Merluccius tasmanicus Matallanas & Lloris 2006 is a junior synonym of M. australis (Hutton 1872) (Gadiformes: Merluciidae) based on morphological and molecular data

Abstract

The high intraspecific variation among and the conservative external morphology of Merluccius spp. have resulted in serious identification difficulties. Four hundred and twenty fresh and preserved specimens of Merluccius were analyzed, including the type series of Merluccius australis, M. tasmanicus and M. hubbsi; specimens of M. hubbsi from Argentina, Brazil and Uruguay, and individuals of M. australis from Argentina and New Zealand were examined. The nomenclatural status of the type specimens of M. australis is discussed and the designation of a lectotype and a paralectotype is proposed. The comparative study of morphology, meristic, traditional and landmark-based morphometry, both external and internal, and through DNA-based Barcoding molecular tools demonstrates that Merluccius tasmanicus is a junior synonym of Merluccius australis. Meristic and morphometric characters of types of M. tasmanicus completely overlap those of M. australis, whereas M. hubbsi show fewer scales along the lateral line, total vertebrae, second dorsal and anal-fin rays. A trend of a longer snout and wider head in M. australis and M. tasmanicus, and larger eyes and longer pelvic fins, in M. hubbsi was observed. While discriminant characters were found in the internal elements (hyomandibula, urohyal and sagitta otolith) between M. hubbsi and M. australis, none were observed between M. australis and those reported for M. tasmanicus. DNA barcoding analyses found no evidence of the existence of other species of Merluccius besides M. hubbsi and M. australis.

Phylogenetic prospecting for cryptic species of the genus Merluccius (Actinopterygii: Merlucciidae)

“…For instance, the six clones of the M. hubbsi paratype from the Beagle Channel (HUBBM91 and HUBBM92) shared ITS1Nes variants with all other morphotypes, including M. patagonicus (PATAM101 and PATAM111). After the description of the M. patagonicus 23 some additional analyses suggested its synonymy with M. hubbsi 29,31 . However, the three paratypes of M. patagonicus did not share any sequence variant with true specimens of M. hubbsi (e.g.…”

“…Also, meristic (see Fig. 1 from 23 ) and molecular analyses 29,30 showed that M. patagonicus could be synonymous with M. hubbsi and that M. tasmanicus could be synonymous with M. australis 31 . Taxonomic uncertainties are expected in closelyrelated species that show extensive overlap in morphological and meristic traits.…”

“…The molecular background of the morphotypes distributed between the Western Pacific South of New Zealand and the western Atlantic South of Argentina is compatible with their hybrid origin between M. gayi and both, M. australis or M. hubbsi, respectively.The genus Merluccius comprises 11 valid species that occur on most temperate and tropical continental shelves except the Asian shores of the Pacific Ocean 1 . Hakes show an anti-tropical distribution in the Atlantic Ocean and the Eastern Pacific and a latitudinal bathymetric overlap between isotherms 7 °C and 23 °C [2][3][4] . Based on osteological data 5,6 it is believed that genus Palaeogadus as ancestor of genus Merluccius, arose near Greenland in the early Eocene (ca.…”

DNA barcodes from century‐old type specimens using next‐generation sequencing

“…; Antoni et al . ) or when it indicates that a long‐known species is actually a complex of two or more morphologically similar taxa (e.g. Hausmann et al .…”