Alberto Vicentini

Leaf and wood functional traits of trees are related to growth, reproduction, and survival, but the degree of phylogenetic conservatism in these relationships is largely unknown. In this study, we describe the variability of strategies involving leaf, wood and demographic characteristics for tree genera distributed across the Amazon Region, and quantify phylogenetic signal for the characteristics and their relationships. Leaf and wood traits are aligned with demographic variables along two main axes of variation. The first axis represents the coordination of leaf traits describing resource uptake and use, wood density, seed mass, and survival. The second axis represents the coordination between size and growth. Both axes show strong phylogenetic signal, suggesting a constrained evolution influenced by ancestral values, yet the second axis also has an additional, substantial portion of its variation that is driven by functional correlations unrelated to phylogeny, suggesting simultaneously higher evolutionary lability and coordination. Synthesis. Our results suggest that life history strategies of tropical trees are generally phylogenetically conserved, but that tree lineages may have some capability of responding to environmental changes by modulating their growth and size. Overall, we provide the largest‐scale synopsis of functional characteristics of Amazonian trees, showing substantial nuance in the evolutionary patterns of individual characteristics and their relationships. Read the free Plain Language Summary for this article on the Journal blog.

Habitat fragmentation could potentially affect tree architecture and allometry. Here, we use ground surveys of terrestrial LiDAR in Central Amazonia to explore the influence of forest edge effects on tree architecture and allometry, as well as forest biomass, 40 years after fragmentation. We find that young trees colonising the forest fragments have thicker branches and architectural traits that optimise for light capture, which result in 50% more woody volume than their counterparts of similar stem size and height in the forest interior. However, we observe a disproportionately lower height in some large trees, leading to a 30% decline in their woody volume. Despite the substantial wood production of colonising trees, the lower height of some large trees has resulted in a net loss of 6.0 Mg ha⁻¹ of aboveground biomass – representing 2.3% of the aboveground biomass of edge forests. Our findings indicate a strong influence of edge effects on tree architecture and allometry, and uncover an overlooked factor that likely exacerbates carbon losses in fragmented forests.

Myrcia is the sole genus of the Myrciinae, one of the nine subtribes of Myrteae (Myrtaceae). The Amazon forest holds about one-quarter of the Brazilian species of Myrcia, but the genus is still understudied in this whole region. In this context, this study presents a floristic survey of Myrcia in the permanent plots of the Biological Dynamics of Forest Fragments Project (BDFFP), in Amazonas state, Brazil. The genus is represented by 36 species in the study area, comprehending 32% of its total richness in the Brazilian Amazon forest, with 19 of them endemic to this domain. Myrcia neospeciosa is reported as a new occurrence for Amazonas state and M. grandis is recorded for the first time from upland terra firme forests on clayish soils. Myrcia cuspidata, a species with calyptrate flowers, is classified under Myrcia sect. Aulomyrcia, representing the second taxon of the genus with this feature removed from Myrcia sect. Calyptranthes. Finally, morphological aspects of the infra-generic categories of Myrcia are reported more overlapping than previously thought. A map containing the location of the study area, an identification key, descriptions, comments, and figures are provided.

Summary: Admixture is a mechanism by which species of long‐lived plants may acquire novel alleles. However, the potential role of admixture in the origin and maintenance of tropical plant diversity is unclear. We ask whether admixture occurs in an ecologically important clade ofEschweilera(Parvifolia clade, Lecythidaceae), which includes some of the most widespread and abundant tree species in Amazonian forests. Using target capture sequencing, we conducted a detailed phylogenomic investigation of 33 species in the Parvifolia clade and investigated specific hypotheses of admixture within a robust phylogenetic framework. We found strong evidence of admixture among three ecologically dominant species,E.coriacea,E.wachenheimiiandE.parviflora, but a lack of evidence for admixture among other lineages. Accepted species were largely distinguishable from one another, as was geographic structure within species. We show that hybridization may play a role in the evolution of the most widespread and ecologically variable Amazonian tree species. While admixture occurs among some species ofEschweilera, it has not led to widespread erosion of most species’ genetic or morphological identities. Therefore, current morphological based species circumscriptions appear to provide a useful characterization of the clade's lineage diversity.

Myrcia is the sole genus of the Myrciinae, one of the nine subtribes of Myrteae (Myrtaceae). The Amazon forest holds about one-quarter of the Brazilian species of Myrcia, but the genus is still understudied in this whole region. In this context, this study presents a floristic survey of Myrcia in the permanent plots of the Biological Dynamics of Forest Fragments Project (BDFFP), in Amazonas state, Brazil. The genus is represented by 36 species in the study area, comprehending 32% of its total richness in the Brazilian Amazon forest, with 19 of them endemic to this domain. Myrcia neospeciosa is reported as a new occurrence for Amazonas state and M. grandis is recorded for the first time from upland terra firme forests on clayish soils. Myrcia cuspidata, a species with calyptrate flowers, is classified under Myrcia sect. Aulomyrcia, representing the second taxon of the genus with this feature removed from Myrcia sect. Calyptranthes. Finally, morphological aspects of the infra-generic categories of Myrcia are reported more overlapping than previously thought. A map containing the location of the study area, an identification key, descriptions, comments, and figures are provided.

Three new Amazonian species of the Myrcia splendens group from Brazil are proposed based on morphology and near-infrared spectroscopy of leaves and compared with similar taxa. Myrcia eveae resembles M. splendens and may be recognised mostly by large and oblong leaf blades that tapers abruptly at the apex and large bracts; Myrcia otocalyx also resembles M. splendens, being recognised mainly by pyriform flower buds, campanulate hypanthia that are longitudinally ridged, and sepals of different shapes that are patent on fruit; and Myrcia prismatica is similar to M. deflexa, being recognised essentially by chartaceous leaf blades, pedicels clustered at the tips of inflorescence axes, and oblong fruits with longitudinal edges. Spectral data revealed a unique pattern for each one of the new species and the putative related ones, reinforcing the morphological propositions. This is the first study to use morphology and spectroscopy of leaves combined to propose new species of Myrtaceae. Information on geographical distribution, habitat, conservation status, and an identification key are also provided.

Thermal sensitivity of tropical trees: A key uncertainty in climate change models is the thermal sensitivity of tropical forests and how this value might influence carbon fluxes. Sullivan et al. measured carbon stocks and fluxes in permanent forest plots distributed globally. This synthesis of plot networks across climatic and biogeographic gradients shows that forest thermal sensitivity is dominated by high daytime temperatures. This extreme condition depresses growth rates and shortens the time that carbon resides in the ecosystem by killing trees under hot, dry conditions. The effect of temperature is worse above 32°C, and a greater magnitude of climate change thus risks greater loss of tropical forest carbon stocks. Nevertheless, forest carbon stocks are likely to remain higher under moderate climate change if they are protected from direct impacts such as clearance, logging, or fires. Science , this issue p. 869

Protium santamariae is described and illustrated. The new species is restricted to the Pacific Coast of Costa Rica but shares morphological similarities with two South American species, P. kleinii and P. krukoffii. We provide a description, a distribution map, notes on its taxonomy, and a key to distinguish it from morphologically similar species.