[1] We study the seasonal dynamics of the eastern Pacific (CHOCO) and Caribbean lowlevel jets (LLJ), and aerial rivers (AR) acting on tropical and subtropical South America. Using the ERA-Interim reanalysis , we show that the convergence of both LLJs over the eastern Pacific-western Colombia contributes to the explanation of the region's world-record rainfall. Diverse variables involved in the transport and storage of moisture permit the identification of an AR over northern South America involving a midtropospheric easterly jet that connects the Atlantic and Pacific Oceans across the Andes, with stronger activity in April to August. Other major seasonal AR pathways constitute part of a large gyre originating over the tropical North Atlantic, veering to the southeast over the eastern Andes and reaching regions of northern Argentina and southeastern Brazil. We illustrate the distribution of average seasonal precipitation along the LLJs and AR pathways with data from the Tropical Rainfall Measuring Mission (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011), combined with considerations of CAPE, topography, and land cover. In addition, the theory of the biotic pump of atmospheric moisture (BiPAM) is tested at seasonal time scales, and found to hold in 8 out of 12 ARs, and 22 out of 32 forest-covered tracks (64% in distance) along the ARs. Deviations from BiPAM's predictions of rainfall distribution are explained by the effects of topography, orography, and land cover types different from forests. Our results lend a strong observational support to the BiPAM theory at seasonal time scales over South American forested flat lands.

We classified and characterized precipitation features (PFs) at annual and diurnal timescales during 1998–2011 over the tropical Americas and adjoining oceans using data from two instruments on board the Tropical Rainfall Measuring Mission (TRMM). Our scope included geographic distribution, frequency, area, rainfall rate, and polarization‐corrected temperatures (PCTs) of PFs in an effort to contrast different regions over Colombia, the Amazon River Basin, and the adjoining oceanic regions (Pacific Ocean and Caribbean Sea). Our results showed that mesoscale convective systems (MCSs) over the Caribbean Sea exhibited colder minimum PCTs than Pacific Ocean MCSs. Pacific Ocean MCSs had higher rainfall rates, however, than Caribbean Sea MCSs. Despite the fact that MCSs represented <1% of the total precipitation systems found, the MCSs contributed more rainfall over the study regions. Over the Pacific Ocean, for example, MCSs contributed approximately 57% of the total rainfall contributed by all precipitation systems identified over that region. Additionally, MCSs over the Pacific coast have their maximum frequency during the morning hours (0000–0600 Local Time) offshore and centred over the Pacific Ocean at 77.5°W. The annual cycle of PFs showed a marked bimodal annual cycle over Colombia, whereas over the Amazon Basin, Pacific Ocean, and Caribbean Sea, PFs were characterized by a unimodal annual cycle.

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How ecological context shapes mutualistic relationships remains poorly understood. We combined long-term tree census data with ant censuses in a permanent 25-ha Amazonian forest dynamics plot to evaluate the effect of the mutualistic ant Myrmelachista schumanni (Formicinae) on the growth and survival of the common Amazonian tree Duroia hirsuta (Rubiaceae), considering its interactions with tree growth, population structure, and habitat. We found that the mutualist ant more than doubled tree relative growth rates and increased odds of survival. However, host tree size and density of conspecific neighbors modified the effect of the ant. Smaller trees hosting the mutualist ant consistently grew faster when surrounded by higher densities of conspecifics, suggesting that the benefit to the tree outweighs any negative effects of high conspecific densities. Moreover, our findings suggest that the benefit afforded by the ant diminishes with plant age and also depends on the density of conspecific neighbors. We provide the first long-term large-scale evidence of how mutualism affects the population biology of an Amazonian tree species.