Marine species exhibiting wide distributional ranges are frequently subdivided into discrete genetic units over limited spatial scales. This is often due to specific life-history traits or ...oceanographic barriers that prevent gene flow. Fine-scale sampling studies revealed distinct phylogeographic patterns in the northeastern Atlantic and the Mediterranean, ranging from panmixia to noticeable population genetic structure. Here, we used mitochondrial sequence data to analyse connectivity in the bogue Boops boops throughout most of its widespread distribution. Our results identified the existence of three clades, one comprising specimens from the Azores and eastern Atlantic/Mediterranean, another with individuals from the Canary Islands, Madeira and Cape Verde archipelagos, and the third with samples from Mauritania only. One of the branches of the northern subtropical gyre (Azores Current) that drifts towards the Gulf of Cádiz promotes a closer connection between the Azores, southern Portugal and the Mediterranean B. boops populations. The Almería-Oran Front, widely recognised as an oceanographic barrier for many organisms to cross the Atlantic-Mediterranean divide, does not seem to affect the dispersal of this benthopelagic species. The southward movement of the Cape Verde Frontal Zone during the winter, combined with the relatively short duration of the pelagic larval stage of B. boops, may be potential factors for preventing the connectivity between the Atlantic oceanic archipelagos and Mauritania shaping the genetic signature of this species.
Despite being one of the most speciose fish families in the Mediterranean Sea, knowledge about the diversity of gobies (Actinopterygii: Gobiidae) in this sea is still unsatisfactory, as documented by ...recent descriptions of a number of new species. Although very common in shallow water, Gobius incognitus Kovačić & Šanda, 2016, had escaped attention until 2016, when it was discovered. Due to its overall superficial morphological similarity, G. incognitus used to be confused with a much rarer species, Gobius bucchichi Steindachner, 1870, which was considered one of the most common shallow-water gobies in the Mediterranean Sea. In this work, we tested the suitability of the genetic data (mitochondrial gene encoding cytochrome b) for identifying and distinguishing between these two goby species, and assessed the congruency between the distribution records based on genetic data and those based on morphological identification. We analysed material of 304 specimens of G. incognitus and G. bucchichi from 49 localities covering a considerable part of the Mediterranean Sea, Black Sea, and the Atlantic Ocean near Gibraltar, representing 19 geographically well-separated areas. We detected 270 sequences of G. incognitus, and only 34 of G. bucchichi. In both species, a high haplotype variability was observed. The sequence species identity matched morphological identification for all specimens for which vouchers were available. The mean uncorrected p-distance between G. incognitus and G. bucchichi was 13%, while the mean intraspecific distances were much lower (0.63% and 0.68%, respectively). We found 79 fixed mutations between these two species. Data on distribution based on genetic identification are completely congruent with published results based on morphological identification. The results of this study support molecular methods as a reliable tool for distinguishing morphologically similar fish species, which is particularly useful when only tissue is available for determination.
Abstract
The high diversity of extant gobiids (Gobiidae: Teleostei) makes taxonomic and phylogenetic interpretation of fossil members of the clade a difficult task. To facilitate future taxonomic and ...systematic work on the group, we have assembled a morphological reference database encompassing skeletal characters, an otolith atlas and otolith morphometric data of 25 present-day species from the European Gobius lineage (s.l.) that represent 18 different genera and include all nine sublineages. We show that: (1) skeletal traits and morphometric otolith variables can be diagnostic for a sublineage; (2) otolith morphology allows identification at the genus and species levels; and (3) the number of anal-fin rays and details of the otolith margins can be used to discriminate closely related dwarf gobies. The skeletal and otolith characters are largely stable in the marine gobies analysed here, whereas freshwater gobies (Padogobius, Ponto-Caspian gobies) are far more variable. This might be related to the conquest by Padogobius and Ponto-Caspian gobies of freshwater and low-salinity habitats, in which environmental conditions can fluctuate widely. We anticipate that the database presented here can be used as a valuable reference tool to assess the relationships of fossil gobiids and increase our knowledge of the evolutionary history of the group as a whole.
PDF
