Bathygobius antilliensis

Tornabene, Luke & Pezold, Frank, 2011, Phylogenetic analysis of Western Atlantic Bathygobius (Teleostei: Gobiidae), Zootaxa 3042, pp. 27-36 : 30

Bathygobius antilliensis group

This group includes B. ramosus , B. lineatus , B. curacao and B. antilliensis . Bathygobius curacao was recovered as the basal member of this group, followed by the two Eastern Pacific species, and B. antilliensis . The B. antilliensis group is part of a polytomy containing the B. soporator group plus B. geminatus , a clade containing two Indopacific B. fuscus and B. coalitus , and B. mystacium .

Miller & Smith’s (1989) most parsimonious Wagner tree (based on 46 morphological characters) placed B. ramosus in a clade with three Indo-Pacific Bathygobius species ( B. cyclopterus ( Valenciennes, 1837) , B. cotticeps ( Steindachner, 1879) , and B. niger ( Smith, 1960) , this group being basal to the remaining 11 Bathygobius species on their tree (including B. soporator , B. andrei , B. curacao and B. mystacium ). The group consisting of B. ramosus and its Indo-Pacific allies was characterized by having a complex multifurcate branching pattern on the first two free pectoral fin rays, although B. ramosus lacks the head scales and the projection on the tubular anterior naris that are present on the Indo-Pacific species ( Miller & Smith 1989; Miller & Stefanni 2001). B. antilliensis also lacks head scales and the projection on the anterior naris, and this species also typically possesses a more extensive pectoral fin ray branching pattern than other western Atlantic congeners, although the branching is not usually as extensive as observed B. ramosus and is somewhat variable within the species. A pattern of multifurcate free pectoral fin rays may be a synapomorphy of the more derived members of the B. antilliensis group (both B. curacao and B. lineatus have a single branching point on upper pectoral rays), and possibly a larger clade that contains the Indo-Pacific B. cyclopterus , B. cotticeps , and B. niger . Alternatively, Miller & Stefanni (2001) questioned the homology of this character, as it has been demonstrated to be homoplasious in the Atlantic-Mediterranean genera Gobius and Mauligobius ( Miller 1984, 1986; Brito and Miller 2001). Two hypotheses were suggested to explain the relationship between B. ramosus and its potential Indo-Pacific allies ( Miller & Smith 1989; Miller & Stefanni 2001): B. ramosus arose from an invasion across the Eastern Pacific barrier by western Pacific stock; or B. ramosus represents a Pacific survival of circumtropical post-Tethyan stock, whose Atlantic sister-species must have gone extinct. The recent discovery of the Atlantic sister-species ( B. antilliensis ) supports the latter hypothesis. If B. antilliensis and B. ramosus are sister species isolated by the closure of the Isthmus of Panama, then the speciation events separating B. curacao , B. lineatus , and the common ancestor of B. antilliensis and B. ramosus must have predated this closure.

In terms of both morphology and genetics, B. curacao is very divergent from all other species in our analysis including other members of the B. antilliensis group. Miller & Smith (1989) hypothesized that B. curacao’s closest allies are the West African species B. burtoni (O'Shaughnessy 1875) and B. casamancus ( Rochebrune 1880) , and the Indo-Pacific species B. cocosensis ( Bleeker 1854) and B. petrophilus ( Bleeker 1853) . While B. petrophilus , B. burtoni and B. casamancus were not available for our analysis, our molecular analyses show no evidence of a close relationship between B. curacao and the Indo-Pacific B. cocosensis . A combined molecular and morphological analysis that includes additional old-world Bathygobius species would further clarify the relationship between the B. antilliensis group and potential old-world allies.