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

ABSTRACT

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.

GRAPHICAL ABSTRACT

KEYWORDS:

• Assembly rules
• environmental filtering
• functional diversity
• local scale
• phylogenetic signal
• species coexistence
• species richness; tropical forest

Acknowledgments

We thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, National Council for Scientific and Technological Development) for the doctorate scholarship of Lucas Costa, the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) for the doctorate ‘sandwich’ internship (process 88881.189293/2018-01), the Laboratório de Química do Solo of the Universidade Federal Rural de Pernambuco for supporting soil analysis, and Cucau and Trapiche Mills for logistic support during the fieldwork.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Additional information

Funding

This study was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) under the Finance Code 001.