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Hurtado LA, Mateos M, Wang C, Santamaria CA, Jung J, Khalaji-Pirbalouty V, Kim W.2017. Out of Asia: Mitochondrial evolutionary history of the globally introduced supralittoral isopod Ligia exotica. PeerJ Preprints5:e3497v1https://doi.org/10.7287/peerj.preprints.3497v1
The native ranges and invasion histories of many marine species remain elusive due to a dynamic dispersal process via marine vessels. Molecular markers can aid in identification of native ranges and elucidation of the introduction and establishment process. The supralittoral isopod Ligia exotica has a wide tropical and subtropical distribution, frequently found in harbors and ports around the globe. This isopod is hypothesized to have an Old World origin, from where it was unintentionally introduced to other regions via wooden ships and solid ballast. Its native range, however, remains uncertain. Recent molecular studies uncovered the presence of two highly divergent lineages of L. exotica in East Asia, and suggest this region is a source of nonindigenous populations. In this study, we conducted phylogenetic analyses (Maximum Likelihood and Bayesian) of a fragment of the mitochondrial 16S ribosomal (r)DNA gene using a dataset of this isopod that greatly expanded previous representation from Asia and putative nonindigenous populations around the world. For a subset of samples, sequences of 12S rDNA and NaK were also obtained and analyzed together with 16S rDNA. Our results show that L. exotica is comprised of several highly divergent genetic lineages, which probably represent different species. Most of the 16S rDNA genetic diversity (48 haplotypes) was detected in East and Southeast Asia. Only seven haplotypes were observed outside this region (in the Americas, Hawai’i, Africa and India), which were identical or closely related to haplotypes found in East and Southeast Asia. Phylogenetic patterns indicate the L. exotica clade originated and diversified in East and Southeast Asia, and only members of one of the divergent lineages have spread out of this region, recently, suggesting the potential to become invasive is phylogenetically constrained.
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Table S1. Information on the samples included in this study. ID labels correspond with those used in the figures.
Table S2. Settings for Maximum Likelihood and Bayesian analyses. A All others default; B Average Standard Deviation of Split Frequencies; C estimated in Tracer v.1.6; D Effective Sample Size; E Potential Scale Reduction Factor for all parameters.
Table S3. A. Support for the clades defined in Figure 2 from different methods and substitution models for the 16S rDNA dataset.
B. Support for the clades defined in Figure 2 from different methods and substitution models for the 16S rDNA and 12S rDNA concatenated dataset. n/a = not applicable (i.e., relationship could not be examined with this dataset).