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1. Rapid Evolution of the Fine-scale Recombination Landscape in Wild House Mouse ( Mus musculus ) Populations

   https://doi.org/10.1093/molbev/msac267  

   Wooldridge, Lydia K; Dumont, Beth L (January 2023, Molecular Biology and Evolution)

   Falush, Daniel (Ed.)

   Abstract Meiotic recombination is an important evolutionary force and an essential meiotic process. In many species, recombination events concentrate into hotspots defined by the site-specific binding of PRMD9. Rapid evolution of Prdm9's zinc finger DNA-binding array leads to remarkably abrupt shifts in the genomic distribution of hotspots between species, but the question of how Prdm9 allelic variation shapes the landscape of recombination between populations remains less well understood. Wild house mice (Mus musculus) harbor exceptional Prdm9 diversity, with >150 alleles identified to date, and pose a particularly powerful system for addressing this open question. We employed a coalescent-based approach to construct broad- and fine-scale sex-averaged recombination maps from contemporary patterns of linkage disequilibrium in nine geographically isolated wild house mouse populations, including multiple populations from each of three subspecies. Comparing maps between wild mouse populations and subspecies reveals several themes. First, we report weak fine- and broad-scale recombination map conservation across subspecies and populations, with genetic divergence offering no clear prediction for recombination map divergence. Second, most hotspots are unique to one population, an outcome consistent with minimal sharing of Prdm9 alleles between surveyed populations. Finally, by contrasting aggregate hotspot activity on the X versus autosomes, we uncover evidence for population-specific differences in the degree and direction of sex dimorphism for recombination. Overall, our findings illuminate the variability of both the broad- and fine-scale recombination landscape in M. musculus and underscore the functional impact of Prdm9 allelic variation in wild mouse populations. 

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2. Interpreting Patterns of X Chromosomal Relative to Autosomal Diversity in Aye‐Ayes ( Daubentonia madagascariensis )

   https://doi.org/10.1002/ajp.70091  

   Terbot, John W; Soni, Vivak; Versoza, Cyril J; Milhaven, Mark; Calahorra‐Oliart, Adriana; Shah, Devangana; Pfeifer, Susanne P; Jensen, Jeffrey D (December 2025, American Journal of Primatology)

   ABSTRACT We here present high‐quality, population‐level sequencing data from the X chromosome of the highly‐endangered aye‐aye,Daubentonia madagascariensis. Using both polymorphism‐ and divergence‐based inference approaches, we quantify fine‐scale mutation and recombination rate maps, study the demographic and selective processes additionally shaping variation on the X chromosome, and compare these estimates to those recently inferred from the autosomes in this species. Results suggest that an equal sex ratio is most consistent with observed patterns of variation, and that no sex‐specific demographic patterns are needed to fit the empirical site frequency spectrum. Further, reduced rates of recombination were observed relative to the autosomes as would be expected, whereas mutation rates were inferred to be similar. Utilizing the estimated population history together with the mutation and recombination rate maps, we evaluated evidence for both recent and recurrent selective sweeps as well as balancing selection across the X chromosome, finding no significant evidence supporting the action of these episodic processes. Overall, these analyses provide new insights into the evolution of the X chromosome in this species, which represents one of the earliest splits in the primate clade. 

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3. A whole-genome scan for evidence of positive and balancing selection in aye-ayes ( Daubentonia madagascariensis ) utilizing a well-fit evolutionary baseline model

   https://doi.org/10.1093/g3journal/jkaf078  

   Soni, Vivak; Terbot, John W; Versoza, Cyril J; Pfeifer, Susanne P; Jensen, Jeffrey D (April 2025, G3: Genes, Genomes, Genetics)

   Macdonald, S (Ed.)

