Abstract

The Bromeliaceae is a family of Neotropical plants that displays enormous diversity in terms of morphology, growth habit, and ecology. Representatives can be found in a wide range of macro- and micro-habitats, from coastal deserts to tree-crowns in montane cloud forests. The evolutionary innovations that are hypothesised to have generated these rapid adaptive radiations include specialised absorbent trichomes, water- and nutrient-impounding ‘tanks’, the epiphytic habit, crassulacean acid metabolism (CAM), and ornithophilous pollination. In terms of environmental physiology, the photosynthetic properties of different ecological types of bromeliads have been investigated extensively, but our understanding of the possible role of hydrophysiological adaptation in bromeliad diversification is more incomplete. By examining the hydrophysiological characteristics of bromeliad taxa sampled from across the family’s phylogeny and linking these to the distributions and habitat preferences of these taxa, I aim to develop a clearer picture of evolutionary trends in bromeliad water relations. The focus falls particularly on xylem and mesophyll hydraulic conductivity, leaf water capacitance and turgor properties, and stomatal responses to vapour pressure deficit. In parallel with this broad phylogenetic assessment, an investigation into the physiological basis of niche differentiation between two congeneric bromeliads in Trinidad is under way. The extent of the segregated distributions of these species is being recorded and related to climatic and topographical factors. Measurements of the anatomical architecture and physiological tolerances of each species will then be made in an attempt to provide a mechanistic explanation for the observed distributions.