Emerson M. Vieira

Vertical stratification of small mammals in the Atlantic rain forest of south-eastern Brazil

Patterns of vertical stratification and canopy utilization by rodents and marsupials were analysed in two contiguous Atlantic forests at different altitudes (100 m and 900 m asl). Twenty-two species were captured using live traps placed at ground level, in the understorey (1.5–2.0 m), and in the canopy (6–15 m) over 2 y; seven species (32%) were mainly or exclusively arboreal. Community composition and relative abundance of species in the different vertical strata were not similar, with a general reduction in the number of species, and in abundance in the upper layers. The following species were captured mainly or exclusively in the canopy: Micoureus demerarae and Gracilinanus microtarsus (Didelphimorphia, Didelphidae); Wilfredomys pictipes , Oecomys aff. concolor , and Rhipidomys aff. macrurus (Rodentia, Muridae); and Nelomys nigrispinus (Rodentia, Echimyidae). Our results indicated that altitudinal changes in Atlantic forest areas may alter the community composition of different forest layers but they do not seem to alter greatly specific patterns of vertical habitat utilization. Similar-sized species tended to differ in their patterns of vertical utilization of habitat with the exception of terrestrial akodontine rodents (genera Akodon , Thaptomys , Oxymycterus and Brucepattersonius ). Rodents (mainly Oryzomys russatus ) dominated captures at ground level at both sites but Akodontinii were numerous only at the highest site. Unlike other neotropical forests, marsupials did not dominate canopy captures.

Post-fire succession of small mammals in the Cerrado of central Brazil

In the Cerrado savannas from Brazil fire events are common and strongly influence the vegetation structure and, consequently, the associated small mammals. In this paper, we investigate changes in the structure of small mammal communities related to sites of different post-fire ages. Mammals were captured in similar Cerrado sites that differed in time since the last burn (1 to 26 yr). We sampled six sites in the wet season of 1997 (phase 1) and, three years later, six sites in the wet and dry seasons (phase 2). Six rodent species and four marsupials were captured. Community composition changed drastically as a function of time since fire. The diversity and abundance of small mammals reached maximum values in the early successional stages. The rodent Calomys tener was present only in early seral stages. The rodent Bolomys lasiurus was more frequent in mid-successional stages and decreased in later seral stages, and the rodent Oryzomys subflavus occupied all successional stages. The marsupial Gracilinanus agilis was dominant in the area that did not burn for at least 23 yr. Changes in composition of the community of small mammals were more accelerated in early successional stages, when there are more drastic vegetational changes. The ability of small mammals to cope with Cerrado fires and the great dissimilarity among post-burning seral stages suggest that a mosaic of areas representing different post-fire seral stages could increase the regional diversity of this group.

Fire Effects on a Palicourea rigida (Rubiaceae) Gall Midge: A Test of the Plant Vigor Hypothesis1

The effects of fire on growth of Palicourea rigida (Rubiaceae) were significant in a comparison between adjacent burned and unburned sites in cerrado savanna vegetation near Brasilia, Brazil. Many more small and young leaves appeared after the fire in the early part of the wet season, and leaves after the burn were much less tough for a given leaf length class than in the unburned area (unburned area leaves were 150% tougher). Growth of host plants after fire resulted in higher colonization of a leaf-galling midge in the genus Contarinia (Diptera: Cecidomyiidae) as yet unnamed at the species level. On the highest intensity of attack per leaf length class, galls were over five times more abundant per leaf in the burn than in the unburned area. Within the galls larvae survived better in the burned site, and numbers of surviving larvae at the end of the first generation were 5.4 times higher per leaf than in the unburned area. An even stronger effect of fire was observed in the second generation of gallers after the fire, when no living larvae could be found in the unburned area, but 17 living larvae per 100 leaves occurred in the burned site. These results supported the Plant Vigor Hypothesis, because regrowth after fire produced younger more tender leaves favorable for herbivore attack. The importance of fire in a landscape as a disturbance factor in cerrado, which rejuvenates plant growth, increasing favorability for many insect herbivores, deserves more attention and study.

