Congolius, a new genus of African reed frog endemic to the central Congo: A potential case of convergent evolution

Abstract

The reed frog genus Hyperolius (Afrobatrachia, Hyperoliidae) is a speciose genus containing over 140 species of mostly small to medium-sized frogs distributed in sub-Saharan Africa. Its high level of colour polymorphism, together with in anurans relatively rare sexual dichromatism, make systematic studies more difficult. As a result, the knowledge of the diversity and taxonomy of this genus is still limited. Hyperolius robustus known only from a handful of localities in rain forests of the central Congo Basin is one of the least known species. Here, we have used molecular methods for the first time to study the phylogenetic position of this taxon, accompanied by an analysis of phenotype based on external (morphometric) and internal (osteological) morphological characters. Our phylogenetic results undoubtedly placed H. robustus out of Hyperolius into a common clade with sympatric Cryptothylax and West African Morerella. To prevent the uncovered paraphyly, we place H. robustus into a new genus, Congolius. The review of all available data suggests that the new genus is endemic to the central Congolian lowland rain forests. The analysis of phenotype underlined morphological similarity of the new genus to some Hyperolius species. This uniformity of body shape (including cranial shape) indicates that the two genera have either retained ancestral morphology or evolved through convergent evolution under similar ecological pressures in the African rain forests.

Filling the gaps: The mitogenomes of Afrotropical egg-guarding frogs based on historical type material and a re-assessment of the nomenclatural status of Alexteroon Perret, 1988 (Hyperoliidae)

“…As the taxonomic status of several lineages within Hyperolius are not resolved and because the clade herein recognized as Alexteroon is monophyletic and can be diagnosed by morphological and ethno-ecological characters, we treat Alexteroon as a subgenus of Hyperolius containing the three taxa Hyperolius (Alexteroon) hypsiphonus, Hyperolius (Alexteroon) obstetricans, and Hyperolius (Alexteroon) jynx until the data required for such a revision are available and the taxonomic position of Alexteroon can conclusively be resolved. Evidence is accumulating that several branches within the larger Hyperolius tree require a re-assessment (Nečas et al, 2021) and recently published research that shows the genus Kassinula Laurent, 1940 to be nested within the genus Afrixalus Laurent, 1944, despite readily observed morphological differences (Conradie et al 2020) points in a similar direction in another species rich hyperoliid group. Splitting the genus Hyperolius into smaller monophyletic taxonomic entities to depict the natural groupings more accurately therefore warrants serious consideration.…”

“…As with other underappreciated and neglected hyperoliid taxa (e.g. the monotypic genera Arlequinus Perret 1988, Callixalus Laurent 1950, Chrysobatrachus Laurent 1951, a reassessment of Alexteroon and the integration of extended molecular data into available family level phylogenies and large amphibian supertrees would also open new avenues for a better understanding of evolutionary patterns in these lineages (compare also Conradie et al 2020;Nečas et al, 2021).…”