Morphology, molecular phylogenetics and biogeography of Impatiens akomensis (Balsaminaceae), a new species from Cameroon

Abstract

Background and aims - A recent field expedition in the Campo-Ma’an/Akom II region in Cameroon resulted in the collection of a previously unknown Impatiens species, which resembles Impatiens macroptera and Impatiens pseudomacroptera. This study aims to describe and infer the evolutionary history of this novelty by using phylogenetics, biogeographic inference and dating estimation analyses. Methods - The new species was subject to a palynological, molecular phylogenetic and biogeographical analysis. In addition, a thorough morphological comparison with its closely related species was conducted. Key results - Morphological comparison and molecular phylogenetics corroborate its status as a new species, which is given the name Impatiens akomensis. Molecular data, based on ImpDEF1, ImpDEF2 and ITS indicate that Impatiens akomensis is most closely related to the Cameroonian I. macroptera, whereas the lineage towards I. macroptera and the novelty is sister to the Gabonese I. pseudomacroptera. Impatiens akomensis differs from I. macroptera and I. pseudomacroptera in having very strongly asymmetric white flowers, much thicker leaves, a narrowly elliptic leaf shape and a serrulate leaf margin, smaller lateral united petals (23.1-24.2 mm) and larger bracts (12-20 mm). The new species qualifies for endangered status under IUCN criteria B2 and probably B1. Conclusions - Dating analyses in combination with biogeographic inference, and ecological and environmental interpretation of the novelty and its closely related species allows us to infer the putative evolutionary history of Impatiens akomensis.