Distinct Leaf-trait Syndromes of Evergreen and Deciduous Trees in a Seasonally Dry Tropical Forest

Abstract

In seasonally dry tropical forests, tree species can be deciduous, remaining without leaves throughout the dry season, or evergreen, retaining their leaves throughout the dry season. Deciduous and evergreen trees specialize in habitats that differ in water availability (hillside and riparian forest, respectively) and in their exposure to herbivore attack (seasonal and continuous, respectively). We asked whether syndromes of leaf traits in deciduous and evergreen trees were consistent with hypothesized abiotic and biotic selective pressures in their respective habitat. We measured seven leaf traits in 19 deciduous and 11 evergreen tree species in a dry tropical forest in Western Mexico, and measured rates of herbivory on 23 of these species. We investigated the covariance of leaf traits in syndromes related to phenology and associated physiology, and to anti-herbivory defense. We found evidence for syndromes that separated phenological strategies among four traits: toughness, water content, specific leaf area, and carbon:nitrogen (C:N) ratios. We found a trade-off between two other traits: trichomes and latex. Overall, evergreen species exhibited lower rates of herbivory than deciduous species. Lower rates of herbivory were explained by a syndrome of higher toughness, lower water content, and higher C:N ratios, which are traits representative of evergreen trees. Phenology and trait syndromes did not exhibit significant phylogenetic signal, consistent with the hypothesis of evolutionary convergence among phenologies and associated leaf-trait syndromes. Our results suggest that deciduous and evergreen trees could respond to differential water availability and herbivory in their respective habitats by converging on distinct leaf-trait syndromes. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp.