Intraspecific Variation on Palm Leaf Traits of Co-occurring Species—Does Local Hydrology Play a Role?

The study of plant species and trait distributions can provide answers to many of the ecological challenges of our times, from climate change to the biodiversity crisis. Although traits are classically measured at the species level, understanding intraspecific variation is necessary to determine the type of response species will have to climate change. Here we measured and analyzed seven leaf traits (leaf area—LA, specific leaf area—SLA, leaf thickness—LT, leaf dry mass content—LDMC, venation density—VD, stomata length—SL, and stomata density—SD) across 14 locally dominant palm species (10 individuals/species) distributed along hydro-topographic gradients (1.4–37 m of terrain height above nearest drainage) of a central Amazonian forest to disentangle the role of species identity, relatedness, and local hydrology on trait variation and covariation. Our results show that trait variation is not always larger between species than within species as expected. Intraspecific variation accounted for 23–74% of trait variation depending on the trait. Most of the variation happened at species level for SL, LA, LT, and SD but not for SLA, VD, and LDMC. For a third of the traits (LDMC, SLA, and SD), we found some evidence of phylogenetic inertia. This lack of independency among traits is confirmed by the maintenance of strong correlation among some of those traits after controlling for local environmental conditions. Intraspecific variation, however, was not related to height above nearest drainage for any of the traits. Most of the trait–environment relationships were species-specific. Therefore, the change in palm trait composition detected along topography, from higher community means of SLA and LA, lower LT, LDMC, SL, and SD in the wet valleys to opposite traits in drier plateaus, is mostly due to the turnover in species composition and relative abundance variation. We conclude these palm species have well-defined hydrological niches, but their large intraspecific variation in leaf traits does not contribute to the adjustment of individuals to the local hydrological conditions in this Amazonian forest.

Case Report: Gold Miner’s Lung: A Case of Chronic Hypersensitivity Pneumonia in Amazonian Forest

The hostile conditions at informal and illegal mining sites in the Amazonian forest erode the miner’s health, exposing workers to a broad range of diseases because most of the gold is extracted using mercury (Hg). The Hg vapor used daily at gold panning sites presents an environmental threat to the ecosystems and human health. We report the case of a 58-year-old man who has worked in gold panning for over 30 years, presented with diffuse interstitial pneumonia characterized by bilateral images of ground glass and mosaic opacities on the chest CT scan. Based on the negative differential diagnosis (cardiovascular, infectious, autoimmune or cancer), the context of chronic exposure to Hg in a patient who has been working for decades on illegal gold panning sites, we concluded to a chronic form of heavy metal hypersensitivity pneumonia. This hypothesis was supported by high levels of mercury in blood and urine. Mercury hypersensitivity pneumonia might be more frequent than presently thought with thousands of workers chronically exposed to high mercury concentrations among others pollutants. Medical practitioners should systematically seek for chronic respiratory illnesses associated with pollutants exposure in these vulnerable workers with poor health.