From Antarctica or Asia? New colonization scenario for Australian-New Guinean narrow mouth toads suggested from the findings on a mysterious genus Gastrophrynoides

Abstract

BackgroundMicrohylidae is a geographically widespread family of anurans. Although several extensive molecular analyses have attempted to elucidate their subfamilial relationships, and correlate these with Mesozoic and Cenozoic continental drifts, consensus has not been reached. Further, generic level relationships have not been well investigated in some microhylid subfamilies, and therefore subfamilial affiliations of some genera are still unclear. To elucidate the phylogenetic positions of two mysterious Asian genera, Gastrophrynoides and Phrynella, and to better understand the trans-continental distributions of microhylid taxa, we performed molecular phylogenetic and dating analyses using the largest molecular dataset applied to these taxa to date.ResultsSix nuclear and two mitochondrial genes (approx. 8 kbp) were sequenced from 22 microhylid frog species representing eight subfamilies. The maximum likelihood and Bayesian analyses could not fully elucidate the subfamilial relationships, suggesting a rapid radiation of these taxa between 85 and 66 million years ago. In contrast, generic relationships of Asian microhylines were generally well resolved.ConclusionOur results clearly showed that one of two problematic Asian genera, Phrynella, was nested in the clade of the Asian subfamily Microhylinae. By contrast, Gastrophrynoides occupied the most basal position of the Australian-New Guinean subfamily Asterophryinae. The estimated divergence of Gastrophrynoides from other asterophryine was unexpectedly around 48 million years ago. Although a colonization scenario via Antarctica to the Australian-New Guinean landmass has been suggested for Asterophryinae, our finding suggested a novel colonization route via Indo-Eurasia.

Molecular phylogeny of microhylid frogs (Anura: Microhylidae) with emphasis on relationships among New World genera

“…In contrast to our analyses, other studies recovered the most basal lineages as: Phrynomerinae [11,15,44], Phrynomerinae-Gastrophryninae [16], or Kalophrynus ( Synapturanus ( Phrynomantis Micryletta ))] [9]. The somewhat basal position of Scaphiophryninae in our analyses has not been suggested previously; this taxon was found either closely related to Microhylinae [9] or Cophylinae [16].…”

“…Regarding incertae sedis taxa originating from the Old World, we recovered Gastrophrynoides as a basal member of the Asterophryinae and Phrynella nested within Metaphrynella in the subfamily Microhylinae (Figures 2, 3). These findings are in overall agreement with a recent study, except that Phrynella was previously found as the sister taxon to Metaphrynella [44]. Consequently, herein we place Gastrophrynoides in the Asterophryinae and Phrynella in the Microhylinae.…”

“…The somewhat basal position of Scaphiophryninae in our analyses has not been suggested previously; this taxon was found either closely related to Microhylinae [9] or Cophylinae [16]. The close relationship between Dyscophinae and Microhylinae has been suggested before, but with alternative sister relationships to either Asterophryinae [15,16,44] or to (Kalophryninae-(Melanobatrachinae-Asterophryinae)) [11]. An arrangement in which Microhylinae is closely related to Scaphiophryninae and Dyscophinae to Asterophryinae has also been suggested [9].…”

“…Previous analyses recovered a Phrynomerinae basal to all microhylids [11,15,16]; Phrynomantis was considered incertae sedis [9]. Kalophryninae or Otophryninae were not sampled [16,44] and Kalophryninae was recovered in a clade with Cophylinae and Melanobatrachinae [15] or in a clade with Melanobatrachinae and Asterophryinae [11]. …”

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

“…Relationships among the subfamilies of Microhylidae (one of the largest anuran families, including 8.8% of all species), which have significant radiations on most continents and the large islands Madagascar and New Guinea, have proven difficult to resolve (4,6,7,(15)(16)(17)(18)(19). In contrast, our Bayesian tree has strong support; all 10 of the deepest nodes have a BPP of 1.0 (Fig.…”