title: Geographic and phylogenetic evidence for dispersed nuclear introgression in a daphniid with sexual propagules.
abstract: The role of among-species gene flow in eukaryotic evolution remains controversial. Putative hybrid lineages are common in water fleas, but their ecological success is often associated with polyploidy and the production of asexual propagules. Advanced hybrid lineages with sexual propagules are expected to be geographically restricted because their successful dispersal is contingent on overcoming fertility complications, assimilation by parent taxa, and competition with parent taxa. Here we provide evidence that a diploid lineage of Daphnia has been formed by introgression between distantly related species and attained a broad distribution (Nearctic) despite its requirement for sexual propagules. The evidence is based on geographical discordance, phylogenetic discordance, recombinant genotypes and additive genotypes of the nuclear internal transcribed spacer regions (ITS) and mitochondrial DNA. Additive genotypes also provided evidence of hybridization between introduced European Daphnia and North American Daphnia. We argue that the unique biology of Holarctic lacustrine water fleas and the spatial separation of lineages during Pleistocene glaciation have promoted hybridization and its evolutionary consequences.
authors.affiliation: Department of Biological Sciences, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA. djtaylor@acsu.buffalo.edu
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Taylor
authors.forename: Heather L
authors.initials: HL
authors.lastname: Sprenger
authors.forename: Seiji
authors.initials: S
authors.lastname: Ishida
mesh_terms: D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D003001:Cloning, Molecular; D017931:DNA Primers; D004272:DNA, Mitochondrial / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003621:Daphnia / Q000235:genetics*; D005060:Europe; D005828:Genetics, Population; D005838:Genotype; D005843:Geography; D006824:Hybridization, Genetic; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009656:North America; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial; D021903:DNA, Ribosomal Spacer