Two new intertidal oribatid mite species from the Indo-pacific region are described. Indopacifica iohanna sp. n. was found on the coasts of the Philippines and can be distinguished from its congeners by the lack of a ventral tooth on the claws. The larva and nymphs of this species show the same type of plication and setation typical for juveniles of other selenoribatid mites. Indopacifica mauritiana sp. n. was discovered on the coast of Mauritius and can be separated from its congeners by possessing only vestigial lamellar setae. A morphometric comparison of these two species and Indopacifica pantai from Thailand and Malaysia showed a clear separation between the three species. The known distribution of the genus Indopacifica stretches now from Mauritius in the West to the Philippines in the East and further occurrences within this area should be expected.
This study demonstrates for the first time the presence of marine-associated mites in the Andaman Sea and Strait of Malacca and reveals a relatively high diversity of these taxa with six species from two different families: Selenoribatidae and Fortuyniidae. Indopacifica, a new genus of Selenoribatidae, is described from Thailand and Malaysia, with two new species, Indopacifica pantai n. sp. and Indopacifica parva n. sp. The genus is characterized by the unique combination of following characters: lacking lamellar ridges, incomplete dorsosejugal suture, fourteen pairs of notogastral setae, and presence of epimeral foveae. A phylogenetic reconstruction based on 18S ribosomal RNA sequences clearly confirms the distinctness of the new genus Indopacifica and places it close to the genus Rhizophobates. The lack of molecular genetic data of possible relatives impedes a clear assessment, and hence, we emphasize the need for further combined approaches using morphological and molecular genetic sequence data. All species show wide distribution areas within this geographic region suggesting that these taxa are good dispersers despite their minute size and wingless body. Molecular genetic data demonstrate recent gene flow between far distant populations of I. pantai n. sp. from the coasts of Thailand and two islands of Malaysia and hence confirm this assumption. The seasonally changing surface currents within this geographic area may favor hydrochorous dispersal and hence genetic exchange. Nevertheless, morphometric data show a slight trend to morphological divergence among the studied populations, whereas this variation is suggested to be a result of genetic drift but also of habitat differences in one population of Alismobates pseudoreticulatus.