Taxonomic diversity and distribution of the genus Proterorhinus (Teleostei: Gobiidae) in the Caucasus biodiversity hotspot with conservation implications

Abstract

1. The magnitude of biodiversity in the Caucasus biodiversity hotspot remains largely unknown, because species diversity is usually assessed based on morphology. One ecologically important fish group with cryptic diversity is the tubenose goby members of the genus Proterorhinus, for which recent studies have shown that species assignments are difficult.2. Using mitochondrial COI data (652 bp) from 59 widespread localities, a phylogenetic and phylogeographical framework is applied to assess the specieslevel status of different Caucasian populations of Proterorhinus, previously classified as Proterorhinus nasalis. We infer how post-Miocene evolution of the Caspian basin may have shaped the present diversity and distribution of P. nasalis. The results suggest thatProterorhinus diversity in the Caucasus has been underestimated: (i) specimens from Azerbaijan and the Samur River delta on the Caspian shore share haplotypes with Proterorhinus semipellucidus; (ii) specimens from the Black Sea shore at Kodori Bay, the Kintrishi, and Mcnishta rivers of Georgia share haplotypes with two lineages of Proterorhinus semilunaris; and (iii) south Caspian specimens from the Iranian sites studied belong to P. nasalis. 4. A pattern of low haplotype and nucleotide diversity was observed in P. nasalis, suggesting a founder event by a single or a few mitochondrial haplotypes following the isolation between the Black and Caspian seas in the early Pliocene or a demographic bottleneck during salinity and lake-level changes in the Babadjanian, Balakhanian and Tyurkyanian stages. 5. Integrative use of genetic assessments for monitoring Caucasian biodiversity will help to understand the extent of biodiversity and reliably assess threat status for critical species. Considering the species' narrow distribution range, small population size and low genetic variability, P. nasalis may merit an upgrade from Least Concern to an IUCN Red List Threatened Category (i.e. Vulnerable, Endangered or Critically Endangered).

An integrative insight into the diversity, distribution, and biogeography of the freshwater endemic clade of the Ponticola syrman group (Teleostei: Gobiidae) in the Caucasus biodiversity hotspot

“…The ancestor of P. iranicus + P. patimari adapted to freshwater, while “marine” P. syrman adapted to increased salinity of the Caspian Sea in the Tyurkyanian period, so the ecological gap and isolation between them also increased. A similar effect has been outlined for evolution of several other aquatic species in the south Caspian basin (e.g., Sands et al, 2019 ), including the radiation of Ponticola hircaniaensis (Zarei, Esmaeili, Kovačić, et al, 2022a ) and a possible bottleneck in Proterorhinus nasalis (Zarei, Esmaeili, Schliewen, & Abbasi, 2022b ). Evolution in south Caspian refugia have been also reported for several species in other groups, e.g., rock lizards of the genus Darevskia , Arribas, 1999 (Ahmadzadeh et al, 2013 ; Saberi‐Pirooz et al, 2018 ), the Caspian green lizard Lacerta strigata Eichwald, 1831 (Saberi‐Pirooz et al, 2021 ), the Caucasian pit viper Gloydius halys caucasicus (Nikolsky, 1916) (Asadi et al, 2019 ), the Anatolian mountain frogs of the genus Rana Linnaeus, 1758 (Veith et al, 2003 ), and the freshwater crab Potamon ibericum (de Bieberstein, 1808) (Parvizi et al, 2018 ).…”

“…The ancestor of P. iranicus + P. patimari adapted to freshwater, while "marine" P. syrman adapted to increased salinity of the Caspian Sea in the Tyurkyanian period, so the ecological gap and isolation between them also increased. A similar effect has been outlined for evolution of several other aquatic species in the south Caspian basin (e.g., Sands et al, 2019), including the radiation of Ponticola hircaniaensis (Zarei, Esmaeili, Kovačić, et al, 2022a) and a possible bottleneck in Proterorhinus nasalis (Zarei, Esmaeili, Schliewen, & Abbasi, 2022b).…”

Otoliths of Caspian gobies (Teleostei: Gobiidae): Morphological diversity and phylogenetic implications

“…Fish sampling was approved by the Ethic Committee of Biology Department, Shiraz University (SU-9630190). Taxonomic identifications were accomplished using available keys, primary taxonomic literature, and DNA sequence analysis [ 5 , 7 , 30 , 31 , 33 – 35 , 39 , 41 ]. The skull of each specimen was opened dorsally with a scalpel and the left sagittal otolith was extracted using fine forceps, cleaned in 5% KOH solution (~5 min), washed in distilled water (~5 min), and dried at room temperature.…”

“…Since the mid-2000s, Caspian Sea gobiid studies have examined the molecular phylogeny and biogeography of a limited number of species [7,29,30,35], with several new species described in recent years [5,[36][37][38][39]. On the other hand, detailed discussions of their morphological characters have become rare, and these molecular-based studies suggest phylogenetic relationships that have not been considered with morphological information and therewith inspire new comparative studies to test those relationships.…”