Distribution of the xeric clade species of Pitcairnioideae (Bromeliaceae) in South America: a perspective based on areas of endemism

Aim The main goals were to assess the distributional concordance among taxa of the xeric clade of Pitcairnioideae (Bromeliaceae) to establish biogeographical units (i.e. endemic areas), and to use the results to identify conservation priorities. Location Geographical data were analysed between parallels -1 degrees and -47 degrees S and meridians 35 degrees 6' and 80 degrees 1' W, which includes the Andean region, the Chacoan subregion and the South American Transition Zone, and three global hotspots (Atlantic Forest, Cerrado and Tropical Andes). Methods Two methods were employed, parsimony analysis of endemicity (PAE) and endemicity analysis (EA), to search for the biogeographical congruence between endemic areas for 220 species. Two grid cell sizes (2 degrees and 3 degrees) and three criteria were employed to delimit the areas of endemism. Results The results of the PAE demonstrated eight candidate areas of endemism when applying a grid cell size of 2 degrees and six areas of endemism with 3 degrees. The EA optimization method, using a grid size of 2 degrees, recovered six (consensus 75%) and four (consensus 5%) areas, and a size of 3 degrees recovered eight (consensus 75%) and three (consensus 5%) areas. Based on consistent results of the three combined criteria and the congruence of areas of endemism, we delimited three biogeographical areas of endemism for the clade in the Chacoan subregion of South America. The following areas in Brazil were delimited: (1) south-eastern Minas Gerais, (2) north-eastern Minas Gerais, and (3) northeastern Goias. Main conclusions Endemic species with congruent occurrence patterns were identified to propose primary biogeographical homologies and to highlight areas that should be prioritized for conservation of species in the xeric clade of Pitcairnioideae. Furthermore, we suggest that evolutionary and historical processes (adaptive radiation; glacial and interglacial period in the Quaternary), as well as ecological factors, could have induced the high diversification rates for this clade in South America.