Population genomics revealed independent colonisation events of a global ascidian invader
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1
Center for Advanced Studies of Blanes, Superior Council of Scientific Investigations, Spain
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2
Department of Genetics, Microbiology and Statistics, Faculty of Biology, University of Barcelona, Spain
Invasive species constitute a major threat to biodiversity and can cause high economic and ecological negative impacts. To assess genomic diversity and population structure of non-indigenous species it is crucial to develop adequate management strategies. We developed a protocol combining whole genome amplification (WGA) and genotyping-by-sequencing (GBS). WGA is suitable for small sized organisms, colonial forms with small zooids, or studies where only trace material (scales, hairs…) is available, as is often the case for elusive and/or endangered species. This protocol was applied to the worldwide invasive colonial ascidian Didemnum vexillum using a single zooid per colony to avoid any genetic heterogeneity (chimeras). The obtained reads were filtered and analysed using the GIbPSs toolkit to get the loci dataset. WGA-GBS performance was first tested using half zooids, providing empirical demonstration for genotyping reliability. The Percentage of Shared Genotypes (PSG) was calculated from the table of haplotypic genotypes to determine the reliability of the WGA-GBS protocol. Then, we analysed 296 individuals from 12 localities worldwide including native and main invaded areas. PSG identified some clones, always within the same locality, and only one sample per clone pair was kept for further analyses. Polymorphic loci datasets generated by locality, area and globally, identified genetic differentiation at all levels. The two groups found in Japan, the native area, matched Cytochrome Oxidase I (COI) clades and were strongly differentiated at the genomic level suggesting reproductive isolation and a speciation process. Our genomic analyses confirmed that only one COI clade spread worldwide. Genetic diversity and differentiation was high in the introduced localities as well as in the native area. MDS and STRUCTURE analyses showed that three independent colonisation events determined the distribution of the species, although all population pairwise comparisons were significant. Human-mediated transportation seems to drive the distribution pattern of this species worldwide and regionally, as there is a lack of isolation by distance within introduced areas. Diverse and well differentiated populations point to a high expansion potential of this worrisome worldwide invader.
Acknowledgements
We are indebted to all people that contributed samples for this study: Gretchen Lambert, Ian Davidson, Judith Pederson, and Gaku Kumano. We specially thank Carles Bori, Davide Tagliapietra, Marco Sigovini and Irene Guarneri for their help during sampling in Ebro Delta and Venice. This research was funded by project PopCOmics (TM2017-88080) from the Spanish Government. This is a contribution from the Consolidated Research Group “Benthic Biology and Ecology” SGR2017-1120 (Catalan Government).
Keywords:
invasive species,
Population Genomics,
genotyping-by-sequencing,
whole genome amplification,
Didemnum vexillum
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Oral Presentation
Topic:
Global Change, Invasive Species and Conservation
Citation:
Turon
X,
Casso
M and
Pascual
M
(2019). Population genomics revealed independent colonisation events of a global ascidian invader.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00043
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Received:
14 May 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Prof. Xavier Turon, Center for Advanced Studies of Blanes, Superior Council of Scientific Investigations, Blanes, Spain, xturon@ceab.csic.es