Morphological and mitochondrial DNA divergence validates blackmouth, Galeus melastomus, and Atlantic sawtail catsharks, Galeus atlanticus, as separate species

Abstract

A total of 60 morphometric traits and nucleotide sequences of the entire mtDNA NADH dehydrogenase subunit 2 (ND2) gene [1047 base pair (bp)] in 23 individuals of blackmouth, Galeus melastomus, and 13 individuals of sawtail catsharks, Galeus atlanticus, caught in Southern Portugal, were examined to test the validity of these two taxa. These sharks closely resemble each other, have overlapping geographical ranges and are difficult to identify by morphological characters. Non-metric multidimensional scaling of morphometric variables indicates a clear separation between the two species, with 10 characters each contributing 2Á12-2Á45% of the total variability between species. Maximum likelihood, parsimony and neighbour-joining trees revealed two major mtDNA haplotype clades, corresponding to the two species, with an average corrected sequence divergence between them of 3Á39 AE 0Á56%. Within species divergences between haplotypes averaged 0Á27 AE 0Á18% in G. melastomus and 0Á12 AE 0Á08% in G. atlanticus. A total of 35 diagnostic nucleotide site differences and four restriction fragment length polymorphism recognition sites in the ND2 gene can be used to distinguish the two species. # 2007 The Authors Journal compilation # 2007 The Fisheries Society of the British Isles

A Ranking System for Reference Libraries of DNA Barcodes: Application to Marine Fish Species from Portugal

“…DNA barcodes from our specimens initially identified as G. melastomus were distributed into two distinct clusters diverging on average by 2.7%. The moderate divergence raised uncertainty about the accuracy of the species assignment, and barcodes were ranked grade D. Supported by morphometric and molecular evidence, Castilho et al (2007) [12] confirmed the occurrence of G. atlanticus in Portuguese waters. Because the loci used by Castilho et al (2007) [12] did not include COI-5P, we were not able to compare them directly with our sequences, but we were provided access to tissue samples of both species [12] .…”

“…A total of 659 DNA barcodes were assembled from 102 fish species using the protocol detailed below. Among these, 9 barcode sequences were obtained from tissue samples of the species Galeus melastomus and Galeus atlanticus obtained from a separate study [12] . DNA barcodes for 33 fish species were generated and are publicly available for the first time.…”

Barcoding deep-water chondrichthyans from mainland Portugal

“…It also extended to the centre of Portugal the distribution range of Galeus atlanticus, which was previously known only from the southern coast (Rey et al 2006). This species is easily confounded with Galeus melastomus (Castilho et al 2007), so it is likely that these sympatric species have been misidentified in the past. Most putative species showed divergence values higher than 2% from their congeners.…”

Morphological and molecular differentiation of smooth-hound sharks (GenusMustelus, Family Triakidae) from the Gulf of California

“…The combination of morphological and genetic analyses has been recently used to successfully resolve the status of species in other problematic elasmobranch genera, such as Galeus (Castilho et al., ), Orectolobus (Corrigan et al., ), and Gymnura (Smith et al., ). In the case of Mustelus , this is the first study combining the use of morphometric and genetic analyses to address their variability and differentiation.…”