Discordant patterns of geographic variation between mitochondrial and microsatellite markers in the Mexican black iguana (Ctenosaura pectinata) in a contact zone

Abstract

To delimit the distribution of matrilines of the black iguana (Ctenosaura pectinata), detect potential contact zones between them, and test the hypothesis of geographic concordance in the structuring of matrilines with respect to genetic structuring across the nuclear genome. Pacific coast of Mexico in the states of Nayarit, Jalisco, Colima, Michoacán in the lowlands adjacent to the western end of the Mexican Volcanic Belt. Tissue samples were obtained every 10–20 km along a transect across the range of three previously described mitochondrial DNA (mtDNA) clades of C. pectinata. Iguanas were genotyped with 11 nuclear microsatellites and maternal lineages were inferred based on mtDNA sequences. Geographic structure and geographic concordance between biparentally and maternally inherited markers were analysed with clustering methods, FST and NST indexes as well as haplotype networks. Geographic structure was evident for both markers and the existence of contact zones confirmed. Nevertheless, the distribution of nuclear and mtDNA genetic variation is not geographically concordant. Four matrilines exist in the area, whereas only two nuclear clusters occur. A contact zone between nuclear clusters extends along a distance of c. 60 km, and introgression is evident in individuals from several localities. High levels of genetic diversity were detected on the western coast of Mexico. Historical and contemporaneous processes seem to shape the distribution of genetic variation in C. pectinata. There are no evident geographic, environmental or ecological barriers that coincide with genetic subdivisions, and the observed mtDNA structure is likely to be the result of past climatic changes. The less structured distribution of nuclear genetic variation is consistent with the homogenizing effect of male-biased dispersal. Our findings have implications for the taxonomy and conservation strategies for this threatened species, and highlight the fact that geographic analyses of both cytoplasmic and nuclear genetic variation are important for the meaningful inference of evolutionary and demographic histories

Rapid genetic assimilation of native wall lizard populations (Podarcis muralis) through extensive hybridization with introduced lineages

“…Our results confirm several recent studies on squamate reptiles in which the combination of nuclear and mtDNA markers revealed discordant patterns (Renoult et al. 2009; Zarza et al. 2011).…”

Patterns of genetic variation across the distribution range of the cockle Cerastoderma edule inferred from microsatellites and mitochondrial DNA

“…It cannot be discarded that the different population differentiation scenarios depicted by microsatellites and cyt b are caused by the existence of a secondary contact scenario as suggested in the case of other species with discordant patterns of geographic variation between mitochondrial and microsatellite markers (Lu et al 2001;Zarza et al 2011). Upon secondary contact, genetically differentiated populations form hybrid zones, interbreeding to various extents, and the level and extension of gene flow for mitochondrial and nuclear genomes might differ (Toews and Brelsford 2012).…”

Broad-scale genetic patterns of New Zealand abalone, Haliotis iris, across a distribution spanning 13° latitude and major oceanic water masses

“…Mitochondrial and nuclear genomes differ in size, structure, location within the cell, copy number, modes of inheritance, replication, segregation, selection pressures and recombination and mutation rates (reviewed in Ballard and Whitlock 2004;White et al 2008;Galtier et al 2009). Discordance among these markers has been reported in instances of varying historical and contemporary gene flow (e.g., Rönkä et al 2012;Zarza et al 2011), sex biased dispersal (e.g., Damm andHadrys 2012, Yannic et al 2012) or sex-based differential selection (e.g., Teske et al 2012). Although congruence among markers for pāua suggests similar dispersal and selection patterns for both males and females, further research examining genetic structure in regards to sex and other markers is necessary.…”