Partitioning of morphospace in larval and adult reed frogs (Anura: Hyperoliidae: Hyperolius) of the Central African Albertine Rift

Reed frogs of the genus Hyperolius inhabit a wide range of habitats from open savannah to montane forests in Sub-Saharan Africa with sympatric species frequently exploiting the same localities at tadpole and adult stage. Niche partitioning with respect to morphological traits related to diet and locomotion is expected to shape local Hyperolius communities. In a case study on Albertine Rift Hyperolius in Rwanda and Burundi, we analysed the partitioning of larval and adult morphospace (three-dimensional volume describing size and shape variation) as affected by phylogenetic relationships and environmental constraints. Morphological features and molecular barcoding demonstrated that the Albertine Rift Hyperolius resolved into 12 terminal groups (=species), which represent five phylogenetic lineages. The major morphological source of variation among species was isometric size variation at tadpole and adult stage. Among-species variation of tadpole size (maximum size reached before metamorphosis) predicted the range of snout-vent length variation in adult males indicating a strong coupling between the two stages. The adaptive decoupling hypothesis is not supported at the taxonomic scale of the Hyperolius genus. Size-independent shape traits were assessed using a principal component analysis. The two traits which explained most of the morphological variance at the two ontogenetic stages were related to feeding (mouth architecture in tadpoles, head shape in adults) and to locomotion (body/tail height in tadpoles, leg morphology in adults). Partitioning of the shape axes indicated that savannah-dwelling and forest-dwelling species exploit different volumes of the available morphospace. Transition from open savannah habitats to closed-canopy forests seems to induce modifications of both tadpole and adult morphology. (C) 2019 Elsevier GmbH. All rights reserved.