Phylogeny of recent billfishes (Xiphioidei)

Billfishes are genetically and morphologically distinct enough from scombroids to merit placement in a separate suborder, Xiphioidei. Two extant families are usually recognized: Xiphiidae (swordfish, Xiphias) and Istiophoridae, currently containing three genera, Istiophorus (sailfishes), Makaira (marlins), and Tetrapturus (spearfishes, white, and striped marlins). Phylogenetic analyses of molecular data from mitochondrial and nuclear gene sequences (mitochondrial control region, ND2, 12S, and nuclear MN 32 regions) show a different picture of relationships. Makaira is not monophyletic: blue marlin cluster with sailfish and placement of black marlin is un-stable. Accepting the molecular phylogeny gives two possible classifications: (1) two genera: blue marlin + sailfish (as Istiophorus) and all the rest (as Tetrapturus), or (2) five genera: blue marlin (Makaira), sailfish (Istiophorus), black marlin (Istiompax), striped and white marlin (Kajikia), and four spearfishes (Tetrapturus). We prefer the latter possibility. There is no genetic evidence to support recognition of separate species of Atlantic and Indo-Pacific sailfishes or blue marlins. Atlantic white marlin, Kajikia albida (Poey, 1860) is closely related to Indo-Pacific striped marlin, Kajikia audax (Philippi, 1887). The four spearfishes are closely related: the three Atlantic species, longbill (Tetrapturus pfluegeri Robins and de Sylva, 1963), Mediterranean (Tetrapturus belone Rafinesque, 1810), and roundscale (Tetrapturus georgii Lowe, 1841), and the one Indo-Pacific species, shortbill (Tetrapturus angustirostris Tanaka, 1915). The roundscale is the most divergent of the spearfishes. A fifth putative Tetrapturus sp., the "hatchet marlin" clusters with roundscale spearfish but these two "species" could not be differentiated in this analysis.