Biology subjects

McKinney, G. J.

Publications and source records attributed to McKinney, G. J..

8 recordsLinked to original sources

bioRxiv2024

Genomic signals of local adaptation in Eleginops maclovinus from Northern Chilean Patagonia

Understanding the evolutionary mechanisms that shape the adaptive divergence across spatially heterogeneous environments is a challenging task for evolutionary ecologists. The Chilean marine Patagonia is a complex ecosystem with diverse geomorphology and physical-chemical oceanographic conditions. There is limited research evaluating the interactions between selective forces and environmental conditions in this area. This study focuses on identifying the genomic signals of local adaptation of the endemic marine fish, Eleginops maclovinus from Chilean North Patagonia. To achieve this goal, we used an environmental marine database (temperature, salinity, oxygen, phosphate nitrate and silicate concentration) with collected from 1995 to 2018 and 11,961 SNPs obtained from 246 individuals from 10 sampling locations across this area. We identified putative adaptive loci using ten bioinformatic software tools, where five were based on population genetic differentiation (PGD) and five based on the genotype-environment association (GEA). We identified 392 adaptative loci using PGD and 2,164 associated with at least one of the six environmental variables analyzed using GEA. A total of 131 loci were shared between the PGD and GEA approaches, of which 37 were associated with genes involved in the growth, metabolism and homeostasis. Then, we evaluated the variation of adaptive loci with environmental variables using polygenic scores and found significant correlations with temperature, salinity, and oxygen, indicating polygenic selection along environmental gradients. This study highlights how polygenic selection drives local adaptation in Eleginops maclovinus and underscores the value of integrating genomic and environmental data for conservation in the Patagonian ecosystem.

evolutionary biology↗

bioRxiv2021

A non-functional copy of the salmonid sex determining gene (sdY) is responsible for the "apparent" XY females in Chinook salmon, Oncorhynchus tshawytscha.

Many salmonids have a male heterogametic (XX/XY) sex determination system, and they are supposed to have a conserved master sex determining gene (sdY), that interacts at the protein level with Foxl2 leading to the blockage of the synergistic induction of Foxl2 and Nr5a1 of the cyp19a1a promoter. However, this hypothesis of a conserved master sex determining role of sdY in salmonids is still challenged by a few exceptions, one of them being the presence of some naturally occurring "apparent" XY Chinook salmon females. Here we show that XY Chinook salmon females have a sdY gene (sdY-N183), which has one missense mutation leading to a substitution of a conserved isoleucine to an asparagine (SdY I183N). In contrast, Chinook salmon males have both a non-mutated sdY-I183 gene and the missense mutation sdY-N183 gene. The 3D model of SdY-N183 predicts that the I183N hydrophobic to hydrophilic amino acid change leads to a local modification of the {beta}-sandwich structure of SdY. Using in vitro cell transfection assays we found that SdY-N183, like SdY-I183, is preferentially localized in the cytoplasm. However, compared to SdY-I183, SdY-N183 is more prone to degradation, its nuclear translocation by Foxl2 is reduced and SdY-N183 is unable to significantly repress the synergistic Foxl2/Nr5a1 induction of the cyp19a1a promoter. Altogether our results suggest that the sdY-N183 gene of XY Chinook females is a non-functional gene and that SdY-N183 is no longer able to promote testicular differentiation by impairing the synthesis of estrogens in the early differentiating gonads of wild Chinook salmon XY females.

genetics↗

bioRxiv2021

Gene flow influences the genomic architecture of local adaptation in six riverine fish species

Understanding how gene flow influences adaptive divergence is important for predicting adaptive responses. Theoretical studies suggest that when gene flow is high, clustering of adaptive genes in fewer genomic regions would protect adaptive alleles from among-population recombination and thus be selected for, but few studies have tested this hypothesis with empirical data. Here, we used RADseq to generate genomic data for six fish species with contrasting life histories from six reaches of the Upper Mississippi River System, USA. We then conducted genome scans for genomic islands of divergence to examine the distribution of adaptive loci and investigated whether these loci were found in inversions. We found that gene flow varied among species, and adaptive loci were clustered more tightly in species with higher gene flow. For example, the two species with the highest overall FST (0.03 - 0.07) and therefore lowest gene flow showed little evidence of clusters of adaptive loci, with adaptive loci spread uniformly across the genome. In contrast, nearly all adaptive loci in the species with the lowest FST (0.0004) were found in a single large putative inversion. Two other species with intermediate gene flow (FST ~ 0.004) also showed clustered genomic architectures, with most islands of divergence clustered on a few chromosomes. These results provide important empirical evidence to support the hypothesis that increasingly clustered architectures of local adaptation are associated with high gene flow. Our study utilized a unique system with species spanning a large gradient of life histories to highlight the importance of gene flow in shaping adaptive divergence.

evolutionary biology↗

bioRxiv2020

A mobile sex-determining region, male-specific haplotypes, and rearing environment influence age at maturity in Chinook salmon

Variation in age at maturity is an important contributor to life history and demographic variation within and among species. The optimal age at maturity can vary by sex, and the ability of each sex to evolve towards its fitness optimum depends on the genetic architecture of maturation. Using GWAS of RAD sequencing data, we show that age at maturity in Chinook salmon exhibits sex-specific genetic architecture, with age at maturity in males governed by large (up to 20Mb) male-specific haplotypes. These regions showed no such effect in females. We also provide evidence for translocation of the sex-determining gene between two different chromosomes. This has important implications for sexually antagonistic selection, particularly that sex-linkage of adaptive genes may differ within and among populations based on chromosomal location of the sex-determining gene. Our findings will facilitate research into the genetic causes of shifting demography in Chinook salmon as well as a better understanding of sex-determination in this species and Pacific salmon in general.

evolutionary biology↗

bioRxiv2020

A GT-seq panel for walleye (Sander vitreus) provides a generalized workflow for efficient development and implementation of amplicon panels in non-model organisms.

