Biology subjects

Guzella, T.

Publications and source records attributed to Guzella, T..

4 recordsLinked to original sources

bioRxiv2022

Phenotypic stasis with genetic divergence

1Whether or not genetic divergence on the short-term of tens to hundreds of generations is compatible with phenotypic stasis remains a relatively unexplored problem. We evolved predominantly outcrossing, genetically diverse populations of the nematode Caenorhabditis elegans under a constant and homogeneous environment for 240 generations, and followed individual locomotion behavior. Although founders of lab populations show highly diverse locomotion behavior, during lab evolution the component traits of locomotion behavior - defined as the transition rates in activity and direction - did not show divergence from the ancestral population. In contrast, transition rates genetic (co)variance structure showed a marked divergence from the ancestral state and differentiation among replicate populations during the final 100 generations and after most adaptation had been achieved. We observe that genetic differentiation is a transient pattern during the loss of genetic variance along phenotypic dimensions under drift during the last 100 generations of lab evolution. These results suggest that short-term stasis of locomotion behavior is maintained because of stabilizing selection, while the genetic structuring of component traits is contingent upon drift history.

evolutionary biology↗

bioRxiv2019

Selection and drift determine phenotypic stasis despite genetic divergence

1Evolutionary theory suggests that phenotypic stasis is explained by natural selection and genetic drift, or by constraints imposed by mutation and recombination of standing genetic variation. We performed experimental evolution from standing genetic variation with the nematode Caenorhabditis elegans, measuring individual locomotion in outcrossing populations for 240 generations. We find that, in our constant environment, locomotion bias shows no directional divergence, due to both stabilizing and disruptive selection on specific combinations of component traits. Despite phenotypic stasis, the genetic variance-covariance structure between component traits shows clear divergence from the ancestral state and extensive differentiation among replicated populations facing the same environment. Analysis of mutation accumulation experiments and genome-sequenced recombinant inbred lines from the experimental populations indicates that the evolution of the genetic variance-covariance structure is independent of de novo mutation or major effect QTL; being instead explained by the joint action of selection and drift in generating subtle linkage disequilibrium differences between small effect QTL among replicate populations. These findings indicate that phenotypic evolution is repeatable because of selection, even if the genetic structuring of component traits within lineages is mostly contingent upon drift history.

evolutionary biology↗

bioRxiv2018

How differing modes of transgenerational inheritance affect population viability in fluctuating environments

1Different modes of transgenerational inheritance are expected to affect population persistence in fluctuating environments. We here analyze Caenorhabiditis elegans density-independent per capita growth rate time series on 36 populations experiencing 6 controlled sequences of challenging oxygen level fluctuations across 60 generations, and parameterize competing models of transgenerational inheritance that do not involve genetic changes in order to explain observed dynamics. Our analysis shows that phenotypic plasticity and anticipatory maternal effects are sufficient to explain growth rate dynamics, but that a carryover model where epigenetic memory is imperfectly transmitted and might be reset at each generation is a better fit to the data. After validating the models, we use the fitted transgenerational inheritance parameters to forecast population growth rates and find that it is negatively related to the degree of environmental autocorrelation.

ecology↗

bioRxiv2017

Polygenicity And Epistasis Underlie Fitness-Proximal Traits In The Caenorhabditis elegans Multiparental Experimental Evolution (CeMEE) Panel

Understanding the genetic basis of complex traits remains a major challenge in biology. Polygenicity, phenotypic plasticity and epistasis contribute to phenotypic variance in ways that are rarely clear. This uncertainty is problematic for estimating heritability, for predicting individual phenotypes from genomic data, and for parameterizing models of phenotypic evolution. Here we report a recombinant inbred line (RIL) quantitative trait locus (QTL) mapping panel for the hermaphroditic nematode Caenorhabditis elegans, the C. elegans multiparental experimental evolution (CeMEE) panel. The CeMEE panel, comprising 507 RILs, was created by hybridization of 16 wild isolates, experimental evolution at moderate population sizes and predominant outcrossing for 140-190 generations, and inbreeding by selfing for 13-16 generations. The panel contains 22% of single nucleotide polymorphisms known to segregate in natural populations, and complements existing mapping resources for C. elegans by providing high nucleotide diversity across >95% of the genome. We apply it to study the genetic basis of two fitness components, fertility and hermaphrodite body size at time of reproduction, with high broad sense heritability in the CeMEE. While simulations show we should detect common alleles with additive effects as small as 5%, at gene-level resolution, the genetic architectures of these traits does not feature such alleles. We instead find that a significant fraction of trait variance, particularly for fertility, can be explained by sign epistasis with weak main effects. In congruence, phenotype prediction, while generally poor (r2 < 10%), requires modeling epistasis for optimal accuracy, with most variance attributed to the highly recombinant, rapidly evolving chromosome arms.

evolutionary biology↗