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Abstract Gaining a better understanding of the rates and patterns of meiotic recombination is crucial for improving evolutionary genomic modeling, with applications ranging from demographic to selective inference. Although previous research has provided important insights into the landscape of crossovers in humans and other haplorrhines, our understanding of both the considerably more common outcome of recombination (i.e. noncrossovers) as well as the landscapes in more distantly related primates (i.e. strepsirrhines) remains limited owing to difficulties associated with both the identification of noncrossover tracts as well as species sampling. Thus, in order to elucidate recombination patterns in this understudied branch of the primate clade, we here characterize crossover and noncrossover landscapes in aye-ayes utilizing whole-genome sequencing data from six three-generation pedigrees and three two-generation multi-sibling families, and in so doing provide novel insights into this important evolutionary process shaping genomic diversity in one of the world's most critically endangered primate species. 

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. 

Abstract The nocturnal aye-aye, Daubentonia madagascariensis, is one of the most elusive lemurs on the island of Madagascar. The timing of its activity and arboreal lifestyle has generally made it difficult to obtain accurate assessments of population size using traditional census methods. Therefore, alternative estimates provided by population genetic inference are essential for yielding much needed information for conservation measures and for enabling ecological and evolutionary studies of this species. Here, we utilize genomic data from 17 individuals—including 5 newly sequenced, high-coverage genomes—to estimate this history. Essential to this estimation are recently published annotations of the aye-aye genome which allow for variation at putatively neutral genomic regions to be included in the estimation procedures, and regions subject to selective constraints, or in linkage to such sites, to be excluded owing to the biasing effects of selection on demographic inference. By comparing a variety of demographic estimation tools to develop a well-supported model of population history, we find strong support for two demes, separating northern Madagascar from the rest of the island. Additionally, we find that the aye-aye has experienced two severe reductions in population size. The first occurred rapidly, ∼3,000 to 5,000 years ago, and likely corresponded with the arrival of humans to Madagascar. The second occurred over the past few decades and is likely related to substantial habitat loss, suggesting that the species is still undergoing population decline and remains at great risk for extinction. 

Abstract The aye-aye (Daubentonia madagascariensis) is the only extant member of the Daubentoniidae primate family. Although several reference genomes exist for this endangered strepsirrhine primate, the predominant usage of short-read sequencing has resulted in limited assembly contiguity and completeness, and no protein-coding gene annotations have yet been released. Here, we present a novel, fully annotated, chromosome-level hybrid de novo assembly for the species based on a combination of Oxford Nanopore Technologies long reads and Illumina short reads and scaffolded using genome-wide chromatin interaction data—a community resource that will improve future conservation efforts as well as primate comparative analyses.