Evolutionary significance of oral morphology in the carnivorous tadpoles of tiger frogs, genus Hoplobatrachus (Ranidae)

Abstract

We describe the larval stages of three species of the Asian-African tiger frogs Hoplobatrachus chinensis, H. occipitalis and H. tigerinus . The tadpoles of all three species are very similar, with peculiar oral features: (1) double rows of needle-like labial teeth, (2) strong emarginations on the large jaw sheaths and (3) keratinized spurs on the buccal floor. Characters 1 and 2 (and perhaps 3) are probably related to the carnivorous habits of these tadpoles. A molecular phylogeny based on 2430 base pairs of two nuclear and four mitochondrial genes corroborated monophyly of Asian and African Hoplobatrachus, and identified Euphlyctis as their sister group. Tadpoles of the latter genus lack buccal spurs and double labial tooth rows but share large jaw sheaths, the upper with a medial projection. Therefore, the common ancestor of Euphlyctis and Hoplobatrachus probably was also characterized by this state, and may have been facultatively carnivorous. Further carnivorous specializations in Hoplobatrachus could explain why tiger frogs have been so successful in populating arid environments where ponds are at high risk of desiccation. Larval morphology may prove to be the key innovation which enabled them to disperse, in the Late Cenozoic, into their current very wide distribution area in Asia and Africa.

Supplemental Material for 'The amphibian tree of life. (Bulletin of the AMNH ; no. 297)'

“…Our results are broadly consistent with several other studies showing that Hoplobatrachus (Limnonectini) is the sister taxon of Euphlyctis (Dicroglossini) (Bossuyt and Mil- Kosuch et al, 2001;Grosjean et al, 2004;Roelants et al, 2004). Limnonectini (sensu ) is therefore rejected as nonmonophyletic.…”

“…50 [insert], 61, 63). The results are complex but are comparable to a group of smaller studies that dealt overwhelmingly with Asian taxa (Tanaka-Ueno et al, 1998aBossuyt and Milinkovitch, 2000;Emerson et al, 2000a;Marmayou et al, 2000;Bossuyt and Milinkovitch, 2001;Kosuch et al, 2001;Grosjean et al, 2004;Roelants et al, 2004;Jiang and Zhou, 2005). This overall result varies widely from Bossuyt and Milinkovitch (2001), who found Mantellinae ϩ Rhacophorinae as the sister taxon of Nyctibatrachinae ϩ Raninae; this clade sister to Dicroglossinae ϩ Micrixalinae, and Ranixalinae sister to them all.…”

“…40) placed Occidozyga and Phrynoglossus in the subfamily Occidozyginae, and transferred without discussion into Dicroglossini Fejervarya and Hoplobatrachus (from Limnonectini) and Sphaerotheca (from Tomopterninae), and Nannophrys (from Ranixalinae). Grosjean et al (2004), building on the earlier work of Kosuch et al (2001) suggested on the basis of several mtDNA and nuDNA loci that Euphlyctis is the sister taxon of Hoplobatrachus with Fejervarya, Sphaerotheca, Nannophrys, and Limnonectes forming more distant relations, a result that is consistent with the tree of Roelants et al (2004;fig. 35).…”

“…Limnonectini (sensu ) is therefore rejected as nonmonophyletic. Limnonectes (including Taylorana '', as a synonym; a result congruent with Emerson et al, 2000a) forms the sister taxon of a clade formed by Paini (Quasipaa), Nanorana, Nannophrys, and the remaining members of ''Limnonectini'' (Fejervarya, Sphaerotheca, and Hoplobatrachus) and Dicroglossini (Euphlyctis), a result congruent with Grosjean et al (2004). Marmayou et al (2000) found Fejervarya ϩ Sphaerotheca to form the sister taxon of a monophyletic Limnonectes ϩ Hoplobatrachus, but they did not include Euphlyctis in their study.…”

“…CONTENT: [225] Dicroglossinae Anderson, 1871, and [222] Occidozyginae Fei, Ye, and Huang, 1991 (e.g., Bossuyt and Milinkovitch, 2000;Emerson et al, 2000b;Marmayou et al, 2000;Vences et al, 2000c;Kosuch et al, 2001;Grosjean et al, 2004;Roelants et al, 2004;Jiang and Zhou, 2005), although our expanded taxon sampling and data altered some relationships within Dicroglossini.…”