Biogeography of land snail genus Acusta (Gastropoda: Camaenidae): Diversification on East Asian islands.

East Asia has highly diverse and endemic biota due to its complex geological and climatic history and its diversified topography. The continental and insular distributions of land snail genus Acusta in East Asia provide a good opportunity to compare the evolutionary processes in this group under different biogeographical conditions. In this study, we inferred the evolutionary history of the land snail genus Acusta by a molecular phylogeny and investigated how the palaeogeographic events shaped species diversity and the distribution of the Acusta genus within the island arc. A concatenated dataset generated from sequences of one nuclear (ITS2) and two mitochondrial (16S, COI) gene fragments, include most of nominal taxa of the genus, four related species and one outgroup. We constructed the phylogeny and the evolutionary history of the genus through maximum-likelihood and Bayesian inference methods, using a Bayesian molecular clock and ancestral range estimation. Our results suggested that currently recognized species in Acusta are polyphyletic. The traditionally accepted concept of the affinity of Acusta and Bradybaena is not supported. The hypothesis of colonization via land bridges during the Pleistocene glaciations for the biota of East Asian islands is not supported. Instead, the origin and diversification of the genus Acusta was dated to the late Miocene-Pliocene from an area around North and Northeast China to South China and East Asian islands Three major evolutionary lineages were identified. Two of the major lineages demonstrate distinct evolutionary histories, as sympatric speciation is the major speciation process for the continental clade, while the insular clade originated from founder events. Taiwan functioned as an important source of diversification for species on the East Asian islands possibly through passive dispersal of different mechanisms. The sea level fluctuations caused by the Pleistocene glacial cycles play a role in the subsequent dispersion and diversification of species of the continental clade, such as the more recent range expansion of A. redfieldi from South China to Taiwan and Japan.

Descriptions of four new dextral land snails of the genus Camaena (Gastropoda, Eupulmonata, Camaenidae) from south China.

In this study, four new dextral camaenid from China are reported, based on shell morphology, reproductive system anatomy, and molecular phylogenetic analyses: Camaena funingensis Zhou, Wang & Lin, sp. nov., Camaena gaolongensis Zhou, Wang & Lin, sp. nov., Camaena maguanensis Zhou, Wang & Hu, sp. nov., and Camaena yulinensis Zhou, Wang & Hu, sp. nov. Detailed descriptions of the morphological characteristics including shells and genitalia, DNA sequences, and living environments of the four new species are provided, with further comparisons with congeners.

The mitochondrial genome of the land snail Camaenella platyodon (Pfeiffer, 1846) (Stylommatophora, Camaenidae).

The complete mitochondrial genome (mitogenome) of Chinese endemic snail Camaenella platyodon (Pfeiffer, 1846) has been sequenced and annotated in this study. The entire circular genome is 13,985 bp in size and represents the third camaenid mt genome, with 2 ribosomal RNA genes, 22 transfer RNA genes, 13 protein-coding genes. All of genes are divided into two groups, including 24 genes on the majority coding strand (J strand) and others on the minority coding strand (N strand). Phylogenetic analysis of 13 protein-coding genes suggests that C. platyodon is closely related to the species in family Camaenidae.

The mitochondrial genome of the land snail Theba pisana (Müller, 1774) (Stylommatophora: Helicidae): the first complete sequence in the genus Theba.

The complete mitochondrial genome of the white garden snail Theba pisana (Müller, 1774) has been sequenced and annotated in this study. The entire circular genome is 14,795 bp in size and represents the first mitochondrial genome in the genus Theba, with two ribosomal RNA genes, 22 transfer RNA genes, 13 protein coding genes. All of genes are divided into two groups, including 24 genes on the majority coding strand (J strand) and others on the minority coding strand (N strand).The phylogeny supports the relationship of species in Helicidae.

The mitochondrial genome of the land snail Cernuella virgata (Da Costa, 1778): the first complete sequence in the family Hygromiidae (Pulmonata, Stylommatophora).

The land snail Cernuella virgata (da Costa, 1778) is widely considered as a pest to be quarantined in most countries. In this study, the complete mitochondrial genome of Cernuella virgata is published. The mitochondrial genome has a length of 14,147 bp a DNA base composition of 29.07% A, 36.88% T, 15.59% C and 18.46% G, encoding 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes and two ribosomal RNA (rRNA) genes. The complete nucleotide composition was biased toward adenine and thymine, A+T accounting for 69.80%. Nine PCGs and 14 tRNA genes are encoded on the J strand, and the other four PCGs and eight tRNA genes are encoded on the N strand. The genome also includes 16 intergenic spacers. All PCGs start strictly with ATN, and have conventional stop codons (TAA and TAG). All tRNAs fold into the classic cloverleaf structure, except tRNA(Arg) , tRNA(Ser(UCN)) , tRNA(Ser(AGN)) and tRNA(Pro) . The first three lack the dihydrouridine arm while the last lacks the TψC arm. There are 502 bp long noncoding regions and 418bp long gene overlaps in the whole mitochondrial genome, accounting for 3.54% and 2.95% of the total length respectively. Phylogenetic analyses based on the sequences of the protein coding genes revealed a sister group relationship between the Hygromiidae and the Helicidae.

Descriptions of two new species of the genus Camaena from Guangxi, China (Gastropoda, Stylommatophora, Camaenidae).

