Areas of endemism of the North American species of Tigridieae (Iridaceae)

Abstract

The tribe Tigridieae (Iridoideae: Iridaceae) is a New World group with centres of diversity in Mexico and Andean South America. North America harbours 67 of the 172 species recognised within the tribe, 54 being endemic. Our aims were to identify areas of endemism of the North American Tigridieae using endemicity analysis (EA) and to infer their relationships using parsimony analysis of endemicity (PAE). A data matrix with 2769 geographical records of Tigridieae was analysed. The EA allowed to identify six consensus areas of endemism in Mexico. The PAE resulted in one cladogram with four clades and the following five biotic components: northern Mexico, western Mexico, central Mexico, southern Mexico and central–southern Mexico. The richness analysis of these areas of endemism indicated that the greatest concentration of species is located in central Mexico, with 14 species in one grid-cell. Grid-cells with 12 species each were identified in low western Mexico, high western Mexico, southern Mexico and central–southern Mexico. This last area is characterised by the greatest endemism, including nine species. The formation of the Transmexican Volcanic Belt seems to have been a key element to explain the diversification of North American Tigridieae.