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Taxonomically dissimilar epiphyte species can have comparable morphological and physiological traits in similar environmental conditions. However, the degree of trait similarity has not been examined in a comparison of bryophytic and vascular epiphytes across elevational and tree gradients. We assess whether epiphyte species that occupy comparable realised niche spaces within host tree and landscape scale gradients have similarities in taxonomy, morphology or physiology. Vascular and moss epiphytes were surveyed within four height zones at five elevations (300-1100 m asl) in the sub-tropical rainforest of Australia. Epiphyte species distributions were agglomeratively classified using Ward’s method. Chi square tests were used to test for differences in the incidences of taxonomic groups, life forms, leaf thickness, photosynthetic pathways and other drought resistant morphologies between these distributional groups. These traits were also tested for correlation with light and humidity. Six groups were identified based on distribution. Vascular epiphytes with CAM, thickened leaves and other drought-mitigating morphologies were common in the groups that occupied the most xeric situations. All drought resistant traits were associated with high light and low humidity. Vascular species with few to no drought-mitigating characteristics were common in groups that occupied moister situations. Moss morphology was less congruent with environmental conditions than vascular plant morphology, suggesting that moss life forms are responding to a different scale of environmental variation.
Twenty-one riparian vascular plant communities are defined, mapped and described using presence/absence data from 460 sites from relatively unmodified stretches of rivers and streams on mainland Tasmania. The process of classification involved selection of groups of floristically distinct sites from a sorted table produced by a polythetic divisive process. The communities have strong geographic patterns. Many communities have a wide range of structural expression and/or dominants. Nearly half of the native vascular flora of Tasmania is present in the sites, including a large number of conservation-significant species, some of which are concentrated in riparian vegetation. In the drier, lowland parts of the State there are large areas with little or no native riparian vegetation remaining. Several of the communities that occur in this environment appear to be totally unreserved, while most of the communities from colder and more humid areas are represented within secure reserves.