A molecular phylogeny is presented for 25 newly sequenced specimens of Gastropteridae. The present phylogeny was estimated by analysing the nuclear fragment 28S and two mitochondrial fragments cytochrome c oxidase I (COI) and 16S using maximum likelihood and Bayesian analyses. The distinctness of eight new species of Gastropteridae is supported by the molecular phylogeny and by subsequent Automatic Barcode Gap Discovery (ABGD) analysis. Morphological data also support the distinctness of these species. The following species are described here: Gastropteron minutum Ong and Gosliner sp. nov., Gastropteron multo Ong and Gosliner sp. nov., Sagaminopteron multimaculatum Ong and Gosliner sp. nov., Siphopteron vermiculum Ong and Gosliner sp. nov., Siphopteron flavolineatum Ong and Gosliner sp. nov., Siphopteron nakakatuwa Ong and Gosliner sp. nov., Siphopteron makisig Ong and Gosliner sp. nov. and Siphopteron dumbo Ong and Gosliner sp. nov. All of these species, spanning much of the phylogenetic tree of Gastropteridae, are found in a single, highly diverse region of the Philippines, the Verde Island Passage. These data support the hypothesis that this region is an area of high species richness as well as phyletic diversity. This study also supports strong correlation between morphological characters and the molecular phylogeny within the species of Siphopteron. Molecular studies also indicate the distinctness of specimens of Siphopteron quadrispinosum from Hawaii and those from the western Pacific. Western Pacific specimens should be regarded as Siphopteron leah. Siphopteron pohnpei is transferred to Sagaminopteron based on the molecular phylogeny. Other species complexes indicating the presence of geographically separated cryptic species indicate that further detailed study of this group is warranted and that hidden diversity is likely to increase with additional study.
Based on our morphological studies and molecular phylogeny, we confirmed that the eight new species hypothesized from our field observations of living animals all represent new species that are described here. Our molecular phylogeny also indicates the likely existence of geographically isolated cryptic species within previously classified specimens. Sagaminopteron psychedelicum from Madagascar appears to represent a cryptic species distinct from western Pacific populations, as is Sagaminopteron nigropunctatum from Saudi Arabia. Also, the western Indian Ocean specimen of S. tigrinum represents a cryptic species distinct from the western Pacific S. tigrinum. The lack of strong support for the monophyly of Gastropteron and Siphopteron requires additional study of taxa to determine whether greater support of these lineages is found when taxon sampling is increased. Also the phylogenetic and systematic relationship of Enotepteron needs to be examined when members of this taxon become available for molecular studies.
Elise Ong, Joshua M Hallas and Terrence M Gosliner. 2017. Like A Bat Out of Heaven: the Phylogeny and Diversity of the Bat-winged Slugs (Heterobranchia: Gastropteridae). Zoological Journal of the Linnean Society. 180(4); 755–789. DOI: 10.1093/zoolinnean/zlw018