Molecular species delimitation of marine trematodes over wide geographical ranges: spp. (Digenea: Haplosplanchnidae) in needlefishes (Belonidae) from the Pacific Ocean and Gulf of Mexico.

Geographical distribution plays a major role in our understanding of marine biodiversity. Some marine fish trematodes have been shown to have highly restricted geographical distributions, while some are known to occur over very wide ranges; however, very few of these wide distributions have been demonstrated genetically. Here, we analyse species of the genus (Haplosplanchnidae) parasitizing beloniforms from the tropical west Pacific, the eastern Pacific and the Gulf of Mexico (GoM). We test the boundaries of these trematodes by integrating molecular and morphological data, host association, habitat of the hosts and geographical distribution, following a recently proposed and standardized delineation method for the recognition of marine trematode species. Based on the new collections, is here synonymized with the type-species of the genus, ; is now considered to be widely distributed, from the GoM to the western Pacific. Additionally, we describe a new species, n. sp., from and (Belonidae) from La Carbonera coastal lagoon, northern Yucatán, GoM. We briefly discuss the role of host association and historical biogeography of the hosts as drivers of species diversification of infecting beloniforms.