Revisiting Metternichia (Solanaceae) through an integrative approach: A monotypic genus?

Improving species delimitation and knowledge on species complexes is
crucial for many areas of study in Biology, especially conservation.
Integrative taxonomy contributes to this topic by using different
approaches to better delineate taxonomic boundaries. Metternichia
(Solanaceae), historically a monospecific genus, has a geographic range
that comprises contrasting environments. Metternichia principis was
described as having two varieties: the typical variety, found in the humid
forests of eastern Brazil (Atlantic Forest region), and M. principis var.
macrocalyx, which presents larger calyx and inhabits mostly semi-arid
areas (Caatinga region). In this study we tested the validity of such
groups by integrating environmental, phenological, morphometric and
palynological data; applying uni and multivariate tests; and evaluating
the conservation status of each taxon. Our results support the recognition
of two morphological groups within Metternichia, largely in agreement with
the original circumscription of the varieties. Multivariate analyses
clearly indicate different ecological niches, with each taxon inhabiting
environments with distinct mean annual precipitation and temperature.
Phenological data show some differences between the varieties regarding
months with the highest number of flowering and fruiting records. In
general, M. principis var. macrocalyx presents larger flower and pollen
characters, and smaller fruit characters compared to the typical variety.
Based on these findings, we elevate the variety to the status of species,
as the new combination Metternichia macrocalyx. Following IUCN guidelines,
both taxa are here considered endangered (EN).