Winkler et al. 2007 (Article) Catopsis, Tillandsia

Population dynamics of epiphytic bromeliads: Lifestrategies and the role of host branches

Author(s):—M. Winkler, K. Hülber & P. Hietz

Corresponding email:—mwinkler@groupwise.boku.ac.at

Publication:—Basic and Applied Ecology 8: 183-196. (2007) — DOI

Abstract:—Epiphytes need to balance the trade-off between long-term survival and colonizingnew branches in their resource-limited and high-risk canopy habitats. We censusedpopulations of five bromeliad species over two years and calculated matrixpopulation models to determine the key factors influencing population growthrates. Additionally, logistic regression models were applied to study howdemographic features change with microsite characteristics and disturbance.The bromeliads studied are slow-growing, with species preferring thinnerbranches maturing faster. Population growth rates were below unity in all speciesexcept for the drought-resistant
Tillandsia juncea
. Population growth ratesdepended almost exclusively on survival, above all of adult plants. Fecundity hadonly little impact, even in species of the outer canopy where branchfall-relateddisturbance and mortality are frequent.Survival rates and the probability to become reproductive increased with lightavailability in most species. Microsite characteristics had the greatest impact onseedling survival, although this contributed very little to population growth rates.We conclude that branchfall-related mortality is a key factor for populationpersistence of epiphytes dwelling in the outer canopy, and that resource availabilityconstrains the possibility to counteract disturbance with higher fecundity. Forspecies of the outer canopy an increased disturbance by more frequent strong windscould further constrain population growth. Because population persistence stronglyrelies on the survival of adult plants, harvesting bromeliads for ornamental or otherpurposes should be restricted to immature individuals. In the future, better modelsof epiphyte populations in a habitat with highly patchily dynamics should be basedon a metapopulation approach.
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2006 Gesellschaft fu¨r O¨kologie. Published by Elsevier GmbH. All rights reserved.

Keywords:—Bromeliaceae;Catopsis;Disturbance;Elasticity;Epiphytes;Matrix populationmodels;Mexico;Tillandsia;Vital rates