Distinct Leaf-trait Syndromes of Evergreen and Deciduous Trees in a Seasonally Dry Tropical Forest Elizabeth G. Pringle 1,4 , Rachel I. Adams 1 , Eben Broadbent 1,2 , Posy E. Busby 1 , Camila I. Donatti 1 , Erin L. Kurten 1 , Katherine Renton 3 , and Rodolfo Dirzo 1 1 Department of Biology, Stanford University, Stanford, California 94305, U.S.A. 2 Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, U.S.A. 3 Estaci ´ on de Biolog´ ıa Chamela, Instituto de Biolog´ ıa, Universidad Nacional Aut ´ onoma de Me ´ xico, Apartado Postal 21, San Patricio Jalisco 48980, Me ´ xico 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 avail- ability 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. Key words: Chamela-Cuixmala Biosphere Reserve; evolutionary convergence; herbivory; leaf-trait syndromes; Mexico; trade-offs; water limitation. LEAF TRAITS EXPERIENCE SELECTION FROM BOTH ABIOTIC AND BIOTIC FORCES within the plant’s environment. Abiotic factors have long been recognized to select for distinct leaf traits (e.g., Maximov 1929). Indeed, leaf traits that play critical roles in physiology, such as longevity, mass per area, nitrogen content, and photosynthetic capacity, co-vary in predictable syndromes in plants around the world (Reich et al. 1997, Wright et al. 2004, see Curtis & Ackerly 2008 for a review). These syndromes can be modeled by trade-offs between: (1) photosynthetic capacity and leaf lifespan (Kikuzawa 1991) and (2) photosynthetic capacity and leaf thickness and nitro- gen content (Shipley et al. 2006). Physiological studies propose strategy continua bounded by syndromes in which leaves are either short-lived, thin, and high in nitrogen and photosynthetic capacity, or long-lived, thick, and low in nitrogen and photosynthetic capac- ity. In addition, leaves with different characteristic lifespans may be associated with different phenologies. Herbivory also exerts significant selective pressure on leaf traits (Ehrlich & Raven 1964, Coley et al. 1985, Becerra 1997, Fine et al. 2004, Fine et al. 2006). For example, several studies have found that leaf toughness is negatively correlated with herbivory (Coley 1983, Kursar & Coley 2003, Agrawal & Fishbein 2006, Fine et al. 2006). Plant strategies for avoiding or withstanding herbivore pressure, such as escape or physical and chemical defenses, may also be associated with different phenological habits. Recently, Agrawal and Fishbein (2006) predicted that a continuum of anti-herbivory defense would be bounded by three types of syndromes: (1) poorly defended plants with phenological escape mechanisms; (2) plants with nutritious, edible leaves that have physical and chemical defenses; and (3) plants with tough, inedible leaves. These predictions highlight that there is considerable overlap between proposed trait syndromes for anti- herbivory defense strategies and those for physiological strategies. Seasonally dry tropical forests are distributed throughout the world’s tropical regions (Miles et al. 2006) and were once the pri- mary ecosystem along the Pacific coast of Middle America (Janzen 1988). They experience low annual rainfall, and yearly rainy sea- sons are interspersed with severe dry seasons (Mooney et al. 1995). Trees in these forests primarily exhibit one of two possible phenol- ogies: (1) deciduous species that are leafless throughout the dry season, flushing leaves with the first rains, and (2) evergreen species that retain their leaves throughout the year (Rzedowski 1994). Deciduous species predominate on hillsides where the soil has low water retention (Maass et al. 2002), whereas evergreen species occur along watercourses and in riparian areas (Lott 1993). Although phenology does not necessarily predict leaf lifespan (Brodribb & Holbrook 2005), deciduous and evergreen species can have fundamentally different physiologies, which may be reflected in leaf traits. Deciduous trees have a limited time each year to pho- tosynthesize and should require high nitrogen for efficient photo- synthesis (Field & Mooney 1986). Thinner leaves would allow Received 5 February 2010; revision accepted 30 May 2010. 4 Corresponding author; e-mail: epringle@stanford.edu BIOTROPICA 43(3): 299–308 2011 10.1111/j.1744-7429.2010.00697.x r 2010 The Author(s) 299 Journal compilation r 2010 by The Association for Tropical Biology and Conservation