Bird species richness in High-Andean forest fragments : habitat quality and topography matter

Montane forests worldwide are known centers of endemism and biodiversity but are highly threatened by fragmentation processes. Using data collected in 15 Polylepis forest remnants covering 2000 hectares, we investigated how bird species richness and bird community composition, particularly for species of conservation concern, are influenced by habitat quality and topography in the Tunari National Park in the High Andes of Bolivia. Bird species richness was highest in topographically complex, low-elevation Polylepis patches located in areas with a high potential to retain rainwater. Bird communities differed strongly between Polylepis lanata and P. subtusalbida remnants, each supporting different threatened and endemic species. Within the P. subtusalbida forest, high-elevation fragments characterized by high amounts of sunlight and low anthropogenic disturbance were more likely to contain threatened species. Surprisingly, we found no effect of fragment size on the diversity or composition of bird communities or the presence of bird species of conservation concern. The presence of exotic plantations (Pinus and/or Eucalyptus spp.) in or outside forest remnants was negatively associated with the number of bird species as well as with occurrence of the endangered Cochabamba-mountain finch (Compsospiza garleppi). To support the different communities found in Polylepis forests, these results suggest that conservation efforts should be directed towards both forest types (P. subtusalbida and P. lanata) present in the area. For an efficient management of avian diversity, exotic plantations should be established away from native remnants while existing patches should be managed to maintain or increase habitat quality. Finally, the importance of local topography in determining avian species richness and community composition in forest fragments, mainly through topographic controls on moisture distribution and the amount of sunlight received by the fragments, should be considered when planning conservation and reforestation schemes

Contribuição para o estudo dos mecanismos de transmissão do agente etiológico da doença de Chagas A contribution to the study of the mechanisms of transmission of the etiological agent of "Chagas" disease

Foram capturados no Município de Ribeirão Preto, SP, Brasil, exemplares de gambá, Didelphis albiventris. Na medida em que os exemplares chegavam ao laboratório foram submetidos a exames de sangue a fresco, hemoculturas e xenodiagnósticos, com o propósito de descartar a hipótese de infecção natural. Em cativeiro os animais passaram a ter, como parte de sua alimentação, camundongos parasitados pela cepa Bolívia do Tripanosoma cruzi ou exemplares de triatomíneos comprovadamente infectados pela mesma cepa do parasita. Vinte e cinco dias após a última refeição, foram realizados xenodiagnósticos nos animais em experimentação, cujo índice de infecção nos animais que ingeriram camundongos infectados foi de 60,0% e naqueles que ingeriram triatomíneos foi de 83,3%. Os resultados revelaram que os gambás apresentaram altos índices de infecção, mostrando a importância da via oral como porta de entrada do T. cruzi, bem como a importância do D. albiventris como reservatório do parasita nos focos naturais de infecção e elo de ligação entre o ambiente silvestre e o domicílio.<br>The infection of several opossums Didelphis albiventris, male, female and young, by oral means by feeding them either on infected triatomines or on mice experimentally infected by Tripanosoma cruzi, is studied. After feeding uncontaminated opossums on carcasses or living specimens of baby mice, infected with the Bolivian strain of T.cruzi, a 60.0% infection index was obtained on xenodiagnoses. On the other hand, after feeding uncontaminated opossums on infected triatomines, an 83.3% index was obtained on xenodiagnoses. These results indicate that the feeding on infected mammals, as well as the ingestion of infected triatomines by omnivorous animals gives high infection indices and demonstrates the importance of the oral route as the means of access of T. cruzi. The also show the importance of opossums as reservoirs of the parasite in the natural focci of infection and as carriers of T. cruzi to the domicile because of their migratory habits

Cortical thickness across the lifespan in a Colombian cohort with autosomal-dominant Alzheimer's disease: A cross-sectional study

Introduction Cortical thinning is a marker of neurodegeneration in Alzheimer's disease (AD). We investigated the age-related trajectory of cortical thickness across the lifespan (9-59 years) in a Colombian kindred with autosomal dominant AD (ADAD). Methods Two hundred eleven participants (105 presenilin-1 [PSEN1] E280A mutation carriers, 16 with cognitive impairment; 106 non-carriers) underwent magnetic resonance imaging. A piecewise linear regression identified change-points in the age-related trajectory of cortical thickness in carriers and non-carriers. Results Unimpaired carriers exhibited elevated cortical thickness compared to non-carriers, and thickness more negatively correlated with age and cognition in carriers relative to non-carriers. We found increased cortical thickness in child carriers, after which thickness steadied compared to non-carriers prior to a rapid reduction in the decade leading up to the expected age at cognitive impairment in carriers. Discussion Findings suggest that cortical thickness may fluctuate across the ADAD lifespan, from early-life increased thickness to atrophy proximal to clinical onset

Efeito da variabilidade da precipitação pluvial e do uso e manejo do solo sobre o escoamento superficial e o aporte de sedimento de uma bacia hidrográfica do Distrito Federal Effect of rainfall variability and land use on runoff and sediment in the Pipiripau river basin, in the Distrito Federal, Brazil

O objetivo do presente trabalho foi avaliar o efeito da variabilidade da precipitação sobre o escoamento direto e sobre o aporte de sedimento na bacia do rio Pipiripau (A = 235 km²), no Distrito Federal. Cinco anos típicos da série de precipitação foram selecionados: o ano mais úmido, o ano mais seco, o ano médio e dois anos que representaram os desvios-padrão da série (médio-seco e médio-úmido). Depois de o modelo ser calibrado com dados diários de chuva e vazão da bacia, simulações foram realizadas para cada evento chuvoso de cada um dos cinco anos selecionados da série, e o escoamento direto e o aporte de sedimento da bacia foram calculados com a MUSLE em três diferentes cenários de uso e manejo do solo: o cenário atual, onde predomina o preparo convencional do solo (PC) nas áreas de agricultura da bacia; o passado recente, em que predominava o Cerrado nativo (CER); e o cenário de plantio direto (PD), nas áreas de agricultura da bacia. Apesar de as vazões médias anuais observadas terem apresentado relação linear com os volumes de precipitação pluvial anual, em todos os cenários, o escoamento direto e o aporte de sedimento apresentaram aumento exponencial com o aumento da precipitação pluvial anual, sendo esse mais pronunciado na condição de preparo convencional (PC) do que nos outros cenários estudados (CER e PD). O aumento observado pode ser explicado pela não-linearidade do modelo MUSLE ao volume de precipitação e ao volume de escoamento.<br>The objective of this study was to evaluate the effect of the rainfall variability on the runoff and sediment amount in the Pipiripau river basin (A = 235 km²), in the Distrito Federal, Brazil. To represent the climatic variability of the historic precipitation series, 5 years were selected: the moistest, the driest, an average, and 2 years representing the standard deviations from the series (half-wet and half-dry). After the calibration of the model with basin rainfall and runoff data, each rainfall event was simulated in each one of the selected years, and sediment yields were computed using software MUSLE for three different land-use and management situations: (a) The present conditions, with predominantly conventional agriculture in the agricultural areas (PC); (b) The former scenario, where native (Cerrado) vegetation existed in the basin (CER); and (c) no-till in the agricultural areas (PD). Although the relationship of the mean annual flow rates with the annual rainfall volume was linear, there was an exponential increase in runoff volume and sediment yield with precipitation in all scenarios; the most significant increases were observed for PC, followed by PD and CER. The exponential increase can be explained by the non-linearity of the MUSLE model regarding both precipitation and runoff volume