   Abstract The aye-aye (Daubentonia madagascariensis) is one of the 25 most endangered primate species in the world, maintaining amongst the lowest genetic diversity of any primate measured to date. Characterizing patterns of genetic variation within aye-aye populations, and the relative influences of neutral and selective processes in shaping that variation, is thus important for future conservation efforts. In this study, we performed the first whole-genome scans for positive and balancing selection in the species, utilizing high-coverage population genomic data from newly sequenced individuals. We generated null thresholds for our genomic scans by creating an evolutionarily appropriate baseline model that incorporates the demographic history of this aye-aye population, and identified a small number of candidate genes. Most notably, a suite of genes involved in olfaction—a key trait in these nocturnal primates—were identified as experiencing long-term balancing selection. We also conducted analyses to quantify the expected statistical power to detect positive and balancing selection in this population using site frequency spectrum–based inference methods, once accounting for the potentially confounding contributions of population history, mutation and recombination rate variation, as well as purifying and background selection. This work, presenting the first high-quality, genome-wide polymorphism data across the functional regions of the aye-aye genome, thus provides important insights into the landscape of episodic selective forces in this highly endangered species. 

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4. The recombination landscapes of spiny lizards (genus Sceloporus )

   https://doi.org/10.1093/g3journal/jkab402  

   Versoza, Cyril J; Rivera, Julio A; Rosenblum, Erica Bree; Vital-García, Cuauhcihuatl; Hews, Diana K; Pfeifer, Susanne P (November 2021, G3 Genes|Genomes|Genetics)

   Ross-Ibarra, J (Ed.)

   Abstract Despite playing a critical role in evolutionary processes and outcomes, relatively little is known about rates of recombination in the vast majority of species, including squamate reptiles—the second largest order of extant vertebrates, many species of which serve as important model organisms in evolutionary and ecological studies. This paucity of data has resulted in limited resolution on questions related to the causes and consequences of rate variation between species and populations, the determinants of within-genome rate variation, as well as the general tempo of recombination rate evolution on this branch of the tree of life. In order to address these questions, it is thus necessary to begin broadening our phylogenetic sampling. We here provide the first fine-scale recombination maps for two species of spiny lizards, Sceloporus jarrovii and Sceloporus megalepidurus, which diverged at least 12 Mya. As might be expected from similarities in karyotype, population-scaled recombination landscapes are largely conserved on the broad-scale. At the same time, considerable variation exists at the fine-scale, highlighting the importance of incorporating species-specific recombination maps in future population genomic studies. 

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5. A whole-genome scan for evidence of recent positive and balancing selection in aye-ayes (Daubentonia madagascariensis) utilizing a well-fit evolutionary baseline model

   https://doi.org/10.1101/2024.11.08.622667  

   Soni, Vivak; Terbot, John W; Versoza, Cyril J; Pfeifer, Susanne P; Jensen, Jeffrey D (November 2024, bioRxiv)

   The aye-aye (Daubentonia madagascariensis) is one of the 25 most endangered primate species in the world, maintaining amongst the lowest genetic diversity of any primate measured to date. Characterizing patterns of genetic variation within aye-aye populations, and the relative influences of neutral and selective processes in shaping that variation, is thus important for future conservation efforts. In this study, we performed the first whole-genome scans for recent positive and balancing selection in the species, utilizing high-coverage population genomic data from newly sequenced individuals. We generated null thresholds for our genomic scans by creating an evolutionarily appropriate baseline model that incorporates the demographic history of this aye-aye population, and identified a small number of candidate genes. Most notably, a suite of genes involved in olfaction — a key trait in these nocturnal primates — were identified as experiencing long-term balancing selection. We also conducted analyses to quantify the expected statistical power to detect positive and balancing selection in this population using site frequency spectrum-based inference methods, once accounting for the potentially confounding contributions of population history, recombination and mutation rate variation, and purifying and background selection. This work, presenting the first high-quality, genome-wide polymorphism data across the functional regions of the aye-aye genome, thus provides important insights into the landscape of episodic selective forces in this highly endangered species. 

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