Biodiversity and host specificity of coral barnacles of Galkinia (Cirripedia: Pyrgomatidae) in Taiwan, with descriptions of six new species

Abstract

Galkinia Ross and Newman, 1995 exclusively contains coral-inhabiting barnacles (Pyrgomatidae) with 4-plated shells and a fused scutum and tergum. In the present study, we applied morphological and molecular analyses (mitochondrial DNA: 12S rDNA and COI regions) to identify six new species, in addition to the two previously described congeneric species. These six species exhibit diagnostic characters in the morphology of the external shells, scutum, and tergum that separate them from all described Galkinia. Host specificity varied among various Galkinia in Taiwan. Galkinia indica (Annandale, 1924) is specific to corals in Hydnophora, while G. adamanteus n. sp. and G. equus n. sp. are specific to Favites abdita. Galkinia depressa n. sp. and G. altiapiculus n. sp., however, are epibiotic on a wider range of coral hosts including Goniastrea, Favites, Montipora, Platygyra, and Merulina. We did not analyze the host specificity of G. decima (Ross and Newman, 1973), G. tabulatus n. sp., or G. trimegadonta n. sp. due to limited sample sizes. Based on phylogenetic results, G. altiapiculus n. sp. and G. depressa n. sp. belonged to more-recently evolved phylogenetic clades compared to other species of Galkinia, suggesting a possible evolutionary trend of reduced host specificity by Galkinia.