Geruza Leal Melo

Chewing on the trees: Constraints and adaptation in the evolution of the primate mandible.

Chewing on different food types is a demanding biological function. The classic assumption in studying the shape of feeding apparatuses is that animals are what they eat, meaning that adaptation to different food items accounts for most of their interspecific variation. Yet, a growing body of evidence points against this concept. We use the primate mandible as a model structure to investigate the complex interplay among shape, size, diet, and phylogeny. We find a weak but significant impact of diet on mandible shape variation in primates as a whole but not in anthropoids and catarrhines as tested in isolation. These clades mainly exhibit allometric shape changes, which are unrelated to diet. Diet is an important factor in the diversification of strepsirrhines and platyrrhines and a phylogenetic signal is detected in all primate clades. Peaks in morphological disparity occur during the Oligocene (between 37 and 25 Ma) supporting the notion that an adaptive radiation characterized the evolution of South American monkeys. In all primate clades, the evolution of mandible size is faster than its shape pointing to a strong effect of allometry on ecomorphological diversification in this group.

In and Out the Amazonia: Evolutionary Ecomorphology in Howler and Capuchin Monkeys

The impact of environmental variation on phenotypic diversification is one major issue in evolutionary studies. Environmental variation is thought to be a primary factor in evolution, especially at high latitudes. In contrast, tropical areas are traditionally viewed as the cradle where the long-term effects of biological interactions on phenotypic change reside. We analyse patterns of skull shape variation in two New World monkey groups: capuchins and howlers. These two monophyletic clades are exceptionally similar in terms of the geographic distribution of their species. Yet, their body size and diet are different: howler monkeys are large and almost exclusively folivorous, whereas capuchins are small omnivorous. We found that the size, and direction of vectors of phenotypic changes across South American biomes in those clades are not statistically different. This similarity persists after removing the strong impact of allometry in our data. Additionally, partial least squares and comparative analyses confirm that “allometry free” skull shape is influenced to the same set of environmental variables in both clades. This study remarks the paramount importance of both body size and environmental variation on phenotypic evolution.

Fruit of a contrasting colour is more detectable by frugivores

Determination of the factors that rule the preference of birds for certain fruits is fundamental to the understanding of the co-evolution of plants and their dispersers (Alves-Costa & Lopes 2001). Plants might compete for dispersers, and the response of dispersers will differ according to the variety of fruits available in nature (Denslow & Moermond 1982, Herrera 1981). Seed dispersal by birds is directly related to certain features of fruit, including colour, size, shape, abundance, nutritional value, habitat and distance between plants that are fruiting (Alves-Costa & Lopes 2001, Galetti et al . 2003, Levey et al . 1994, Murray et al . 1993). To understand how birds integrate these features in terms of fruit choice is a complex and widely misunderstood problem (Levey et al . 1994).

Interaction of ectoparasites (Mesostigmata, Phthiraptera and Siphonaptera) with small mammals in Cerrado fragments, western Brazil

We describe ectoparasite fauna associated with small mammals in fragments of Cerrado biome, central-western Brazil. We analyzed the level of associations and the aggregation patterns according to seasonal and host variations. Small mammals were systematically captured in 54 woodland fragments from February 2012 to July 2013. A total of 1040 animals belonging to eight marsupial and 12 rodent species were sampled; 354 individuals were parasitized by 33 ectoparasite species (twenty five Mesostigmata, seven Phthiraptera and one Siphonaptera). A total of 49 ecological relationships between ectoparasites and small mammals were observed, 24 being new association records. The overall specialization index of all ectoparasites and host species was 0.91 with significant deviation from a random host-parasite association, suggesting a high host-parasite specialization in this system. Specialization indices for ectoparasites ranged from moderate to high, while among host was high, for most species. Contrary to the overall pattern, some ectoparasites had higher prevalence and mean intensity of infestation in the dry season. Overall, ectoparasite prevalence and mean intensity of infestation were not significantly associated with host gender. This study provides significant information about the ectoparasites ecology in relation to specificity, seasonality and hosts gender, contributing to the understanding of host-parasite relationships in Brazilian savannah.

