Nícholas F. de Camargo

Frugivoria e potencial dispersão de sementes pelo marsupial Gracilinanus agilis (Didelphidae: Didelphimorphia) em áreas de Cerrado no Brasil central

In the present study, we investigated patterns of fruit consumption and viability of seeds consumed by the marsupial Gracilinanus agilis (Burmeister, 1854) in four cerrado sites in central Brazil. Faecal analysis indicated that this mammal feeds on seeds of pioneer plant species of Melastomataceae (Miconia albicans (Sw.) Triana, M. cuspidata Naudin, M. ferruginata DC., M. pepericarpa DC., M. pohliana Cogn. and Ossaea congestiflora (Naudin) Cogn.), Solanaceae (one unidentified species), and Viscaceae (Phoradendron perrottetii (DC.) Eichler, mistletoe). We recorded the highest reported rate of fruit consumption for Gracilinanus, with about 45% of the scats containing seeds and 86% containing items derived from fruits (N = 422). With the exception of O. congestiflora, the remaining seed species tested did not suffer negative effects on germination rates after passing through the marsupial guts. The analysis of intraspecific variation in the total number of Miconia seeds found in scats indicated that females defecate a significantly greater number of seeds (mean±EP = 21.7±3.8) than males (14.4±3.0) (F = 26.32; P < 0.0001). The factor season was also significant (F=452.22; P<0.0001) as well as the interaction between sex and season (F=30.10; P < 0.0001). Both females and males increased their fruit consumption in the dry season, but in the rainy season females had more seeds than males in their faeces. Later during this season, we observed a higher number of Miconia seeds defecated by reproductive females (24.7±6.6) compared to non-reproductive females (12.9±2.8) (P = 0.031). Our results indicate that G. agilis feeds selectively on Melastomataceae, which suggests these plants play an important role in the diet of this marsupial in relation to energy and water demands, especially during the dry-cool season.

Sexual Dimorphism in Sturnira lilium (Chiroptera, Phyllostomidae): Can Pregnancy and Pup Carrying Be Responsible for Differences in Wing Shape?

Competition is one of the most cited mechanisms to explain secondary sexual dimorphism in animals. Nonetheless, it has been proposed that sexual dimorphism in bat wings is also a result of adaptive pressures to compensate additional weight caused by fetus or pup carrying during the reproductive period of females. The main objective of this study is to verify the existence of sexual dimorphism in Sturnira lilium wings. We employed geometric morphometrics techniques using anatomical landmarks superimposition to obtain size (Centroid Size) and shape variables of wings, which were reduced by Linear Discriminant Analysis (LDA). We also employed classical morphometrics using wing length measurements to compare efficiency between these two morphometric approaches and make comparisons using wing area measurements. LDA indicated significant differences between wing shapes of males and females, with 91% (stepwise classification) and 80% (leave-one-out cross validation) of correct classification. However, the size variable obtained did not contribute to such classifications. We have observed larger areas in female wings, but we found no differences in wing length measurements and no allometric effects in wing length, shape and area measurements. Interestingly, our study has provided evidences of morphological differences where classical morphometrics have failed. LDA and area measurements analyses revealed that females have a different area distribution in distinct portions of the wing, with wider dactylopatagia and plagiopatagia, and wingtips more triangular than males. No differences in body length or relative wing length were observed between the sexes, but pregnant females have more body weight than non-pregnant females and males. Our findings suggest that sexual dimorphism in the wing shape of S. lilium is probably related to the increase in flight efficiency of females during reproductive period. It decreases wing loading in specific portions of the wing and reduces energy cost to maintain a faster and maneuverable flight.

