The Gondwana Breakup and the History of the Atlantic and Indian Oceans Unveils Two New Clades for Early Neobatrachian Diversification

Abstract

The largest anuran diversity belongs to the Neobatrachia, which harbor more than five thousand extant species. Here, we propose a new hypothesis for the historical aspects of the neobatrachian evolution with a formal biogeographical analysis. We selected 12 genes for 144 neobatrachian genera and four archaeobatrachian outgroups and performed a phylogenetic analysis using a maximum likelihood algorithm with the rapid bootstrap test. We also estimated divergence times for major lineages using a relaxed uncorrelated clock method. According to our time scale, the diversification of crown Neobatrachia began around the end of the Early Cretaceous. Our phylogenetic tree suggests that the first split of Neobatrachia is related to the geological events in the Atlantic and Indian Oceans. Hence, we propose names for these clades that indicate this connection, i.e., Atlanticanura and Indianura. The Atlanticanura is composed of three major neobatrachian lineages: Heleophrynidae, Australobatrachia and Nobleobatrachia. On the other hand, the Indianura consists of two major lineages: Sooglossoidea and Ranoides. The biogeographical analysis indicates that many neobatrachian splits occurred as a result of geological events such as the separation between South America and Africa, between India and the Seychelles, and between Australia and South America.

Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary

“…We corroborate the placement of Heleophrynidae, which is from extreme southern Africa, as the sister taxon to all other neobatrachian frogs (Fig. 1A), as found by some authors (4-7, 9), but not by others (10,11). We find that Sooglossidae (known only from the Seychelles Islands) is the sister taxon of Ranoidea (BS = 100%, BPP = 1.0; Figs.…”

“…1A). Overall, our divergence times are notably younger than those found by most other studies (5,10,23,24) (Fig. 1A and Table S2), and especially much younger than those in the mitogenome phylogeny (7).…”

“…The clade of the remaining non-African families is strongly supported (BS = 100%), and the internal branches are strongly supported (BS = 100%, BPP = 1.0), although they are short. In other studies, this group of African lineages is not monophyletic (6,7,10,14,15). The phylogenetic position of the continental African lineages has important biogeographic significance (as detailed later).…”

“…2, 5, 6, 13; but see refs. 4,10), including an analysis of mitogenomes of 90 anuran species (7). Relationships among the early branches of Neobatrachia are identical to the mitogenomic phylogeny (7).…”

“…For example, age estimates for the last common ancestor of extant Neobatrachia, often referred to as "modern frogs" and containing 95% of extant anuran species, span ∼100 Mya (5, 7-11). Furthermore, divergences time estimates among the earliest neobatrachian clades, such as the Heleophrynidae, Myobatrachidae, Calyptocephalellidae, Nasikabatrachidae, and Sooglossidae, range from the Late Jurassic to early Cretaceous (∼150-100 Mya) and have wide CIs (5,(7)(8)(9)(10)(11). In addition to these species-poor groups of neobatrachians, there are two species-rich clades: Ranoidea (39% of extant anuran species, mostly Old World) and Hyloidea (54%; mostly New World).…”