Factors driving trait-convergence linked to leaf economic spectrum in tropical ferns

Environmental filters, competition, and phylogenetic relationships play crucial roles in determining plant functional patterns across different environmental scenarios, scales, and taxa. Patterns of functional convergence and divergence are crucial to understand trait-environment interactions and plant coexistence, which must consider multiple drivers partitioning the ecological, environmental, and evolutionary processes, an integrative approach explored in this study. We analyzed leaf trait convergence and divergence among co-occurring tropical fern species, the relationship between functional and taxonomic components, and the role of local environmental conditions on functional patterns. We established 22 plots in three forest remnants of northeastern Brazil and measured key leaf economic spectrum (LES) traits (leaf area – LA, specific leaf area – SLA, leaf dry-matter content – LDMC) in fern assemblages and quantified local environmental conditions (edaphic variables, basal area of trees, and rock cover). Functional trait convergence dominated the fern assemblages for all LES traits. We found a significant phylogenetic signal for LDMC. The increases in fern species richness show an association with an increase in convergence for LA, whereas changes in fern floristic composition were associated with convergence in LDMC. Regarding the local abiotic factors, increases in soil bases and pH were related to functional convergence in LA, and soil rock cover led to a divergence in SLA. For instance, divergence in LA occurred in poor assemblages and under more acid soils, while divergence in SLA occurred in heterogeneous environments. We conclude that multiple drivers affect fern functional patterns at fine scales in the tropical forest

QUAL O PAPEL DOS FATORES AMBIENTAIS E DE PAISAGEM NAS DIVERSIDADES TAXONÔMICA, FUNCIONAL E FILOGENÉTICA DE BRIÓFITAS NA FLORESTA ATLÂNTICA NORDESTINA?

O entendimento das causas da diversidade de briófitas é extremamente relevante para a Floresta Atlântica, particularmente da porção Nordestina, a mais fragmentada e com menos áreas integralmente protegidas. Objetivou-se avaliar as relações entre a riqueza de espécies e os componentes da diversidade taxonômico, funcional e filogenético, bem como o papel das condições ambientais e da estrutura da paisagem nos padrões observados. Em 13 localidades de Floresta Atlântica Nordestina foram realizadas coletas exploratórias de briófitas e compiladas a temperatura e a precipitação média anual e a variação na elevação, além de métricas de paisagem. Foram elaboradas uma árvore filogenética e uma matriz funcional das espécies. Identificaram-se 196 espécies; a riqueza das localidades variou de 12 a 102 espécies. Observou-se relação positiva entre os componentes de diversidade, indicando que a redução regional de espécies está intimamente relacionada com a perda de diversidade nos variados componentes. Os padrões de riqueza e diversidade foram explicados pelas variações na elevação e temperatura média anual, apontando a importância do grupo como indicador ambiental. Assim, devido a sua sensibilidade às alterações de temperatura, as briófitas podem contribuir para responder questões do quão rápido o aumento da temperatura global afeta as espécies e os ecossistemas, o que deve ser considerado em trabalhos futuros

Putting vascular epiphytes on the traits map

1. Plant functional traits impact the fitness and environmental niche of plants. Major plant functional types have been characterized by their trait spectrum, and the environmental and phylogenetic imprints on traits have advanced several ecological fields. Yet, very few trait data on epiphytes, which represent almost 10% of vascular plants, are available. 2. We collated 76,561 trait observations for 2,882 species of vascular epiphytes and compared these to non-epiphytic herbs and trees to test hypotheses related to how the epiphytic habit affects traits, and if epiphytes occupy a distinct region in the global trait space. We also compared variation in traits among major groups of epiphytes, and investigated the coordination of traits in epiphytes, ground-rooted herbs and trees. 3. Epiphytes differ from ground-rooted plants mainly in traits related to water relations. Unexpectedly, we did not find lower leaf nutrient concentrations, except for nitrogen. Mean photosynthetic rates are much lower than in ground-rooted plants and lower than expected from the nitrogen concentrations. Trait syndromes clearly distinguish epiphytes from trees and from most non-epiphytic herbs. 4. Among the three largest epiphytic taxa, orchids differ from bromeliads and ferns mainly by having smaller and more numerous stomata, while ferns differ from bromeliads by having thinner leaves, higher nutrient concentrations, and lower water content and water use efficiency. 5. Trait networks differ among epiphytes, herbs and trees. While all have central nodes represented by SLA and mass-based photosynthesis, in epiphytes, traits related to plant water relations have stronger connections, and nutrients other than potassium have weaker connections to the remainder of the trait network. Whereas stem-specific density reflects mechanical support related to plant size in herbs and trees, in epiphytes it mostly reflects water storage and scales with leaf water content. 6. Synthesis. Our findings advance our understanding of epiphyte ecology, but we note that currently mainly leaf traits are available. Important gaps are root, shoot and whole plant, demographic and gas exchange traits. We suggest how future research might use available data and fill data gaps.ISSN:0022-047