Contrasting the realized and fundamental niche of the arboreal walking performance of neotropical rodents

Evaluation of the fundamental niche under controlled conditions can provide relevant information about physiological, evolutionary, and ecological aspects of an organism, without the influence of external factors. We investigated how allometric, phylogenetic, and adaptive components contribute to arboreal walking performance by 7 sigmodontine rodents of the Brazilian savanna (Cerrado). We captured the rodents in the field and evaluated their performances by measuring stride length, stride frequency, and velocity on 5 horizontal supports: flat board and cylindrical plastic tubes with diameters of 5.0, 3.5, 2.5, and 2.0 cm. Arboreal rodents exhibited higher velocities than terrestrial species by increasing stride frequency and decreasing stride length on supports with smaller diameters. However, terrestrial species decreased both stride frequency and stride length or tended to maintain stride length and vary stride frequency. Our results reveal a strong association between realized arboreal walking performances (as inferred by proportion of arboreal captures) and stride length and frequency. However, performance metrics were weakly related to body mass and exhibited no phylogenetic effects. Our results are consistent with the hypothesis that dynamically stable arboreal walking is facilitated by increased velocity. Arboreal walking performance is likely related to ecological factors rather than phylogenetic constraints.

Effects of an extensive fire on arboreal small mammal populations in a neotropical savanna woodland

Fire is a major form of disturbance in terrestrial ecosystems, mainly in tropical savannas. In these ecosystems, the effects of large wildfires are potentially high on small and relatively less mobile animals, like small mammals. We investigated the effects of an extensive wildfire (≈ 6,240 ha) in September 2011 on populations of 2 arborealscansorial small mammals—the gracile mouse opossum, Gracilinanus agilis, and the long-tailed climbing mouse, Rhipidomys macrurus—in 4 savanna woodland patches (1 burned, 3 unburned) of the highly threatened Brazilian Cerrado. We assessed population densities from 2009 to 2013 and for G. agilis, we estimated apparent survival and recapture probabilities with Cormack—Jolly—Seber models. Both species showed strong, negative fire responses, including sudden collapse and slow recovery (at least more than 1 year). These observed responses were probably a consequence of both the phytophysiognomic features of the habitat and severity of the fire with the resulting changes on the vertical structure of vegetation. The studied species of Cerrado forested formations were not as resilient to fire disturbance as typical species from savanna or temperate woodlands. As a consequence of human activities and climate changes, fire events are predicted to become larger and more frequent in the Brazilian Cerrado. Therefore, it is imperative to create new management strategies to protect forested physiognomies from fire, especially cerradão, which is very fire sensitive and has a limited and scattered distribution in the landscape.

Adult feeding moths (Sphingidae) differ from non-adult feeding ones (Saturniidae) in activity-timing overlap and temporal niche width

According to classic ecology, resource partitioning by segregation along at least one of the three main niche axes (time, food, and space) must take place for the coexistence of species with similar ecological requirements. We used nocturnal light traps to investigate the assemblage structuration of two moth families: Sphingidae (23 species) and Saturniidae (13 species). Because competition for food among adults potentially occurs only among sphingids, only for this family did we expect less overlap of diel activity patterns than expected by chance and also a greater temporal niche width compared to saturniids. Moreover, we expected a greater number of sphingid species pairs to differ in activity timing compared to saturniid pairs. We also hypothesized that in the case of a lack of temporal structuration, sphingids would be morphologically structured in relation to proboscis length. Contrary to what we expected, both families overlapped their activity patterns more than expected by chance alone and sphingid moths were not morphologically structured. Nevertheless, there were 173 significant pairwise differences in temporal activity between sphingids, contrasting with no interspecific differences between saturniids. Sphingid species also showed a wider temporal niche width than saturniids, as expected. Predation risk and abiotic factors may have caused the overall similarities in activity patterns for both families. The temporal niche seemed not to be determinant for the assemblage structuration of moths as a whole for either of the studied families, but segregation along the temporal niche axis of some potentially competing species pairs can be a relevant factor for the coexistence of nectar-feeding species.

Sexual Dimorphism and Allometric Effects Associated With the Wing Shape of Seven Moth Species of Sphingidae (Lepidoptera: Bombycoidea)

Sexual dimorphism is a pronounced pattern of intraspecific variation in Lepidoptera. However, moths of the family Sphingidae (Lepidoptera: Bombycoidea) are considered exceptions to this rule. We used geometric morphometric techniques to detect shape and size sexual dimorphism in the fore and hindwings of seven hawkmoth species. The shape variables produced were then subjected to a discriminant analysis. The allometric effects were measured with a simple regression between the canonical variables and the centroid size. We also used the normalized residuals to assess the nonallometric component of shape variation with a t-test. The deformations in wing shape between sexes per species were assessed with a regression between the nonreduced shape variables and the residuals. We found sexual dimorphism in both wings in all analyzed species, and that the allometric effects were responsible for much of the wing shape variation between the sexes. However, when we removed the size effects, we observed shape sexual dimorphism. It is very common for females to be larger than males in Lepidoptera, so it is expected that the shape of structures such as wings suffers deformations in order to preserve their function. However, sources of variation other than allometry could be a reflection of different reproductive flight behavior (long flights in search for sexual mates in males, and flight in search for host plants in females).

