SPECIES DELIMITATION, TAXONOMY, AND BIOGEOGRAPHY OF DICTYOTA IN EUROPE (DICTYOTALES, PHAEOPHYCEAE)¹

Abstract

Taxonomy of the brown algal genus Dictyota has a long and troubled history. Our inability to distinguish morphological plasticity from fixed diagnostic traits that separate the various species has severely confounded species delineation. From continental Europe, more than 60 species and intraspecific taxa have been described over the last two centuries. Using a molecular approach, we addressed the diversity of the genus in European waters and made necessary taxonomic changes. A densely sampled DNA data set demonstrated the presence of six evolutionarily significant units (ESUs): Dictyota dichotoma (Huds.) J. V. Lamour., D. fasciola (Roth) J. V. Lamour., D. implexa J. V. Lamour., D. mediterranea (Schiffn.) G. Furnari, D. spiralis Mont., and the newly described D. cyanoloma sp. nov., which was previously reported as D. ciliolata from the Mediterranean Sea. Species distributions, based on DNA-confirmed occurrence records, indicate that all species are geographically confined to the NE Atlantic Ocean with the exception of D. dichotoma and D. implexa, which also occur in South Africa and Bermuda, respectively. To investigate potential hybridization between D. dichotoma and D. implexa, which were previously shown to be sexually compatible in culture, we compiled and analyzed sets of mitochondrial, plastid, and nuclear markers to detect putative hybrids or introgression in natural populations. Failure to detect natural hybrids indicates that effective pre-and postzygotic isolation mechanisms are at play in natural populations and supports the by-product hypothesis of reproductive isolation.

Molecular species discovery in the diatom Sellaphora and its congruence with mating trials.

“…Correlation between different molecular markers, and with other properties such as morphology, reproductive isolation, or ecology, provides further evidence for the presence of distinct species (e.g. Gómez et al 2007;Burns et al 2008;Jargeat et al 2010;Tronholm et al 2010), based on the general notion of species as separately evolving metapopulation lineages (De Queiroz 2007). In groups with a large proportion of (pseudo)cryptic or unstudied species, the availability of model species complexes with well-understood species limits based on a range of properties can be highly useful, for instance to investigate the performance of different molecular markers for large-scale phylogenetic species delimitation (such as applied by e.g.…”

Spatial variability in intertidal macroalgal assemblages on the North Portuguese coast: consistence between species and functional group approaches

“…However, enumerating all the macroalgal species for monitoring programs is labour-intensive and requires a high level of expertise. Moreover, the number of scientists able to identify correctly macroalgae is decreasing (Brodie et al 2009), and molecular studies have revealed cryptic diversity in macroalgae that cannot be detected by morphological observations (Lindstrom 2008;Tronholm et al 2010). In order to reduce the time and resources consumed in identifying taxa, species can be grouped into different categories (functional groups) based on their ecological and morphological attributes (Litter and Litter 1980;Steneck and Dethier 1994;Balata et al 2011).…”

Phylogeography ofPadina boryana(Dictyotales, Phaeophyceae) around the Thai-Malay Peninsula

“…For example, mitochondrial DNA and plastid DNA have been used to study populations, and for phylogenetic reconstruction, in the Fucales (Coyer et al, 2006;Engel et al, 2008;Dixon et al, 2012) and Dictyotales (De Clerck et al, 2006; Tronholm et al, 2010;Ni-Ni-Win et al, 2011;Silberfeld et al, 2013). The nuclear ITS region is also widely used in plants (Feliner & Rosselló, 2007) and marine organisms (Williams et al, 2002;Toews & Brelsford, 2012) for evolutionary studies and unravelling historical species dispersal, and is also useful in macroalgae (Lee et al, 1998;Vidal et al, 2003;Wang et al, 2008;Draisma et al, 2012) due to higher PCR amplification success rates and higher intraspecific variation (Schoch et al, 2012).…”