Diet of the gracile mouse opossum (Gracilinanus microtarsus) (Didelphimorphia: Didelphidae) in a Brazilian cerrado: patterns of food consumption and intrapopulation variation

The diet of the gracile mouse opossum Gracilinanus microtarsus was studied in a cerrado remnant in south-eastern Brazil through the analysis of faeces sampled from adult individuals. Patterns of food resource consumption were assessed using the statistics of per cent occurrence. Intrapopulation variation in the number of food items detected in faeces as a function of relevant factors was inferred using generalized linear models. The latter statistical formalism also allowed variation in the number of food items detected in faeces to be interpreted in terms of rate ratios among levels of significant factors. Insects, spiders, snails and fruits were detected in the faeces of G. microtarsus , with insects, particularly termites, beetles and ants, being the most frequently detected food resource. These food resources were consumed in proportion to their relative abundance in the cerrado, suggesting that G . microtarsus is an opportunistic forager feeding primarily on insects. The generalized linear model identified sex, season and food resource as significant factors affecting the number of food items detected in faeces, as well as interactions between sex and season and season and food resource. Rate ratios calculated between sexes within seasons showed that the number of food items detected in the faeces of males was larger than that detected in the faeces of females in the warm-wet and cool-dry seasons. Rate ratios calculated between seasons within sexes showed different trends in the number of food items detected in faeces for each significant food resource. It is suggested that differences in the number of food items detected in faeces between sexes within season and between seasons within sexes are related to energetic requirements associated with reproduction.     

Variation in the latitudinal reproductive patterns of the genus Didelphis (Didelphimorphia:Didelphidae)

Abstract: The data published on reproduction of the species of the genus Didelphis (Didelphimorphia, Didelphidae) were compiled and analysed to identify general patterns. The duration of the breeding season for the Didelphis species varied from 12 months near the Equator to 6 months at latitude 25°S and varied inversely with latitude and litter size. The mean litter size varied from 4.2 in Colombia to 9.4 in New York and was positively associated with latitude and negatively with the duration of breeding season. We propose that the higher investment in production at higher latitudes was compensated by increased mortality owing to the seasonal variation in food availability and environmental variables in theses latitudes.     

Intra‐ and inter‐individual variation show distinct trends as drivers of seasonal changes in the resource use of a neotropical marsupial

Individual specialization can influence important ecological and evolutionary traits and both inter‐ and intra‐individual variation in resource use can drive niche shifts in natural populations. We evaluated the predominance of these two factors for determining seasonal differences in the trophic niche of the didelphid marsupial Gracilinanus agilis (Burmeister, 1854) in the highly seasonal Brazilian savanna. In the three sampled sites, the population of G. agilis increased its dietary niche width in the warm–wet season, when food resources are more abundant, and there were no differences between sexes and no interaction between season and sex. However, the evaluation of intra‐individual variation indicated that females reduce the number of items consumed during the warm–wet season, whereas males show no seasonal differences. Inter‐individual variation nonetheless followed the overall population pattern because both sexes increased their spread with respect to food‐item consumption in the warm–wet season. Additionally, we found positive relationships between body length and diet only in the warm–wet season, when larger animals fed more on invertebrates and less on fruits than the small ones. Our results show a previously unknown pattern for mammals, in which the trophic niche is wider during the high‐resource season as a result of inter‐individual variation along the body‐size axis. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 737–747.     

Diet of the gracile mouse opossum Gracilinanus agilis (Didelphimorphia: Didelphidae) in a neotropical savanna: intraspecific variation and resource selection

Investigation of the effect of endogenous and exogenous factors on the diet of animals is necessary for a better understanding of their feeding habits. This approach can provide relevant information on the autoecology of a species and its ecological interactions. We investigated the composition and intraspecific variation in the diet of the marsupial Gracilinanus agilis in areas of dry woodland forests (i.e., cerradão) in the Cerrado of Central Brazil, taking into consideration the availability of prey (arthropods) in the environment. We found insects, spiders, birds, and fruits in the scats of G. agilis. Insects (orders Hymenoptera, Isoptera, Hemiptera, and Coleoptera) and fruits were the most frequently consumed resources. Males fed more heavily on insects than females did, whereas during the warm–wet season (October to April), the reproductive females fed on insects more than the nonreproductive females did. On the other hand, the consumption of fruits and vertebrates did not vary between seasons, sexes, or according to female reproductive condition. Moreover, reproductive females fed more frequently on ants and beetles than nonreproductive females did. We also detected both positive (for Isoptera and Hemiptera) and negative (for Hymenoptera) selection of insects during the cool–dry season, whereas in the warm–wet season, these resources were consumed according to their availability in the environment. Our study revealed that G. agilis is an insectivore–omnivore species, but fruits also are a relevant part of its diet. This marsupial seemed to select their prey qualitatively according to its energy demands and nutritional requirements.     

