Disentangling leaf morphology in Daustinia montana (Convolvulaceae)

Daustinia montana (Convolvulaceae) is the only species of the genus, and is notable for its wide leaf variability. To understand whether this plasticity is correlated with the distribution of the species, linear morphometric and leaf contour analyses were performed. Specimens from herbaria were photographed, and pre-established linear measurements were made. A multivariate analysis was then performed to test the strength of associations among morphological characteristics, climatic variables, and distribution of the species. Elliptic Fourier analysis based on 20 harmonics was used to generate shape descriptors, resulting in nine main components. With elliptic Fourier descriptors, a grouping tree was created that suggests the existence of six morphotypes in D. montana. Moreover, clustering analysis revealed two large groups distinguished mainly by leaf width. The present findings indicate that the morphotypes are strongly related to latitude and that other characteristics such as the type of indumentum are related to climatic variables.

Methods
Field expeditions were performed out to collect and herbarium specimens were analyzed. Specimens were collected using standard techniques in taxonomy (Mori et al.1989). The coordinates were matching the labels of the herbarium specimens, of the field collections or Google Earth.  Climate data from the geographic locations was obtained from the WorldClim Global Climate databank (Fick and Hijmans 2017). The extraction of the climate data was performed with the aid of QGIS Development Team (2015). The images were captured using a digital camera, according to created protocol. Linear measurements were performed on the photographed material using ImageJ (Schneider et al. 2012). The images of the leaves were processed using Adobe Photoshop CS6 for the isolation of the leaves, subtraction of the petioles, digitization of the contours, and uniformization of the background. The images were processed using the SHAPE v. 1.3 computational package (Iwata and Ukai 2002) for the evaluation of the contour shape based on elliptical Fourier analysis.