An assessment of diversity within the genus Champia (Rhodymeniales, Rhodophyta) in the Hawaiian Islands

Abstract

The family Champiaceae is one of seven of the order Rhodymeniales, with two genera, Champia and Coelothrix present in Hawaii. While the order has been well-studied at the molecular level, there is a lack of data concerning species boundaries within Champia. In Hawaii there are currently two species reported to be present: C. parvula and C. vieillardii, which are distinguished primarily by the shape of the thallus. This research addresses genetic divergence within the genus Champia in Hawaii using three molecular markers: the nuclear small subunit ribosomal RNA gene (18S), the plastid rubisco large subunit (rbcL), and a portion of the mitochondrial cytochrome c oxidase 1 gene (CO1). Morphological data are analyzed to supplement the molecular data. The results from analyses of all three genes do not support the current distinction of flat morphotypes as C. vieillardii and terete morphotypes as C. parvula. The data indicate the presence of at least five species of the flattened type, supported by both molecular and morphological data. Molecular comparison of Hawaiian species identified as C. parvula with presumed C. parvula species collected elsewhere indicate that misidentification of this supposedly cosmopolitan species is likely occurring. The rbcL and CO1 analyses suggest the possibility of multiple terete species currently identified as C. parvula, though no morphological patterns are found within the terete specimens. This study concludes that species diversity of Champia is grossly underestimated in the Hawaiian Islands, and highlights the need for a global revision of the genus.