Análise florística, síndromes de dispersão e aspectos estruturais em ilhas de vegetação de um afloramento rochoso no agreste paraibano

Abstract

This paper presents a study of the floristic and analysis of floristic similarity, highlighting the types of dispersal syndromes classified anemochory, autocory and zoochory, a rocky outcrop in the municipality of Pocinhos, Paraiba Wasteland, to contribute to a better understanding of the local and regional flora. It was also characterized the structure of the "islands" of vegetation with the objective of determining the patterns of species distribution according to biological and environmental variables besides to verify the effect of island size and distance of the floristic diversity of the islands. Collections of fertile botanical material and observations "in loco" all along the outcrop in the period December 2012 to November 2013 were performed. The taxonomic identification was made by means of literature, visits to regional herbaria (EAN and JPB) and consultations to virtual herbarium, and with the assistance of experts. Based on APG (Angiosperm Phylogeny Group) III it was produced the floristic list. For the detection of the floristic similarity, initially it was made a binary matrix of presence / absence including species recorded in the study area and 12 other areas in the Northeast of Brazil. To the islands of the vegetation, the Unweighted Pair Group Method using Arithmetic averages (UPGMA) method was used to determine the similarity and structure of islands, to test the difference between the two sections (upwind and lee side) regarding to the richness and species abundance it was used the Multivariate Analysis Permutational (PERMANOVA) based on altitudinal environmental variables, slope and island size. 161 species belonging to 127 genera and 50 families of Angiosperms were recorded. The most important families in species richness were Fabaceae (24 species), Asteraceae (12 species) and Convolvulaceae (11 species). With respect to the dispersion syndromes predominated autochory with 50.3% anemochory corresponds to 26.7% and 23.6% zoochory comprised of all species reported. Similarity analysis showed the formation of three welldefined groups, with the highest area located in the micro Cariri. The areas inserted in meso Wasteland also showed a similar flora among themselves, which is related to the climatic conditions and similar geomorphological nature. The lowest rate was observed in an area located in a granitoid complex and a plateau region of Ceará, which is due to topographical and edaphic heterogeneity arising from the geological formation of the area. Regarding to the structure of vegetation islands it was verified that the occurrence of differences between the treatments patterns characterizing the environmental heterogeneity of the outcrop. Thus we observe that the premise that larger islands with a low degree of isolation have a richer biota in relation to smaller and more isolated islands were applied principally strand to upwind, whose predictor variable was not the degree of isolation of island units, as expected, but the slope.