Geographic Variation among Closely Related, Highly Variable Species with a Wide Distribution Range: the South Andean-Patagonian Nassauvia subgenus Strongyloma (Asteraceae, Nassauvieae)

Abstract

Morphological variation among the five species of Nassauvia subgenus Strongyloma was assessed through statistical analyses of morphometric traits in populations throughout the southern Andean-Patagonian region. Uni- and multivariate analyses were used to identify patterns of morphological variation in relation to geography. Additionally, species distribution modeling was implemented to relate these patterns to climatic conditions. No well-defined groups could be recovered through multivariate analyses, although we observed some geographic structure. Latitudinal variation was found in leaves, phyllaries and cypselas, with a cline towards the south, where these structures become shorter and wider. Towards the east, the number of flowers per capitulum decreases, and abaxial corolla lips and cypselas become narrower and shorter. Distribution modeling showed several areas of contact and a large overlap of suitable conditions for more than one species, which ismainly related to themean temperature of winter. Despite an association between morphological variation with geography and climate, actual geographic distributions of the putative species did not entirely match the clinal pattern of morphology, geography, and climate. Further genetic analyses are still needed to identify the probable processes that led to the complex patterns of observed variation.