Do cryptic species exist in Hoplobatrachus rugulosus? An examination using four nuclear genes, the cyt b gene and the complete MT genome

How Does Mitochondrial Protein-Coding Gene Expression in Fejervarya kawamurai (Anura: Dicroglossidae) Respond to Extreme Temperatures?

Unusual climates can lead to extreme temperatures. Fejervarya kawamurai, one of the most prevalent anurans in the paddy fields of tropical and subtropical regions in Asia, is sensitive to climate change. The present study focuses primarily on a single question: how do the 13 mitochondrial protein-coding genes (PCGs) respond to extreme temperature change compared with 25 °C controls? Thirty-eight genes including an extra tRNA-Met gene were identified and sequenced from the mitochondrial genome of F. kawamurai. Evolutionary relationships were assessed within the Dicroglossidae and showed that Dicroglossinae is monophyletic and F. kawamurai is a sister group to the clade of (F. multistriata + F. limnocharis). Transcript levels of mitochondrial genes in liver were also evaluated to assess responses to 24 h exposure to low (2 °C and 4 °C) or high (40 °C) temperatures. Under 2 °C, seven genes showed significant changes in liver transcript levels, among which transcript levels of ATP8, ND1, ND2, ND3, ND4, and Cytb increased, respectively, and ND5 decreased. However, exposure to 4 °C for 24 h was very different in that the expressions of ten mitochondrial protein-coding genes, except ND1, ND3, and Cytb, were significantly downregulated. Among them, the transcript level of ND5 was most significantly downregulated, decreasing by 0.28-fold. Exposure to a hot environment at 40 °C for 24 h resulted in a marked difference in transcript responses with strong upregulation of eight genes, ranging from a 1.52-fold increase in ND4L to a 2.18-fold rise in Cytb transcript levels, although COI and ND5 were reduced to 0.56 and 0.67, respectively, compared with the controls. Overall, these results suggest that at 4 °C, F. kawamurai appears to have entered a hypometabolic state of hibernation, whereas its mitochondrial oxidative phosphorylation was affected at both 2 °C and 40 °C. The majority of mitochondrial PCGs exhibited substantial changes at all three temperatures, indicating that frogs such as F. kawamurai that inhabit tropical or subtropical regions are susceptible to ambient temperature changes and can quickly employ compensating adjustments to proteins involved in the mitochondrial electron transport chain.

Two-Fold ND5 Genes, Three-Fold Control Regions, lncRNA, and the "Missing" ATP8 Found in the Mitogenomes of Polypedates megacephalus (Rhacophridae: Polypedates)

In prior research on the mitochondrial genome (mitogenome) of Polypedates megacephalus, the one copy of ND5 gene was translocated to the control region (CR) and the ATP8 gene was not found. Gene loss is uncommon among vertebrates. However, in this study, we resequenced the mitogenomes of P. megacephalus from different regions using a "primer bridging" approach with Sanger sequencing technologies, which revealed the "missing" ATP8 gene in P. megacephalus as well as three other previously published Polypedates. The mitogenome of this species was found to contain two copies of the ND5 genes and three copies of the control regions. Furthermore, multiple tandem repeats were identified in the control regions. Notably, we observed that there was no correlation between genetic divergence and geographic distance. However, using the mitogenome, gene expression analysis was performed via RT-qPCR of liver samples and it was thus determined that COIII, ND2, ND4, and ND6 were reduced to 0.64 ± 0.24, 0.55 ± 0.34, 0.44 ± 0.21 and 0.65 ± 0.17, respectively, under low-temperature stress (8 °C) as compared with controls (p < 0.05). Remarkably, the transcript of long non-coding RNA (lncRNA) between positions 8029 and 8612 decreased significantly with exposure to low-temperature stress (8 °C). Antisense ND6 gene expression showed a downward trend, but this was not significant. These results reveal that modulations of protein-coding mitochondrial genes and lncRNAs of P. megacephalus play a crucial role in the molecular response to cold stress.

