Zoological Studies

Vol. 46 No. 1, 2007

Cryptic Diversity of the Tetraclita squamosa Complex (Crustacea: Cirripedia) in Asia: Description of a New Species from Singapore

TBenny Kwok-Kan Chan1,2,*, Ling-Ming Tsang3, and Ka-Hou Chu3

1Research Center for Biodiversity, Academia Sinica, Taipei 115, Taiwan
2The Swire Institute of Marine Science, Department of Ecology and Biodiversity, The University of Hong Kong, Pokfulam Road, Hong Kong, China
3Department of Biology, The Chinese University of Hong Kong, Shatin, Hong Kong, China

Benny Kwok-Kan Chan, Ling-Ming Tsang, and Ka-Hou Chu (2007) Tetraclita squamosa is a common intertidal barnacle of the Indo-Pacific. Taxonomic classification of T. squamosa has been confused by its high degree of morphological variation, and it is now considered to be a species complex. Tetraclita squamosa collected from Singapore exhibits diagnostic morphological and genetic differences compared to T. squamosa from the coast of southern China and T. kuroshioensis in the northwestern Pacific (a recently described species formerly recognized as T. squamosa). Tetraclita squamosa from Singapore has a long tergal margin in the scutum and a very straight scutal margin in the tergum when compared to T. kuroshioensis and T. squamosa from southern China. The setae on the cirri of T. squamosa from Singapore are similar to those of T. squamosa from southern China. Barnacles from Singapore and southern China differ from T. kuroshioensis in lacking serrulate setae with 4 rows of setules on cirrus I. From a molecular analysis, T. squamosa from Singapore is differentiated from T. squamosa from southern China, and T. kuroshioensis by more than 19%, 10%, and 11% divergences in the COI, 12S rRNA, and ITS1 sequences, respectively. These values are much higher than those within each taxon (< 1.5% in the most variable COI sequence), revealing that they are genetically distinct. The clear genetic and morphological differences from both T. squamosa and T. kuroshioensis indicate that T. squamosa from Singapore represents a new species of Tetraclita. Tetraclita squamosa in the Indo-West Pacific region is a cryptic species complex with high morphological and genetic diversity. Given the relatively restricted areas investigated to the present, it is likely that more species await discovery in Southeast Asia, Australia, and the Indian Ocean.

Key words: Tetraclita squamosa, Tetraclita singaporensis, cryptic species, species complex, Singapore.

*Correspondence: Tel: 886-2-27893863. Fax: 886-2-27890844. E-mail:chankk@gate.sinica.edu.tw