Bathygobius antilliensis

Abstract

<i>Bathygobius antilliensis</i> group <p> This group includes <i>B. ramosus, B. lineatus</i>, <i>B. curacao</i> and <i>B. antilliensis</i>. <i>Bathygobius curacao</i> was recovered as the basal member of this group, followed by the two Eastern Pacific species, and <i>B. antilliensis</i>. The <i>B. antilliensis</i> group is part of a polytomy containing the <i>B. soporator</i> group plus <i>B. geminatus</i>, a clade containing two Indopacific <i>B. fuscus</i> and <i>B. coalitus</i>, and <i>B. mystacium</i>.</p> <p> Miller & Smith’s (1989) most parsimonious Wagner tree (based on 46 morphological characters) placed <i>B. ramosus</i> in a clade with three Indo-Pacific <i>Bathygobius</i> species (<i>B. cyclopterus</i> (Valenciennes, 1837), <i>B. cotticeps</i> (Steindachner, 1879), and <i>B. niger</i> (Smith, 1960), this group being basal to the remaining 11 <i>Bathygobius</i> species on their tree (including <i>B. soporator</i>, <i>B. andrei</i>, <i>B. curacao</i> and <i>B. mystacium</i>). The group consisting of <i>B. ramosus</i> and its Indo-Pacific allies was characterized by having a complex multifurcate branching pattern on the first two free pectoral fin rays, although <i>B. ramosus</i> 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). <i>B. antilliensis</i> 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 <i>B. ramosus</i> 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 <i>B. antilliensis</i> group (both <i>B. curacao</i> and <i>B. lineatus</i> have a single branching point on upper pectoral rays), and possibly a larger clade that contains the Indo-Pacific <i>B. cyclopterus</i>, <i>B. cotticeps</i>, and <i>B. niger</i>. Alternatively, Miller & Stefanni (2001) questioned the homology of this character, as it has been demonstrated to be homoplasious in the Atlantic-Mediterranean genera <i>Gobius</i> and <i>Mauligobius</i> (Miller 1984, 1986; Brito and Miller 2001). Two hypotheses were suggested to explain the relationship between <i>B. ramosus</i> and its potential Indo-Pacific allies (Miller & Smith 1989; Miller & Stefanni 2001): <i>B. ramosus</i> arose from an invasion across the Eastern Pacific barrier by western Pacific stock; or <i>B. ramosus</i> 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 (<i>B. antilliensis</i>) supports the latter hypothesis. If <i>B. antilliensis</i> and <i>B. ramosus</i> are sister species isolated by the closure of the Isthmus of Panama, then the speciation events separating <i>B. curacao</i>, <i>B. lineatus</i>, and the common ancestor of <i>B. antilliensis</i> and <i>B. ramosus</i> must have predated this closure.</p> <p> In terms of both morphology and genetics, <i>B. curacao</i> is very divergent from all other species in our analysis including other members of the <i>B. antilliensis</i> group. Miller & Smith (1989) hypothesized that <i>B. curacao’s</i> closest allies are the West African species <i>B. burtoni</i> (O'Shaughnessy 1875) and <i>B. casamancus</i> (Rochebrune 1880), and the Indo-Pacific species <i>B. cocosensis</i> (Bleeker 1854) and <i>B. petrophilus</i> (Bleeker 1853). While <i>B. petrophilus</i>, <i>B. burtoni</i> and <i>B. casamancus</i> were not available for our analysis, our molecular analyses show no evidence of a close relationship between <i>B. curacao</i> and the Indo-Pacific <i>B. cocosensis</i>. A combined molecular and morphological analysis that includes additional old-world <i>Bathygobius</i> species would further clarify the relationship between the <i>B. antilliensis</i> group and potential old-world allies.</p>Published as part of <i>Tornabene, Luke & Pezold, Frank, 2011, Phylogenetic analysis of Western Atlantic Bathygobius (Teleostei: Gobiidae), pp. 27-36 in Zootaxa 3042</i> on page 30, DOI: <a href="http://zenodo.org/record/200832">10.5281/zenodo.200832</a&gt