Phylogenetic history of the acquisition of molluscan hosts in acotylean flatworms

The question of how symbionts acquired hosts and diversified phylogenetically during their evolutionary history is a focus of attention in many symbiotic taxa. Marine polyclad flatworms are usually free-living, but some are symbiotic, using animals as hosts. However, the history of their acquisition of symbiotic systems is not well understood. Therefore, we focused on mollusc symbiotic flatworms in the suborder Acotylea and investigated the host specificity and phylogenetic history of symbiotic acquisition. Field surveys revealed that symbiotic flatworms utilized certain molluscs as hosts. In particular, Stylochoplana pusilla and Stylochoplana parasitica utilized different molluscan species as hosts sympatrically. Also, the phylogenetic analysis and the ancestral state reconstruction indicate that the mollusc symbiotic flatworms formed a monophyletic group and that their common ancestor shifted from free-living to mollusc symbiosis. These results suggest that each of the flatworms did n..., To investigate the phylogenetic relationships of the symbiotic flatworms, the whole mitochondrial genome and the nuclear ribosomal sequences of S. pusilla, S. parasitica and Stylochoplana sp. were determined. DNA extraction was conducted using the DNeasy Blood and Tissue Kit (Qiagen, Hilden, Germany). Partial sequences for CO1 and 28S were PCR-amplified following the PCR conditions described by the previous study 1, and were obtained through sequencing on ABI 3130xl automated DNA sequencer at Atmosphere and Ocean Research Institute (AORI), The University of Tokyo (Kashiwa, Chiba). The extracted DNA was quantified using a Nanodrop One (Thermo Scientific, Wilmington, DEL) and used for the library preparation for next-generation sequencing analysis. The DNA shotgun sequencing was conducted using a Miseq System (Illumina, San Diego, CA) with paired-end 300 bp reads at the National Institute for Environmental Studies (Tsukuba, Japan) for S. parasitica, and using DNBSEQ-T7 system (MGI Te..., , # Phylogenetic history of the acquisition of molluscan hosts in acotylean flatworms

[https://doi.org/10.5061/dryad.31zcrjdxm](https://doi.org/10.5061/dryad.31zcrjdxm)

## Description of the data and file structure

This dataset was used in the paper ‘Phylogenetic history of the acquisition of molluscan hosts in acotylean flatworms’ submitted to Biology Letters.

”`AncestralStateEstimation.zip`” is the file used for ancestral state estimation, which was based on the obtained phylogenetic tree and host-use information. 

\>\"bayes.tree\": Phylogenetic tree file used.

\>\"habitat.txt\": Text file showing current traits. The first column is the species name and the second column indicates the trait. Trait A indicates free-living, B indicates mantis shrimp host, C indicates hermit crab host, and D indicates mollusc host.

\>\"run.txt\": Run file showing detailed settings for ancestral trait estimation.

”`PhylogenyMtGenome.zip`” is the file used in the construction of the phylogenetic tree of th...,