DOI: 10.5061/dryad.83bk3j9p1
title: Species distribution, hybridization and connectivity in the genus Chionodraco: unveiling unknown icefish diversity in Antarctica

description: Aim The species of the genus Chionodraco (Notothenioidei) are the most
 abundant icefish on the continental shelf of the Weddell Sea. While
 previous studies indicated that only Chionodraco hamatus and Chionodraco
 myersi inhabit the Weddell Sea, the third Chionodraco species, Chionodraco
 rastrospinosus, was recently sampled in the area. Since C. rastrospinosus
 is supposed to be found only at the Antarctic Peninsula and Scotia Arc,
 this study aimed at confirming the species classification of C.
 rastrospinosus by molecular methods and identifying its putative source
 population. Given the documented evidence of introgression among the three
 species, we tested whether the newly found C. rastrospinosus shared any
 genetic variability with the other Chionodraco species. To explain the
 pattern of distribution of the Chionodraco species, we aimed at estimating
 the hydrodynamic connectivity between the Antarctic Peninsula and the
 Weddell Sea. Location Antarctic Peninsula, southern Scotia Arc and the
 south-eastern Weddell Sea Methods We genotyped 19 microsatellites and
 sequenced the mitochondrial D-loop for 560 Chionodraco individuals. We
 simulated the dispersal of more than 3 million drifters (Lagrangian
 model). Results The molecular analyses support the presence of C.
 rastrospinosus in the Weddell Sea and its homogeneity with C.
 rastrospinosus from the Antarctic Peninsula. Bayesian clustering
 identifies three putative hybrids among C. rastrospinosus and the other
 congenerics. Lagrangian simulations do not support connectivity driven by
 the oceanographic features of the Antarctic Peninsula and Weddell Sea via
 passive larval dispersal only. Main conclusions This study documents, for
 the first time, the presence of C. rastrospinosus in the Weddell Sea
 unveiling more biodiversity than previously known in this region. The
 sympatry of the three Chionodraco species explains the occurrence of
 occasional, ongoing events of hybridization in the genus. Alternative
 possible hypotheses need to be tested in future studies about the
 mechanisms maintaining the interspecific connectivity in Chionodraco spp.
description: Panel of 19 microsatellites loci for 564 individuals belonging to
 the species <em>Chionodraco hamatus</em>,
 <em>Chionodraco myersi</em> and <em>Chionodraco
 rastrospinosus</em>. All loci were previously characterized for the
 three <i>Chionodraco</i> species by Agostini et al.
 (2013). Fragment lengths were estimated by Genoscreen (www.genoscreen.fr)
 on a ABI PRISM 3700 DNA Analyzer (Applied Biosystems). Scoring and binning
 were performed by two operators, independently, with Peak Scanner ver.
 1.0 (Applied Biosystem) and with the Excel macro Flexibin (Amos
 et al., 2007) respectively. The input files were generated with CREATE ver.
 1.38 (Coombs, Letcher, & Nislow, 2008).
 Agostini, C., Papetti, C., Patarnello, T., Mark, F. C., Zane, L., & Marino, I. A. M. (2013). Putative selected markers in the <em>Chionodraco</em> genus detected by interspecific outlier tests. <i>Polar Biology</i>, <i>36</i>(10), 1509–1518. https://doi.org/10.1007/s00300-013-1370-0 Amos, W., Hoffman, J. I., Frodsham, A., Zhang, L., Best, S., & Hill, A. V. S. (2007). Automated binning of microsatellite alleles: Problems and solutions. <i>Molecular Ecology Notes</i>, <i>7</i>(1), 10–14. https://doi.org/10.1111/j.1471-8286.2006.01560.x Coombs, J. A., Letcher, B. H., & Nislow, K. H. (2008). Create: A software to create input files from diploid genotypic data for 52 genetic software programs. <i>Molecular Ecology Resources</i>, <i>8</i>(3), 578–580. https://doi.org/10.1111/j.1471-8286.2007.02036.x
description: There are four different dataset in Genepop format: one that
 includes all species ("all-chionodraco-species") and one for
 each species separately ("hamatus", "myersi",
 "rastrospinosus").<br> Each dataset, according to the
 Genepop format, is made by two files: the proper microsatelite dataset
 (e.g. "name-file-GENEPOP.txt") and a file showing the name of
 the samples which the dataset is divided in (e.g.
 "name-file-POPULATION-NAMES.txt").
 .