The oxidative phosphorylation (OxPhos) pathway is responsible for most aerobic ATP production and is the only pathway with both nuclear and mitochondrial encoded proteins. The importance of the interactions between these two genomes has recently received more attention because of their potential evolutionary effects and how they may affect human health and disease. In many different organisms, healthy nuclear and mitochondrial genome hybrids between species or among distant populations within a species affect fitness and OxPhos functions. However, what is less understood is whether these interactions impact individuals within a single natural population. The significance of this impact depends on the strength of selection for mito-nuclear interactions. We examined whether mito-nuclear interactions alter allele frequencies for ~11,000 nuclear SNPs within a single, natural Fundulus heteroclitus population containing two divergent mitochondrial haplotypes (mt-haplotypes). Between the two mt-haplotypes, there are significant nuclear allele frequency differences for 349 SNPs with a p-value of 1% (236 with 10% FDR). Unlike the rest of the genome, these 349 outlier SNPs form two groups associated with each mt-haplotype, with a minority of individuals having mixed ancestry. We use this mixed ancestry in combination with mt-haplotype as a polygenic factor to explain a significant fraction of the individual OxPhos variation. These data suggest that mito-nuclear interactions affect cardiac OxPhos function. The 349 outlier SNPs occur in genes involved in regulating metabolic processes but are not directly associated with the 79 nuclear OxPhos proteins. Therefore, we postulate that the evolution of mito-nuclear interactions affects OxPhos function by acting upstream of OxPhos.

The study of hybrid zones can provide insight into the genetic basis of species differences that are relevant for the maintenance of reproductive isolation. Hybrid zones can also provide insight into climate change, species distributions, and evolution. The hybrid zone between black‐capped chickadees (Poecile atricapillus) and Carolina chickadees (Poecile carolinensis) is shifting northward in response to increasing winter temperatures but is not increasing in width. This pattern indicates strong selection against chickadees with admixed genomes. Using high‐resolution genomic data, we identified regions of the genomes that are outliers in both time points and do not introgress between the species; these regions may be involved in the maintenance of reproductive isolation. Genes involved in metabolic regulation processes were overrepresented in this dataset. Several gene ontology categories were also temporally consistent—including glutamate signaling, synaptic transmission, and catabolic processes—but the nucleotide variants leading to this pattern were not. Our results support recent findings that hybrids between black‐capped and Carolina chickadees have higher basal metabolic rates than either parental species and suffer spatial memory and problem‐solving deficits. Metabolic breakdown, as well as spatial memory and problem‐solving, in hybrid chickadees may act as strong postzygotic isolation mechanisms in this moving hybrid zone.

Background Examples of rapid evolution are common in nature but difficult to account for with the standard population genetic model of adaptation. Instead, selection from the standing genetic variation permits rapid adaptation via soft sweeps or polygenic adaptation. Empirical evidence of this process in nature is currently limited but accumulating. Results We provide genome-wide analyses of rapid evolution in Fundulus heteroclitus populations subjected to recently elevated temperatures due to coastal power station thermal effluents using 5449 SNPs across two effluent-affected and four reference populations. Bayesian and multivariate analyses of population genomic structure reveal a substantial portion of genetic variation that is most parsimoniously explained by selection at the site of thermal effluents. An F ST outlier approach in conjunction with additional conservative requirements identify significant allele frequency differentiation that exceeds neutral expectations among exposed and closely related reference populations. Genomic variation patterns near these candidate loci reveal that individuals living near thermal effluents have rapidly evolved from the standing genetic variation through small allele frequency changes at many loci in a pattern consistent with polygenic selection on the standing genetic variation. Conclusions While the ultimate trajectory of selection in these populations is unknown and we survey only a minority of genomic loci, our findings suggest that polygenic models of adaptation may play important roles in large, natural populations experiencing recent selection due to environmental changes that cause broad physiological impacts. Electronic supplementary material The online version of this article (10.1186/s12862-019-1392-5) contains supplementary material, which is available to authorized users.

It has been suggested that adaptive evolution on ecological timescales shapes communities. However, adaptation among environments relies on isolation or large selection coefficients that exceed migration effects. This reliance is tempered if adaptation is polygenic-does not depend on one allele completely replacing another but instead requires small allele frequency changes at many loci. Thus, whether individuals can evolve adaptation to fine-scale habitat variation (for example, microhabitats) is not resolved. Here we analyze the genetic divergence of the teleost fish, Fundulus heteroclitus, among microhabitats that are <200 m apart in three separate saltmarshes using 4741 single-nucleotide polymorphisms (SNPs). Among these SNPs, 1.3-2.3% have large and highly significant differences among microhabitats (mean F=0.15; false discovery rate ⩽1%). The divergence among microhabitats for these outlier SNPs is larger than that among populations, exceeds neutral expectation and indicates surprising population structure among microhabitats. Thus, we suggest that polygenic selection is surprisingly effective in altering allele frequencies among many different SNPs that share similar biological functions in response to environmental and ecological differences over very small geographic distances. We acknowledge the evolutionary difficulty of large genetic divergence among well-connected habitats. Therefore, these studies are only the first step to discern whether natural selection is responsible and capable of effecting genetic divergence on such a fine scale.

We measured and took blood samples from large tiger sharks in the wild to determine if their body condition (a metric of health) was related to energy stores (fatty acids). Our results revealed that body condition and fatty acids were positively and significantly correlated. This is important for understanding how large, highly mobile apex predators such as tiger sharks store and use energy required for migration and mating.