Patterns and adaptive trends of life forms, life strategies and ecomorphological structures in tropical epiphytic bryophytes a pantropical synopsis
Kürschner, Harald; Frey, Wolfgang; Parolly, Gerald
This first pantropical survey of distributional patterns of life forms, life strategies, and ecomorphological structures of trunk-epiphytic bryophytes along altitudinal transects in Southeast Asia, Africa, and South America, clearly revealed distinct common adaptive trends which occur regardless of familial relationships and differing species assemblages of the communities. They can be summarized as "functional types" characterizing the different communities of the altitudinal belts. Mat forming "passive" Perennial stayers and Perennial shuttle species with a uniform common "basic architecture" dominate the communities of the tropical lowland and submontane belt. This "functional type" is replaced in the cooler and more humid montane rain forests mainly by fan and weft forming "vegetative" Perennial stayers and Perennial shuttle species with an increased reliance on propagules and clonal growth for population maintenance. They show various ecomorphological structures for an effective and rapid condensation of water vapour from the fogs (e. g., fog-stripping by ciliate leaves), and for water storage and conduction. Within the more open, upper montane forests and oreal ericaceous woodland, where the epiphytes grow under increasingly xeric conditions, short turf, tall turf and cushion forming "generative" Perennial stayers and Perennial shuttle species predominate, characterized additionally by structures such as an abundant rhizoid tomentum and the development of an internal central strand. A third main life strategy category, the Colonists strategy, clearly is of no importance in undisturbed epiphytic communities of the tropics and is, if present, restricted to secondary forests. It can be seen as an indicator of disturbance. These adaptive trends occur worldwide and impressively demonstrate that life forms, life strategies and ecomorphological structures of tropical trunk-epiphytic bryophytes are co-evolved adaptive traits that evolved convergently under similar environmental pressures.