calidad del hábitat. Esto sugiere una conexión con la distribución espacial de alimentos (presas) y las oportunidades de apareamiento.We evaluated several factors that might be related to the home-range size of felids at both inter and intraspecific levels. At the interspecific level, we tested the influence of body mass on home range size of 19 felid species, while controlling for phylogeny. At the species level, we evaluated the effect of sex and habitat type (open vs. closed) on the home range size of three species of felids occurring in America, Panthera onca, Leopardus pardalis and Puma concolor, which are among the most studied species concerning home ranges. Body mass, sex, and home range data were extracted from the Pantheria database (for 19 species, for interspecific comparisons) and from 48 studies for intraspecific comparisons. We assessed the influence of body mass on the home range size of felids using phylogenetic generalized least squares analysis. We evaluated the existence of sexual dimorphism on both home range size and body mass using paired t-tests. Finally, we investigated the influence of habitat type (open vs. closed) on home range size using ANOVA. Our results show that home range size is positively influenced by body mass in felids. At the intraspecific level, we confirmed that both the body mass and home range are larger for males than for the females in P. onca, L. pardalis and P. concolor. Moreover, the average home range size of P. onca is larger in open (i.e., grasslands, deserts and shrublands) than in closed (i.e., forests) habitats. Overall, our results confirm that larger home ranges are associated with larger body sizes in animals that need a large amount of food resources or specific resources (such as the specific prey requirements of felids) to maintain their metabolic rates. Furthermore, home range size of these three felids seems to be strongly influenced by reproductive attributes as well as by habitat quality, suggesting a connection with the spatial distribution of both food (prey) and mates

Which Factors Determine Spatial Segregation in the South American Opossums (Didelphis aurita and D. albiventris)? An Ecological Niche Modelling and Geometric Morphometrics Approach

Didelphis albiventris and D. aurita are Neotropical marsupials that share a unique evolutionary history and both are largely distributed throughout South America, being primarily allopatric throughout their ranges. In the Araucaria moist forest of Southern Brazil these species are sympatric and they might potentially compete having similar ecology. For this reason, they are ideal biological models to address questions about ecological character displacement and how closely related species might share their geographic space. Little is known about how two morphologically similar species of marsupials may affect each other through competition, if by competitive exclusion and competitive release. We combined ecological niche modeling and geometric morphometrics to explore the possible effects of competition on their distributional ranges and skull morphology. Ecological niche modeling was used to predict their potential distribution and this method enabled us to identify a case of biotic exclusion where the habit generalist D. albiventris is excluded by the presence of the specialist D. aurita. The morphometric analyses show that a degree of shape discrimination occurs between the species, strengthened by allometric differences, which possibly allowed them to occupy marginally different feeding niches supplemented by behavioral shift in contact areas. Overlap in skull morphology is shown between sympatric and allopatric specimens and a significant, but weak, shift in shape occurs only in D. aurita in sympatric areas. This could be a residual evidence of a higher past competition between both species, when contact zones were possibly larger than today. Therefore, the specialist D. aurita acts a biotic barrier to D. albiventris when niche diversity is not available for coexistence. On the other hand, when there is niche diversification (e.g. habitat mosaic), both species are capable to coexist with a minimal competitive effect on the morphology of D. aurita