Phylogenetic analysis of the red algal tribe Ceramieae reveals multiple morphological homoplasies but defines new genera

Despite the importance of morphological characters for classification, molecular data are now more widely used than morphology in phylogenetic reconstructions, particularly in studies of algae. The tribe Ceramieae C.Agardh ex Greville (Ceramiaceae) is a widespread, speciose, and morphologically diverse group of valuable red algae with many identified bioactives. We aimed to elucidate phylogenetic relationships in the tribe to delimit genera and provide a new classification. Generic delimitation is currently based on morphological characters, and there has been no overall reassessment of generic circumscriptions and evolutionary relationships using molecular data. We used three molecular markers (mitochondrial COI-5P, plastid rbcL and nuclear LSU). Within the Ceramieae, several clades are recovered, although the relationships among major clades are not supported. These clades are here recognized as genera, with new circumscriptions for Ceramium Roth, Carpoblepharis Kützing, Herpochondria F.Schmitz & Falkenberg, Campylaephora J.Agardh and Celeceras Kützing, and the proposal of Pseudoceramium Barros-Barreto & Maggs, gen. nov., Yoneshiguea Barros-Barreto, Maggs & M.A.Jaramillo, gen. nov. and Stirkia Barros-Barreto & Maggs, gen. nov. The Ceramieae show a high degree of morphological homoplasy among species as well as extreme phenotypic plasticity within species. Genera lack unique synapomorphies and multiple morphological characters are required to define most of them. Molecular data are critical for understanding systematics in this group.