Morphometric analysis of Stemodia hyptoides and S. stricta (Plantaginaceae)

Abstract

Stemodia stricta Cham. & Schltdl. has been regarded by several authors as a synonym for Stemodia hyptoides Cham. & Schltdl., a variety of this taxon or a quite different species. These species have wide morphological variation at the inter and intra-specific level, which occasionally makes it difficult to identify them. In addition, S. hyptoides has diploid (2n = 2x = 22), tetraploid (2n = 4x = 4), and hexaploid (2n = 6x = 66) cytotypes whereas S. stricta is always diploid (2n = 22). To determine the taxonomic position and status of both plants, twenty-five morpho-anatomical traits were analyzed by use of multivariate methods. The results shows that UPGMA and PCoA, tests separate the two species, and the cytotypes of S. hyptoides into three different groups, which suggests that the analyzed taxa are different morphologically and anatomically. The most relevant morphological features separating the specimens studied are the plant height, leaf size, leaf shape, and corolla length. Stemodia stricta is a good species that is clearly separated from S. hyptoides. The diploid specimens of S. hyptoides may be distinguished from the polyploids by a set of morphological features, for example shape, pubescence, and margin of the leaf and corolla length. The morphological features of the polyploid specimens are in accord with the original description of S. hyptoides. As a consequence, the diploid cytotype of S. hyptoides should be regarded as a different species.