The role of hybridization in the origin and spread of asexuality in Daphnia |
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Authors: | Sen Xu David J. Innes Michael Lynch Melania E. Cristescu |
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Affiliation: | 1. Great Lakes Institute for Environmental Research, University of Windsor, , Windsor, ON, Canada N9B 3P4;2. Department of Biology, Indiana University, , Bloomington, IN 47405 USA;3. Department of Biology, Memorial University of Newfoundland, , St. John's, NF, Canada A1B 3X9;4. Department of Biology, McGill University, , Montreal, QC, Canada H3A 1B1 |
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Abstract: | The molecular mechanisms leading to asexuality remain little understood despite their substantial bearing on why sexual reproduction is dominant in nature. Here, we examine the role of hybridization in the origin and spread of obligate asexuality in Daphnia pulex, arguably the best‐documented case of contagious asexuality. Obligately parthenogenetic (OP) clones of D. pulex have traditionally been separated into ‘hybrid’ (Ldh SF) and ‘nonhybrid’ (Ldh SS) forms because the lactase dehydrogenase (Ldh) locus distinguishes the cyclically parthenogenetic (CP) lake dwelling Daphnia pulicaria (Ldh FF) from its ephemeral pond dwelling sister species D. pulex (Ldh SS). The results of our population genetic analyses based on microsatellite loci suggest that both Ldh SS and SF OP individuals can originate from the crossing of CP female F1 (D. pulex × D. pulicaria) and backcross with males from OP lineages carrying genes that suppress meiosis specifically in female offspring. In previous studies, a suite of diagnostic markers was found to be associated with OP in Ldh SS D. pulex lineages. Our association mapping supports a similar genetic mechanism for the spread of obligate parthenogenesis in Ldh SF OP individuals. Interestingly, our study shows that CP D. pulicaria carry many of the diagnostic microsatellite alleles associated with obligate parthenogenesis. We argue that the assemblage of mutations that suppress meiosis and underlie obligate parthenogenesis in D. pulex originated due to a unique historical hybridization and introgression event between D. pulex and D. pulicaria. |
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Keywords: | asexuality
Daphnia pulex
Daphnia pulicaria
hybridization meiosis suppression parthenogenesis |
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