Characterization of Two Mitogenomes of Hyla sanchiangensis (Anura: Hylidae), with Phylogenetic Relationships and Selection Pressure Analyses of Hylidae

Hyla sanchiangensis (Anura: Hylidae) is endemic to China and is distributed across Anhui, Zhejiang, Fujian, Guangdong, Guangxi, Hunan, and Guizhou provinces. The mitogenomes of H. sanchiangensis from two different sites (Jinxiu, Guangxi, and Wencheng, Zhejiang) were sequenced. Phylogenetic analyses were conducted, including 38 mitogenomes of Hylidae from the NCBI database, and assessed the phylogenetic relationship of H. sanchiangensis within the analyzed dataset. Two mitogenomes of H. sanchiangensis showed the typical mitochondrial gene arrangement with 13 protein-coding genes (PCGs), two ribosomal RNA genes (12S rRNA and 16S rRNA), 22 transfer RNA (tRNA) genes, and one non-coding control region (D-loop). The lengths of the 12S rRNA and 16S rRNA genes from both samples (Jinxiu and Wencheng) were 933 bp and 1604 bp, respectively. The genetic distance (p-distance transformed into percent) on the basis of the mitogenomes (excluding the control region) of the two samples was calculated as 4.4%. Hyla sanchiangensis showed a close phylogenetic relationship with the clade of (H. annectans + H. tsinlingensis), which was supported by ML and BI analyses. In the branch-site model, five positive selection sites were found in the clade of Hyla and Dryophytes: Cytb protein (at position 316), ND3 protein (at position 85), and ND5 protein (at position 400) have one site, respectively, and two sites in ND4 protein (at positions 47 and 200). Based on the results, we hypothesized that the positive selection of Hyla and Dryophytes was due to their experience of cold stress in historical events, but more evidence is needed to support this conclusion.

Numerous uncertainties in the multifaceted global trade in frogs’ legs with the EU as the major consumer

The commercial trade in frogs and their body parts is global, dynamic and occurs in extremely large volumes (in the thousands of tonnes/yr or billions of frogs/yr). The European Union (EU) remains the single largest importer of frogs’ legs, with most frogs still caught from the wild. Amongst the many drivers of species extinction or population decline (e.g. due to habitat loss, climate change, disease etc.), overexploitation is becoming increasingly more prominent. Due to global declines and extinctions, new attention is being focused on these markets, in part to try to ensure sustainability. While the trade is plagued by daunting realities of data deficiency and uncertainty and the conflicts of commercial interests associated with these data, it is clear is that EU countries are most responsible for the largest portion of the international trade in frogs’ legs of wild species. Over decades of exploitation, the EU imports have contributed to a decline in wild frog populations in an increasing number of supplying countries, such as India and Bangladesh, as well as Indonesia, Turkey and Albania more recently. However, there have been no concerted attempts by the EU and present export countries to ensure sustainability of this trade. Further work is needed to validate species identities, secure data on wild frog populations, establish reasonable monitored harvest/export quotas and disease surveillance and ensure data integrity, quality and security standards for frog farms. Herein, we call upon those countries and their representative governments to assume responsibility for the sustainability of the trade. The EU should take immediate action to channel all imports through a single centralised database and list sensitive species in the Annexes of the EU Wildlife Trade Regulation. Further, listing in CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) can enforce international trade restrictions. More joint efforts are needed to improve regional monitoring schemes before the commercial trade causes irreversible extinctions of populations and species of frogs.

