Payne RP et al. (2015), The cushion-star Parvulastra exigua in South Af...

ECB-ART-44307

Zookeys 2015 Sep 30;524:1-16. doi: 10.3897/zookeys.524.6145.

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The cushion-star Parvulastra exigua in South Africa: one species or more?

Payne RP , Griffiths CL , von der Heyden S , Koch E .

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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.

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Species referenced: Echinodermata
Genes referenced: LOC115925415 LOC582915 ROCK

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	Figure 1. Abactinal (A) and actinal (B) view of Parvulastra exigua, with equivalent views of Parvulastra dyscrita (E, F), with the Parvulastra exigua mottled color morph found on the east coast of South Africa (C) and an adult Parvulastra exigua laying sticky eggs via oral gonopores onto the underside of a rock (D). All photos by C.L. Griffiths; individuals not to scale, with approximate sizes given in Table 5.
	Figure 2. Map of South Africa demonstrating sampling localities and other locations mentioned in the text.
	Figure 3. Shape and color pattern of four specimens from each of the seven groups of seven specimens as defined in Table 4, and used in the genetic analyses. Letters indicate location of specimen collection as seen in Table 2. Photos by R.P. Payne; individuals not to scale, with approximate sizes given in Table 5.
	Figure 4. Non–metric MDS ordination of all specimens analyzed. Two clear clusters displayed which represent the species Parvulastra dyscrita on the left, and the species Parvulastra exigua on the right. Circles indicate 75% similarity. The specimen causing a cluster overlap is of the species Parvulastra exigua, but has many of the morphological characteristics associated with Parvulastra dyscrita due to its large size and possibly collection location.
	Figure 5. Parsimony haplotype network for (A) 37 Parvulastra exigua and (B) 7 Parvulastra dyscrita specimens. Circle size relates to the frequency of each haplotype, with color indicating origin of the individuals. Smallest circles represent one individual and one haplotype. Extinct or not sampled haplotypes are marked by a blue dot and each line represents one mutational step.

References [+] :

Barrett, Haploview: analysis and visualization of LD and haplotype maps. 2005, Pubmed