Morphologically hypervariable species hinder our knowledge of biodiversity: Daustinia montana (Convolvulaceae) as a case study

Abstract

Cryptic species continue to intrigue taxonomists over time and hamper biodiversity knowledge. An example of what would be considered a cryptic species is Daustinia montana (Convolvulaceae). Its wide leaf morphology plasticity has led to multiple interpretations and contrasting classifications: from a monotypic to a six-taxa hypothesis. For this work, we tested six taxonomic hypotheses, including an explicit test of a monotypic approach, under a robust statistical analysis, using univariate and multivariate methods. Besides that, we performed a niche analysis to verify the niche occupation of the populations recognized here as possible species. Forty-eight micro and macromorphological characters (qualitative and quantitative) from individuals of 16 populations of D. montana were evaluated. The taxonomic hypothesis that recognizes eight distinct species has the highest support as they also have non-overlapping niches. We conclude that the number of species in Daustinia may be greater than its current circumscription. We also highlight the importance of an integrative systematic approach in the study of biodiversity. This research represents a first step in the specific delimitations of the genus and can also serve as a model to study taxa with wide morphological variability.