Evolutionary ecology of driftwood talitrids: a review

Thailandorchestiarhizophila sp. nov., a new genus and species of driftwood hopper (Crustacea, Amphipoda, Protorchestiidae) from Thailand

During a scientific survey, a new genus of driftwood hopper was found in mangrove roots in Ko Kut District, Trat Province, Thailand. We placed this new genus, Thailandorchestia gen. nov., within the family Protorchestiidae. The new genus can be distinguished from the remaining genera by uropod 1 outer ramus with robust setae, uropod 2 outer ramus without robust setae, and pereopod 7 basis without a posterodistal lobe. The type species of Thailandorchestia gen. nov., Thailandorchestiarhizophila sp. nov., is described herein, and an updated key to the genera of the family Protorchestiidae is provided.

Sea–land transition drove terrestrial amphipod diversification in East Asia, with a description of a new species

Sea–land transition caused by marine incursion and regression is hypothesized to be a major driving force in terrestrial biodiversity, providing opportunities for marine ancestors to colonize terrestrial habitats and driving vicariant speciation in distinct geographical regions. Here, we test this hypothesis in East Asia using amphipods of the Morinoia japonica complex. We constructed a dataset from 269 individuals covering all known ranges of this species complex. Phylogenetic and biogeographic analyses revealed that sea–land transition during the Miocene drove the coastal ancestor to invade terrestrial habitats in East Asia and subsequently split into eight biogeographic lineages in eastern China, Korea, Japan and some Pacific islands. Stepping-stone dispersal resulted in a relatively wide distribution of M. japonica, and long-term geographical isolation led to the diversification of the M. japonica complex. Species delimitation analysis suggests that this complex contains eight species. We describe the geographical group from eastern China as a new species, Morinoia aosen sp. nov., based on genetic and morphological comparisons with other geographical groups. Type specimens are deposited in the Institute of Zoology, Chinese Academy of Sciences (IZCAS) in Beijing, China.

Molecular phylogenetic position of Minamitalitrus zoltani elucidates a further troglobisation pattern in cave-dwelling terrestrial amphipods (Crustacea: Talitridae)

Talitrids are a highly diverse group of amphipod crustaceans that have colonized various terrestrial habitats. Three genera have successfully adapted to cave habitats on islands in the Pacific and Atlantic Oceans. However, the evolutionary origin of the Pacific troglobitic talitrids has remained unknown. We estimate the phylogenetic position of the troglobitic Minamitalitrus zoltani, which inhabits limestone caves on Minamidaito Island in the Northwestern Pacific, on the basis of the traditional multi-locus dataset. For the analyzed talitrids, we also reconstruct ancestral states of the maxilliped palp and male gnathopod 2. Our results indicate that Minamitalitrus zoltani is sister to the epigean Nipponorchestia curvatus with a deep divergence. Nipponorchestia curvatus inhabits coastal habitats in Japan, but is not indigenous to Minamidaito Island. A previous study estimated that the Atlantic troglobitic species had invaded subterranean habitats multiple times, but we provide new insight into the troglobisation history in talitrids. We also recover secondary shifts of character states of the maxilliped palp and male gnathopod 2 within the lineage composed of Minamitalitrus and its phylogenetically close genera. Our findings highlight the need for the genus-level reclassification of these genera; we split Nipponorchestia into two genera, establishing a new genus for Nipponorchestia nudiramus.