Relationships between drosophilids (Diptera, Drosophilidae) and the environment in two contrasting tropical vegetations

Although natural populations of drosophilid flies have been the subject of ecological studies, the population ecology of these insects in the tropics is still poorly known. This paper discusses aspects of the relationship between drosophilids and their environment, based on 28 monthly collections made in two contrasting vegetations of the Brazilian Cerrado biome: gallery forest and savanna. Exotic species were found in both types of environment; but 14 of the 30 captured Neotropical species occurred exclusively in the gallery forests, probably because of their climatic stability and greater environmental heterogeneity. Even though some endemic species were more abundant in the dry and cold months, most populations exhibited peaks of abundance in the wet season. The species diversity indexes (H' and D), higher in the dry season, were probably affected by increased evenness at this time of year, when the populations of practically all the species are greatly reduced. As species richness in the savanna vegetation clearly decreased in the dry season, increasing again in the wet season, it is suggested that some drosophilids migrate to the forests when climatic conditions are too stressful in the savannas.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 233–247.     

Polyembryony and apomixis in Eriotheca pubescens (Malvaceae - Bombacoideae)

Apomixis and adventitious polyembryony have been reported for several species of Bombacoideae, including Eriotheca pubescens, a tree species of the Neotropical savanna (Cerrado) areas in Brazil. However, the origin of polyembryonic seeds and their importance for the reproduction of the species remained to be shown. Here, we analyzed the early embryology of this species to establish the apomictic origin of extranumerary embryos. We also observed the geographic distribution of polyembryony in E. pubescens, and tested if apomixis was related to the source of pollen (self or cross) and population density. Moreover, we tested if polyembryonic apomictic embryos would develop normally into seedlings. In the observed seed primordia, after a relatively long quiescent period, the zygote developed into a sexual embryo concurrently with adventitious apomictic embryos which developed from nucellus cells. Adventitious embryos develop faster than sexual ones and are morphologically similar, so that 44 days after anthesis it was virtually impossible to distinguish and trace the fate of the sexual embryo. Polyembryony is widely distributed in populations some 400 km distant, and only one strictly monoembryonic individual was observed during the study. The number of embryos per seed varied between fruits and individuals but was significantly higher in seeds from cross-pollinations than from selfs, although fruit and seed set after crosses were much lower than after selfs. Embryo development into seedlings depended on their weight at germination, but polyembryonic seeds germinated and produced up to seven seedlings per seed in greenhouse conditions. Adventitious embryony and apomictic seedlings would explain the mostly clonal populations suggested by molecular studies.     

Variation in toxicity of copper pyrithione among populations and families of the barnacle,Balanus amphitrite

Inter- and intra-population variation in the toxicity of the antifouling biocide copper pyrithione (CuPT) was examined for nauplius larvae of the barnacle Balanus amphitrite. Nauplii were collected from brooding adults from four sites within the Newport River estuary (NC), chosen based on an initial estimation of recent and historical human activities that affect local contamination levels. Each site was characterized for the presence of polycyclic aromatic hydrocarbons and for the frequency of gastropod imposex, an indicator of contamination by organotins. Sensitivity of nauplii to CuPT varied significantly across the sites/populations, with LC₅₀ values ranging from 4.0 μg l^?1 to 6.1 μg l^?1. Larvae from the most contaminated site were the most sensitive to CuPT. Intrapopulation variation in toxicity was investigated by exposing nauplius larvae from 15 maternal families to a fixed concentration of CuPT (6.1 μg l^?1). Variation in larval mortality among the families was significant, ranging from 15.1% to 98.9%.     

