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Given the problems of species delimitation in algae using morphology or sexual compatibility, molecular data are becoming the standard for delimiting species and testing their traditional boundaries. The idea that species are separately evolving metapopulation lineages, along with theoretical progress in phylogenetic and population genetic analyses, has led to the development of new methods of species delimitation. We review these recent developments in DNA-based species delimitation methods, and discuss how they have changed and continue to change our understanding of algal species boundaries. Although single-locus approaches have proven effective for a first rapid and large-scale assessment of species diversity, species delimitation based on single gene trees falls short due to gene tree–species tree incongruence, caused by confounding processes like incomplete lineage sorting, trans-species polymorphism, hybridization and introgression. Data from unlinked loci and multi-species coalescent methods, which combine principles from phylogenetics and population genetics, may now be able to account for these complicating factors. Several of these methods also provide statistical support regarding species boundaries, which is important because speciation is a process and therefore uncertainty about precise species boundaries is inevitable in recently diverged lineages. [ABSTRACT FROM AUTHOR]

Despite a rich seaweed flora, information about Vietnamese seaweeds is scattered throughout a large number of often regional publications and, hence, difficult to access. This paper presents an up-to-date checklist of the marine macroalgae of Vietnam, compiled by means of an exhaustive bibliographical search and revision of taxon names. A total of 827 species are reported, of which the Rhodophyta show the highest species number (412 species), followed by the Chlorophyta (180 species), Phaeophyceae (147 species) and Cyanobacteria (88 species). This species richness is comparable to that of the Philippines and considerably higher than Taiwan, Thailand or Malaysia, which indicates that Vietnam possibly represents a diversity hotspot for macroalgae. A comparison of the species composition with neighbouring countries yielded surprisingly low similarities. Rather than an indication of a biogeographical pattern, we are of the opinion that the low similarity with neighbouring countries is primarily an artifact resulting from taxonomic inconsistencies. The checklist presented here could serve as a valuable tool to reveal the seaweed diversity in Vietnam and to stimulate intraregional comparative research. [ABSTRACT FROM AUTHOR]