A revision of the genus Sargassum (Fucales, Phaeophyceae) in South Africa

Abstract

a b s t r a c t Edited by WA StirkKeywords: cox3 Diversity Indian Ocean ITS-2 mt23S Phylogeny RuBisCO Seaweeds Systematics A total of 27 different Sargassum epithets are listed in the literature for South Africa. The main aim of our study was to revise this species list using newly collected specimens in order to provide a reliable and illustrated tool for the identification of South African Sargassum. Based on morphological and molecular analyses of the nuclear ITS2, chloroplastic partial RuBisCO operon and mitochondrial cox3 and 23S, we identified a total of seven taxa including two new records (*) for South Africa: Sargassum elegans, Sargassum cymosum var. scabriusculum, Sargassum ilicifolium, Sargassum ilicifolium var. acaraeocarpum*, Sargassum incisifolium, Sargassum obovatum and, Sargassum polycystum*. As a result of our taxonomic revision, we conclude that a number of the species listed in the literature for South Africa were misapplied or not current and we propose five new taxonomic synonyms. We provide an exhaustive list of the Sargassum species present in South Africa, a key for identification and detailed illustrations.

Historical biogeography of the widespread macroalga Sargassum (Fucales, Phaeophyceae)

“…Specifically, we preferred sequences generated in the recent Sargassum ‐focused taxonomic work by Mattio et al. (, , , , , 2010), Mattio and Payri (), followed by sequences from other published studies (Camacho et al ) and, lastly, unpublished sequences uploaded by taxonomists. After this screening process, data were found to be available for 99 species, representing 28% of all valid Sargassum species (Guiry and Guiry ).…”

“…Recent availability of DNA sequence data for a large number of Sargassum species has improved our understanding of phylogenetic relationships within the group (Mattio et al. , , , Mattio and Payri , Yip et al. ).…”

“…For example, Mattio et al. () utilized hydrodynamic models to characterize dispersal patterns between isolated islands of the western Indian Ocean, while Phillips () invoked ocean circulation to explain why the western Pacific is more diverse than eastern Pacific despite higher endemism in the latter. By leveraging on a more robust understanding of the Sargassum phylogeny, biogeographic analyses of species ancestral ranges could be performed to reconstruct macroevolutionary processes that have shaped present species distributions and diversity gradients.…”

“…Species distribution data were then consolidated from isolated diversity studies over the last decade (Mattio et al. , , , Mattio and Payri , Nguyen ) and analyzed in conjunction with the phylogeny using a biogeographic model to estimate ancestral ranges and macroevolutionary processes (dispersal‐extinction‐cladogenesis; Ree and Smith ). Our reconstruction supports a Central Indo‐Pacific origination and initial diversification of Sargassum with very recent (<1.5 mya) independent dispersals into the Atlantic, resulting in high species richness in the Pacific but limited diversity and endemism in the Atlantic.…”

Insights into the species diversity of the genus Sargassum (Phaeophyceae) in the Mediterranean Sea, with a focus on a pre-viously unnoticed taxon from Algeria

“…On the basis of genetic studies, a reappraisal of the Sargassum taxonomy is now available in e.g. western and central Pacific islands, Korea, the Oman Sea, Australia and South Africa (Zhao et al, 2007;Mattio et al, 2008Mattio et al, , 2009Mattio et al, , 2010Mattio & Payri, 2011;Noormohammadi et al, 2011;Cho et al, 2012;Dixon et al, 2012Dixon et al, , 2014Dixon & Huisman, 2015;Mattio et al, 2015). Unfortunately, this is not yet the case for the Mediterranean.…”