Allozyme analyses of the genus Trisopterus: taxonomic status and population structure of the poor cod

Abstract

Genetic analysis of the four Trisopterus (Gadidae) taxa suggests that the interrelationships of the two morphs of poor cod (T. minutus minutus in the Atlantic and T. minutus capelanus in the Mediterranean) should be reconsidered. The Mediterranean poor cod T. m. capelanus is more closely related to bib T. luscus than to the Atlantic poor cod, so the population structure in the Atlantic and Mediterranean poor cod must be considered separately. Among 635 Atlantic individuals there was some evidence of poor cod population differentiation (allele frequency heterogeneity test Pc0·0005; F ST =0·0135, Pc0·0005). Levels of genetic variation were similar to those reported for related gadoid species. Some differentiation was present on the Norwegian coast (samples from Trondheimsfjord) and between the Faeroe Islands (Faeroe Bank) and the adjacent European coastal location. In contrast no statistically significant population differentiation was evident in Mediterranean poor cod, but fewer samples and individuals were screened. 2000 The Fisheries Society of the British Isles

Taxonomy, Distribution and Evolution of Trisopterine Gadidae by Means of Otoliths and Other Characteristics

“…Genetic data support this close relationship very well: both the complete mitochondrial DNA of cytochrome b and the nuclear DNA of the rhodopsin genes point to a much closer relationship of T. luscus and T. capelanus than any other combination of two of the four trisopterine species [21,22]. This is a strong confirmation of earlier research in which was found that both species shared the highest number of loci with the same alleles extracted from muscle and liver tissue [18].…”

“…Closer relationships between A. minutus and N. esmarkii, compared with the other trisopterines, are demonstrated by otolith characteristics and genetics. The greater taxonomic distance of A. minutus and N. esmarkii to T. luscus and T. capelanus is based upon various characteristics of the fishes, such as otolith morphology and genetic data [18,22], and also upon phylogenetic data inferable from fossil otoliths. These data together do not allow including A. minutus in the genus Trisopterus or Neocolliolus.…”

“…Since the beginning of the 21st century a series of papers have been published about genetic characteristics of trisopterine species [18][19][20][21][22]69]. Allele frequencies at polymorphic loci obtained from muscle and liver tissues by Mattiangeli et al [18] were not conclusive enough to unravel the closest relationship of A. minutus with one of the other trisopterines. They found that A. minutus and N. esmarkii share the most common allele at GPI-2*, while the most common allele at ADA-3* is shared by P. minutus and T. capelanus.…”

“…Therefore, these data are contradictory. According to their calculated Nei's genetic distance Mattiangeli et al [18] concluded that N. esmarkii would be more closely related to T. luscus and T. capelanus than to A. minutus. Their dendrogram of the intraspecific relationships among A. minutus from the various investigated areas (ibidem, Figure 3), however, shows an incorrect picture of the most related connections, giving proof of their indecisive phylogenetic data.…”

“…The taxonomy and evolution of the trisopterine Gadidae have been the subject of several specific studies since the beginning of the 21st century, stimulated by new genetic data within this group [18][19][20][21][22], and by new genetic data of a larger group of Gadiformes including some trisopterine species [7,8]. The profound investigations by Delling et al [21] moreover are indispensable because they have straightened up the taxonomic mess in the trisopterines that started already in the beginning of scientific taxonomy before Linnaeus and continued up to their publication.…”