Leaflet shape in the endemic South American Oxalis sect. Alpinae: An integrative approach using molecular phylogenetics and geometric morphometrics

Abstract

Oxalis section Alpinae grows along the Andes, from Ecuador to the austral part of the South American continent. Across the section, leaves are always trifoliolate, but leaflets exhibit wide diversity in shape and size and have often been used as a diagnostic character. This study provides a comprehensive morphometric and phylogenetic framework of Oxalis sect. Alpinae. Thus, the shapes of 312 leaflets representing 14 species of O. sect. Alpinae are examined and elliptic Fourier analysis is used, which is a morphometric approach for the comparison of outlines in order to recognize patterns in shape evolution and to assess if the leaflets are an accurate diagnostic character at the species level. Moreover, a new molecular phylogenetic reconstruction is provided, and it is compared with the morphological space. The leaflet shape diversity cannot be fully explained by phylogenetic relations among species. However, different patterns of shape evolution can be distinguished, and there might be a spectrum from evolutionary lability to the conservatism of shape.