Succession and Survival Strategies in Lichen Populations on a Palm Trunk

(1) Lichen populations on a palm trunk in Brisbane were treated as a chronosequence for which ages could be estimated. The effects of succession and environmental stress on species cover were examined. (2) Growth rates of five foliose lichens were estimated and, using a morphological index, these species were located in a triangular ordination with the poles representing competitive, stress-tolerating and ruderal survival strategies. Using data from this study and other published sources, the place of lichens in such a triangular ordination in relation to herbaceous plants is examined and lichens are shown to be extreme stress tolerators. (3) During a twenty-eight year succession the mean strategy of the population shifts from a relatively ruderal to a more competitive nature. This shift occurs more slowly on the more strongly irradiated and therefore drier aspects of the trunk.