The deciduousness of tropical trees and communities depend on ecosystems characteristics such as plant species diversity, and strength of the dry season. Based on seven years of phenological observations, we provide the first long‐term description of leafing patterns of a woody cerrado community, aiming to investigate (1) the leaf exchange strategies considering the interannual variation in the degree of deciduousness of individuals and species and quantify the community deciduousness; (2) the relationship between interannual patterns of leaf fall and leaf flush according to the species’ leaf exchange strategies and climate; (3) the onset of cerrado growing season and its relation to climate seasonality. To detect seasonality and leafing onset we applied circular statistics and to understand the relationships between environmental predictors and leaf exchange strategies, we used generalized additive models. From 106 species observed, we classified 69 as deciduous (26 species), semi‐deciduous (25) or evergreen (18) and defined the studied cerrado as a semi‐deciduous vegetation. Leaf phenology was markedly seasonal and similar among years. Leaf fall peaked in the dry season, and leaf flush in the dry‐to‐wet transition. Leaf fall patterns related to temperature and leaf flush to day length and rainfall. Semi‐deciduous and deciduous species were more constrained by climate than the evergreen ones. The cerrado growing season started in the dry‐to‐wet season transition. Interannual variations in rainfall and temperature affected the individuals’ and, consequently, species’ degree of deciduousness, highlighting individual and species variability, and suggesting that cerrado leafing patterns are likely susceptible to future climate change scenarios.

& Introduction The reproductive phenology of plants is expected to be influenced by climatic factors and by the phylogenetic history of the species. In savannas, the peaks of flowering and fruiting are associated with climate seasonality. However, there is still a controversy about the reproductive phenology of plants in riparian forests, a vegetation type that does not experience a severe water shortage. & Methods We tested whether the reproductive peaks in riparian forests are different from those of the savannas. We also tested if the number of species in flower is correlated with rainfall and day length. We sought evidence of phylogenetic signals in the reproductive periods of the species. & Results Most of species in savannas and riparian forests flowered and fruited in the wet season. The number of flowering species was positively correlated with monthly rainfall and day length. However, we did not find phylogenetic signals in the reproductive periods. & Conclusions The phenological pattern of riparian forests was similar to that of savannas. At the community level, the reproductive periods of plants may not be under phylogenetic constraints, as observed in forests under nonseasonal climate. Sun-related variables seem to be the main cues for the reproductive phenology of plants in savannas and riparian forests.

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The cyanobacterial genus Trichodesmium is biogeochemically significant because of its dual role in nitrogen and carbon fixation in the oligotrophic ocean. Trichodesmium species form colonies that can be easily enriched from the water column and used for shipboard rate measurements to estimate their contribution to oceanic carbon and nitrogen budgets. During a July 2010 cruise near the Hawaiian Islands in the oligotrophic North Pacific Subtropical Gyre, a specific morphology of Trichodesmium puff-form colonies were examined under epifluorescent microscopy and found to harbor a colonial endobiont, morphologically identified as the heterocystous diazotrophic cyanobacterium Calothrix. Using unialgal enrichments obtained from this cruise, we show that these Calothrix-like heterocystous cyanobionts (hetDA for 'Trichodesmium-associated heterocystous diazotroph') fix nitrogen on a diurnal cycle (maximally in the middle of the light cycle with a detectable minimum in the dark). Gene sequencing of nifH from the enrichments revealed that this genus was likely not quantified using currently described quantitative PCR (qPCR) primers. Guided by the sequence from the isolate, new hetDA-specific primers were designed and subsequent qPCR of environmental samples detected this diazotroph from surface water to a depth of 150 m, reaching densities up to B9 Â 10 3 l À 1 . Based on phylogenetic relatedness of nifH and 16S rRNA gene sequences, it is predicted that the distribution of this cyanobiont is not limited to subtropical North Pacific but likely reaches to the South Pacific and Atlantic Oceans. Therefore, this previously unrecognized cohabitation, if it reaches beyond the oligotrophic North Pacific, could potentially influence Trichodesmium-derived nitrogen fixation budgets in the world ocean.

A central problem in ecology is to understand how human impacts affect plant-animal interactions that lead to effective seed dispersal services for plant communities. Seed dispersal services are the outcome of plant-frugivore interactions that often form local networks of interacting species. Recent work has shown that some frugivorous bird species are more critical to network organization than others. Here, we explore how patch size and the potential local extinctions of obligate frugivorous birds affect the reorganization of seed dispersal networks. We examined the structure of 20 empirical seed dispersal networks documented across tropical avian assemblages occupying widely variable habitat patch sizes, a surrogate of the amount of remaining habitat. Networks within small forest patches consistently supported both lower plant and bird species richness. Forest patch size was positively associated with nestedness, indicating that reductions in patch size disrupted the nested organization of seed dispersal networks. Obligate frugivores, especially large-bodied species, were almost entirely absent from small forest patches. Analysis at the species level showed that obligate frugivores formed the core of interacting species, connecting species within a given seed dispersal network. Our combined results revealed that patch size reduction erodes frugivorous bird diversity, thereby affecting the integrity of seed dispersal networks. We highlight the importance of conserving large forest patches to maintain tropical forest functionality.