RESUMO

Identifying the ecological factors that shape parasite distributions remains a central goal in disease ecology. These factors include dispersal capability, environmental filters and geographic distance. Using 520 haemosporidian parasite genetic lineages recovered from 7,534 birds sampled across tropical and temperate South America, we tested (a) the latitudinal diversity gradient hypothesis and (b) the distance-decay relationship (decreasing proportion of shared species between communities with increasing geographic distance) for this host-parasite system. We then inferred the biogeographic processes influencing the diversity and distributions of this cosmopolitan group of parasites across South America. We found support for a latitudinal gradient in diversity for avian haemosporidian parasites, potentially mediated through higher avian host diversity towards the equator. Parasite similarity was correlated with climate similarity, geographic distance and host composition. Local diversification in Amazonian lineages followed by dispersal was the most frequent biogeographic events reconstructed for haemosporidian parasites. Combining macroecological patterns and biogeographic processes, our study reveals that haemosporidian parasites are capable of circumventing geographic barriers and dispersing across biomes, although constrained by environmental filtering. The contemporary diversity and distributions of haemosporidian parasites are mainly driven by historical (speciation) and ecological (dispersal) processes, whereas the parasite community assembly is largely governed by host composition and to a lesser extent by environmental conditions.

Assuntos

RESUMO

Understanding latitudinal variation in avian life-history traits has been a focus of many demographic studies around the world. However, we still know little about annual or intra-annual demographic variation within tropical regions or about how factors such as breeding season and precipitation influence demographic rates. In this study, we estimated intra-annual apparent survival of the White-lined Tanager (Tachyphonus rufus) using capture-mark-recapture data from northeastern Brazil. We tested whether survival varied seasonally (breeding vs. non-breeding), with rainfall, by age and residence status in our study area. Intra-annual apparent survival was correlated with the reproductive cycle, being lower during the breeding (0.65 ± 0.16 SE) vs. the non-breeding season (0.97 ± 0.05 SE). The annual apparent survival (~0.6) was relatively low for a tropical species. In both years, we observed highest abundance in spring (November, 3.1-3.7 birds/ha) and lowest abundance in autumn-winter periods (May-August, 1.1-1.4 bird/ha). The low survival during the breeding season probably reflects the trade-off between survival and reproduction and the cost of reproduction. Our findings represent an advance in the understanding of the demography of tropical birds because we did not find a predicted high annual apparent survival, and we elucidated some aspects of intra-annual variation in survival. Further exploration of latitudinal variation in demographic traits, especially in diverse, but poorly known habitats is needed to fully vet and develop life history theories.

Assuntos

RESUMO

In northeastern Brazil, the reduction of the natural forest cover to a series of small, isolated fragments has had negative consequences for the local avian fauna, in particular, a loss of the more specialized species, while the populations of some generalists have tended to increase. The present study focuses on the composition and trophic groups of a bird community on a farm in the northeastern Brazilian state of Alagoas. Monthly surveys were conducted between November 2008 and October 2009, based on mist-netting and systematic observations. Overall, 112 species were recorded, of which 76 were associated with the two forest fragments surveyed, while all the others were observed exclusively in the surrounding matrix of pasture and orchards. The bird community presented a predominance of insectivorous species, followed by omnivores. However, specialized trunk-creeping and understory insectivores accounted for only around 15% of the species in this feeding category. The reduced diversity of other guilds and species with more specialized diets, and the complete absence of sensitive species such as large parrots and raptors, reflects the severe fragmentation and degradation of the local forests, which has greatly reduced the availability of dietary resources and breeding sites.

Assuntos

RESUMO

The Pernambuco Center of Endemism (PCE) in northeastern Brazil is highly fragmented and degraded. Despite its potential conservation importance the bird fauna in this area is still relatively unknown and there are many remnant fragments that have not been systematically surveyed. Here, we report the results of bird surveys in five forest fragments (one pioneer, two ombrophilous and two seasonal). In total, 162 taxa were recorded, 12 of which are endemic to the PCE. The frequency of endangered species was lower than what has been reported in studies from the same area and most of the taxa considered to be at risk of extinction were sub-species of uncertain taxonomic validity. The comparatively low number of endemic/threatened species may be due to the small size of the fragments in the present study - a consequence of the high levels of habitat loss in this region. Analysis of species richness patterns indicates that ombrophilous forest fragments are acting as refuges for those bird species that are most sensitive to environmental degradation.

O Centro de Endemismo Pernambuco (PCE), a área de Floresta Atlântica ao norte do rio São Francisco no nordeste do Brasil é altamente fragmentado e degradado. Apesar de sua importância nacional e global, a avifauna desta área é relativamente pouco estudada e há muitos fragmentos remanescentes que não foram sistematicamente pesquisados. Aqui, nós relatamos os resultados de pesquisas com a avifauna de cinco fragmentos florestais (um de floresta pioneira, dois de floresta ombrófila e dois de floresta sazonal). No total, 162 taxa foram registrados, 12 dos quais são endêmicos do PCE. No geral a frequência de espécies ameaçadas foi mais baixa do que em estudos similares e a maioria dos taxa considerados em risco de extinção foram subespécies de validade taxonômica incerta. Os principais fatores desse contraste podem ser o tamanho relativamente pequeno dos fragmentos do presente estudo e o elevado nível de fragmentação e degradação do habitat. A análise do padrão de riqueza de espécies pode indicar que os fragmentos de floresta ombrófila estão atuando como refúgio importante para espécies de aves que são sensíveis à degradação ambiental.

Assuntos

RESUMO

The Pernambuco Center of Endemism (PCE) in northeastern Brazil is highly fragmented and degraded. Despite its potential conservation importance the bird fauna in this area is still relatively unknown and there are many remnant fragments that have not been systematically surveyed. Here, we report the results of bird surveys in five forest fragments (one pioneer, two ombrophilous and two seasonal). In total, 162 taxa were recorded, 12 of which are endemic to the PCE. The frequency of endangered species was lower than what has been reported in studies from the same area and most of the taxa considered to be at risk of extinction were sub-species of uncertain taxonomic validity. The comparatively low number of endemic/threatened species may be due to the small size of the fragments in the present study - a consequence of the high levels of habitat loss in this region. Analysis of species richness patterns indicates that ombrophilous forest fragments are acting as refuges for those bird species that are most sensitive to environmental degradation.(AU)

O Centro de Endemismo Pernambuco (PCE), a área de Floresta Atlântica ao norte do rio São Francisco no nordeste do Brasil é altamente fragmentado e degradado. Apesar de sua importância nacional e global, a avifauna desta área é relativamente pouco estudada e há muitos fragmentos remanescentes que não foram sistematicamente pesquisados. Aqui, nós relatamos os resultados de pesquisas com a avifauna de cinco fragmentos florestais (um de floresta pioneira, dois de floresta ombrófila e dois de floresta sazonal). No total, 162 taxa foram registrados, 12 dos quais são endêmicos do PCE. No geral a frequência de espécies ameaçadas foi mais baixa do que em estudos similares e a maioria dos taxa considerados em risco de extinção foram subespécies de validade taxonômica incerta. Os principais fatores desse contraste podem ser o tamanho relativamente pequeno dos fragmentos do presente estudo e o elevado nível de fragmentação e degradação do habitat. A análise do padrão de riqueza de espécies pode indicar que os fragmentos de floresta ombrófila estão atuando como refúgio importante para espécies de aves que são sensíveis à degradação ambiental.(AU)

Assuntos