The Genetic Diversity and the Divergence Time in Extant Primitive Mayfly, Siphluriscus chinensis Ulmer, 1920 Using the Mitochondrial Genome

In this study, the mitochondrial (mt) genomes of Siphluriscus chinensis (Ephemeroptera: Siphluriscidae) were evaluated in specimens collected from two sites in China: Niutou Mountain, Zhejiang Province (S. chinensis NTS) and Leigong Mountain, Guizhou Province (S. chinensis LGS) and were successfully sequenced. The lengths of the mt genomes of S. chinensis NTS and S. chinensis LGS were 15,904 bp (ON729390) and 15,212 bp (ON729391), respectively. However, an in-depth comparison of the two mt genomes showed significant differences between the specimens collected from the two sites. A detailed analysis of the genetic distance between S. chinensis NTS and S. chinensis LGS was undertaken to further achieve an accurate delimitation of S. chinensis. The genetic distance between S. chinensis NTS and the other three species within Siphluriscidae was a high value, above 12.2%. The two mt genomes were used to reconstruct phylogenetic relationships and estimate divergence time. The results demonstrated robust differences between S. chinensis NTS and S. chinensis LGS, which revealed that a kind of cryptic species existed. Maximum likelihood (ML) and Bayesian inference (BI) analyses produced well-supported phylogenetic trees that showed evolutionary relationships between Siphluriscidae (((S. chinensis HQ875717 + S. chinensis MF352165) + S. chinensis LGS) + S. chinensis NTS). The most recent common ancestor (MRCA) of four species within Siphluriscidae began to diversify during the Neogene [11.80 million years ago (Mya); 95% highest posterior densities (HPD) = 6.17–19.28 Mya], and S. chinensis NTS was first to diverge from the branches of S. chinensis LGS. In short, based on mitochondrial genomes, our results showed that the specimens collected from Leigong Mountain, Guizhou Province (S. chinensis LGS) belonged to S. chinensis, and the specimens collected from Niutou Mountain, Zhejiang Province (S. chinensis NTS) were a cryptic species of S. chinensis.

The Genetic Diversity in Thereuonema tuberculata (Wood, 1862) (Scutigeromorpha: Scutigeridae) and the Phylogenetic Relationship of Scutigeromorpha Using the Mitochondrial Genome

Based on morphological characteristics to make species identification, the cryptic species of the Scutigeromorpha can be greatly underestimated. The mitochondrial genome provides a desirable tool for the biological identifications and the discovery of the cryptic species. The capacity to acquire mitochondrial genome sequences has substantially improved in recent years using next-generation sequencing (NGS) technology. On the basis of the next-generation sequencing, we obtained four complete mitochondrial genomes of Thereuonema tuberculata (Wood, 1862) from Nanyang, Henan Province (NY), Nanchang, Jiangxi Province (NC), Jinan, Shandong Province (JN), and Dali, Yunnan Province (DL) in China with GenBank numbers OK513221, OL449685, ON058988 and ON058989, respectively. The lengths of the four mitochondrial genomes ranged from 14,903 to 14,909 bp. The composition and order of genes of the four mitochondrial genomes were identical to the published mitochondrial genome of Scutigera coleoptrata (Linnaeus, 1758) (Scutigeromorpha: Scutigerdae). It was the first time that the tandem repeats in the control region were detected in Scutigeromorpha. We also calculated the corrected pairwise genetic distance of four complete mitochondrial genomes of T. tuberculata, ranging from 7.7 to 15.2%. The results showed that the T.tuberculata NC belonged to the typical sample of T. tuberculata, and T. tuberculata DL was hypothesized as a cryptic species of T. tuberculata. Meanwhile, T. tuberculata NY and T. tuberculata JN were hypothesized as potential cryptic species of T. tuberculata in this study. In both BI and ML trees, the monophyly of Scutigeromorpha, Scolopendromorpha, Geophilomorpha, and Lithobiomorpha was forcefully advocated. Moreover, Scutigeromorpha was recovered as the sister clade of (Scolopendromorpha + (Lithobiomorpha + Geophilomorpha)). Four specimens of T. tuberculata were clustered into one clade, which was the sister to the clade of S. coleoptrata.