Use of camera-traps in natural trails and shelters for the mammalian survey in the Atlantic Forest

In order to evaluate the efficiency of different mammalian survey methods, we compared traditional sampling techniques (use of camera-traps on roads and artificial trails, track censuses, and direct field visualization) with an alternative sampling design (camera-traps positioned in natural areas such as natural trails and shelters). We conducted the study in a deciduous Atlantic-Forest park in southern Brazil, and additionally compared our results with a previous intensive study carried out in the same area. Our considerably smaller sampling effort (example: 336 trap.day for our camera-traps versus 2,154 trap.day for the earlier study) registered the presence of 85% of the local known species, with camera-traps being 68% efficient. Moreover, shelter camera-traps revealed a different species composition regarding most of other sampling methods. This sampling strategy involving natural forest sites was therefore able to effectively optimize the chances of evaluating species composition in a shorter period, especially with respect to lower-density and cryptic species, as well as to detect species that avoid open, disturbed sites such as roads and man-made forest trails.

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.

Local randomness, vegetation type and dispersal drive bird and mammal's diversity in a tropical South American region

How dispersal, environmental filters, and local extinctions affect species diversity depends on the species requirements for habitat, dispersal limitations, and abundance. Few studies have been able to properly separate these processes and to show how they affect the beta diversity patterns for multiple organisms. We investigated how the composition of birds and mammals changed along geographical and environmental gradients in an environmentally complex South American region. Using mantel tests and a null model approach we disentangled the effects of dispersal, environment, and stochastic processes in the species beta diversities. The similarity on species composition was negatively associated with the geographical distance separating areas for both groups. The changes in bird species composition likely resulted from their dispersal limitation over large geographical regions. In contrast, the composition of mammals in a given area was a partially random subset of the regional species pool, to some extent, filtered by the vegetation. Small communities tended to have more variable species composition, whereas dispersal limited birds showed a stronger distance-decay pattern. Neither local randomness nor dispersal limitation prevented species from being filtered by the environment. Other groups are likely to show similar patterns depending on their dispersal abilities, environmental requirements and community size.

Microhabitat of small mammals at ground and understorey levels in a deciduous, southern Atlantic forest.

Each animal species selects specific microhabitats for protection, foraging, or micro-climate. To understand the distribution patterns of small mammals on the ground and in the understorey, we investigated the use of microhabitats by small mammals in a deciduous forest of southern Brazil. Ten trap stations with seven capture points were used to sample the following microhabitats: liana, fallen log, ground litter, terrestrial ferns, simple-trunk tree, forked tree, and Piper sp. shrubs. Seven field phases were conducted, each for eight consecutive days, from September 2006 through January 2008. Four species of rodents (Akodon montensis, Sooretamys angouya, Oligoryzomys nigripes and Mus musculus) and two species of marsupials (Didelphis albiventris and Gracilinanus microtarsus) were captured. Captured species presented significant differences on their microhabitat use (ANOVA, p = 0.003), particularly between ground and understorey sites. Akodon montensis selected positively terrestrial ferns and trunks, S. angouya selected lianas, D. albiventris selected fallen trunks and Piper sp., and G. microtarsus choose tree trunks and lianas. We demonstrated that the local small-mammal assemblage does select microhabitats, with different types of associations between species and habitats. Besides, there is a strong evidence of habitat selection in order to diminish predation.

First record of the invasive alien species Axis axis (Erxleben, 1777) (Artiodactyla: Cervidae) in Brazil

The exotic alien species Axis axis was introduced in the Americas at the beginning of last century and since then has established itself, expanding its distribution. This is the first record of this species in Brazil. In the extreme south of the country, an individual of A. axis was recorded with a camera trap in the Espinilho State Park. The area is close to the border of Uruguay and Argentina, countries where the species is established and from where this individual presumably originated. The Pampas biome is strongly disturbed by human activity in Brazil and since many native mammal species such as the Pampas deer Ozotoceros bezoarticus are threatened regionally. It is alarming that exotic populations can potentially rapidly expand their ranges in the region, as A. axis deer has done in Uruguay and Argentina. Possible consequences for this invasion are discussed.

Association of the southern Amazon red squirrel Urosciurus spadiceus Olfers, 1818 with mixed-species bird flocks

Abstract The first record of Urosciurus spadiceus participating in mixed-species bird flocks is reported in the Pantanal biome. Three groups of U. spadiceus were seen participating in mixed-species bird flocks, with Cantorchilus guarayanus being the avian nuclear species. Observations were carried out in the riparian forest of the Paraguay River, municipality of Corumbá, in the north-west of the state of Mato Grosso do Sul, Brazil. Hypotheses about the association between the squirrels and mixed-species bird flocks in South America are considered.