Taxonomy and molecular phylogeny of the Neotropical genus Atlantoscia (Oniscidea,Philosciidae): DNA barcoding and description of two new species

Identification to the species level using morphology is challenging when usual diagnostic characters are similar amongst related taxa. Within the Neotropical genus Atlantoscia, differences between nominal species are generally small and restricted to a few characters. Despite the power of DNA sequencing to identify and distinguish between species, molecular phylogenies of terrestrial isopods from the Neotropics have not been determined. In this study, two new species of Atlantoscia were described and molecular markers were used to verify both the validity of the current taxonomy and the relationships amongst the species within this genus. All of the recognized Atlantoscia species were strongly supported in the generated phylogenetic trees. The average congeneric distance was 14.7%, with Atlantoscia ituberasensis and Atlantoscia rubromarginata showing the highest genetic divergence. Our results demonstrate the utility of the cytochrome c oxidase subunit I gene together with DNA barcoding to reliably distinguish Atlantoscia species. They also show that DNA barcoding may be helpful in those cases in which classical taxonomy does not provide clear‐cut species resolution. © 2015 The Linnean Society of London     

Intra‐specific variability in Rhinoleucophenga punctulata populations (Diptera: Drosophilidae) from Neotropical biomes: Combined analyses of morphological and molecular data

Despite the fact that Drosophilidae is a very diverse and well‐studied taxon, the New World genus Rhinoleucophenga is yet poorly understood even in regard to species distribution and morphological variability pattern. In this sense, R. punctulata is a species widely distributed in the Neotropical region. Specimens of R. punctulata were collected from different biomes in Brazil: Pampa, Cerrado and Caatinga sensu strictu, and a southern Amazonian savannah enclave area. Geographical variations in the external body morphology and in the morphology of spermatheca were noticed among the different populations. The hypothesis that each population could be a different species was tested through molecular data. A fragment of the mitochondrial cytochrome c oxydase subunit I (COI) gene was sequenced to perform phylogenetic analyses through neighbor‐joining and Bayesian inferences. Pairwise genetic divergences of COI sequences were calculated using DNA barcode premises. The analyzed populations presented different variation levels in both morphology and molecular traits. However, new species were not proposed because the intra‐population nucleotide variations exceeded the inter‐population ones. The noticeable morphological and genetic variations revealed among the four studied populations of R. punctulata in different biomes of Brazil suggest the necessity that morphological, distributional and molecular data at the population level should be integrated into complementary datasets to better understand the biological diversity of Rhinoleucophenga through Neotropical environments.     

Effect of maternal foraging habitat on offspring quality in the loggerhead sea turtle (Caretta caretta)

Exploring a trade‐off between quantity and quality of offspring allows differences in the fitness between alternative life histories to be accurately evaluated. We addressed the mechanism that maintains alternative life histories (small oceanic planktivores vs. large neritic benthivores) observed in a loggerhead sea turtle (Caretta caretta) population, which has been suggested to be environmental, based on the lack of genetic structure and a large difference in reproductive output. We examined whether maternal foraging habitat affects offspring quality, by measuring the morphology, emergence success, and righting response of hatchlings following incubation in a common open sand area over the whole nesting season at Yakushima Island, Japan, and by recording early growth and survival of offspring that were reared in a common environment at a Japanese aquarium. Furthermore, we tested whether sea turtles adjust egg size in response to temporal shifts of the incubation environment. There were no significant differences in any hatchling traits between oceanic and neritic foragers (which were classified by stable isotope ratios), except for clutches laid during the warmest period of the nesting season. There were also no significant differences in the growth and survival of offspring originating from the two foragers. The size of eggs from both foragers significantly increased as the season progressed, even though the rookery had heavy rainfall, negating the need to counteract heat‐related reduction in hatchling morphology. In comparison, the sizes of adult body and clutches from both foragers did not vary significantly. The results further support our previous suggestions that the size‐related foraging dichotomy exhibited by adult sea turtles does not have a genetic basis, but derives from phenotypic plasticity. Adjustment in reproductive investment may be associated with: (1) predation avoidance, (2) founder effect, and/or (3) annual variation in egg size.     

Post‐Establishment Seedling Success in the Brazilian Cerrado: A Comparison of Savanna and Forest Species1

Due to frequent fire, low nutrient availability, and prolonged drought, tropical savanna is a stressful environment for the survival and growth of woody plant seedlings. To understand why forest species do not succeed in this environment while savanna species are able to persist, the effects of fire and woody cover on seedlings of these two functional groups were investigated in the Brazilian Cerrado. Seedlings were established in experimental plots under three densities of woody cover, in sites protected from fire and sites to be subjected to fire. There was a clear difference in the ability of savanna and forest species to survive fire. None of the three forest species were able to survive fire during the first two years of life, whereas eight of the nine savanna species were able to resprout following fire. The small seed size of the ninth savanna species, Miconia albicans, predisposed its seedlings to be sensitive to fire, because there was a strong positive correlation between seed size and survivorship. Savanna species were less dependent on woody cover than were forest species, which exhibited higher growth and survival under tree canopies than in open grassland. The low rates of establishment and survival of forest trees in savanna, combined with high sensitivity to fire, appear sufficient to prevent the expansion of forest into savanna under current fire regimes in the Cerrado.     

