Neotropical savannas comprise a biome of extraordinary diversity and endemism, which faces pervasive threats from human development. A basic understanding of ecological dynamics is required for effective conservation, but has not yet been achieved. This study seeks to address the abiotic underpinnings of vegetation assembly on the island of Utila, Bay Islands, Honduras. Floristic heterogeneity was assessed across multiple environmental gradients—of surface hydrology, microtopography, nutrient levels and pH—using Braun-Blaquet cover abundance in a stratified systematic sampling design. Detrended correspondence analysis (DCA) and non-parametric multiplicative regression (NPMR) were applied to identify community types and to model species' responses to environmental gradients. Habitats were categorized as three basic types: (1) sedge meadow; (2) Blechnum-Cladium parkland; and (3) woody hammock. Within each, many species distributions can be predicted by environmental gradients; but other species—notably Acoelorraphe wrightii and Chrysobalanus icaco—are generalists, whose distributions may reflect past disturbance. Microtopography is critical in determining distribution for a suite of species that occur only on mound formations in areas subject to prolonged inundation. Disturbance, particularly by hurricanes and fire, may promote within-habitat diversity: 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 reveal fewer than half of the 40 savanna species found on Utila were present in any other single savanna site. Two species of Cyperaceae, Fuirena scirpoidea and Rhynchospora tracyi, and a bromeliad, Tillandsia izabalensis, are new records for Honduras.
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|Advisor:||Rebertus, Alan J.|
|Commitee:||Lindsay, Alec R., Strand, Mac|
|School:||Northern Michigan University|
|School Location:||United States -- Michigan|
|Source:||MAI 51/03M(E), Masters Abstracts International|
|Subjects:||Plant biology, Ecology, Plant sciences|
|Keywords:||Acoelorraphe wrightii, Blechnum serrulatum, Caribbean, Cladium jamaicense, Honduras|
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