Spatial Distribution of Catopsis and Guzmania (Bromeliaceae) in Southern Florida

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Abstract
The habitat preference and spatial distribution within a habitat of Guzmania monostachia (L.) Rusby ex Mez., Catopsis berteroniana (Schultes f.) Mez., C. floribunda L. B. Smith, and C. nutans (Swartz) Grisebach were examined in southern Florida. These epiphytic bromeliads are not randomly distributed but are patchy, confined to Fraxinus caroliniana-Annona glabra swamps. Distribution within the habitat is subject to a number of constraints: temperature and light gradients, aspect, location of host species in the habitat and distribution among hosts. Host morphology is also an important distribution factor. The number of principal vertical stems produced by a single tree (DBH) or the basal area of all host plants per clump were positively correlated with abundance of all epiphytic species. Host DBH had little effect on species abundance, except for the number of C. nutans per stem. The four species were distributed over vertical stem gradients in the following sequence (low-high); Guzmania, C. nutans, C. floribunda and C. berteroniana. The distribution, then, of Guzmania and Catopsis is not random but is patchy because of 3 or 4 factors: clumping in preferred habitats (Fraxinus-Annona swamps); habitat constraints such as temperature, light, aspect and location of suitable hosts within the habitat; and the host morphology. In this study, the number of host stems per clump was significantly correlated with the number of epiphytic individuals per clump, and accounted for 24-63% of the variation in this variable. A fourth factor in patchiness may be the location of optimal germination sites within a clump. Seeds and seedlings were more abundant on epiphytic bryophytes than on exposed bark.

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