Abstract
Neotropical savannas exhibit unique patterns of diversity of plant and animal life that are poorly understood. Effective conservation of these often imperiled ecosystems requires a basic understanding of species occurrence as well as the site-specific factors that influence plant community composition. This study focuses on the savanna flora of the island of Utila, Bay Islands, Honduras. Compositional trends were assessed across multiple environmental gradients including surface hydrology, microtopography, nutrient levels and pH using Braun-Blanquet cover abundance in a stratified systematic sampling design. Non-metric multidimensional scaling and non-parametric multiplicative regression were applied to identify community types and to model species’ responses to environmental gradients. We separated habitats into three basic types: sedge meadow, Blechnum-Cladium parkland and woody hammock. Compositional gradients along ordination axes were highly correlated with depth of the water table, pH and conductivity. Disturbance history, especially time since fire, was also linked to an indirect gradient. Some species – notably Acoelorrhaphe wrightii and Chrysobalanus icaco – are generalists, and their distributions may reflect past disturbance. Microtopography was critical in determining distribution for a suite of species that occurred only on mound formations in areas subject to prolonged inundation during the rainy season. Disturbance, particularly by hurricanes and fire, may promote within-habitat diversity; for example, the exposed lignotubers and rhizomes of trees killed by saline inundation provide habitat for less flood-tolerant species in wet areas, while burned clones of A. wrightii and surrounding peat areas permit colonization by many herbaceous species. Pair-wise floristic comparisons between Utila and eight other neotropical savannas revealed fewer than half of the 40 savanna species found on Utila were present in any other site. Two species of Cyperaceae, Fuirena scirpoidea and Rhynchospora tracyi, are new records for Honduras.
Published Version
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