Systematics and Biogeography of the Red Algal GenusYonagunia(Halymeniaceae, Rhodophyta) from the Indo-Pacific Including the Description of Two New Species from Taiwan

Abstract

Carpopeltis maillardiihas been regarded as a widely distributed species in the Indo-Pacific region. In this study, we analyzed the genetic diversity ofC. maillardiiand related species collected from Taiwan and the Indian Ocean based onrbcL sequences, in order to elucidate species boundaries, diversity, and biogeographic patterns. Our analyses show thatC. maillardiispecimens are only distantly related to the genusCarpopeltis(type:C. phyllophora) but instead form a clade together with species ofYonagunia. We therefore propose the new combinationYonagunia maillardiicomb. nov. In addition, two new species (Yonagunia palmatasp. nov. andYonagunia taiwani-borealissp. nov.) are described from Taiwan. The close relationship ofYonaguniatoGrateloupiais corroborated by detailed observations of the female reproductive structures, which demonstrate that the development of auxiliary cell ampullae before and after diploidization is similar to that ofGrateloupiasensu stricto. Namely, the ampullae are composed of only two orders of unbranched filaments in which only a few ampullar cells are incorporated into a basal fusion cell after diploidization of the auxiliary cell and the pericarp consists almost entirely of secondary medullary filaments. Of allYonaguniaspecies,Y. maillardiihas the widest distribution in the Indo-Pacific, and can be identified in the field by its relatively thin, feathery, and highly branched morphology. Most other species, including those that occur in Taiwan, are seemingly more range-restricted. Our phylogenetic analyses resulted in a well-resolved phylogeny ofYonagunia, with an origin estimated in the Eocene-Oligocene, and diversification of species mainly in the Miocene.