Seed Morphological Properties Related to Taxonomy in Silene L. Species

Abstract

Silene taxonomy, traditionally based on morphological characteristics, is now driven by DNA sequence analysis. While the usefulness of both morphological and molecular methods remains undisputed, there is an interest in the identification of the morphological characteristics useful in taxonomy. A quantitative morphological analysis of seeds belonging to Silene species is presented here and is based on seed image samples for 95 populations belonging to 52 species (49 species of Silene and 3 related species). According to the silhouette of lateral views of their seed images, Silene species are classified into three groups: smooth, rugose and echinate. The measurements taken for the lateral and dorsal views of the seeds include area, circularity, roundness, aspect ratio and solidity; differences between groups are found for all characteristics. Solidity is the ratio between the area of the seed silhouette and the corresponding convex hull. It is related to seed convexity and is the measurement with the lowest coefficient of variation. In the lateral views, solidity values are conserved, while in the dorsal views, differences are found between the three groups. The group of echinate seeds has the highest values of solidity in the dorsal views, and their species belong to S. subg. Behenantha and S. subg. Lychnis. The group of smooth seeds contains mainly species corresponding to S. subg. Silene, while species of S. subg. Lychnis are absent.