The sinistral Camaena species are mainly distributed in southern China and northern Vietnam. There is a total of eight species or subspecies of sinistral Camaena recorded at present. By systematically collecting specimens in Guangdong, Guangxi and Yunnan in southern China and the northern areas in Vietnam, two new species, Camaena lingyunensis Zhou & Lin, sp. n. and Camaena detianensis Zhou & Lin, sp. n. have been discovered. These new species are here characterised based on the comparison of shells, their reproductive system, the molecular phylogenetic analyses of the mitochondrial genes COI and 16S, and the nuclear gene ITS2. Detailed descriptions of the morphological characters, the DNA sequences, and the habitat of the two new species are given. Differential comparisons with related species are provided as well as a key to the sinistral species of Camaena.

Revision of sinistral land snails of the genus Camaena (Stylommatophora, Camaenidae) from China based on morphological and molecular data, with description of a new species from Guangxi, China.

The camaenid land snail genus Camaena is widely distributed throughout Southeast Asia. Thirteen species are found in China alone. Among these, Camaena cicatricosa (Müller, 1774) is the most widely distributed species, including four subspecies, Camaena cicatricosa ducalis (Ancey, 1885), Camaena cicatricosa inflata (Möllendorff, 1885), Camaena cicatricosa obtecta (Fischer, 1898) and Camaena cicatricosa connectens (Dautzenberg & Fischer, 1906). The systematics of these taxa is revised herein based on comparative shell morphology and anatomy as well as analyses of DNA sequences of two mitochondrial genes (COI, 16S rRNA) and one nuclear marker, ITS2. We found that all subspecies form well-supported clades in a molecular phylogeny and are well-differentiated from each other by genetic distances that are consistent with amounts of interspecific differentiation. In addition, they clearly differ from each other in reproductive features. Based on these observations, we elevate all four subspecies to the rank of full species. Moreover, based on morphological and mitochdondrial differentiation, we describe a new species, Camaena poyuensis sp. n. from Guangxi, China. The new species conspicuously differs from its sibling species Camaena cicatricosa in having a larger and more depressed shell, a completely covered umbilicus, more or less purplish peristome, an obtuse angle at the junction of the basal and columellar lip, longer pedunculus of the bursa copulatrix, thicker epiphallus and penis, and short conic verge. Previous named species are also redescribed on their shell and anatomical characters, because the original descriptions are uninformative.

Revision of three camaenid and one bradybaenid species (Gastropoda, Stylommatophora) from China based on morphological and molecular data, with description of a new bradybaenid subspecies from Inner Mongolia, China.

We have revised the taxonomy of three camaenid and one bradybaenid species from China and described one new subspecies of the genus Bradybaena (Family Bradybaenidae) from Inner Mongolia, China. The genitalia of three Satsuma (Family Camaenidae) species S. mellea stenozona (Moellendorff, 1884), S. meridionalis (Moellendorff, 1884), comb. n. and S. uncopila (Heude, 1882), comb. n. assigned to the genus Bradybaena previously,lack a dart sac and mucous glands. Moreover, the molecular phylogeny has revealed close relationships between the three species and the genus Satsuma. Two species, S. stenozona (Moellendorff, 1884) from Fuzhou and Ganesella citrina Zilch, 1940 from Wuyi Mountain, are considered as synonymous and should be a subspecies of S. mellea mellea (Pfeiffer, 1866) because of the morphological and molecular similarities. Meanwhile, the other two are placed in the genus Satsuma: S. meridionalis (Moellendorff, 1884), comb. n. and S. uncopila (Heude, 1882), comb. n. G. virgo Pilsbry, 1927 differs from species of the genera Ganesella and Satsuma not only in its shell, but also in anatomical characters, such as having a dart sac and mucous gland, and lacking a flagellum. Additionally, phylogenetic analyses highly support the sister relationship with other Bradybaena species. Thus, placement of G. virgo Pilsbry, 1927 in the genus Bradybaena issuggested.

The mitochondrial genome of the land snail Camaenacicatricosa (Müller, 1774) (Stylommatophora, Camaenidae): the first complete sequence in the family Camaenidae.

The complete mitochondrial (mt) genome of the snail Camaenacicatricosa (Müller, 1774) has been sequenced and annotated in this study. The entire circular genome is 13,843 bp in size and represents the first camaenid mt genome, with content of 31.9%A, 37.9%T, 13.5%C and 16.7%G. Gene content, codon usage and base organization show similarity to a great extent to the sequenced mt genome from Stylommatophora, whereas, gene order is different from them, especially the positions of tRNA(Cys) , tRNA(Phe) , COII, tRNA(Asp) , tRNA(Gly) , tRNA(His) and tRNA(Trp) . All protein coding genes use standard initiation codons ATN except for COII with GTG as start signal. Conventional stop codons TAA and TAG have been assigned to all protein coding genes. All tRNA genes possess the typical clover leaf structure, but the TψC arm of tRNA(Asp) and dihydrouridine arm of tRNA(Ser(AGN)) only form a simple loop. Shorter intergenic spacers have been found in this mt genome. Phylogenetic study based on protein coding genes shows close relationship of Camaenidae and Bradybaenidae. The presented phylogeny is consistent with the monophyly of Stylommatophora.