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.
Bibliographical noteFunding Information:
Funding was provided by an NSF grant DEB 0743782 to Luis A. Hurtado and Mariana Mateos, TAMU-CONACyT grants to Luis A. Hurtado, and Hispanic Leaders in Agriculture and the Environment Program Fellowship and Community Impact Funds to Carlos A. Santamaria. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
We thank the following individuals and institutions for specimens: Aska Yamaki (Yokohama National University, Japan); Jeng-Di Lee (Institute of Marine Affairs, National Sun Yat-sen University, Kaohsiung, Taiwan); Dr. Ravichandran (Annamalai University, India), Charles Griffiths; Jesser Fidelis de Souza Filho (Museu de Oceanografia/UFPE, Recife, PE, Brazil); Paulo C. Paiva and Gustavo Mattos (Departamento de Zoologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil); I Tomasco; D Macedo; Florida Museum of Natural History. Funding was provided by an NSF grant DEB 0743782 to Luis A. Hurtado and Mariana Mateos, TAMU-CONACyT grants to Luis A. Hurtado, and Hispanic Leaders in Agriculture and the Environment Program Fellowship and Community Impact Funds to Carlos A. Santamaria. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The following grant information was disclosed by the authors:: DEB 0743782. TAMU-CONACyT
© 2018 Hurtado et al.
- Gulf of Mexico
- New world
- Old world