Evolutionary history of the river frog genus Amietia (Anura: Pyxicephalidae) reveals extensive diversification in Central African highlands

Abstract

The African river frog genus Amietia is found near rivers and other lentic water sources throughout central, eastern, and southern Africa. Because the genus includes multiple morphologically conservative species, taxonomic studies of river frogs have been relatively limited. We sampled 79 individuals of Amietia from multiple localities in and near the Albertine Rift (AR) of Burundi, Democratic Republic of the Congo, and Uganda. We utilized single-gene (16S) and concatenated (12S, 16S, cyt b and RAG1) gene-tree analyses and coalescent species-tree analyses to construct phylogenetic trees. Two divergence dating approaches were used in BEAST, including secondary calibration points with 12S, 16S, cyt b and RAG1, and a molecular clock with the 12S, 16S, and cyt b genes. All analyses recovered Amietia as monophyletic with strong support, and revealed several well-supported cryptic lineages, which is consistent with other recent phylogeography studies of AR amphibians. Dating estimates were similar, and Amietia diversification is coincident with global cooling and aridification events in the Miocene and Pliocene, respectively. Our results suggest additional taxonomic work is needed to describe multiple new species of AR Amietia, some of which have limited geographic distributions that are likely to be of conservation concern.

Cryptic diversity in Rhampholeon boulengeri (Sauria: Chamaeleonidae), a pygmy chameleon from the Albertine Rift biodiversity hotspot

“…Among the AR Rhampholeon species, diversification events since the mid-Miocene were most common, a finding that is similar to several other forest-adapted taxa in the region (e.g., Tolley et al, 2011; Greenbaum et al, 2015; Portillo et al, 2015; Larson et al, 2016; Hughes et al, in press). Short internodes and low support among the species in the R. boulengeri complex are consistent with a rapid radiation event across the Miocene–Pliocene boundary (ca.…”

“…Speciation in forest refugia that formed in response to Pleistocene climatic changes have been implicated as biogeographic drivers among small mammals (Demos et al, 2014, 2015), land snails (Boxnick et al, 2015; Wronski and Hausdorf, 2008), and birds (Bowie et al, 2006; Voelker et al, 2013). In contrast, several other taxa, including frogs (Larson et al, 2016; Portillo et al, 2015), chameleons (Hughes et al, in press; Tolley et al, 2011), and snakes (Greenbaum et al, 2015; Menegon et al, 2014) likely diversified during pre-Pleistocene biogeographic events, such as the reduction of forests in response to global cooling in the Miocene. Afromontane forests have functioned as stable refugia during ancient climate changes and thereby promoted vicariance-driven diversification in some AR taxa (e.g., Hughes et al, in press); however, this model does not fully account for the lack of genetic structure found in some widespread AR species (e.g., Greenbaum et al, 2013, 2015).…”

Tectonics, climate and the diversification of the tropical African terrestrial flora and fauna

“…In African woodpeckers, despite the absence of an absolute time frame, the main process of diversification proposed was repeated cycles of fragmentation followed by allopatric speciation (Fuchs, Pons, & Bowie, 2017). Frog lineages also show a strong pre‐Pleistocene diversification pattern, especially from the Late Miocene into the Pliocene (Evans et al ., 2015; Bittencourt‐Silva et al ., 2016; Larson et al ., 2016; Liedtke et al ., 2016; Zimkus et al ., 2017; Portik et al ., 2019). For example, speciation in clawed frogs started during the Late Miocene, and high diversity in central Africa was linked to persistence of forest refugia that remain today (Evans et al ., 2015).…”

Comparative Phylogeography of Ethiopian anurans: impact of the Great Rift Valley and Pleistocene climate change

“…The systematics of frogs belonging to the genus Amietia is still debated. Although populations from Ethiopia have been assigned to the species Amietia angolensis [ 2 , 3 ], it is highly likely that this name recovers a species complex [ 18 , 19 ] and that Ethiopian populations belong to a separate species. We refer to those frogs as Amietia sp.…”