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The question of how closely related species coexist in the heavily shadowed understory of tropical forests is still not properly clarified. We studied the magnitude of trait variation in twelve morphological, nutritional, and physiological traits related to light response in 85 individuals belonging to nine co-occurring Rubiaceae species in the understory of a tropical forest in Southeast Brazil. Three topographic habitats were chosen from shadowed and more fertile soils in the valley to more open canopies and less fertile soils at slopes and ridge, which were characterized using soil and canopy cover variables. Light curves (A/PAR) were adjusted in five leaves (one leaf per individual plant) for each species and habitat. We compared soil and canopy variables among the topographic habitats, quantified trait dispersion among the nine species, and tested for differences in trait values among habitats and species. Ridge habitat showed the lowest resource availabilities, soil nutrients and water, and a more open canopy. Species distributions in the gradient were best explained by specific leaf area (SLA) and leaf thickness. The Rubiaceae species showed a great investment in leaf nitrogen, regardless of habitat or species. Ridge species maintained low dark respiration rates and light compensation points. Higher SLA values for valley plants allowed greater light-saturated net photosynthetic rates on a mass basis, providing higher positive net carbon balance when compared to the plants in the slope and ridge. Living and survival of these shade plants are possible by very low mean light compensation points. We show that trait differences among topographic habitats in coexisting species of Rubiaceae are important to understanding the organization of tropical forests understory “species swarms”.

A new endemic and critically endangered species of Rudgea (Rubiaceae) from Southeastern Brazil is described and illustrated. Rudgea minutifolia Bruniera & Torres-Leite is distinguished by its small leaves, a character found in only a handful of species in this genus. The indumentum of the branches, leaves and stipules, low number of secondary veins, corniculate corolla lobes, and vinaceous to almost black mature fruits are also characteristic of this species. Discovered in a forest remnant within the Atlantic Rainforest domain in the south of Espírito Santo state, this species is found only in the municipality of Castelo, an area that has been recognized as prioritary for conservation. Besides the description, taxonomic comments, conservation status, images and illustrations are provided.

Two new species of Rudgea (Rubiaceae), R. quisquiliae and R. axilliflora, from Southeastern Brazil present true axillary inflorescences , a very distinct characteristic in the genus. Rudgea was previously characterized by the presence of usually terminal inflorescences, with pseudo-axillary inflorescences occurring in a single species, R. stipulacea . Rudgea quisquiliae is morphologically distinct within the genus by the combination of its large leaf-blades (15 – 33.5 × 7.5 – 15 cm), and axillary inflorescences. Rudgea axilliflora can be distinguished by its sheathing stipules with dorsal, glandular appendages, medium-sized leaf-blades (7–11 x 2.5–4 cm), lanceolate to elliptic, with 7–9 pairs of secondary veins, absence of domatia, axillary inflorescences and flowers with a distinctly lobed calyx. The new species were discovered in ombrophilous rainforest remnants in the south of Espirito Santo, one of the most diverse states in the Atlantic Forest biome.

Resumo Este estudo apresenta o inventário florístico atualizado para Rubiaceae no Parque Estadual de Mata das Flores (PEMF), município de Castelo, no Espírito Santo. O remanescente florestal estudado está localizado em uma das áreas prioritárias para conservação da Floresta Atlântica ao sul do estado. A listagem elaborada embasou a análise da similaridade florística de Rubiaceae no fragmento estudado com outras 17 áreas de Floresta Atlântica, por meio de análise de agrupamentos e métodos de ordenação. Foram identificadas 45 espécies e duas subespécies, pertencentes a 20 gêneros. Psychotria (8 spp.) foi o gênero mais representativo, seguido de Faramea (6 spp.) e Rudgea (4 pp.). Quatro táxons constituem novas espécies para a ciência. Quatro táxons estão listados em diferentes categorias de ameaça. As análises de agrupamento e ordenação evidenciaram que Mata das Flores se distingue das demais áreas comparadas da Floresta Atlântica quanto à composição florística de Rubiaceae. Os resultados indicam que o Parque Estadual de Mata das Flores é um importante centro de diversidade para Rubiaceae no Espírito Santo. Abstract This study presents the updated floristic inventory of the family Rubiaceae in Mata das Flores State park (MFSP), Castelo, Espírito Santo. The studied forest remnant is located in one of the priority areas for Atlantic Forest conservation on the southern portion of the state. The list gave support to the analysis of floristic similarity between the studied fragment and 17 other areas of the Atlantic Forest, using cluster analysis and ordination methods. A total of 45 species and two subspecies were identified. They belong to 20 genera. Psychotria (8 spp.) was the most representative genus, followed by Faramea (6 spp.) and Rudgea (4 spp.). Four taxa are new species to science. Four taxa are listed in different threat categories. Cluster and ordination analysis revealed that Mata das Flores is distinct from the other areas in the Atlantic Forest. The results point to the Mata das Flores State Park as an important center of diversity for Rubiaceae in Espirito Santo.