Palm Physiology and Distribution in Response to Global Environmental Change

Abstract

Palms (Arecaceae) represent one of the oldest surviving monocot fam- ilies maintaining a presence in tropical rainforest-like biomes throughout history. Comprising a variety of plant growth forms (arborescent, acaulescent, lianoid), palms are one of the few monocots that achieve significant heights. In doing so, they face many of the same environmental and physiological constraints as dicotyledonous trees including long-distance water transport and longevity making them an important, but largely missing, component of comparative tree physio- logical studies. Palms differ from dicot trees in several key ways including lacking dormancy mechanisms that restrict them to mainly tropical climates. Palms also lack a vascular cambium and the constant addition of new conduits, and instead, rely exclusively on vascular bundles for fluid transport and mechanical stability. The majority of arborescent palm species also possess only one apical meristem complex from which all new leaf and stem growth originates thereby limiting their options for leaf positioning and light acquisition. These differences will likely alter the response of palms to global change compared with dicot species. Temperature increases have the potential to extend palm distributions to higher elevations and latitudes, but could negatively affect individual palm carbon balance. Within the tropics, precipitation has been shown to have the strongest positive effect on palm species richness and future changes in rainfall patterns will likely alter palm dis- tributions. Therefore, global change has the potential to alter both palm distribu- tions and individual physiological functioning, but palms will likely continue to have a considerable presence in many tropical ecosystems.