Geographic Variation in Daily Temporal Activity Patterns of a Neotropical Marsupial (Gracilinanus agilis)

The temporal activity of animals is an outcome of both biotic and abiotic factors, which may vary along the geographic range of the species. Therefore, studies conducted with a species in different localities with distinct features could elucidate how animals deal with such factors. In this study, we used live traps equipped with timing devices to investigate the temporal activity patterns of the didelphid Gracilinanus agilis in two dry-woodland areas of the Brazilian savanna (Cerrado). These areas were located about 660 km apart, one in Central Brazil and the other in Southeastern Brazil. We compared such patterns considering both reproductive and non-reproductive periods, and how it varies as a function of temperature on a seasonal basis. In Central Brazil, we found a constant, and temperature-independent activity during the night in both reproductive and non-reproductive periods. On the other hand, in Southeastern Brazil, we detected a constant activity during the reproductive period, but in the non-reproductive period G. agilis presented a peak of activity between two and four hours after sunset. Moreover, in this latter we found a relation between temporal activity and temperature during the autumn and spring. These differences in temporal activity between areas, observed during the non-reproductive period, might be associated with the higher seasonal variability in temperature, and lower mean temperatures in the Southeastern site in comparison to the Central one. In Southeastern Brazil, the decrease in temperature during the non-reproductive season possibly forced G. agilis to be active only at certain hours of the night. However, likely due to the reproductive activities (intensive foraging and searching for mates) this marsupial showed constant, temperature-independent activity during the night in the reproductive period at both sites.

The Response of Bats (Mammalia: Chiroptera) to Habitat Modification in a Neotropical Savannah:

The Brazilian savanna (Cerrado) is a biodiversity hotspot with high deforestation rates that lead to extensive habitat changes, especially around protected areas (PAs). In our study, we analyzed how bats are affected by habitat changes comparing assemblages inside and outside Cerrado PAs. We compared diversity patterns of bats in relation to species composition, number of captured bats, as well as body condition and reproductive condition in cerrado sensu stricto (s.s.) and gallery forests. From September 2007 to June 2008, we captured 495 bats belonging to 25 species, 4 families, and 6 foraging guilds. When comparing captured bats inside and outside PAs, we found different patterns for both habitats, but with no differences in species richness for both habitats in relation to habitat perturbation. In relation to the degree of preservation, bat assemblages tend to be dissimilar between cerrado s.s. and similar between gallery forests. Besides that, in cerrados s.s., bats are less captured, or negatively affected, by habitat disturbance outside PAs; while in gallery forests, they are positively affected. Likewise, some bat species in gallery forests present higher body condition and more reproductive individuals outside PAs. Finally, we suggest that the intense habitat change in cerrado s.s. does cause negative effects on bats, while the positive effects found in degraded gallery forests may be due to the higher resource availability derived mainly from pioneer plants. Therefore, the presence of both nectarivorous bats in cerrado s.s. and frugivorous bats in gallery forests can be considered good indicators for habitat disturbance.

Predation upon small mammals by Caluromys lanatus (Didelphimorphia: Didelphidae) and Callithrix penicillata (Primates: Callitrichidae) in the Brazilian savanna

Abstract The identification of interactions by predation in field can be considered as valuable complementary information for studies on feeding and interaction ecology. Here we report and describe two cases of opportunistic predation upon small mammals in forests of the Brazilian savanna (Cerrado): by the didelphid brown-eared woolly opossum Caluromys lanatus on the sigmodontine rodent Rhipidomys macrurus, and by the black-tufted-ear marmoset Callithrix penicillata on the didelphid Gracilianus agilis. Our observations suggest that opportunistic predation events on vertebrates can be advantageous for animals that feed mainly on plant items, as a way to obtain protein-rich resources.