Dataset Information

Extreme mito-nuclear discordance in a peninsular lizard: the role of drift, selection, and climate.

ABSTRACT: Nuclear and mitochondrial genomes coexist within cells but are subject to different tempos and modes of evolution. Evolutionary forces such as drift, mutation, selection, and migration are expected to play fundamental roles in the origin and maintenance of diverged populations; however, divergence may lag between genomes subject to different modes of inheritance and functional specialization. Herein, we explore whole mitochondrial genome data and thousands of nuclear single nucleotide polymorphisms to evidence extreme mito-nuclear discordance in the small black-tailed brush lizard, Urosaurus nigricaudus, of the Peninsula of Baja California, Mexico and southern California, USA, and discuss potential drivers. Results show three deeply divergent mitochondrial lineages dating back to the later Miocene (ca. 5.5?Ma) and Pliocene (ca. 2.8?Ma) that likely followed geographic isolation due to trans-peninsular seaways. This contrasts with very low levels of genetic differentiation in nuclear loci (FST?

SUBMITTER: Bernardo PH

PROVIDER: S-EPMC6781153 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Extreme mito-nuclear discordance in a peninsular lizard: the role of drift, selection, and climate.

Bernardo Pedro Henrique PH Sánchez-Ramírez Santiago S Sánchez-Pacheco Santiago J SJ Álvarez-Castañeda Sergio Ticul ST Aguilera-Miller Eduardo Felipe EF Mendez-de la Cruz Fausto Roberto FR Murphy Robert W RW

Heredity 20190304 3

Nuclear and mitochondrial genomes coexist within cells but are subject to different tempos and modes of evolution. Evolutionary forces such as drift, mutation, selection, and migration are expected to play fundamental roles in the origin and maintenance of diverged populations; however, divergence may lag between genomes subject to different modes of inheritance and functional specialization. Herein, we explore whole mitochondrial genome data and thousands of nuclear single nucleotide polymorphi ...[more]

PMID: 30833746

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Project description:As hybrid zones exhibit selective patterns of gene flow between otherwise distinct lineages, they can be especially valuable for informing processes of microevolution and speciation. The bumble bee, Bombus melanopygus, displays two distinct color forms generated by Müllerian mimicry: a northern "Rocky Mountain'' color form with ferruginous mid-abdominal segments (B. m. melanopygus) and a southern "Pacific'' form with black mid-abdominal segments (B. m. edwardsii). These morphs meet in a mimetic transition zone in northern California and southern Oregon that is more narrow and transitions further west than comimetic bumble bee species. To understand the historical formation of this mimicry zone, we assessed color distribution data for B. melanopygus from the last 100 years. We then examined gene flow among the color forms in the transition zone by comparing sequences from mitochondrial COI barcode sequences, color-controlling loci, and the rest of the nuclear genome. These data support two geographically distinct mitochondrial haplogroups aligned to the ancestrally ferruginous and black forms that meet within the color transition zone. This clustering is also supported by the nuclear genome, which, while showing strong admixture across individuals, distinguishes individuals most by their mitochondrial haplotype, followed by geography. These data suggest the two lineages most likely were historically isolated, acquired fixed color differences, and then came into secondary contact with ongoing gene flow. The transition zone, however, exhibits asymmetries: mitochondrial haplotypes transition further south than color pattern, and both transition over shorter distances in the south. This system thus demonstrates alternative patterns of gene flow that occur in contact zones, presenting another example of mito-nuclear discordance. Discordant gene flow is inferred to most likely be driven by a combination of mimetic selection, dominance effects, and assortative mating.

Project description:BackgroundPatterns of spatial variation in discrete phenotypic traits can be used to draw inferences about the adaptive significance of traits and evolutionary processes, especially when compared to patterns of neutral genetic variation. Population divergence in adaptive traits such as color morphs can be influenced by both local ecology and stochastic factors such as genetic drift or founder events. Here, we use quantitative color measurements of males and females of Skyros wall lizard, Podarcis gaigeae, to demonstrate that this species is polymorphic with respect to throat color, and the morphs form discrete phenotypic clusters with limited overlap between categories. We use divergence in throat color morph frequencies and compare that to neutral genetic variation to infer the evolutionary processes acting on islet- and mainland populations.ResultsGeographically close islet- and mainland populations of the Skyros wall lizard exhibit strong divergence in throat color morph frequencies. Population variation in throat color morph frequencies between islets was higher than that between mainland populations, and the effective population sizes on the islets were small (Ne:s < 100). Population divergence (FST) for throat color morph frequencies fell within the neutral FST-distribution estimated from microsatellite markers, and genetic drift could thus not be rejected as an explanation for the pattern. Moreover, for both comparisons among mainland-mainland population pairs and between mainland-islet population pairs, morph frequency divergence was significantly correlated with neutral divergence, further pointing to some role for genetic drift in divergence also at the phenotypic level of throat color morphs.ConclusionsGenetic drift could not be rejected as an explanation for the pattern of population divergence in morph frequencies. In spite of an expected stabilising selection, throat color frequencies diverged in the islet populations. These results suggest that there is an interaction between selection and genetic drift causing divergence even at a phenotypic level in these small, subdivided populations.

Dataset Information

Extreme mito-nuclear discordance in a peninsular lizard: the role of drift, selection, and climate.

Publications

Extreme mito-nuclear discordance in a peninsular lizard: the role of drift, selection, and climate.

Similar Datasets

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