Mitochondrial gene expression in different organs of Hoplobatrachus rugulosus from China and Thailand under low-temperature stress

Background

Hoplobatrachus rugulosus (Anura: Dicroglossidae) is distributed in China and Thailand and the former can survive substantially lower temperatures than the latter. The mitochondrial genomes of the two subspecies also differ: Chinese tiger frogs (CT frogs) display two identical ND5 genes whereas Thai tiger frogs (TT frogs) have two different ND5 genes. Metabolism of ectotherms is very sensitive to temperature change and different organs have different demands on energy metabolism at low temperatures. Therefore, we conducted studies to understand: (1) the differences in mitochondrial gene expression of tiger frogs from China (CT frogs) versus Thailand (TT frogs); (2) the differences in mitochondrial gene expression of tiger frogs (CT and TT frogs) under short term 24 h hypothermia exposure at 25 °C and 8 °C; (3) the differences in mitochondrial gene expression in three organs (brain, liver and kidney) of CT and TT frogs.

Results

Utilizing RT-qPCR and comparing control groups at 25 °C with low temperature groups at 8 °C, we came to the following results. (1) At the same temperature, mitochondrial gene expression was significantly different in two subspecies. The transcript levels of two identical ND5 of CT frogs were observed to decrease significantly at low temperatures (P < 0.05) whereas the two different copies of ND5 in TT frogs were not. (2) Under low temperature stress, most of the genes in the brain, liver and kidney were down-regulated (except for COI and ATP6 measured in brain and COI measured in liver of CT frogs). (3) For both CT and TT frogs, the changes in overall pattern of mitochondrial gene expression in different organs under low temperature and normal temperature was brain > liver > kidney.

Conclusions

We mainly drew the following conclusions: (1) The differences in the structure and expression of the ND5 gene between CT and TT frogs could result in the different tolerances to low temperature stress. (2) At low temperatures, the transcript levels of most of mitochondrial protein-encoding genes were down-regulated, which could have a significant effect in reducing metabolic rate and supporting long term survival at low temperatures. (3) The expression pattern of mitochondrial genes in different organs was related to mitochondrial activity and mtDNA replication in different organs.

Cryptic Species Exist in Vietnamella sinensis Hsu, 1936 (Insecta: Ephemeroptera) from Studies of Complete Mitochondrial Genomes

Ephemeroptera (Insecta: Pterygota) are widely distributed all over the world with more than 3500 species. During the last decade, the phylogenetic relationships within Ephemeroptera have been a hot topic of research, especially regarding the phylogenetic relationships among Vietnamellidae. In this study, three mitochondrial genomes from three populations of Vienamella sinensis collected from Tonglu (V. sinensis TL), Chun’an (V. sinensis CN), and Qingyuan (V. sinensis QY) in Zhejiang Province, China were compared to discuss the potential existence of cryptic species. We also established their phylogenetic relationship by combining the mt genomes of 69 Ephemeroptera downloaded from NCBI. The mt genomes of V. sinensis TL, V. sinensis CN, and V. sinensis QY showed the same gene arrangement with lengths of 15,674 bp, 15,674 bp, and 15,610 bp, respectively. Comprehensive analyses of these three mt genomes revealed significant differences in mt genome organization, genetic distance, and divergence time. Our results showed that the specimens collected from Chun’an and Tonglu in Zhejiang Province, China belonged to V. sinensis, and the specimens collected from Qingyuan, Zhejiang Province, China were a cryptic species of V. sinensis. In maximum likelihood (ML) and Bayesian inference (BI) phylogenetic trees, the monophyly of the family Vietnamellidae was supported and Vietnamellidae has a close relationship with Ephemerellidae.

