According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors, and yet they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. Contrarily, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most likely mechanisms underpinning this pattern and rare species persistence. The

More tree species can increase the carbon storage capacity of forests (here referred to as the more species hypothesis) through increased tree productivity and tree abundance resulting from complementarity, but they can also be the consequence of increased tree abundance through increased available energy (more individuals hypothesis). To test these two contrasting hypotheses, we analyse the most plausible pathways in the richness-abundance relationship and its stability along global climatic gradients. We show that positive effect of species richness on tree abundance only prevails in eight of the twenty-three forest regions considered in this study. In the other forest regions, any benefit from having more species is just as likely (9 regions) or even less likely (6 regions) than the effects of having more individuals. We demonstrate that diversity effects prevail in the most productive environments, and abundance effects become dominant towards the most limiting conditions. These findings can contribute to refining cost-effective mitigation strategies based on fostering carbon storage through increased tree diversity. Specifically, in less productive environments, mitigation measures should promote abundance of locally adapted and stress tolerant tree species instead of increasing species richness.

Se han elaborado los mapas de distribución de los licófitos y helechos del suroccidente europeo (Andorra, España continental, Portugal continental e Islas Baleares) empleando la malla UTM de 10 km de lado. La síntesis corológica incluye citas bibliográficas y fuentes electrónicas georreferenciadas de acceso público para un total de 128 taxones presentes en el territorio.

are endemic to Mucugê. In M. pulchra the columella is persistent, a character described for the first time for the genus. The four new species are here described, discussed and illustrated. Conservation assessments based on IUCN criteria are also given. Resumo. Microlicia D. Don (Melastomataceae) possui aproximadamente 120 espécies concentradas no Brasil central. Durante o levantamento florístico de Microlicieae em Mucugê,

Resumo AbstractThis study provides a taxonomic survey of Microlicieae tribe in the Mucugê municipality, Chapada Diamantina, Bahia, Brazil. We identified 27 species belonging to three genera: Lavoisiera (L. harleyi and L. nervulosa), Microlicia (24 species) and Trembleya parviflora. Except for Microlicia fasciculata, M. viminalis and Trembleya parviflora, the others species found in Mucugê are endemic to Chapada Diamantina, Bahia. Among the species of Microlicia, four were recently described, and four others still require further studies for its identification. Polysporangiate anthers were described for the first time for 11 species of Microlicia. The species of Microlicieae are found mainly in rocky field vegetation, between 900-1.500 m altitude, in sandy or rocky soils, sometimes associated to water streams.