Luciobrotula Smith & Radcliffe 1913

Genus Luciobrotula Smith & Radcliffe, 1913

Molecular phylogeny and species delimitation

The COI dataset comprised 13 aligned sequences including three newly obtained sequences from the collected specimens, three additional sequences of L. bartschi from the South China Sea and Western Australia, five sequences of L. coheni from the Eastern Pacific, plus two outgroup sequences (Table 1). The length of the aligned sequences of the dataset is 618 bp. Figure 2 shows the phylogenetic tree inferred from the ML analysis based on the dataset. The monophyly of the genus Luciobrotula is strongly supported (bootstrap value =98%), and ingroup sequences form three clades or lineages among which two contain sequences from the two known species (Fig. 2). While two of our newly obtained sequences (ASIZP 0913925 and PNG 1082) fall into the L. bartschi clade, the third one (PNG 2363) appears to be a previously unknown lineage. Advanced species delimitation analyses with ABGD and bPTP based on the same COI dataset reveal a congruent result with a prediction of three OTUs, corroborating the phylogenetic finding (Fig. 2). The delimited OTUs (or inferred species) are genetically distinct from each other. The unknown lineage is distinct from others by 37 unique nucleotide sites based on CBB analysis. The average genetic distances measured using the K2P model among them are from 0.130 to 0.138 at the COI locus. Further morphological examination on the specimens indicates that the features of the sample collected from the Solomon Sea (PNG 2363) are unique among all known Luciobrotula species (see below), and we validate it herein as a new species.