Diversity, distribution and molecular species delimitation in frogs and toads from the Eastern Palaearctic

Biodiversity analyses can greatly benefit from coherent species delimitation schemes and up-to-date distribution data. In this article, we have made the daring attempt to delimit and map described and undescribed lineages of anuran amphibians in the Eastern Palaearctic (EP) region in its broad sense. Through a literature review, we have evaluated the species status considering reproductive isolation and genetic divergence, combined with an extensive occurrence dataset (nearly 85k localities). Altogether 274 native species from 46 genera and ten families were retrieved, plus eight additional species introduced from other realms. Independent hotspots of species richness were concentrated in southern Tibet (Medog County), the circum-Sichuan Basin region, Taiwan, the Korean Peninsula and the main Japanese islands. Phylogeographic breaks responsible for recent in situ speciation events were shared around the Sichuan Mountains, across Honshu and between the Ryukyu Island groups, but not across shallow water bodies like the Yellow Sea and the Taiwan Strait. Anuran compositions suggested to restrict the zoogeographical limits of the EP to East Asia. In a rapidly evolving field, our study provides a checkpoint to appreciate patterns of species diversity in the EP under a single, spatially explicit, species delimitation framework that integrates phylogeographic data in taxonomic research.

Using the 2020 global pandemic as a springboard to highlight the need for amphibian conservation in eastern Asia

Emerging infectious diseases are on the rise in many different taxa, including, among others, the amphibian batrachochytrids, the snake fungal disease and the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) virus, responsible for Coronavirus disease 2019 (COVID-19) in mammals. Following the onset of the pandemic linked to COVID-19, eastern Asia has shown strong leadership, taking actions to regulate the trade of potential vector species in several regions. These actions were taken in response to an increase in public awareness, and the need for a quick reaction to mitigate against further pandemics. However, trade restrictions rarely affect amphibians, despite the risk of pathogen transmission, directly, or indirectly through habitat destruction and the loss of vector consumption. Thus, species that help alleviate the risk of zoonoses or provide biological control are not protected. Hence, in view of the global amphibian decline and the risk of zoonoses, we support the current wildlife trade regulations and support measures to safeguard wildlife from overexploitation. The current period of regulation overhaul should be used as a springboard for amphibian conservation. To mitigate risks, we suggest the following stipulations specifically for amphibians. I) Restrictions to amphibian farming in eastern Asia, in relation to pathogen transmission and the establishment of invasive species. II) Regulation of the amphibian pet trade, with a focus on potential vector species. III) Expansion of the wildlife trade ban, to limit the wildlife-human-pet interface. The resulting actions will benefit both human and wildlife populations, as they will lead to a decrease in the risk of zoonoses and better protection of the environment.

SIGNIFICANCE STATEMENT

There is an increasing number of emerging infectious diseases impacting all species, including amphibians, reptiles and mammals. The latest threat to humans is the virus responsible for COVID-19, and the resulting pandemic. Countries in eastern Asia have taken steps to regulate wildlife trade and prevent further zoonoses thereby decreasing the risk of pathogens arising from wild species. However, as amphibians are generally excluded from regulations we support specific trade restrictions: I) Restrictions to amphibian farming; II) regulation of the amphibian pet trade; III) expansion of the wildlife trade ban. These restrictions will benefit both human and wildlife populations by decreasing the risks of zoonoses and better protecting the environment.

Pattern of Gonadal Sex Differentiation in the Rice Field Frog Hoplobatrachus rugulosus (Anura: Dicroglossidae)

Sex differentiation during gonadal development is diversified among anuran amphibian species. In this study, the anuran experimental species Hoplobatrachus rugulosus was examined. The pattern of gonadal sex differentiation was observed by morphological and histological approaches. The gonad was observed morphologically at Gosner stage 33, while distinct testis and ovary were evident from 3-4 weeks after metamorphosis ended. Histological analysis showed that genital ridge formation began at stage 25 and ovarian differentiation began at stage 36. The developing ovary appeared with numerous primary oogonia, which developed into oocytes, while the medulla regressed to form an ovarian cavity. During metamorphosis, only an ovary was observed. Testicular differentiation seemed to begin later, during the first week after metamorphosis, and occurred via an intersex condition. The intersex gonads contained developing testicular tissue with both normal and atretic oocytes. The fully developed testis was first identified at 6 weeks after metamorphosis. Comparing the times of gonadal differentiation and somatic development revealed that the ovary exhibited a basic rate of differentiation while the testis exhibited a retarded one. These results establish that males of this species develop later than do females, and the testis develops through an intersex gonad, as is evident from its seminiferous cord formation, the presence of testis-ova, and atretic oocytes in the tissue. Thus, the pattern of gonadal sex differentiation in H. rugulosus is an undifferentiated type, in which only female gonads are observed during metamorphosis and intersex and male gonads are observed later. These results are crucial for further research on the sexual development of anurans.

