Evolution of leaflet shape in endemic Oxalis sect. Alpinae: an integrative approach using phylogeny and geometric morphometrics.

LÓPEZ, A.; SASSONE, A. B.; MORELLO, S.

Forth Worth, Texas

Congreso; Botany Conference 2017; 2017

Botanical Society of America

Oxalis secc. Alpinae includes 17 species distributed along the Andes. This section constitutes a monophyletic group according to molecular data. In the present work, the morphological variation of leaflets assigned to 12 species of Oxalis is analyzed. Here we present an integrative approach to elucidate the evolution of leaftet shape in species of Oxalis, with the following aims: 1) to analyze the morphological variation; 2) to determine if morphological traits of the leaflet can be used as diagnostic characters; 3) to further test the monophyly of the section; and 4) to assess the genetic and environmental processes involved in the evolution of the leaflet of species of Oxalis. Leaflets were scanned and 262 contours were obtained. A total of 312 outline coordinates were extracted from the binary images and two landmarks were used to align samples. Elliptic Fourier Analysis (EFA) was performed on these outlines. Further methods were carried on R using Momocs package, and we chose a number of eight harmonics. A principal component analysis (PCA) was used to summarize the information. In order to study the phylogenetic relationships in the section, Bayesian inference was performed from ITS sequences. EFA allowed us to characterize the shape of analyzed leaflets and to distinguish 3 groups of species from their morphological similarity. PCA analysis revealed more than 99% of total variation is absorbed by the first 6 PCs. More than 90% of the leaflets shape variance, represented by PC1 and PC2, is influenced by width and the incision. PCA shows that species are loosely grouped but there is a continuous of leaflet shape variation. Negative values of PC1 and PC2 represent typical heart shapes of Oxalis leaflets like those found in O. micrantha. Positive values of PC2 distinguish leaflets with shallow or null incision, like leaflets of O. holosericea and O. hypsophylla. Phylogenetic branches in morphospace did not tend to radiate. Instead, they crossed one another repeatedly, and distantly related terminals were often found in close proximity in morphospace, and sister clades are often found in opposite regions. Geometric morphometric data corroborated the subjective impression that there is an overlap in leaflet shape among species of the section Alpinae. Leaflets shape does not always reflect phylogenetic relationships. These results contribute to the understanding of the patterns of morphological variation of Oxalis secc. Alpinae.