DNA barcoding of sponges (Phylum Porifera) in South Africa

Abstract

Abstract : South Africa is renowned for its biological diversity and is a hotspot for marine invertebrates (Griffith et al., 2010), including sponges (Porifera). Despite their pivotal role for the functionality of the marine ecosystem, a reliable estimate of the species richness of sponges in South Africa is difficult. Using morphological characters for species identification has its limitations: it is hindered by the paucity and plasticity of morphological characters (Blanquer & Uriz 2007, Sperling et al., 2011) which may result in numerous species being morphologically indistinguishable, i.e. “cryptic” species. The sponge fauna of South Africa is also understudied, although this issue has begun to be addressed, with more than 40 new species described from this region over the last 10 years. It is likely that the current estimate of sponge biodiversity nonetheless remains a considerable underestimate, and numerous suspected new species remain to be described (Samaai, pers. comm.). Over the last five years, increased efforts were placed on documenting South African biodiversity, with sponges as one of the focus groups. The present study is part of this initiative, and constitutes the first genetic study on South African sponges aimed at complementing morphological data to help resolve sponge taxonomy. The results indicate that South African sponges are not as widespread as previously thought, but comprise cryptic and genetically distinct evolutionary lineages. Importantly, the results show that sponges identified from South Africa as southern hemisphere are representatives of supposedly cosmopolitan species that have been misidentified. Moreover, some species assumed to be widespread in southern Africa actually turned out to be subdivided into regional evolutionary lineages with distinct distribution ranges. In some cases the molecular data corroborated the morphological species identification, whereas in other instances the combined approach revealed the presence of species complexes. This study represents a first step in constructing a reference library for South African sponges and to advance our understanding of the diversity, biogeography and evolutionary adaptability of South African sponges.M.Sc. (Zoology