Skip to main content

Adaptive significance of Non Genetic Inheritance

Periodic Reporting for period 3 - ANGI (Adaptive significance of Non Genetic Inheritance)

Reporting period: 2019-03-01 to 2020-08-31

Our ability to predict adaptation and the response of populations to selection is limited. Solving this issue is a fundamental challenge of evolutionary ecology with implications for applied sciences such as conservation, and agronomy. Non genetic inheritance (NGI; e.g. ecological niche transmission, epigenetic transmission) is suspected to play a foremost role in adaptive evolution but such hypothesis remains untested. Using quantitative genetics in wild plant populations, selection experiments, and epigenetics, we are assessing the potential role of NGI in the adaptive response to selection of plant populations. The ANGI project follows the subsequent research program: (1) Using long-term survey data, we are measuring natural selection in wild populations of snapdragon plants within their heterogeneous array of micro-habitats. (2) Using a statistical approach that we developed, we are estimating the quantitative genetic and nongenetic variation of traits. (3) We are identifying potential phenotypic changes caused by fitness that are based on genetic variation and NGI and assess their respective roles in adaptive evolution. (4) In controlled conditions, we will assess mechanisms underlying selection. (5) We will build on our results to develop the theory on genetic and non genetic natural selection
Why will this project have a broad impact on life sciences?
This project will integrate new findings into an inclusive theory of natural selection.
Genetic diversity is the key parameter used to study the evolution of species, predict their adaptive potential, manage genetic resources in agronomy, plan biological conservation strategies and communicate with a general audience on these topics. There is an emerging demand for clarifications about the role of the transgenerational environmental effects on the response to selection and more generally on the adaptive potential. There is also a demand by fundamental researchers to account for these effects in quantitative estimates and parameterize models of adaptive dynamics. Evolutionary biologists investigating the paradoxical absence of genetic evolution in response to selection in natural populations are also calling for empirical data on environmental effects shortcutting genetic selection. The ANGI project will participate to answer those demands.
During the first 54 months of the project:
We have conducted five exhaustive surveys (2016-2020) of the six natural populations occurring in the fragmented habitat of the abandoned saltmarsh between Peyriac de Mer and Bages in Southern France and characterized 15000 plants in natural populations (phenotype, geographic coordinates, 25 genetic [microsatellite] marker genotypes, microenvironment on the basis of photos). We have mapped the geographic patches were environmental conditions are more likely to be shared (e.g. open habitat on rocks, grassland). We are currently constructing the pedigree by genetically assigning parenthood to reach 3000 plants included in a highly reliable pedigree.
Experiments in controlled conditions allowed us to expose plants to different treatments (different levels of shade exposure and climate conditions). Experiments conducted in natural conditions were used to identify traits that might be involved with snapdragon plant adaptive evolution. Other experiments conducted in more controlled conditions (greenhouse and growth chambers) were conducted to test for an epigenetic basis of trait variation, with a focus on the developmental response to shade of snapdragon plants. We used Antirrhinum majus highly inbred lines and Arabidopsis thaliana Recombinant Inbred Lines, where the genome was fixed by generations of self-fertilization into a homozygous state, to investigate fundamental ecological and evolutionary mechanisms related to epigenetic trait variation.
In terms of results linked to the study of natural populations (WP1-2-3), we have obtained preliminary results and are extending the datasets to reach an acceptable level of statistical power and prepare scientific publications. These results indicate low connectivity between fragmented populations, heterogeneous selection, and low genetic heritability for fitness related traits.
In terms of results linked to experimental approaches (WP4), we have obtained several results that were published or submitted for publication. These results show that snapdragon plants exhibit strong phenotypic plasticity in response to shade (SLA, stem elongation in response to shade, etc.). Although we detected a strong phenotypic response, and detected some epigenetic changes in methylation patterns, our findings collectively point out towards an only small potential epigenetic variation associated with the snapdragon plant response to shade.
In terms of results linked to theoretical and conceptual developments (WP5). We have developed and published a methodological guide and opinion papers on how and why the potential role of epigenetic and genetic variation in the response to selection should be studied simultaneously and what are the potential implications for agronomic sciences.
At this stage of the project (54 months), most advances beyond the state of art were provided by the conceptual and methodological frameworks that we built.There is still a lot of debate animating the scientific community about the evolutionary significance of non genetic inheritance (e.g. ecological niche transmission and epigenetic transmission). Evidence keeps accumulating that plasticity and epigenetic variation can be inherited. However, most experimental results are based on studies where genetic variation was excluded (e.g. by using one lineage of clones). Evidence for a direct role played by non genetic variation in the evolution od wild populations in nature where there is also genetic variation is still scarce. We have developed methods to quantify the effect of ecological and epigenetic transgenerational variation in experimental and wild populations. We have synthesized the current knowledge on the potential role that non genetic inheritance could play in the adaptive evolution of wild populations, with a focus on epigenetic variation because it is at the center of the current debate. So far, our progress supports the need for empirical assessments. Until a strong empirical background is available, our findings lead us to think that no strong conclusion can be reached yet on the role of non genetic inheritance in the evolutionary response of wild populations on the basis of the existing scientific literature. This is because available empirical studies did not separate genetic and non genetic transgenerational effects simultaneously albeit they can be confounded. This reasoning goes against several papers published in the scientific literature that argue one way or another. We will assess empirically whether alternative sources of adaptive evolution can be identified in natural populations by taking into account both genetic and non genetic variation simultaneously. Such knowledge would have implications for building original strategies in applied conservation based on the non genetic adaptive potential of populations. We expect our results will raise public awareness and interest for these issues.