Water-related leaf traits associated with epiphytism in the Neotropical megadiverse genus Anthurium (Araceae)

Abstract

Background and Aims Epiphytes comprise approximately 10% of global vascular plant diversity and play key roles in many tropical ecosystems. They possess traits allowing survival under limited water availability (i.e. the epiphytic trait syndrome), but knowledge of these trait combinations is taxonomically biased and their generality remains unclear. The megadiverse genus Anthurium (Araceae), with ~600 epiphytic species, offers an opportunity to address this gap by examining patterns of leaf trait covariation, their phylogenetic context, and differences among life forms. Methods A common garden experiment was conducted using 40 species from 13 sections spanning a gradient of epiphytic incidence. Twenty-one anatomical, morphological, and physiological leaf traits were quantified. Patterns of trait variation were assessed, and associations between leaf traits and epiphytism were evaluated both with and without accounting for phylogenetic relationships. Key Results Leaf trait variation was captured by two principal components. The first axis was negatively associated with stomatal density and size, leaf thickness, and leaf water content, while the second axis described a trade-off between leaf mass per area (LMA) and water loss rate. Epiphytic species generally exhibited smaller, more numerous stomata and higher LMA, consistent with adaptations for water retention. Epiphytism showed a phylogenetic signal; however, trait covariation patterns were not influenced by phylogenetic relatedness. Conclusions We found consistent associations between epiphytism and several water-related leaf traits in Anthurium, but some of these associations departed from general expectations of an epiphytic trait syndrome. Water-related traits showed variable phylogenetic signal and reflected multiple functional strategies for coping with intermittent water supply. These findings highlight the diversity of functional strategies underlying epiphytism and expand current understanding beyond well-studied taxa.