title: Untangling the evolutionary history of a highly polymorphic species: introgressive hybridization and high genetic structure in the desert cichlid fish Herichtys minckleyi.
abstract: Understanding the origin of biodiversity requires knowledge on the evolutionary processes that drive divergence and speciation, as well as on the processes constraining it. Intraspecific polymorphisms can provide insight into the mechanisms that generate and maintain phenotypic, behavioural and life history diversification, and can help us understand not only the processes that lead to speciation but also the processes that prevent local fixation of morphs. The 'desert cichlid' Herichtys minckleyi is a highly polymorphic species endemic to a biodiversity hotspot in northern Mexico, the Cuatro Ciénegas valley. This species is polymorphic in body shape and trophic apparatus, and eco-morphotypes coexist in small spring-fed lagoons across the valley. We investigated the genetic structure of these polymorphisms and their phylogeographic history by analysing the entire control region of the mitochondrial DNA and 10 nuclear microsatellite markers in several populations from different sites and morphs. We found two very divergent mitochondrial lineages that most likely predate the closing of the valley and are not associated with morphotypes or sites. One of these lineages is also found in the sister species Herichthys cyanoguttatus. Data from neutral microsatellite markers suggest that most lagoons or drainages constitute their own genetic cluster with sympatric eco-morphotypes forming panmictic populations. Alternative mechanisms such as phenotypic plasticity and a few loci controlled traits provide possible explanations for the sympatric coexistence of discrete nonoverlapping eco-morphotypes with apparent lack of barriers to gene flow within multiple lagoons and drainages.
authors.affiliation: Museo Nacional de Ciencias Naturales, CSIC, José Gutierrez Abascal 2, 28006, Madrid, Spain.
authors.forename: Isabel S
authors.initials: IS
authors.lastname: Magalhaes
authors.affiliation: Departamento de Zoología, Autónoma de Querétaro, Av. de las Ciencias s/n, Juriquilla 76230, México.|Universidad Nacional Autónoma de México, México, D.F., Circuito Interior Ciudad Universitaria, CP 04510, Mexico.
authors.forename: Claudia Patricia
authors.initials: CP
authors.lastname: Ornelas-Garcıa
authors.affiliation: Museo Nacional de Ciencias Naturales, CSIC, José Gutierrez Abascal 2, 28006, Madrid, Spain.
authors.forename: Mariana
authors.initials: M
authors.lastname: Leal-Cardin
authors.affiliation: Museo Nacional de Ciencias Naturales, CSIC, José Gutierrez Abascal 2, 28006, Madrid, Spain.
authors.forename: Tania
authors.initials: T
authors.lastname: Ramírez
authors.affiliation: Museo Nacional de Ciencias Naturales, CSIC, José Gutierrez Abascal 2, 28006, Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Barluenga
mesh_terms: D000818:Animals; D005075:Biological Evolution; D023681:Cichlids / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D060146:Ecotype; D051456:Gene Flow; D005828:Genetics, Population; D006239:Haplotypes; D006824:Hybridization, Genetic; D008800:Mexico; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010641:Phenotype; D058974:Phylogeography; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: cichlid fish; genetic structure; phylogeography; polymorphism