Is the labellum informative to distinguish species of Scaphyglottis(Orchidaceae)? Insights from geometric morphometrics

Abstract

Scaphyglottis Poepp. & Endl. (Orchidaceae) is a neotropical genus with 78 species, 14 of which are found in Brazil. Some of these taxa have an intricate taxonomy, especially due to the morphological similarity among species and the existence of species complexes. Our study aims to test if the labellum shape, the main source of species diagnostic characters, can confirm the proposed circumscription of Brazilian species of Scaphyglottis . We analyzed 136 flowers from 12 species, to which we applied 12 landmarks, using a geometric morphometrics approach. Our results show that most species can be distinguished. Most of the variation is observed in the claw and apices of labellum lobes, confirming that the labellum is important tool in taxon distinction. Species with distinctly 3-lobed labellum showed some overlap but, for these taxa, we have found distinction specially in the lateral lobes. Our study showed new morphologically variable features in Scaphyglottis that can be used in future taxonomic studies. For widely distributed species we suggest a population-level approach, as local environmental factors can impact morphology, causing expected intraspecific variation.