Daily activity patterns of small mammals in a cerrado area from central Brazil

Nos investigamos os padrōes diarios de atividade de quatro especies de pequenos mamiferos em uma area de cerrado no Brasil central. As armadilhas do tipo alcapāo eram revisadas de tres em tres horas ao longo da noite. Bolomys lasiurus e Calomys tener (Rodentia, Muridae), dois competidores em potencial, diferiram significativamente quanto aos seus ritmos diarios de atividade. Bolomys lasiurus apresentou picos ao entardecer e ao amanhecer, enquanto que C. tener apresentou uma atividade mais constante ao longo da noite, com um pico entre 2200 e 0100 h. Thalpomys cerradensis (Rodentia, Muridae) foi mais ativo imediatamente depois do por do sol e nas tres ultimas horas antes do sol nascer. Thylamys velutinus (Marsupialia, Marmosidae) foi exclusivamente noturno, apresehtando uma maior atividade no inicio da noite. Outros fatores, tais como pressao de predacāoe preferencias alimentares, podem ser importances para determinar os padrōes de atividade observados neste estudo.

Population responses of small mammals to food supply and predators: a global meta-analysis.

1. The relative importance of food supply and predation as determinants of animal population density is a topic of enduring debate among ecologists. To address it, many studies have tested the potential effects of food on population density by experimentally supplementing natural populations, with much focus on terrestrial vertebrates, especially small mammals. 2. Here we perform a meta-analysis of such experiments, testing two complementary hypotheses: (i) small mammal populations are bottom-up limited and (ii) population increases in response to food supplementation are constrained by predation, a top-down limitation. 3. In the 148 experiments recorded, food supplementation had an overall positive and significant effect, increasing population densities by 1.5-fold. Larger population increases occurred when predation was reduced and populations were open to immigration. Predation appeared to be unimportant when populations were closed to immigration. Immigration was the major mechanism underlying increases in abundance by increasing local population density and crowding. Contributions of increased reproductive rate could be detected, but were minor compared to immigration, and no effects were detected from survival. 4. Our analyses support the view that animal population density is determined by both bottom-up and top-down forces. They also suggest the possibility that food supplementation experiments might unintentionally create ecological traps by aggregating both prey and predators in small areas of the landscape. We suggest an alternative experimental design to increase the contribution that food supplementation experiments can make in future.

Produção de frutos e distribuição espacial de angiospermas com frutos zoocóricos em uma Floresta Ombrófila Mista no Rio Grande do Sul, Brasil

We investigated, during 14 months, patterns of fruit production of animal dispersed angiosperms in a patch of Mixed Ombrophilous Forest (MOF) in the National Park of Aparados da Serra, State of Rio Grande do Sul, south Brazil. For a total of 570 individuals sampled in a 2.56 ha area we identified 27 species of animal dispersed angiosperms (13 families). The most abundant families were: Myrtaceae (eight species), Melastomataceae, Solanaceae, and Rubiaceae (three species each). Most sampled life forms were shrubs (46.0% of all individuals 37.0% of species total), followed by treelets (31.9% and 22.2%), herbs (10.2% and 18.5%), trees (8.7% and 18.5%), and epiphytes (3.2% and 3.7%). Red (22.2%) and orange (18.5%) fruits prevailed, as well as small fruits (70% of fruit total with size of 1-10 mm × 1-10 mm), and fruits with one to ten small seeds (96% of total species with seed size of 1-10 mm × 1-10 mm). The three species that produced the greatest amount of fruits were: Myrceugenia miersiana (Gardner) D. Legrand & Kausel (Myrtaceae) (tree - 61.0% of total production of fruits), and the melastomes Leandra variabilis Cogn. (shrub - 18.1%) and Miconia cinerascens Miq. (shrub - 8.6%). These species showed an aggregated dispersion pattern (Standardized Morisita index > 0.5 for all of them). The monthly number of fruiting species was significantly correlated with monthly temperature in the same month (rs = 0,70; p < 0,01), and with rainfall in the previous month (rs = 0,67; p < 0,02). The seed production of Araucaria angustifolia (Bertol.) Kuntze occurred during the period with the lowest number of angiosperm species producing animal-dispersed fruits. This non-overlapping between events might favor the occurrence of frugivorous animals, enabling a higher resource offer during the entire year.

