Phylogenetic relationships and distribution of Gelidium crinale and G. pusillum (Gelidiales, Rhodophyta) using cox1 and rbcL sequences

The taxonomic distinctiveness and cosmopolitan distributions of the red algae $Gelidium$ $crinale$ and $G.$ $pusillum$ remain unclear. Both species were first described in Devon in southwestern England; namely in Ilfracome for $G.$ $crinale$ and Sidmouth for $G.$ $pusillum$. We analyzed mitochondrial $cox$1 and plastid $rbc$L sequences from specimens collected in East Asia, Australia, Europe and North America. In all phylogenetic analyses of $cox$1 and $rbc$L sequences, $G.$ $crinale$ was distinct from congeners of the genus. The analyses also revealed a sister relationship with the $G.$ $coulteri$ and $G.$ $capense$ clade. Nineteen $cox$1 haplotypes were identified for $G.$ $crinale$, and they were likely geographically structured. Despite the distinctiveness in both $cox$1 and $rbc$L datasets, the sister relationship of $G.$ $pusillum$ in the genus was not resolved. Our $cox$1 and $rbc$L datasets indicate that $G.$ $crinale$ is a cosmopolitan species, found in East Asia, Australia, Europe and North America, while the distribution of $G.$ $pusillum$ is restricted to Europe and Atlantic North America. Our results suggest that infraspecific classification of $G.$ $pusillum$ may be abandoned.