Interspecies introgressive hybridization in spiny frogs Quasipaa (Family Dicroglossidae) revealed by analyses on multiple mitochondrial and nuclear genes.

Introgression may lead to discordant patterns of variation among loci and traits. For example, previous phylogeographic studies on the genus Quasipaa detected signs of genetic introgression from genetically and morphologically divergent Quasipaa shini or Quasipaa spinosa. In this study, we used mitochondrial and nuclear DNA sequence data to verify the widespread introgressive hybridization in the closely related species of the genus Quasipaa, evaluate the level of genetic diversity, and reveal the formation mechanism of introgressive hybridization. In Longsheng, Guangxi Province, signs of asymmetrical nuclear introgression were detected between Quasipaa boulengeri and Q. shini. Unidirectional mitochondrial introgression was revealed from Q. spinosa to Q. shini. By contrast, bidirectional mitochondrial gene introgression was detected between Q. spinosa and Q. shini in Lushan, Jiangxi Province. Our study also detected ancient hybridizations between a female Q. spinosa and a male Q. jiulongensis in Zhejiang Province. Analyses on mitochondrial and nuclear genes verified three candidate cryptic species in Q. spinosa, and a cryptic species may also exist in Q. boulengeri. However, no evidence of introgressive hybridization was found between Q. spinosa and Q. boulengeri. Quasipaa exilispinosa from all the sampling localities appeared to be deeply divergent from other communities. Our results suggest widespread introgressive hybridization in closely related species of Quasipaa and provide a fundamental basis for illumination of the forming mechanism of introgressive hybridization, classification of species, and biodiversity assessment in Quasipaa.

The advertisement calls of Quasipaa shini (Ahl, 1930) (Anura: Dicroglossidae).

The genus Quasipaa (Family Dicroglossidae) is currently composed of 11 species distributed in China and Southeast Asia: Quasipaa acanthophora (Dubois & Ohler 2009), Q. boulengeri (Günther 1889), Q. courtoisi (Angel 1922), Q. delacouri (Angel 1928), Q. exilispinosa (Liu & Hu, 1975), Q. fasciculispina (Inger 1970), Q. jiulongensis (Huang & Liu, 1985), Q. shini (Ahl 1930), Q. spinosa (David 1875), Q. verrucospinosa (Bourret 1937), Q. yei (Chen, Qu & Jiang 2002) (Frost 2016). These species are morphologically similar, and their taxonomy is subject to controversy (Che et al. 2009). Analyses of nuclear and mitochondrial genes suggest the genus likely encompass additional cryptic species (Ye et al. 2013). Bioacoustics has contributed to studies on the taxonomy of the genus (Ye et al. 2013; Shen et al. 2015), however, to date, only the advertisement calls of Q. spinosa are known (Yu & Zheng 2009; Chen et al. 2012; Shen et al. 2015). Here, we describe the advertisement calls of Q. shini, which inhabits streams in the southern part of central China(Guizhou, Hunan, Guangxi and Jiangxi) and is characterized by the presence of keratinized skin spines on the lateral surfaces of the body.

Different ionic conditions prompt NHE2 and NHE3 translocation to the plasma membrane.

We tested whether NHE3 and NHE2 Na(+)/H(+) exchanger isoforms were recruited to the plasma membrane (PM) in response to changes in ion homeostasis. NHE2-CFP or NHE3-CFP fusion proteins were functional Na(+)/H(+) exchangers when transiently expressed in NHE-deficient PS120 fibroblasts. Confocal morphometry of cells whose PM was labeled with FM4-64 measured the fractional amount of fusion protein at the cell surface. In resting cells, 10-20% of CFP fluorescence was at PM and stable over time. A protocol commonly used to activate the Na(+)/H(+) exchange function (NH(4)-prepulse acid load sustained in Na(+)-free medium), increased PM percentages of PM NHE3-CFP and NHE2-CFP. Separation of cellular acidification from Na(+) removal revealed that only NHE3-CFP translocated when medium Na(+) was removed, and only NHE2-CFP translocated when the cell was acidified. NHE2/NHE3 chimeric proteins demonstrate that the Na(+)-removal response element resides predominantly in the NHE3 cytoplasmic tail and is distinct from the acidification response sequence of NHE2.