Amazon tree dominance across forest strata

The forests of Amazonia are among the most biodiverse plant communities on Earth. Given the immediate threats posed by climate and land-use change, an improved understanding of how this extraordinary biodiversity is spatially organized is urgently required to develop effective conservation strategies. Most Amazonian tree species are extremely rare but a few are common across the region. Indeed, just 227 'hyperdominant' species account for >50% of all individuals >10 cm diameter at 1.3 m in height. Yet, the degree to which the phenomenon of hyperdominance is sensitive to tree size, the extent to which the composition of dominant species changes with size class and how evolutionary history constrains tree hyperdominance, all remain unknown. Here, we use a large floristic dataset to show that, while hyperdominance is a universal phenomenon across forest strata, different species dominate the forest understory, midstory and canopy. We further find that, although species belonging to a range of phylogenetically dispersed lineages have become hyperdominant in small size classes, hyperdominants in large size classes are restricted to a few lineages. Our results demonstrate that it is essential to consider all forest strata to understand regional patterns of dominance and composition in Amazonia. More generally, through the lens of 654 hyperdominant species, we outline a tractable pathway for understanding the functioning of half of Amazonian forests across vertical strata and geographical locations.

Diversity patterns of hematophagous insects in Atlantic forest fragments and human-modified areas of southern Bahia, Brazil

There have been several important outbreaks of mosquito-borne diseases in the Neotropics in recent years, particularly in Brazil. Some taxa are also considered to be indicators of environmental health. Despite the importance of understanding insect abundance and distribution to the understanding of disease dynamics and design strategies to manage them, very little is known about their ecology in many tropical regions. We studied the abundance and diversity of mosquitoes and sand flies in the Bahia State of Brazil, a point of origin for arbovirus outbreaks, including Zika and Chikungunya fever. During 2009-2014, 51 mosquito taxa were identified, belonging to three dipteran families, Ceratopogonidae, Culicidae, and Psychodidae. The family Culicidae, including the Sabethini tribe, were the most abundant (81.5%) and most taxa-rich (n=45). While season (winter and summer) was a strong factor determinant of the occurrence of the most abundant taxa, the stratification level in the forest (ground or tree level) had a strong effect and the dominant taxa at ground level were completely different from the dominant species collected at tree level. We suggest that sites with a mix of forest and agroforestry systems support the highest biodiversity of hematophagous insects as compared to highly disturbed landscapes.

Surveillance of Arboviruses in Primates and Sloths in the Atlantic Forest, Bahia, Brazil

From 2006 through 2014, we conducted seroepidemiological surveys on non-human primates and sloths to investigate the possible circulation of arboviruses in Bahia Atlantic Forest, Brazil. We collected a total of 196 samples from 103 Leontopithecus chrysomelas, 7 Sapajus xanthosternos, 22 Bradypus torquatus and 7 Bradypus variegatus. Serum samples were tested using neutralization test and hemagglutination inhibition test to detect total antibodies against 26 different arboviruses. The overall prevalence of arboviruses was 36.6% (51/139), with the genus Flavivirus having the highest prevalence (33.1%; 46/139), followed by Phlebovirus (5.0%; 7/139), Orthobunyavirus (4.3%; 6/139) and Alphavirus (0.7%; 1/139). Monotypic reactions suggest that the wild animals were exposed naturally to at least twelve arboviruses. Added results from the neutralization test, animals were exposed to thirteen arboviruses. Most of these viruses are maintained in transmission cycles independent of human hosts, although antibodies against dengue virus serotypes 1, 2 and 3 were found in this study. To our knowledge, this is the first study reporting exposure to arboviruses in L. chrysomelas, S. xanthosternos and B. torquatus. Our results also highlight that the Southern Bahia Atlantic Forest has a variety of vertebrate hosts and potential vectors, which may support the emergence or re-emergence of arboviruses, including those pathogenic to humans.