PHYLOGENY OF THE GENUS ROSTANGA (NUDIBRANCHIA), WITH DESCRIPTIONS OF THREE NEW SPECIES FROM SOUTH AFRICA

Abstract

Rostanga elandsia sp. nov., Rostanga aureamala sp. nov. and Rostanga phepha sp. nov. are characterized by having the radula with slender innermost lateral teeth, which lack denticles on the inner side of the cusp and have a single denticle on the outer side. The outermost lateral teeth of these three species are elongate, but shorter than in other species of the genus. In addition, R. aureamala is the only species of the genus with rachidian teeth and R. phepha is unique within the genus Rostanga by virtue of its white coloration with dark spots. A phylogenetic analysis shows that the three new species from South Africa and Rostanga setidens (Odhner, 1939) are the sister group of the rest of the genus. The species from Japan and Marshall Islands (North Pacific Ocean) are basal in the sister clade containing the other species of Rostanga Bergh, 1879. The tropical Indo-Pacific species of Rostanga are not monophyletic. The Atlantic and Eastern Pacific species form a monophyletic, derived clade, being the sister group of Rostanga australis Rudman & Avern, 1989, which has a narrow range restricted to south eastern Australia. The widespread IndoPacific species Rostanga bifurcata Rudman & Avern, 1989, is the sister group of Rostanga dentacus Rudman & Avern, 1989, also widespread in the tropical western Pacific. This phylogeny suggests a vicariant origin of the South African, Atlantic-Eastern Pacific, and probably North Pacific species, whereas in the tropical Indo-Pacific most sister species are sympatric. SPECIES DESCRIPTIONS Rostanga elandsia new species (Figs 1A, 2 and 3) Rostanga sp. 1 Gosliner, 1987, p. 71, Fig. 97 Type material: Holotype: Bakoven Bay, Atlantic Coast of Cape Peninsula, Cape Province, South Africa, 4 April 1982, 19 mm preserved length, collected by T.M. Gosliner (CASIZ 073383). Paratypes: Bakoven Bay, Atlantic Coast of Cape Peninsula, Cape Province, South Africa, 4 April 1982, five specimens 12–20 mm preserved length, collected by T.M. Gosliner (CASIZ 115234). Off Llandudno, Atlantic Coast of Cape Peninsula, Cape Province, South Africa, February 1981, one specimen 11 mm preserved length, collected by T.M. Gosliner (CASIZ 086910); 30 March 1981, four speciJOCELYN B. GAROVOY, ANGEL VALDES & TERRENCE M. GOSLINER 132 Figure 1. Living animals. A. Rostanga elandsia sp. nov., specimen from Bakoven Bay, photo by T.M. Gosliner. B. Rostanga aureamala sp. nov., specimen from Algoa Bay, photo by T.M. Gosliner. C. Rostanga phepha sp. nov., specimen from Llandudno Bay, photo by T.M. Gosliner. mens 8–16 mm preserved length, collected by T.M. Gosliner (SAM A35406); 9 October 1982, two specimens 12–14 mm preserved length, collected by T.M. Gosliner (CASIZ 073382). Kommetjie, Atlantic Coast of Cape Peninsula, Cape Province, South Africa, 29 April 1938, eight specimens 7–12 mm preserved length, collected by U.C.T. Ecological Survey (SAM A54475); May 1963, three specimens 6–10 mm preserved length, collected by U.C.T. Ecological Survey (SAM A54487); 31 January 1980, two specimens 13–14 mm preserved length (SAM A35407). PHYLOGENY AND NEW SPECIES OF ROSTANGA 133 Figure 2. Rostanga elandsia sp. nov. (CASIZ 115234), scanning electron micrographs. A. Inner lateral teeth, scale 25 m. B. Mid-lateral teeth, scale 30 m. C. Outer lateral teeth, scale 43 m. D. Caryophyllidia, scale 75 m. Additional material: Hottentot’s Huisie, Atlantic Coast of Cape Peninsula, Cape Province, South Africa, October 1980, one specimen 14 mm preserved length, collected by T.M. Gosliner (CASIZ 086934); February 1981, one specimen 15 mm preserved length, collected by T.M. Gosliner (SAM A 35404). Llandudno, Atlantic Coast of Cape Peninsula, Cape Province, South Africa, 16 March 1980, one specimen 12 mm preserved length, collected by T.M. Gosliner (SAM A35408). Etymology: The name elandsia is an abbreviation for the elandsboontjie root (Elephantorrhiza elephantina), used by the Khoisan people of South Africa to make a red pigment, in reference to the colour of this species.