Biology subjects

Milot, E.

Publications and source records attributed to Milot, E..

4 recordsLinked to original sources

bioRxiv2026

Epistasis and an oligogenic architecture underlie the strength of a plant-herbivore interaction

1. Interaction strength between consumers and resources is a fundamental driver of eco-evolutionary dynamics, and its genetic architecture is key to predicting the pace of such dynamics. Our understanding of this architecture is limited for three reasons: (i) defense phenotypes do not necessarily translate to interaction strength; (ii) interaction strength is difficult to measure in ways tied to consumer-resource theory; and (iii) association studies typically prioritize detecting large-effect loci rather than characterizing whether interactions are polygenic (many small-effect genes) or oligogenic (few large-effect genes). 2. We address these gaps by examining how genomic variation in the plant Arabidopsis thaliana influences interactions with the aphid herbivore Lipaphis pseudobrassicae in a greenhouse experiment. We grew 390 accessions spanning the species' natural range and measured aphid per-capita population growth as our interaction-strength metric. To test whether a previously identified plant defense gene (AOP2) acts additively or epistatically with other defense loci, we integrated our estimates of aphid population growth with public data on defense chemistry and gene expression. To determine whether the genetic architecture of interaction strength was polygenic or oligogenic, we used a Bayesian sparse linear mixed model that partitions these two components. 3. AOP2 showed epistasis with two other defense genes (MAM1 and GS-OH), indirectly modifying aphid population growth via the production of a specific defense compound (glucosinolate 2-hydroxy-3-butenyl). More broadly, interaction strength showed an oligogenic architecture: top single nucleotide polymorphisms (SNPs) occurred at low minor allele frequencies (< 3%) and grouped into six linkage disequilibrium blocks, including candidate genes outside canonical plant defense pathways. These six blocks explained 47% of the genetic variance in interaction strength, with only 3% additional variance attributable to polygenic effects. 4. Taken together, these results show that plant genomic variation modifies herbivore interaction strength through epistasis among defense genes and rare alleles at few loci. This oligogenic architecture imposes multiple constraints on the potential for rapid evolution, highlighting the need to integrate genomic effects into eco-evolutionary models.

ecology↗

bioRxiv2025

Contrasting evolutionary outcomes in a human life history trait which is heritable and under consistent unbiased directional selection

Microevolution is well documented in natural populations, yet its persistence as an adaptive process remains debated. Despite widespread directional selection on heritable traits, including life-history traits, evolutionary stasis often prevails, with no detectable microevolutionary response. However, evidence of microevolution in some populations raises a key question: do populations under similar ecological conditions and selective pressures exhibit parallel evolution in the same traits? To address this, we examined age at first reproduction (AFR) in three contemporary human populations considered semi-independent replicates, sharing a genetic, demographic, and historical background, with pedigree data available for [~]7 generations. Across all populations, we found strong directional selection favoring earlier AFR, yet quantitative genetic analyses revealed consistently low heritability (h2 {approx} 0.11). Only in the Charlevoix population did AFR show a negative genetic correlation with relative fitness, where more than 50% of the standardized phenotypic selection gradient was explained by the genetic selection gradient. Using the Breeders Equation and Robertsons Secondary Theorem of Selection, we predicted an evolutionary response to selection for AFR, which emerged only in Charlevoix. However, neither phenotypic nor breeding values of AFR showed temporal trends, indicating evolutionary stasis. These findings demonstrate that even under consistent directional selection and moderate additive genetic variation, microevolutionary responses may vary across replicate populations. Our results underscore the prevalence of evolutionary stasis, challenging assumptions about the inevitability of microevolution in response to natural selection.

evolutionary biology↗

bioRxiv2022

Assessing the impact of pedigree quality on the validity of quantitative genetic parameterestimates

Investigating the evolutionary dynamics of complex traits in nature requires the accurate assessment of their genetic architecture. Using a quantitative genetic (QG) modeling approach (e.g., animal model), relatedness information from a pedigree combined with phenotypic measurements can be used to infer the amount of additive genetic variance in traits. However, pedigree information from natural systems is not perfect and might contain errors or be of low quality. Published sensitivity analyses revealed a limited impact of expected error rates on parameter estimates. However, natural systems will differ in many respects (e.g., mating system, data availability, pedigree structure), thus it can be inappropriate to generalize outcomes from one system to another. French-Canadian (FC) genealogies are extensive and deep-rooted (up to 9 generations in this study) making them ideal to study how the quality and properties (e.g., errors, completeness) of pedigrees affect QG estimates. We conducted simulation analyses to infer the reliability of QG estimates using FC pedigrees and how it is impacted by genealogical errors and variation in pedigree structure. Broadly, results show that pedigree size and depth are important determinants of precision but not of accuracy. While the mean genealogical entropy (based on missing links) seems to be a good indicator of accuracy. Including a shared familial component into the simulations led to on average a 46% overestimation of the additive genetic variance. This has crucial implications for evolutionary studies aiming to estimate QG parameters given that many traits of interest, such as life history, exhibit important non-genetic sources of variation.

evolutionary biology↗

bioRxiv2021

The effective family size of immigrant founders predicts their long-term demographic outcome: from Quebec settlers to their 20th-century descendants

Human evolution involves population splits, size fluctuations, founder effects, and admixture. Population history reconstruction based on genetic diversity data routinely relies on simple demographic models while projecting the past. No specific demographic assumptions are needed to understand the genetic structure of the founder population of Quebec. Because genealogy and genetics are intimately related, we used descending genealogies of this population to pursue the fate of its founder lineages. Maternal and paternal lines reflect the transmission of mtDNA and the Y-chromosome, respectively. We followed their transmission in real-time, from the 17th century down to its 20th-century population. We counted the number of married children of immigrants (i.e., their effective family size, EFS), estimated the proportion of successful immigrants in terms of their survival ratio, and assessed net growth rates and extinction. Likewise, we evaluated the same parameters for their Quebec-born descendants. The survival ratio of the first immigrants was the highest and declined over time in association with the decreasing immigrants EFS. Parents with high EFS left plentiful married progeny, putting EFS as the most important variable determining the parental demographic success throughout time for generations ahead. The 17th and 18th-century immigrants bear the most remarkable demographic and genetic impact on the 20th-century population of Quebec. Lessons learned from Quebec genealogies can teach us about the consequences of founder effects and migrations through real peoples history. The effective family size of immigrant founders predicts their long-term demographic outcome.

evolutionary biology↗