Subtropical species of Sinningia (Gesneriaceae): Distribution patterns and limiting environmental factors

The neotropical genus Sinningia Nees encompasses tuberous herbs or subshrubs which occupy a wide range of environments with respect to climate and soil or substrate types. The genus has more than 70 species distributed from Southern Mexico to Northern Argentina, with a diversity centre in the Brazilian Atlantic Rainforest. In this ecosystem, a large number of species occur in several particular vegetation types, occupying terrestrial, rupestrial and epiphytic substrates. The aims of this study were to describe the distribution patterns of subtropical Sinningia species, and to determine possible limiting factors for their range extension. We summarized environmental data for 21 subtropical species. Ten geographical and ecological variables were subdivided into several regional or local conditions. The occurrence of species in each of these conditions was obtained from published material, herbarium reviews and field expeditions. We used exploratory multivariate approaches, (cluster and ordination analyses) to assess the contribution of these variables to species’ ecological and geographical distributions. Comparisons between groups of species were uated using randomization tests. Two major patterns of geographic distribution were identified for subtropical Sinningia species: widespread and restricted. Species richness according to spatial and climatic variables showed four distinct patterns. Habitat tolerance of the species also distinguished two groups in a wider continuum context. Cluster analysis resulted in two stable groups, which coincided almost entirely with an a priori classification based on geographic range. Ordination analysis showed a distinction between widespread and restricted species, as well as a gradient of substrate occupancy. Patterns of ecological and geographical distribution were strongly related to the evolutionary history of the genus. The southern distribution limit of Sinningia is mainly linked to shifts in vegetation types around the 30°S parallel, where the northern forested Atlantic and Paranean biogeographic provinces give place to the southern non-forested Espinal and Pampean provinces.