Targeted amplicon sequencing methods, such as genotyping-in-thousands by sequencing (GT-seq), facilitate rapid, accurate, and cost-effective analysis of hundreds of genetic loci in thousands of individuals, but studies describing detailed workflows of GTseq panel development are rare. Here, we develop a dual-purpose GT-seq panel for walleye (Sander vitreus) and discuss trade-offs associated with different development and genotyping approaches. Our GT-seq panel was developed using restriction site-associated DNA data from 954 individuals sampled from 23 populations in Minnesota and Wisconsin, USA. We then conducted simulations to test the utility of loci for parentage analysis and genetic stock identification and designed 600 primer pairs to maximize joint accuracy for these analyses. We conducted three rounds of primer optimization to remove loci that overamplified and our final panel consisted of 436 loci. Optimization focused on reducing variation in amplification rate among loci and minimizing the proportion of off-target sequence, both of which are important considerations for developing large GT-seq panels. We also explored different approaches for DNA extraction, multiplexed polymerase chain reaction (PCR) amplification, and cleanup steps during the GT-seq process and discovered the following: (1) inexpensive Chelex extractions performed well for genotyping, (2) the exonuclease I and shrimp alkaline phosphatase (ExoSAP) procedure included in some current protocols did not improve results substantially and was likely unnecessary, and (3) it was possible to PCR amplify panels separately and combine them prior to adapter ligation. Well-optimized GT-seq panels are valuable resources for conservation genetics and our findings should aid in their construction in myriad taxa.

genomics↗

bioRxiv2019

Comparative genomic analyses and a novel linkage map for cisco (Coregonus artedi) provides insight into chromosomal evolution and rediploidization across salmonids

Whole-genome duplication (WGD) is hypothesized to be an important evolutionary mechanism that can facilitate adaptation and speciation. Genomes that exist in states of both diploidy and residual tetraploidy are of particular interest, as mechanisms that maintain the ploidy mosaic after WGD may provide important insights into evolutionary processes. The Salmonidae family exhibits residual tetraploidy, and this, combined with the evolutionary diversity formed after an ancestral autotetraploidization event, makes this group a useful study system. In this study, we generate a novel linkage map for cisco (Coregonus artedi), an economically and culturally important fish in North America and a member of the subfamily Coregoninae, which previously lacked a high-density haploid linkage map. We also conduct comparative genomic analyses to refine our understanding of chromosomal fusion/fission history across salmonids. To facilitate this comparative approach, we use the naming strategy of protokaryotype identifiers (PKs) to associate duplicated chromosomes to their putative ancestral state. The female linkage map for cisco contains 20,292 loci, 3,225 of which are likely within residually tetraploid regions. Comparative genomic analyses revealed that patterns of residual tetrasomy are generally conserved across species, although interspecific variation persists. To determine the broad-scale retention of residual tetrasomy across the salmonids, we analyze sequence similarity of currently available genomes and find evidence of residual tetrasomy in seven of the eight chromosomes that have been previously hypothesized to show this pattern. This interspecific variation in extent of rediploidization may have important implications for understanding salmonid evolutionary histories and informing future conservation efforts.

genomics↗

bioRxiv2019

Patterns of linkage disequilibrium reveal genome architecture in chum salmon

Many studies exclude loci exhibiting linkage disequilibrium (LD); however, high LD can signal reduced recombination around genomic features such as chromosome inversions or sex-determining regions. Chromosome inversions and sex-determining regions are often involved in adaptation, allowing for the inheritance of co-adapted gene complexes and for the resolution of sexually antagonistic selection through sex-specific partitioning of genetic variants. Genomic features such as these can escape detection when loci with LD are removed; in addition, failing to account for these features can introduce bias to analyses. We examined patterns of LD using network analysis to identify an overlapping chromosome inversion and sex-determining region in chum salmon. The signal of the inversion was strong enough to show up as false population substructure when the entire dataset was analyzed, while the signal of the sex-determining region was only obvious after restricting genetic analysis to the sex chromosome. Understanding the extent and geographic distribution of inversions is now a critically important part of genetic analyses of natural populations. The results of this study highlight the importance of analyzing and understanding patterns of LD in genomic dataset and the perils of ignoring or excluding loci exhibiting LD.

genomics↗

bioRxiv2019

Y-chromosome haplotypes drive variation in size and age at maturity in male Chinook salmon

Variation in size and age at maturity is an important component of life history that is influenced both by environmental and genetic factors. In salmonids, large size confers a direct reproductive advantage through increased fecundity and egg quality in females, while larger males gain a reproductive advantage by monopolizing access to females. In addition, variation in size and age at maturity in males can be associated with different reproductive strategies; younger smaller males may gain reproductive success by sneaking in among mating pairs. In both sexes there is a trade-off between older age and increased reproductive success and increased risk of mortality by delaying reproduction. We identified four Y-chromosome haplogroups that showed regional and population-specific variation in frequency using RADseq data for 21 populations of Alaska Chinook salmon. We then characterized the range-wide distribution of these haplogroups using GT-seq assays. These haplogroups exhibited associations with size at maturity in multiple populations suggesting that the lack of recombination between X and Y-chromosomes has allowed Y-chromosome haplogroups to capture different alleles that influence size at maturity. Ultimately, conservation of life history diversity in Chinook salmon may require conservation of Y-chromosome haplotype diversity.

evolutionary biology↗