SHORT COMMUNICATION Herbaceous monocot plant form and function along a tropical rain-forest light gradient: a reversal of dicot strategy

Whole plant form and function vary spectacularly across the seed plants. In recent years, plant evolutionary ecologists have begun to document this diversity on large geographic scales by analysing ‘functional traits’ that are indicative of whole plant performance across environmental gradients (Swenson & Enquist 2007, Wright et al. 2004). Despite the high degree of functional diversity in tropical forests, convergence in function does occur locally along successional or light gradients (Bazzaz & Pickett 1980, Swaine & Whitmore 1988). The adaptive differentiation between light-demanding (LD) dicot tropical tree species versus shade-tolerant (ST) species has been well documented. For example, LD tree species generally have thin leaves that have higher rates of carbon assimilation per unit mass, short leaf life spans, low tissue water content, less dense stem tissue and higher mortality rates. Conversely, ST species tend to exhibit the exact opposite trait composition (reviewed in Bazzaz & Pickett 1980, Swaine & Whitmore 1988). The trait strategies of LD species are therefore considered to be adaptations for colonization and rapid growth and primary forest species are assumed to be adapted to delay their emergence, growth and mortality. In sum, there appear to be pervasive adaptive strategies in whole plant form and function across light gradients in diocotyledonous trees in tropical rain forests (Bazzaz & Pickett 1980, Swaine & Whitmore 1988). Tropical herbaceous monocot species spanning similar light gradients, have received considerably less attention (Rundel et al. 1998). To date interspecific comparative analyses of tropical monocots focusing on leaf traits suggest that herbaceous monocots may have a gradient in leaf form and function along light gradients that is