Feeding of small rodents on seeds and fruits: a comparative analysis of three species of rodents of theAraucaria forest, southern Brazil

We investigated the feeding of three small-sized sigmodontine rodents (Oligoryzomys nigripes Olfers, 1818,Akodon montensis Thomas, 1913, andDelomys dorsalis Hensel, 1872) on fruiting plants in theAraucaria forest of southern Brazil. We offered to wild-captured animals fruits of 22 plant species in 14 families. For each individual, we recorded consumption patterns of pulp and seed. We also analyzed fecal samples to determine the relative abundance of invertebrates, fruit and seed parts, and fungi. The three rodents showed marked potential frugivory, feeding on most species offered. OnlyO. nigripes showed differences in relation to seed-size categories, consuming a high proportion of ‘small’ (diameter ≤2.5 mm) vs ‘large’ seeds. The rodents may be involved in seed dispersion of three plant species, by defecation of viable seeds of twoLeandra (Melastomataceae) species and also by removing the pulp ofMyrceugenia miersiana (Myrtaceae) fruits without swallowing or damaging their relatively large seeds, thus, potentially increasing germination rates ofM. miersiana. Diet analyses indicated no significant difference among proportions of seed/fruit in the fecal samples of the three species of rodents (33 to 41% of plant material). Our results suggest that the three focal species are the main small-mammal seed predators on the ground ofAraucaria forests.

Terrestrial flatworm (Platyhelminthes: Tricladida: Terricola) diversity versus man-induced disturbance in an ombrophilous forest in southern Brazil

Terrestrial flatworms, or Terricola, are sensitive to environmentalchanges and therefore might be excellent indicators of the conservation statusof natural habitats. The present study aimed to answer two main questions: (1)is terrestrial planarian diversity affected by human disturbances, and (2) isthere any species or group of species that indicates such disturbance? The studysite, National Forest of São Francisco de Paula, Brazil, was originallycovered by a mixed ombrophilous forest, but successive reforestations andselective logging have modified the original landscape. We studied Terricoladiversity in the four main habitats in the study area: mixed ombrophilous forest(NA), ombrophilous forest with selective Araucariaangustifolia logging (N), A. angustifoliareforestation (A), and reforestation of Pinus elliottii(P). According to an increasing degree of disturbance, the habitats might beordered as follows: (NA)<(N)<(A)<(P). We conducted 24 surveys in eachhabitat over a period of 1 year. Our results indicate that: (1)Terricola diversity is inversely related to the degree of habitat disturbance;(2) there are species (Geoplana franciscana,Geoplana sp. 5, and possibly Geoplanidae 3 andNotogynaphallia guaiana) that prefer habitats located onthe extreme right along the main axis of a detrended correspondence analysisordination and therefore can be considered as indicators of well preserved,natural habitats. On the other hand there are species(Xerapoa sp. 1, Choeradoplanaiheringi, G. marginata sensu Marcus andGeoplana sp. 2) preferring more disturbed habitats, whichmay form biological indicators of such disturbances.

Nests and nesting sites of Brazilian forest rodents (Nectomys squamipes andOryzomys intermedius) as revealed by a spool-and-line device

Patterns of nest construction and nest site selection of two murid rodents of the Brazilian Atlantic rainforest were described. The animals were captured in an area of about 1.5 ha of primary forest, marked, equipped with a spool-and-line device and released at the capture point. The next day we followed the thread to find their nests. In total 11 nests ofNectomys squamipes (Brants, 1827) and 13 ofOryzomys intermedius (Leche, 1886) were found. They were all egg-shaped, about 15 cm long and 10 cm wide, without any apparent entrance and consisted of dry leaves and grass. The two species differed in the selection of nest sites. The nests ofN. squamipes were close to streams and built inside decomposed fallen logs or using natural entrances between the soil and tangled roots or rocky crevices. Nests ofO. intermedius were built under or inside fallen logs and inside aerial root systems of palms. The spool-and-line technique used here is useful to provide detailed information on several aspects of the ecology and natural history of small mammals.

Macrophyte rafts as dispersal vectors for fishes and amphibians in the Lower Solimoes River, Central Amazon

*Departamento de Zoologia, Instituto de Biocieˆncias, Universidade de Sa˜o Paulo, CP 20520, 01452-990, Sa˜o Paulo-SP, Brazil†Coordenac¸a˜o de Pesquisas em Biologia Aqua´tica, Caixa Postal 478, Instituto Nacional de Pesquisas da Amazoˆnia, 69083–970, Manaus-AM, Brazil‡Nu´cleo de Altos Estudos Amazoˆnicos-NAEA, Universidade Federal do Para´ 67070-100, Bele´m-PA, Brazil§Departamento de Biologia, Universidade do Amazonas, 69970-000, Manaus-AM, Brazil¶UNESP-Rio Claro, PG Zoologia, Avenida 24-A, 1515, C.P. 199, 13506-900, Rio Claro-SP, Brazil#Laborato´rio de Ecologia de Mami´feros, Centro de Cieˆncias da Sau´de, UNISINOS, CP 275, 93022-000, Sa˜o Leopoldo-RS, Brazil(