On the Trail of Morphological Traits: Morphometry Helps to Clarify Morphological Variation in Section Viperella (Sisyrinchium).

Sisyrinchium, a large genus of the Iridaceae family, is divided into ten sections and defined by genetic, morphological and phylogenetic traits. The section Viperella, though monophyletic, encounters taxonomic hurdles, particularly within the Sisyrinchium palmifolium L. and Sisyrinchium vaginatum Spreng complexes, resulting in numerous misidentifications. The taxonomic confusion in the group may stem from various factors, emphasizing extensive morphological variations, leading to overlapping characteristics. We used morphometric approaches to better characterize the species belonging to two complexes, assess their variation and identify diagnostic traits for taxonomy enhancement. We assessed 16 quantitative traits for the S. palmifolium complex and 15 for the S. vaginatum complex, totaling 652 specimens recorded across 15 herbaria covering the entire species' distribution area. In the S. vaginatum complex, 66.5% of the variations were accounted for in the first two axes, while in the S. palmifolium complex, the first two axes explained 55.3%. Our findings revealed that both complexes exhibited many morphological variations, leading to a characteristic overlap. These characteristics may have arisen due to recent diversifications of the group and niche overlaps. Additionally, we identified some morphological characteristics that are useful for distinguishing species. Finally, we compiled a section gathering all useful characteristics for species delimitation within the group, aiming to facilitate non-experts in deciphering this species complex.