Taxonomic circumscription of heterogeneous species <i><scp>N</scp>eogoniolithon brassica‐florida</i> (<scp>C</scp>orallinales, <scp>R</scp>hodophyta) in <scp>J</scp>apan

Abstract

Summary The nongeniculate species N eogoniolithon brassica‐florida ( H arvey) S etchell et M ason is circumscribed as a polymorphic species with various gross morphologies due to it being synonymized with several previous species. However, small subunit rDNA and cox 1 analyses showed that N . brassica‐florida was polyphyletic, and strongly imply that crustose species lacking any protuberances such as N eogoniolithon fosliei ( H eydrich) S etchell et M ason and species with protuberances or branches such as N . brassica‐florida and N . frutescens ( F oslie) S etchell et M ason should be treated as genetically different groups (species). Therefore, we propose the resurrection of N . frutescens . We also confirmed that N . trichotomum was distinguished from N . frutescens by slender uniform diameter branches, a conceptacle with a prominent ostiole, and large cox 1 interspecific sequence differences. Male and female reproductive structures of N . trichotomum were illustrated for the first time. Neogoniolithon fosliei, was divided into three clades, each of which was recognized as a species complex based on interspecific level sequence differences within clade and morphological differences. Therefore, we treated the clade most similar to N . fosliei as N . fosliei complex ( C lade B ), and the other clades as respective complexes of N . cf. fosliei with yellow conceptacles ( C lade A ) or N . cf. fosliei with large conceptacles ( C lade C ). Of two species complexes ( C lade A and B ) were morphologically consistent with two entities of N . fosliei previously reported in the R yukyu I slands, J apan, which is supported by their niche partitioning. DNA barcoding research of nongeniculate corallines can promote the finding of more reliable taxonomic characters and the understanding of their biological aspects.