<p><strong>Molecular assessment of the genus <em>Sargassum</em> (Fucales, Phaeophyceae) from the Mexican coasts of the Gulf of Mexico and Caribbean, with the description of <em>S. xochitlae sp. nov</em>.</strong></p>

Abstract

The recognition of many species of Sargassum has been difficult because morphological characters show significant phenotypic variation depending on habitat, season, or even differences at the population level. To resolve some of these systematic issues along the Mexican Atlantic coast, molecular analyses of Sargassum species were carried out using DNA sequences of the COI-5P, ITS-2 and rbcL_S genetic markers. Of the 16 species recorded for the area, five species (S. acinarium, S. mathiesonii, S. pteropleuron, S. pusillum and S. ramifolium) were not found during the collections and their status remains undefined. Phylogenetic analyses of the three molecular markers showed that 10 species with their varieties (S. bermudense, S. buxifolium, S. cymosum, S. filipendula, S. fluitans, S. furcatum, S. hystrix, S. natans, S. polyceratium, and S. vulgare) were grouped into a polytomy, with low genetic diversity. If we consider these markers as suitable for proxy for species delimitation, these species should be synonymized under S. cymosum, the older name. Taxonomic independence was confirmed only for S. platycarpum and our data revealed a new morphologically and molecularly independent species within the genus, described here as Sargassum xochitlae.

The Marine Benthic Algal Flora of Puerto Rico, I. Ochrophyta: Phaeophyceae, Pelagophyceae, and Xanthophyceae

“…Wynne (2011) noted their species transfer was invalid and made the correct combination. González-Nieto et al (2020) referred their Mexican specimens identified as S. buxifolium to a large species complex, S. cf. cymosum (see also Comments herein under Sargassum).…”

“…Both Schnetter (1976) and Camacho et al (2015) reported the species to be highly polymorphic. González-Nieto et al (2020), on the basis of Mexican specimens, referred a number of Caribbean Sargassum species to S. cf. cymosum (see also Comments herein under Sargassum).…”

Challenges and Opportunities in Relation to Sargassum Events Along the Caribbean Sea

“…The great variability of morphological characteristics between individuals of the same species or even in the same individual in response to climatic and environmental conditions (Kilar et al, 1992) complicates the delineation and identification of Sargassum species in the Atlantic (Parr, 1939;Mattio and Payri, 2011;Schell et al, 2015). Therefore, studies in recent years have included molecular and biochemical characters (Amaral-Zettler et al, 2017;González-Nieto et al, 2020;Rosado-Espinosa et al, 2020;Hernández-Bolio et al, 2021). Nevertheless, molecular markers (ITS, psaA, RuBisCO spacer, rbcl, COI, cox3, 23S-tRNA val spacer and partial mt23S) are not conclusive and the taxonomy of the group needs further analysis (Stiger et al, 2003;Mattio and Payri, 2011;Amaral-Zettler et al, 2017;González-Nieto et al, 2020).…”

“…Therefore, studies in recent years have included molecular and biochemical characters (Amaral-Zettler et al, 2017;González-Nieto et al, 2020;Rosado-Espinosa et al, 2020;Hernández-Bolio et al, 2021). Nevertheless, molecular markers (ITS, psaA, RuBisCO spacer, rbcl, COI, cox3, 23S-tRNA val spacer and partial mt23S) are not conclusive and the taxonomy of the group needs further analysis (Stiger et al, 2003;Mattio and Payri, 2011;Amaral-Zettler et al, 2017;González-Nieto et al, 2020). Recent studies in the Caribbean and Gulf of México have confirmed the presence of the holopelagic species Sargassum natans (morphotypes I and VIII) and S. fluitans (morphotype III) in the recent Sargassum events (García-Sánchez et al, 2020) (Figure 1).…”

A Natural History of Floating Sargassum Species (Sargasso) from Mexico

“…Sargassum species diversity is likely to be overestimated [56]. A recent phylogenetic analyses using three independent molecular markers (COI-5P, ITS-2, and rbcL) for Mexican species found that ten previously reported species (S. bermudense, S. buxifolium, S. cymosum, S. filipendula, S. furcatum, S. hystrix, S. polyceratium, and S. vulgare) were grouped into a single polytomy, A Natural History of Floating Sargassum Species (Sargasso) from Mexico DOI: http://dx.doi.org/10.5772/intechopen.97230 with low genetic diversity [29]. Surprisingly, the two pelagic species, S. fluitans and S. natans, were also included in this polytomy.…”