Characterization of the mitochondrial genomes of two toads, Anaxyrus americanus (Anura: Bufonidae) and Bufotes pewzowi (Anura: Bufonidae), with phylogenetic and selection pressure analyses

Mitogenomes are useful in analyzing phylogenetic relationships and also appear to influence energy metabolism, thermoregulation and osmoregulation. Much evidence has accumulated for positive selection acting on mitochondrial genes associated with environmental adaptation. Hence, the mitogenome is a likely target for environmental selection. The family Bufonidae (true toads) has only nine complete and four partial mitogenomes published compared to the 610 known species of this family. More mitogenomes are needed in order to obtain a clearer understanding of the phylogenetic relationships within Bufonidae that are currently controversial. To date, no mitogenomes have been reported from the genera Anaxyrus and Bufotes. Anaxyrus americanus can live in low temperature environments and Bufotes pewzowi can live in high salinity environments. We sequenced the mitogenomes of these two species to discuss the phylogenetic relationships within Bufonidae and the selection pressures experienced by specimens living in low temperature or saline environments. Like other toads, the circular mitogenomes of both species contained the typical 37 genes. Anaxyrus americanus had the highest A+T content of the complete mitogenome among the Bufonidae. In addition, A. americanus showed a negative AT-skew in the control region, whereas Bufotes pewzowi showed a positive AT-skew. Additionally, both toad species had unique molecular features in common: an ND1 gene that uses TTG as the start codon, an extra unpaired adenine (A) in the anticodon arm of trnS (AGY), and the loss of the DHU loop in trnC. The monophyly of Bufonidae was corroborated by both BI and ML trees. An analysis of selective pressure based on the 13 protein coding genes was conducted using the EasyCodeML program. In the branch model analysis, we found two branches of A. americanus and Bufotes pewzowi that were under negative selection. Additionally, we found two positively selected sites (at positions 115 and 119, BEB value > 0.90) in the ND6 protein in the site model analysis. The residue D (119) was located only in A. americanus and may be related to adaptive evolution in low temperature environments. However, there was no evidence of a positively selected site in Bufotes pewzowi in this study.

The complete mitochondrial genome of Pyxicephalus adspersus: high gene rearrangement and phylogenetics of one of the world's largest frogs

The family Pyxicephalidae including two subfamilies (Cacosterninae and Pyxicephalinae) is an ecologically important group of frogs distributed in sub-Saharan Africa. However, its phylogenetic position among the Anura has remained uncertain. The present study determined the complete mitochondrial genome sequence of Pyxicephalus adspersus, the first representative mitochondrial genome from the Pyxicephalinae, and reconstructed the phylogenetic relationships within Ranoidae using 10 mitochondrial protein-coding genes of 59 frog species. The P. adspersus mitochondrial genome showed major gene rearrangement and an exceptionally long length that is not shared with other Ranoidae species. The genome is 24,317 bp in length, and contains 15 protein-coding genes (including extra COX3 and Cyt b genes), four rRNA genes (including extra 12S rRNA and 16S rRNA genes), 29 tRNA genes (including extra tRNALeu (UAG), tRNALeu (UUR), tRNAThr , tRNAPro , tRNAPhe , tRNAVal , tRNAGln genes) and two control regions (CRs). The Dimer-Mitogenome and Tandem duplication and random loss models were used to explain these gene arrangements. Finally, both Bayesian inference and maximum likelihood analyses supported the conclusion that Pyxicephalidae was monophyletic and that Pyxicephalidae was the sister clade of (Petropedetidae + Ptychadenidae).

