The role of climatic and geological events in generating diversity in Ethiopian grass frogs (genusPtychadena)

Abstract

Ethiopia is a world biodiversity hotspot and harbours levels of biotic endemism unmatched in the Horn of Africa, largely due to topographic—and thus habitat—complexity, which results from a very active geological and climatic history. Among Ethiopian vertebrate fauna, amphibians harbour the highest levels of endemism, making amphibians a compelling system for the exploration of the impacts of Ethiopia's complex abiotic history on biotic diversification. Grass frogs of the genus Ptychadena are notably diverse in Ethiopia, where they have undergone an evolutionary radiation. We used molecular data and expanded taxon sampling to test for cryptic diversity and to explore diversification patterns in both the highland radiation and two widespread lowland Ptychadena. Species delimitation results support the presence of nine highland species and four lowland species in our dataset, and divergence dating suggests that both geologic events and climatic fluctuations played a complex and confounded role in the diversification of Ptychadena in Ethiopia. We rectify the taxonomy of the endemic P. neumanni species complex, elevating one formally synonymized name and describing three novel taxa. Finally, we describe two novel lowland Ptychadena species that occur in Ethiopia and may be more broadly distributed.

Diversification of African tree frogs (genus Leptopelis) in the highlands of Ethiopia

“…The split between the Ethiopian Leptopelis and their sister taxon from other regions occurred about 16 million years ago, as the Ethiopian species appear to be the sister group to the majority of other Leptopelis(Figures 2 and 5). These result emphasizes the unique nature of the Ethiopian Highlands as an ancient centre of diversification for amphibians, as was previously shown in several genera of anurans, including Balebreviceps(Loader et al, 2014), Ericabatrachus(Siu-Ting et al, 2014) and PtychadenaSmith et al, 2017). This is consistent with the large fraction of endemic frog taxa in the region, including a number of endemic genera such as Altiphrynoides, Balebreviceps, Ericabatrachus and Paracassina(Largen & Spawls, 2010).…”

“…The Great Rift Valley (GRV) crosses the highlands from NE to SW, dividing them into two main blocks, which are the Abyssinian massif to the north, and the Harar massif to the south (see Figure ). The GRV is known to be an important barrier to the dispersal of a multitude of taxa (Evanno, Regnaut, & Goudet, ; Freilich et al., ; Gottelli, Marino, Sillero‐Zubiri, & Funk, ; Kebede, Ehrich, Taberlet, Nemomissa, & Brochmann, ; Manthey, Reyes‐Velasco, Freilich, & Boissinot, ; Reyes‐Velasco, Manthey, Bourgeois, Freilich, & Boissinot, ; Smith, Noonan, & Colston, ). Other hydrological features also played an important role in the complex geology of the region and in the diversification of Ethiopian taxa, in particular the Omo River Valley and the Blue Nile Valley (Evans, Bliss, Mendel, & Tinsley, ; Freilich et al., ; Gottelli et al., ; Manthey et al., ; Reyes‐Velasco et al., ).…”

Revisiting the phylogeography, demography and taxonomy of the frog genus Ptychadena in the Ethiopian highlands with the use of genome-wide SNP data

“…Multiple programs for conducting BSD are now available, including BPP [ 67 ], SpedeSTEM [ 68 ], BFD* [ 69 ] and more recently PHRAPL [ 70 ], to name a few. Despite the importance of describing biological diversity of the planet, and the ability of BSD to help describe this diversity, many authors use the results of BSD analyses as the only diagnostic evidence when naming species [ 20 , 71 ]. Several authors have pointed out multiple issues with the use of BSD as the only evidence for describing taxa [ 72 , 73 ], but we would like to emphasize a few issues, which are particularly relevant to Ethiopian Ptychadena .…”

“…Recently Smith et al . [ 20 ] assigned new names to multiple Ptychadena from Ethiopia. However, the new names lack appropriate diagnostic characters as defined by the International Commission on Zoological Nomenclature [ 21 ].…”

Correction to ‘The role of climatic and geological events in generating diversity in Ethiopian grass frogs (genus Ptychadena )’

“…(ii) Highland taxa— Ptychadena neumanni species complex. These taxa are a group of highly morphologically variable and similar species that can be identified in the field according to their distribution and ecology ([ 1 ], Table 2).…”