Abstract
Pyura stolonifera is a large solitary ascidian found in Africa, Australasia and South America. The taxonomic status of different populations of this species is disputed, especially since there is evidence for several distinct morphological and genetic units that point towards the existence of multiple cryptic species. While some researchers still recognize P. stolonifera as a single species, others treat the different populations as distinct species. Here, we present a revision of the P. stolonifera species complex based on the examination of samples from all regions where there are reliable reports of this taxon. We recognize four species that are both morphologically and genetically distinct, one of which is new to science and is formally described here. This species is morphologically distinct from the other three members of the species complex in terms of the colour and texture of the tunic, the arrangement of the gonads within the gut and the shape of the dorsal tubercle, among other characters. We name the new species Pyura dalbyi after Dr. J.E. Dalby Jr., whose research on its ecology and distribution provided the incentive for examining this species more closely.References
Bach, J. (1976) A maritime history of Australia. Sydney, 481 pp.
Bennett, I. & Pope, E.C. (1960) Intertidal zonation of the exposed rocky shores of Tasmania and its relationship with the rest of Australia. Australian Journal of Marine and Freshwater Research, 11, 182–221.
Branch, G.M., Griffiths, C.L., Branch, M.L. & Beckley, L.E. (2002) Two Oceans: A guide to the marine life of southern Africa. David Philip, Cape Town & Johannesburg, 360 pp.
Castilla, J.C., Collins, A.G., Meyer, C.P., Guiñez, R. & Lindberg, D.R. (2002) Recent introduction of the dominant tunicate, Pyura praeputialis (Urochordata, Pyuridae) to Antofagasta, Chile. Molecular Ecology, 11, 1579–1584.
Castilla, J.C., Guiñez, R., Alvarado, J.L., Pacheco, C. & Varas, M. (2000) Distribution, population structure, population biomass and morphological characteristics of the tunicate Pyura stolonifera in the Bay of Antofagasta, Chile. Marine Ecology, 21, 161–174.
Dalby, J.E., Jr. (1995) Consequences of aggregated living in the ascidian Pyura stolonifera: Evidence for non-contact intraspecific competition. Marine and Freshwater Research, 46, 1195–1199.
Dalby, J.E., Jr. (1996) Nemertean, copepod, and amphipod symbionts of the dimorphic ascidian Pyura stolonifera near Melbourne, Australia: specificities to host morphs, and factors affecting prevalences. Marine Biology, 126, 231–243.
Dalby, J.E., Jr. (1997a) Dimorphism in the ascidian Pyura stolonifera near Melbourne, Australia, and its evaluation through field transplant experiments. Marine Ecology, 18, 253–271.
Dalby, J.E., Jr. (1997b) Reproductive and electrophoretic evidence for genetic maintenance of dimorphism in the ascidian Pyura stolonifera near Melbourne, Australia. Ophelia, 47, 227–243.
Edkins, M.T., Teske, P.R., Griffiths, C.L. & Papadopulos, I. (2007) Genetic and morphological analyses suggest that southern African crown crabs, Hymenosoma orbiculare, represent five distinct species. Crustaceana, 80, 667–683.
Hayward, B.W. & Morley, M.S. (2009) Introduction to New Zealand of two sea squirts (Tunicata, Ascidiacea) and their subsequent dispersal. Records of the Auckland Museum, 46, 5–14.
Kott, P. (1985) The Australian Ascidiacea, Part 1. Phlebobranchia and Stolidobranchia. Memoirs of the Queensland Museum, 23, 1–438.
Kott, P. (2006) Observations on non-didemnid ascidians from Australian waters. Journal of Natural History, 40, 169–234.
Lafargue, F. & Wahl, M. (1986–1987) Contribution to the knowledge of littoral ascidians (Ascidiacea, Tunicata) of the Senegalese coast. Bulletin de l'Institut Fondamental d'Afrique Noire, 46, 385–402.
Millar, R.H. (1955) On a collection of ascidians from South Africa. Proceedings of the Zoological Society of London, 125, 169–221.
Millar, R.H. (1962) Further descriptions of South African ascidians. Annals of the South African Museum, 46, 113–221.
Monniot, C. & Bitar, G. (1983) Sur la présence de Pyura stolonifera (Tunicata, Ascidiacea) à Ras Achaccar (côte nord atlantique marocaine). Comparaison anatomique distinctive avec Pyura praeputialis. Bulletin de l'Institut Scientifique, Rabat, 7, 83–91.
Monniot, C. & Monniot, F. (1994) Additions to the inventory of eastern tropical Atlantic ascidians; arrival of cosmopolitan species. Bulletin of Marine Science, 54, 71–93.
Monniot, C., Monniot, F., Griffiths, C.L. & Schleyer, M. (2001) South African ascidians. Annals of the South African Museum, 108, 1–141.
Monniot, C., Monniot, F. & Laboute, P. (1991) Coral reef ascidians of New Caledonia. Éditions de L'Orstom, Paris, 247 pp.
Monniot, F. (2007) Some comments on the Ascidians of New Caledonia. In: Payri, C.E. & Richer de Forges, B. (Eds.), Compendium of marine species from New Caledonia. Institute de Recherche pour le Développement (IRD), Nouméa, pp. 349–356.
Ridgway, T.M., Stewart, B.A., Branch, G.M. & Hodgson, A.N. (1998) Morphological and genetic differentiation of Patella granularis (Gastropoda: Patellidae): recognition of two sibling species along the coast of southern Africa. Journal of Zoology, 245, 317–333.
Rius, M., Branch, G.M., Griffiths, C.L. & Turon, X. (2010) Larval settlement behaviour in six gregarious ascidians in relation to adult distribution. Marine Ecology Progress Series, 418, 151–163.
Teske, P.R., McLay, C., Sandoval-Castillo, J., Papadopoulos, I., Newman, B.K., Carvalho, D., Griffiths, C.L., McQuaid, C.D., Barker, N.P., Borgonie, G. & Beheregaray, L.B. (2009) Tri-locus sequence data reject a “Gondwanan origin hypothesis” for the African/South Pacific crab genus Hymenosoma. Molecular Phylogenetics and Evolution, 53, 23–33.
Teske, P.R., Papadopoulos, I., Newman, B.K., Dworschak, P.C., McQuaid, C.D. & Barker, N.P. (2008) Oceanic dispersal barriers, adaptation and larval retention: an interdisciplinary assessment of potential factors maintaining a phylogeographic break between sister lineages of an African prawn. BMC Evolutionary Biology, 8, 341.
Van Name, W.G. (1931) New North and South American ascidians. Bulletin of the American Museum of Natural History, 61, 207–225.
Van Name, W.G. (1945) The North and South American ascidians. Bulletin of the American Museum of Natural History, 84, 1–476.