Soil-vegetation relationships in cerrado (Brazilian savanna) and semideciduous forest, Southeastern Brazil

Several studies pointed out soil properties as the prime determinant ofcerrado (the Brazilian savanna) physiognomies, and a gradient from campocerrado (a shrub savanna) to cerradão (a tallwoodland) has been correlated with a soil fertility gradient. Based on thishypothesis, we investigated soil-vegetation relationships in thePé-de-Gigante Reserve (São Paulo State,SoutheasternBrazil). We randomly distributed 10 quadrats (10 × 10 m) oneach ofthe following physiognomies: campo cerrado, cerradosensu stricto, cerradão, andseasonal semideciduous forest, previously defined by the analysis of satelliteimages (LANDSAT-5). We sampled the woody individuals with stem diameter> 3 cm at soil level, identifying their species. In each quadrat, wecollectedsoil samples at the depths of 0–5, 5–25, 40–60, and80–100 cm, and determined pH, K, Ca, Mg, P, Al, H + Al, basesaturation, aluminium saturation, cation exchange capacity, and percentage ofsand, clay and loam. Obtained data were submitted to a canonical correspondenceanalysis (CCA) and to a detrended correspondence analysis (DCA). Our resultsshowed a clear distinction between semideciduous forest and the cerradophysiognomies, based in soil parameters. The former was related to higherconcentrations of cations and clay in the soil, while the latter was related tohigher concentrations of exchangeable aluminium in the soil surface. The threecerrado physiognomies – campo cerrado, cerradosensu stricto, and cerradão– could not be distinguished considering plant density and the analysedsoil features.     

Variation in growth in the blue tit (Parus caeruleus)

The pattern and amount of phenotypic and genetic variation in growth was analysed using the infinite-dimensional model in natural populations of the blue tit (Parus caeruleus). A size-index was used to analyse patterns of variation and covariation across ages (2, 5, 8, 11 and 14 days). Genetic variation was analysed using mother-, father-, and midparent-offspring regressions in the blue tit. Phenotypic variation in growth was limited to a few dimensions only, while heritabilities were close to zero at all ages except at 2 days when a significant mother-offspring relation was found. The phenotypic variance-covariance matrix over ages was found to be singular, which suggests that there are trajectories for which there is no phenotypic variation, and which therefore they cannot evolve. The phenotypic growth trajectory associated with the largest amount of variation basically showed a high to moderately high covariation across ages. These results have macroevolutionary implications in terms of the outcome of selection which generally will be in terms of overall size changes but with a slow rate of change due to low heritabilities; an outcome consistent with macro-evolutionary patterns of morphological variation in birds. A simulation study supported the conclusion that high covariances among traits and ages can impose considerable constraint on a microevolutionary scale.     

Demographic history and the low genetic diversity in Dipteryx alata (Fabaceae) from Brazilian Neotropical savannas

Genetic effects of habitat fragmentation may be undetectable because they are generally a recent event in evolutionary time or because of confounding effects such as historical bottlenecks and historical changes in species'' distribution. To assess the effects of demographic history on the genetic diversity and population structure in the Neotropical tree Dipteryx alata (Fabaceae), we used coalescence analyses coupled with ecological niche modeling to hindcast its distribution over the last 21 000 years. Twenty-five populations (644 individuals) were sampled and all individuals were genotyped using eight microsatellite loci. All populations presented low allelic richness and genetic diversity. The estimated effective population size was small in all populations and gene flow was negligible among most. We also found a significant signal of demographic reduction in most cases. Genetic differentiation among populations was significantly correlated with geographical distance. Allelic richness showed a spatial cline pattern in relation to the species'' paleodistribution 21 kyr BP (thousand years before present), as expected under a range expansion model. Our results show strong evidences that genetic diversity in D. alata is the outcome of the historical changes in species distribution during the late Pleistocene. Because of this historically low effective population size and the low genetic diversity, recent fragmentation of the Cerrado biome may increase population differentiation, causing population decline and compromising long-term persistence.     

A Pictorial Key for the Symphylan Families and Genera of the Neotropical Region South of Central Mexico (Myriapoda,Symphyla)

A pictorial key in English and Portugese is given for 2 families and 6 genera of the class Symphyla currently known from the Neotropical region, viz. Central America south of central Mexico, the Caribbean and entire South America.