Geographic distribution and richness of the genus Cosmos (Asteraceae: Coreopsideae) [Distribución geográfica y riqueza del género Cosmos (Asteraceae: Coreopsideae)]

Abstract

Cosmos is a monophyletic genus and one of the most diverse groups within the tribe Coreopsideae (Asteraceae). It includes 35 species and 4 infraspecific taxa found in the Americas. The aim of this study was to evaluate the geographical distribution and richness of Cosmos using a geographical information system (GIS). We estimated the geographic range of taxa with more than one record. The species richness was analyzed by political region, geological province, biogeographical province and an 80 × 80 km cell grid. Finally, we assessed the geographical distribution patterns of Cosmos according to growth habit. We found 3 areas of greatest richness, all in México, in the states of Jalisco, Durango and Mexico. Annual herbs, perennials herbs and subshrub had different patterns of geographical distribution. The annual herbs were the most widespread. In contrast, the perennial herbs were more diverse but exhibited a restricted distribution. The Trans-Mexican Volcanic Belt has been the scenario of Cosmos diversification and poliploidy seems to have been the primary mechanism of speciation.