Origin of sex chromosomes in six groups of Rana rugosa frogs inferred from a sex‐linked DNA marker

Abstract

Each vertebrate species, as a general rule, has either the XX/XY or ZZ/ZW chromosomes by which sex is determined. However, the Japanese Rana (R.) rugosa frog is an exception, possessing both sex-determining combinations within one species, varying with region of origin. We collected R. rugosa frogs from 104 sites around Japan and South Korea and determined the nucleotide sequences of the mitochondrial 12S ribosomal RNA gene. Based on the sequences, R. rugosa frogs were divided into four groups from Japan and one from South Korea. The ZZ/ZW type is reportedly derived from the XX/XY type, although recently a new ZZ/ZW type of R. rugosa was reported. However, it still remains unclear from where the sex chromosomes in the five groups of this species were derived. In this study, we successfully isolated a sex-linked DNA maker and used it to classify R. rugosa frogs into several groupings. From the DNA marker as well as from nucleotide analysis of the promoter region of the androgen receptor (AR) gene, we identified another female heterogametic group, designated, West-Central. The sex chromosomes in the West-Central originated from the West and Central groups. The results indicate that a sex-linked DNA marker is a verifiable tool to determine the origin of the sex chromosomes in R. rugosa frogs in which the sex-determining system has changed, during two independent events, from the male to female heterogamety.

Novel genetic sex markers reveal high frequency of sex reversal in wild populations of the agile frog (Rana dalmatina) associated with anthropogenic land use

“…Alternatively, a mutation on chromosome Y at Rds3 (e.g. at the primer binding site, resulting in null allele) or a more complicated sex‐determination system present on the East side could cause spatial genetic population structure (Oike et al., 2017; Rodrigues et al., 2014). These alternative explanations could be ruled out using phylogeographic information based on neutral autosomal loci in our populations, or by sexing laboratory‐raised froglets from the eastern populations as well, but unfortunately, such data are not available.…”

Genetic and morphological variation analyses of Glandirana rugosa with description of a new species (Anura, Ranidae)

“…Within frogs long called G. rugosa, several names were given for each geographic and genetic population (Nishioka et al 1993;Ogata et al 2008;Oike et al 2017Oike et al , 2020. In this study, we follow the known mtDNA phylogeny and recognize five groups: East (E), North (N), Central (C), and West (W), and Southeastern Kyushu (se-K).…”

“…For analyzing intraspecific genetic variation of G. rugosa, allozyme electrophoresis (Nishioka et al 1993), mtDNA (Ogata et al 2008;Oike et al 2017Oike et al , 2020Sekiya et al 2010), and sex-linked genes (Ogata et al 2008) have hitherto been applied. However, these frog species apparently have experienced evolution in which introgressive hybridization occurred between populations once differentiated (Ogata et al 2008), and analyses targeting only particular portions of the genome will probably not reflect their true evolutionary history.…”

Taxonomic identity of four groups of Glandirana rugosa (Anura, Ranidae) in Japan revealed by the complete mitochondrial genome sequence analysis

“…Later, the species was transferred into the genus Glandirana (Frost 2013). The Glandirana rugosa is now separated into four groups, designated as the West, East, North, and Central groups, based on the mitochondrial 12S rRNA gene (Oike et al 2017). This suggests that the Japanese G. rugosa probably consists of cryptic species.…”

“…The West group likely represents G. rugosa s.str., because it contains individuals from the supposed type locality, Nagasaki (Oike et al. 2017 ). We argue that the East and Central groups should have a new species name.…”