title: Do relaxed selection and habitat temperature facilitate biased mitogenomic introgression in a narrowly endemic fish?
abstract: Introgression might be exceptionally common during the evolution of narrowly endemic species. For instance, in the springs of the small and isolated Cuatro Ciénegas Valley, the mitogenome of the cichlid fishHerichthys cyanoguttatuscould be rapidly introgressing into populations of the trophically polymorphicH. minckleyi. We used a combination of genetic and environmental data to examine the factors associated with this mitochondrial introgression. A reduced representation library of over 6220 single nucleotide polymorphisms (SNPs) from the nuclear genome showed that mitochondrial introgression intoH. minckleyiis biased relative to the amount of nuclear introgression. SNP assignment probabilities also indicated that cichlids with more hybrid ancestry are not more commonly female providing no support for asymmetric backcrossing or hybrid-induced sex-ratio distortion in generating the bias in mitochondrial introgression. Smaller effective population size inH. minckleyiinferred from the SNPs coupled with sequences of all 13 mitochondrial proteins suggests that relaxed selection on the mitogenome could be facilitating the introgression of "H. cyanoguttatus" haplotypes. Additionally, we showed that springs with colder temperatures had greater amounts of mitochondrial introgression fromH. cyanoguttatus. Relaxed selection inH. minckleyicoupled with temperature-related molecular adaptation could be facilitating mitogenomic introgression intoH. minckleyi.
authors.affiliation: Department of Biology University of Konstanz Universitätstraße 10 78457 Konstanz Germany.
authors.forename: Christopher Darrin
authors.initials: CD
authors.lastname: Hulsey
authors.affiliation: Department of Biology Texas State University, San Marcos 601 University Drive 78666 San Marcos Texas.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Bell
authors.affiliation: Laboratorio de Genética para la Conservación Centro de Investigaciones Biológicas del Noroeste PO Box 128 La Paz B.C.S. Mexico.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: García-de-León
authors.affiliation: Department of Biology Texas State University, San Marcos 601 University Drive 78666 San Marcos Texas.
authors.forename: Chris C
authors.initials: CC
authors.lastname: Nice
authors.affiliation: Department of Biology University of Konstanz Universitätstraße 10 78457 Konstanz Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Meyer
keywords: Mexico; molecular convergence; sympatric speciation; trophic polymorphism