Recent diversification in an ancient lineage of Notothenioid fishes (Bovichtus: Notothenioidei)

Fitting Together the Evolutionary Puzzle pieces of the Immunoglobulin T Gene from Antarctic Fishes

“…Based on these observations, we propose a timeline for the loss of the Cτ2 exon, which might have occurred after the divergence of Pseudaphritioidea from the main notothenioid lineage, but before the split between Eleginopsioidea and Cryonotothenioidea. This temporal placement would be consistent with the recently revised phylogeny of Notothenioidei [35]. Several observations suggest that this process may have been initiated by the modifications of the two introns flanking the Most certainly, the reconstruction of this scenario suffers from missing data and significant "evolutionary gaps" due to the high phylogenetic distance between the genera we took into account [35].…”

“…As expected, the sequences from the Bovichtidae C. gobio and B. diacanthus were placed as outgroups in a monophyletic clade at the base of the notothenioid IgT tree, whereas the sequences from P. urvillii and E. maclovinus occupied, with high statistical support (100% posterior probability in both cases), intermediate positions. These were well consistent with the recently proposed position of Pseudaphritioidea and Eleginopsioidea [35]. Curiously, the two variants from E. maclovinus shared closer homology with the Antarctic species than with P. urvillii and Bovichtidae, confirming the high relevance of this key species for the investigation of IgT evolution in Notothenioidei and further supporting the observation of shared indels, which may indicate a process of progressive loss of the Cτ1-Cτ2 intron.…”

“…The two variants cloned in E. maclovinus displayed a partially deleted Cτ2 exon (30 or 36 nt long in Ema1 and Ema2, respectively; see Table 1), revealing a Cτ2 exon structure similar to Antarctic Notothenioidei. On the other hand, we have previously shown that B. diacanthus, a non-Antarctic species more distantly related with Cryonotothenioidea, retains the entire Cτ2 exon (285 nt) [35] ( Table 1). Although Antarctic species and E. maclovinus shared the peculiar structure of Cτ2, their sequences differed due to several characteristic codon indels.…”

“…Pseudaphritis urvillii (family Pseudaphritioidae) and Eleginops maclovinus (family Eleginopsioidea). More recently, much attention has been dedicated to these notothenioid taxa, due to their early divergence from the polar lineage, which occurred before the climatic and geographic isolation of Antarctica, the drastic reduction in water temperature, and prior to the morpho-physiological diversification of cryonotothenioid species [35]. The study of the evolutionary history of Bovichtidae, based on mitochondrial and nuclear DNA molecular phylogeny, as well as on morphological and meristic characters, has been an essential factor for clarifying the process that drove the diversification between Cryonotothenioidea and their non-Antarctic relatives.…”

“…The study of the evolutionary history of Bovichtidae, based on mitochondrial and nuclear DNA molecular phylogeny, as well as on morphological and meristic characters, has been an essential factor for clarifying the process that drove the diversification between Cryonotothenioidea and their non-Antarctic relatives. Indeed, the evolutionary radiation of the genus Bovichtus and of the closely related cryonotothenioid species are characterized by a similar timeline, and therefore the patterns of diversification and extinction observed in these two lineages are expected to closely match each other [35]. Moreover, the revised positioning of E. maclovinus as the sister lineage of Cryonotothenioidea (it was previously considered as closely related to the nototheniid lineage Dissostichus) [30], provides another key information for the study of the evolution of these fishes.…”