Paradactylodon

Abstract: Paradactylodon, a genus of Hynobiidae, is distributed in mountainous regions of the Middle East. This genus comprises three species, Paradactylodon mustersi (Afghanistan), Paradactylodon persicus, and Paradactylodon gorganensis (Iran). Initially, P. persicus was reported from Talysh Mountains, and afterward, P. gorganensis was described from the eastern Alborz Mountains. Although these two Iranian Paradactylodon species were distinguished based on morphological features, there are arguments about their systematic status. In this contribution, 30 samples of hynobiid salamanders were collected from Talysh and Alborz Mountains and the phylogenetic relationship between the two species was assessed using two mtDNA markers (COI and 16S). Additionally, in order to survey the potential habitat suitability for the species, Species Distribution Models (SDMs) were performed and projected on climate scenarios that reflect current and past (6 ky and 21 ky before present) conditions. Our results indicated that P. gorganensis is nested within P. persicus. Overall, both SDM and molecular analyses suggest that the Iranian Paradactylodon population was affected by the Quaternary glacial period, and according to haplotype networks, haplotype diversity was higher in the western part of the distribution range of the species. Given the low genetic distance among all samples, we suggest P. gorganensis be synonymized with P. persicus. Considering the conservational values and numerous threats that this endemic species is facing, we encourage a revision of the IUCN Red List category of the species immediately.

Abstract: The Hyrcanian Forests present a unique Tertiary relict ecosystem, covering the northern Elburz and Talysh Ranges (Iran, Azerbaijan), a poorly investigated, unique biodiversity hotspot with many cryptic species. Since the 1970s, two nominal species of Urodela, Hynobiidae, Batrachuperus (later: Paradactylodon) have been described: Paradactylodon persicus from northwestern and P. gorganensis from northeastern Iran. Although P. gorganensis has been involved in studies on phylogeny and development, there is little data on the phylogeography, systematics, and development of the genus throughout the Hyrcanian Forests; genome-wide resources have been entirely missing. Given the huge genome size of hynobiids, making whole genome sequencing hardly affordable, we aimed to publish the first transcriptomic resources for Paradactylodon from an embryo and a larva (9.17 Gb RNA sequences; assembled to 78,918 unigenes). We also listed 32 genes involved in vertebrate sexual development and sex determination. Photographic documentation of the development from egg sacs across several embryonal and larval stages until metamorphosis enabled, for the first time, comparison of the ontogeny with that of other hynobiids and new histological and transcriptomic insights into early gonads and timing of their differentiation. Transcriptomes from central Elburz, next-generation sequencing (NGS) libraries of archival DNA of topotypic P. persicus, and GenBank-sequences of eastern P. gorganensis allowed phylogenetic analysis with three mitochondrial genomes, supplemented by PCR-amplified mtDNA-fragments from 17 museum specimens, documenting <2% uncorrected intraspecific genetic distance. Our data suggest that these rare salamanders belong to a single species P. persicus s.l. Humankind has a great responsibility to protect this species and the unique biodiversity of the Hyrcanian Forest ecosystems.

Abstract: To elucidate the effect of natural selection on the evolution of mitochondrial DNA (mtDNA) in Asiatic salamanders of the family Hynobiidae, nucleotide sequences of 12 protein-coding genes were analyzed. Using a mixed effects model of evolution, it was found that, in spite of the pronounced effect of negative selection on the mtDNA evolution in Hynobiidae (which is typical for the animals in general), two phylogenetic clusters, the West Asian one, represented by the genera Ranodon and Paradactylodon, and North Eurasian one, represented by the genus Salamandrella, were formed under the influence of episodic positive selection. Analysis of protein sequences encoded by the mitochondrial genome also supported the influence of positive selection on the evolution of Hynobiidae at some stages of their cladogenesis. It is suggested that the signatures of adaptive evolution detected in the mtDNA of Hynobiidae were determined by the complex and long-lasting history of their formation, accompanied by adaptation to the changing environment.