DOI: 10.3897/vz.75.e139103

Authors: Anna B. Vassilieva, Trung Duc Nguyen, Pavel A. Sorokin

Abstract: Abstract Dicroglossid tadpoles are an important element of pond and stream communities in Southeast Asia. They are often found in syntopy but belong to different trophic guilds, from generalized detritophages to specialized predators. In the present research, the external and internal larval morphologies of seven anuran species of the family Dicroglossidae distributed in Vietnam (Fejervarya limnocharis, Fejervarya moodiei, Hoplobatrachus rugulosus, Limnonectes dabanus, Occidozyga lima, Occidozyga martensii, and Quasipaa verrucospinosa) are described and compared. An integrated approach is followed in the study by describing external and mouthparts morphologies, gross structure of the digestive tract, and the structure of chondrocranium and hyobranchium, which revealed the main trophic adaptations of tadpoles. Different trends in the evolution of larval macrophagy in Dicroglossidae led to the formation of fundamentally different larval forms. In the first case, the tadpoles are opportunistic predators that retain the ability to use a wide range of food resources (Hoplobatrachus); they have extremely specialized mouthparts but moderately transformed digestive tract and larval skeleton. In the other case, tadpoles are highly specialized obligate carnivores (Occidozyga) that have completely lost omnivory, with a radically transformed digestive tract, chondrocranium and hyobranchium. A comparison with generalized tadpoles revealed that in dicroglossids, the transformations of the larval skeleton due to carnivory mainly affect the labial cartilages and the palatoquadrate cartilage, as well as the hyobranchium. These transformations are common to macrophagous tadpoles of different taxonomic groups and result in greater larval morphological diversity.

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DOI: 10.3897/vz.74.e114285

Authors: Stephen Mahony, Rachunliu G. Kamei, Rafe M. Brown, Kin Onn Chan

Abstract: Abstract Although the differentiation of clades at the species level is usually based on a justifiable and testable conceptual framework, the demarcation of supraspecific boundaries is less objective and often subject to differences of opinion. The increased availability of large-scale phylogenies has in part promulgated a practice of what we consider excessively splitting clades at the “genus” level. Many of these new genus-level splits are predicated on untenable supporting evidence (e.g., weakly supported phylogenies and purportedly “diagnostic” but actually variable, non-exclusive, or otherwise problematic opposing character state differences) without careful consideration of the effects on downstream applications. As case studies, we critically evaluate several recent examples of splitting established monophyletic genera in four amphibian families that resulted in the creation/elevation of 20 genus-level names (Dicroglossidae: Phrynoglossus, Oreobatrachus, Frethia split from Occidozyga; Microhylidae: Nanohyla split from Microhyla; Ranidae: Abavorana, Amnirana, Chalcorana, Humerana, Hydrophylax, Indosylvirana, Papurana, Pulchrana, Sylvirana split from Hylarana; Rhacophoridae: Tamixalus, Vampyrius, Leptomantis, Zhangixalus split from Rhacophorus, Rohanixalus split from Feihyla, Orixalus split from Gracixalus, and Taruga split from Polypedates), and also address the taxonomic status of the monotypic genus Pterorana relative to Hylarana. We reassess the original claims of diagnosability and justifications for splitting and argue that in many cases, the generic splitting of clades is not only unnecessary but also destabilizes amphibian taxonomy, leading to a host of downstream issues that affect categories of the user community (stakeholders such as taxonomists, conservationists, evolutionary biologists, biogeographers, museum curators, educators, and the lay public). As an alternative, we advocate for the use of the subgenus rank in some cases, which can be implemented to establish informative partitions for future research without compromising on information content, while avoiding gratuitous (and often transient) large-scale binomial (genus-species couplet) rearrangements. We encourage taxonomists to consider the actual needs and interests of the larger non-taxonomic end-user community who fund the majority of taxonomic research, and who require a system that remains reasonably stable and is relatively intuitive, without the need for inaccessible laboratory equipment or advanced technical scientific knowledge to identify amphibian species to the genus level.

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DOI: 10.3897/vz.72.e79496

Authors: Sonali Garg, Sivaperuman Chandrakasan, G. Gokulakrishnan, C. Gopika, Indraneil Das, S. D. Biju

Abstract: Since the description of Charles Darwin’s frog as Rana charlesdarwini in 1998, its generic placement has been a taxonomic enigma. Subsequent studies first transferred this species to the dicroglossid genus Limnonectes, and then considered it as a ceratobatrachid of the genus Ingerana, which has since been moved to the family Dicroglossidae. However, recent works have doubted this generic placement and also suggested the possibility of its sister relationship with the genus Liurana, within Ceratobatrachidae. Nonetheless, there have been no detailed investigations to ascertain the generic placement of this taxon by confirming its phylogenetic position or using integrative taxonomic approaches. Here, we provide the first molecular assessment of Ingerana charlesdarwini based on mitochondrial and nuclear DNA and reveal that it is nested in the dicroglossid genus Minervarya. A member of the Minervarya andamanensis species group, Minervarya charlesdarwini comb. nov. is sister taxon to M. andamanensis and shows relatively shallow genetic distances (2.8–3.6%) in the 16S gene. Both species are widely distributed, occur sympatrically, and exhibit high morphological variations, leading to long-standing confusions with other dicroglossid frogs reported from the region. Our combined morphological and molecular studies on dicroglossid frogs sampled across the known ranges of these species suggest that reports of Limnonectes doriae (Boulenger, 1887) and L. hascheanus (Stoliczka, 1870) from the Andamans are misidentifications of the former two, pointing to the absence of genus Limnonectes from the Andaman Islands. Our study also reveals the novel record of Minervarya agricola from the Andamans, a species that appears to have been confused with Fejervarya limnocharis and Minervarya keralensis in the literature and misidentified museum specimens, and is found to be widely distributed across these islands. We further find another congener from the Nicobar group of Islands, M. nicobariensis, to be closely related to M. charlesdarwini. Similar to the case of Andaman dicroglossids, our work emphasises on the need for further studies to ascertain the taxonomic identities and generic placement of Minervarya and Limnonectes species reported from the Nicobars.

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DOI: 10.3897/vz.71.e60312

Authors: Gunther Köhler, Joseph Vargas, Ni Lar Than, Tilman Schell, Axel Janke, Steffen U. Pauls, Panupong Thammachoti

Abstract: We revise the frogs of the genus Phrynoglossus from Indochina based on data of external morphology, bioacoustics and molecular genetics. The results of this integrative study provide evidence for the recognition of three distinct species, one of which we describe as new. Phrynoglossus martensii has a vast geographic distribution from central and southern Thailand across southern China to Vietnam, Laos, and Cambodia. Phrynoglossus myanhessei sp. nov. is distributed in central Myanmar whereas Phrynoglossus magnapustulosus is restricted to the Khorat Plateau, Thailand. These three species occur in allopatry and differ in their mating calls, external morphology, and in genetic distances of the 16S gene of 3.8–5.9%. Finally, we discuss and provide evolutionary evidence for the recognition of Phrynoglossus as a genus distinct from Occidozyga. Members of both genera form reciprocal monophyletic groups in our analyses of mtDNA data (16S) and are well differentiated from each other in morphology and ecology. Furthermore, they differ in the amplexus mode with Phrynoglossus having an inguinal amplexus whereas it is axillary in Occidozyga. We further provide a de novo draft genome of the holotype based on short-read sequencing technology to a coverage of 25-fold. This resource will permanently link the genetic characterization of the species to the name-bearing type specimen.

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