EPIPHYTIC GROWTH HABITS OF CHILEAN GESNERIACEAE AND THE EVOLUTION OF EPIPHYTES WITHIN THE TRIBE CORONANTHEREAE

Three monotypic and endemic genera of epiphytic Gesneriaceae (Gesnerioideae, Coronanthereae) occur in temperate rainforests of southern South America. In this article, intraspecific differences in rooted substrate and interspecific variation in epiphytic growth habits among these three Gesneriaceae species were assessed. The presence or absence of plants on the ground and main rooted substrate when growing epiphytically on trees were used to characterize epiphytic growth habits in two old-growth temperate rainforests of northern Chiloe Island (42 degrees 30'S) in Chile. An evolutionary interpretation based on reported phylogenies and morphologies within the Coronanthereae is proposed. Two species of Chilean Gesneriaceae, Mitraria coccinea Car, and Astemnthera ovata (Cav.) Hanst., originate from the forest floor, then climb on trees while maintaining their main roots in the ground, and are classified as secondary hemiepiphytes. The third species, Sarmienta renews Ruiz & Priv., was found exclusively on tree trunks and branches of living and dead trees and thus may be classified as a holoepiphyte. Based on reported phylogenies and biogeographical, ecological, and morphological data, the mechanically independent arboreal habit appears to be the ancestral condition in the Coronanthereae, which in turn gave rise to the climbing habit and finally the holoepiphytic habit. This may be a common evolutionary pathway toward holoepiphytism within other lineages in the Gesneriaceae.