title: The cushion-star Parvulastra exigua in South Africa: one species or more?
abstract: The cushion-star Parvulastra exigua (Lamarck, 1816) is a widely distributed member of the temperate intertidal fauna in the southern hemisphere. In South Africa, it occurs in sympatry with the endemic Parvulastra dyscrita (Clark, 1923), the two species being differentiated predominantly by gonopore placement. Several recent studies have suggested that there may be additional cryptic species within the Parvulastra exigua complex in South Africa, based variously on color morphology, genetic evidence and the differential placement of the gonopores. This paper attempts to resolve whether one or more species are represented within Parvulastra exigua. A total of 346 Parvulastra exigua and 8 Parvulastra dyscrita were collected from sites on the west and south-west coasts of South Africa; morphological, anatomical and genetic analyses were performed to determine whether cryptic species and/or Parvulastra exigua specimens with aboral gonopores were present. Results show that neither cryptic species nor Parvulastra exigua specimens with aboral gonopores occur at these sites. This study thus refutes previous claims of the existence of aboral gonopores in South African Parvulastra exigua, and suggests that a single species is represented. The distinction between Parvulastra exigua and Parvulastra dyscrita is also confirmed, and features separating these two species are clarified and documented.
authors.affiliation: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa ; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa ; Present address: Department of Biodiversity and Conservation Biology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
authors.forename: Robyn P
authors.initials: RP
authors.lastname: Payne
authors.affiliation: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa ; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa.
authors.forename: Charles L
authors.initials: CL
authors.lastname: Griffiths
authors.affiliation: Evolutionary Genomics Group, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa.
authors.forename: Sophie
authors.initials: S
authors.lastname: von der Heyden
authors.affiliation: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa ; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, Cape Town, South Africa.
authors.forename: Erich
authors.initials: E
authors.lastname: Koch
keywords: Cryptic species; Parvulastra dyscrita; Parvulastra exigua; Patiriella; gonopore; starfish