The identity ofEucheuma perplexum(Solieriaceae, Gigartinales) and its distinction fromEucheuma serraas exemplified by a proposed new epitype

Abstract

Eucheuma perplexum is based on specimens from Patotsu, Taiwan. This species is morphologically difficult to distinguish from other eucheumatoids that exhibit a broad range of habit forms, particularlyBetaphycus gelatinus,Eucheuma denticulatum, andE. serra. Here, the Philippine and topotype specimens ofE. perplexumhave been examined, their distinguishing morphological features highlighted, and their phylogenetic relationships inferred from several gene sequences. Our results showed thatE. perplexumis distinct fromB. gelatinusand is a sister species toE. denticulatumandE. serra. Confusion also existed in a rather nebulous species circumscription ofE. serra. We therefore conducted morphological and molecular taxonomic studies of conspecific specimens from Lord Howe Island, Australia. From the variety of forms there with identical DNA profiles, we propose to nominate an epitype that closely resembles Kylin's illustration of the Mauritian holotype.