Foliose Halymenia species (Halymeniaceae, Rhodophyta) from Southeast Asia, including a new species, Halymenia malaysiana sp. nov.

Abstract

Abstract Despite the large number of species discovered in Halymenia, many remain poorly known due to the scarce information available. In order to facilitate species discrimination of foliose Halymenia species in Southeast Asia, molecular analysis and morphological studies were made on Halymenia collections from Malaysia, the Philippines, and Indonesia. The rbcL phylogenetic analyses showed that there are at least six taxa of foliose Halymenia occurring in Southeast Asia. Among the six taxa, a new species, Halymenia malaysiana P.-L. Tan, P.-E. Lim, S.-M. Lin et S.-M. Phang, is proposed based on both rbcL sequence analyses and morphological observations. Halymenia malaysiana is characterized by thalli possessing oblong or suborbiculate blades with a supple cartilaginous structure and gelatinous (slimy) texture, arising from a small discoid holdfast without a stipe, abruptly expanding into a broad blade and having a smooth surface with sinusoidally undulated margins. The phylogenetic analyses also revealed that Halymenia is a polyphyletic genus, which requires further taxonomic studies.