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Competitive Exclusion Along a Habitat Gradient Between Two Species of Salamanders (Desmognathus) in Western Florida
D. Bruce Means
Journal of Biogeography
Vol. 2, No. 4 (Dec., 1975), pp. 253-263
Published by: Wiley
Stable URL: http://www.jstor.org/stable/3037999
Page Count: 11
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The geographic distributions of two congeneric salamanders interdigitate in western Florida. A Coastal Plain endemic species (Desmognathus auriculatus) occurs throughout coastal swamps in and between major drainages; it disperses upstream into drainages from population centres near drainage mouths. Desmognathus fuscus is a northern species (at its southern distributional limits in Florida) that disperses downstream in drainages from headwater population centres. Florida habitats occupied by either species can be ordered along a gradient ranging from lotic waters of first order streams (including the unique 'steepheads') to lentic conditions of swamps, sloughs, and lake margins. When allopatric, D. auriculatus occurs over the entire range of habitats and especially in steepheads; but where sympatric with D. fuscus, D. auriculatus occurs only in stream habitats greater than order 2. In several adjacent drainages analysed in detail, a repeated pattern of habitat shifts occurs for D. auriculatus that is adduced as evidence for competitive exclusion betweeen these two species. The smaller D. fuscus is postulated to spatially displace D. auriculatus from headwater habitats (especially from steepheads) wherever the former species gains entry into a drainage already occupied by the latter.
Journal of Biogeography © 1975 Wiley