Living with marginal coral communities: Diversity and host-specificity in coral-associated barnacles in the northern coral distribution limit of the East China Sea

Abstract

Corals and their associated fauna are extremely diverse in tropical waters and form major reefs. In the high-latitude temperate zone, corals living near their distribution limit are considered marginal communities because they are particularly extremely sensitive to environmental and climatic changes. In this study, we examined the diversity and host usage of coral-associated barnacles on Jeju Island, Korea, the northern coral distribution limit in the East China Sea. In this study, only three coral-associated barnacles—from two genera in two subfamilies—were collected. The Pyrgomatinid barnacles Cantellius arcuatus and Cantellius cf. euspinulosum were found only on the corals Montipora millepora and Alveopora japonica, respectively. The Megatrematinid barnacle Pyrgomina oulastreae, relatively a generalist, was found on Psammocora spp. (both profundacella and albopicta) and Oulastrea crispata corals. The host usage of these three barnacles does not overlap. DNA barcode sequences of the C. arcuatus specimens collected in the present study matched those collected in Kochi in Japan, Taiwan, Malaysia and Papua New Guinea, suggesting that this species has a wide geographical distribution. C. arcuatus covers a wider host range in Taiwan waters, inhabiting Montipora spp. and Porites spp., which suggests that the host specificity of coral-associated barnacles varies with host availability. C. cf. euspinulosum probably has a very narrow distribution and host usage. The sequences of C. cf. euspinulosum on Jeju Island do not match those of any known sequences of Cantellius barnacles in the Indo-Pacific region. P. oulastreae probably prefers cold water because it has been reported in temperate regions. Coral-associated barnacles in marginal communities have considerably lower diversity than their subtropical and tropical counterparts. When host availability is limited, marginal coral-associated barnacles exhibit higher host specificity than those in subtropical and tropical reef systems.

Biogeography of intertidal and subtidal native and invasive barnacles in Korea in relation to oceanographic current ecoregions and global climatic changes

“…Island within the East China Sea ecoregion (also see Chan et al, 2018). These barnacle species did not contribute to the significant species assemblage between the Yellow Sea and East China Sea ecoregion because they are only recorded in Jeju Island within the East China Sea ecoregion.…”

“…These barnacle species did not contribute to the significant species assemblage between the Yellow Sea and East China Sea ecoregion because they are only recorded in Jeju Island within the East China Sea ecoregion. At the same latitude on the Pacific Ocean side of Japan, ~30 coral-inhabiting barnacles and 100 hard coral species have been reported (Chan et al ., 2018). The warm Kuroshio in the East China Sea ecoregion is relatively weak, resulting in reduced diversity of scleractinian coral species.…”

“…Three species of coral-inhabiting barnacles ( Cantellius arcuatus , Cantellius sp. and Pyrgomina oulastreae ) were identified exclusively from five scleractinian corals at Jeju Island within the East China Sea ecoregion (also see Chan et al ., 2018). These barnacle species did not contribute to the significant species assemblage between the Yellow Sea and East China Sea ecoregion because they are only recorded in Jeju Island within the East China Sea ecoregion.…”

DNA-based diversity assessment reveals a new coral barnacle, Cantellius alveoporae sp. nov. (Balanomorpha: Pyrgomatidae) exclusively associated with the high latitude coral Alveopora japonica in the waters of southern Korea

“…Coral communities occurring at high latitudes are termed as marginal communities, as they are at the marginal distribution of coral triangles. Marginal coral communities are characterized by low diversity, slow growth rates, and high susceptibility to global climatic changes ( Chan et al, 2018 ).…”

“…These corals include the high latitude coral Alveopora japonica , which is a common foundation species, with its spatial distribution (and hence abundance) recently expanding due to global climate change. Chan et al (2018) studied the molecular diversity of coral barnacles in the waters around the Jejudo Island, and recorded three coral barnacle species growing on four Scleractinian coral hosts. The barnacle Cantellius arcuatus was only found on the coral Montipora millipora .…”