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Transition in sexual system and sex chromosome evolution in the tadpole shrimp Triops cancriformis

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posted on 24.04.2015, 13:43 by T. C. Mathers, Robert L. Hammond, R. A. Jenner, B. Hänfling, J. Atkins, A. Gómez
Transitions in sexual system and reproductive mode may affect the course of sex chromosome evolution, for instance by altering the strength of sexually antagonistic selection. However, there have been few studies of sex chromosomes in systems where such transitions have been documented. The European tadpole shrimp, Triops cancriformis, has undergone a transition from dioecy to androdioecy (a sexual system where hermaphrodites and males coexist), offering an excellent opportunity to test the impact of this transition on the evolution of sex chromosomes. To identify sex-linked markers, to understand mechanisms of sex determination and to investigate differences between sexual systems, we carried out a genome-wide association study using Restriction-site Associated DNA sequencing (RAD-seq) of 47 males, females and hermaphrodites from one dioecious and one androdioecious population. We analyzed 22.9 Gb of paired-end sequences and identified and scored >3,000 high coverage novel genomic RAD markers. Presence/absence of markers, SNP association, and read depth identified 52 candidate sex- linked markers. We show that sex is genetically determined in T. cancriformis, with a ZW system conserved across dioecious and androdioecious populations and hermaphrodites likely having evolved from females. We also show that the structure of the sex chromosomes differs strikingly, with a larger sex-linked region in the dioecious population compared to the androdioecious population.


Part of T.C.M.’s Ph.D. project ‘The genetics and evolutionary dynamics of reproductive mode in tadpole shrimps’ funded by a NERC CASE Studentship (NE/G012318/1). RAD library preparation and Illumina sequencing was funded by a NERC-NBAF grant (NBAF400). A.G. was funded by an Advanced NERC fellowship (NE/B501298/1)



Heredity (2015) 115, 37–46

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/Organisation/COLLEGE OF MEDICINE, BIOLOGICAL SCIENCES AND PSYCHOLOGY/School of Biological Sciences/Department of Biology


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Heredity (2015) 115


Nature Publishing Group for Genetics Society, Genetics Society of Great Britain





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The sequence data produced in this study is available via the Sequence Read Archive through accession number PRJEB7851 (http://www.ebi.ac.uk/ena/data/view/PRJEB7851)