The complete mitochondrial genome of Fejervarya kawamurai (Anura: Dicroglossidae) and its phylogeny

The mitochondrial genome of Fejervarya kawamurai is a circular molecule of 17,650 bp in length, containing 13 protein-coding genes, two rRNA genes, 23 tRNA genes (including an extra tRNA-Met), and the control region. The AT content of the whole genome is 56.9%. In Bayesian inference (BI) and Maximum likelihood (ML) analyses, we found that F. kawamurai is a sister clade to F. multistriata and F. limnocharis. The monophyly of Fejervarya, Quasipaa, Nanorana was well supported (1.00 in BI and 100% in ML).

The complete mitochondrial genome of the hybrid of Hoplobatrachus chinensis (♀)×H. rugulosus (♂) and its phylogeny

The complete mitochondrial genome sequence of the hybrid of Hoplobatrachus chinensis (♀) × H. rugulosus (♂) was obtained in this study. The circular mitochondrial genome was 20,282 bp in length (including extra ND5 genes). Compared with the complete mitogenome of the parents, the results indicated that the mitochondria of the hybrid tiger frog was consistent with a maternal inheritance. Phylogenetic analyses using concatenated nucleotide sequences of the 11 protein-coding genes with two different methods (maximum likelihood and MrBayes analysis) both highly supported a close relationship of the hybrid frogs with the Chinese tiger frog (=H. chinensis).

Complete mitochondrial genomes of Nanorana taihangnica and N. yunnanensis (Anura: Dicroglossidae) with novel gene arrangements and phylogenetic relationship of Dicroglossidae

BACKGROUND

Complete mitochondrial (mt) genomes have been used extensively to test hypotheses about microevolution and to study population structure, phylogeography, and phylogenetic relationships of Anura at various taxonomic levels. Large-scale mt genomic reorganizations have been observed among many fork-tongued frogs (family Dicroglossidae). The relationships among Dicroglossidae and validation of the genus Feirana are still problematic. Hence, we sequenced the complete mt genomes of Nanorana taihangnica (=F. taihangnica) and N. yunnanensis as well as partial mt genomes of six Quasipaa species (dicroglossid taxa), two Odorrana and two Amolops species (Ranidae), and one Rhacophorus species (Rhacophoridae) in order to identify unknown mt gene rearrangements, to investigate the validity of the genus Feirana, and to test the phylogenetic relationship of Dicroglossidae.

RESULTS

In the mt genome of N. taihangnica two trnM genes, two trnP genes and two control regions were found. In addition, the trnA, trnN, trnC, and trnQ genes were translocated from their typical positions. In the mt genome of N. yunnanensis, three control regions were found and eight genes (ND6, trnP, trnQ, trnA, trnN, trnC, trnY and trnS genes) in the L-stand were translocated from their typical position and grouped together. We also found intraspecific rearrangement of the mitochondrial genomes in N. taihangnica and Quasipaa boulengeri. In phylogenetic trees, the genus Feirana nested deeply within the clade of genus Nanorana, indicating that the genus Feirana may be a synonym to Nanorana. Ranidae as a sister clade to Dicroglossidae and the clade of (Ranidae + Dicroglossidae) as a sister clade to (Mantellidae + Rhacophoridae) were well supported in BI analysis but low bootstrap in ML analysis.

CONCLUSIONS

We found that the gene arrangements of N. taihangnica and N. yunnanensis differed from other published dicroglossid mt genomes. The gene arrangements in N. taihangnica and N. yunnanensis could be explained by the Tandem Duplication and Random Loss (TDRL) and the Dimer-Mitogenome and Non-Random Loss (DMNR) models, respectively. The invalidation of the genus Feirana is supported in this study.