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The Role of Pleiotropy and Epistasis on Evolvability and Robustness in a Two-Peak Fitness Landscape
Dalarna University, School of Information and Engineering, Microdata Analysis.ORCID iD: 0000-0001-9523-6689
Dalarna University, School of Information and Engineering, Microdata Analysis. Department for MicroData Analytics, Dalarna University, 791 88 Falun, Sweden;BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI 48824, USA.ORCID iD: 0000-0002-4872-1961
2024 (English)In: Biology, E-ISSN 2079-7737, Vol. 13, no 12, article id 1003Article in journal (Refereed) Published
Abstract [en]

Understanding the balance between robustness and evolvability is crucial in evolutionary dynamics. This study aims to determine how varying mutation rates and valley depths affect this interplay during adaptation. Using a two-peak fitness landscape model requiring populations to cross a fitness valley to reach a higher peak, we investigate how mutation rates and valley depths influence both evolvability—the capacity to generate beneficial mutations—and mutational robustness, which stabilizes populations at the highest peak. Our experiments reveal that at low mutation rates, populations struggle to cross fitness valleys, reducing the occurrence of pioneers. As mutation rates increase, valley crossing becomes more frequent, but organisms forming a majority at the highest peak are less common and tend to arise at intermediate mutation rates. Although pioneers reach the highest peak, they are often replaced by more mutationally robust organisms that later form a majority. This suggests that while evolvability aids in valley crossing, long-term stability at the highest peak requires greater mutational robustness. Our findings highlight that adaptations in epistasis and pleiotropy facilitate the trade-off between evolvability and robustness, providing insights into how organisms navigate complex fitness landscapes. These results can also inform the design of genetic algorithms that balance evolvability with robustness to optimize outcomes. © 2024 by the authors.

Place, publisher, year, edition, pages
2024. Vol. 13, no 12, article id 1003
Keywords [en]
epistasis; evolvability; pleiotropy; robustness; survival of the flattest
National Category
Evolutionary Biology
Identifiers
URN: urn:nbn:se:du-49953DOI: 10.3390/biology13121003PubMedID: 39765670Scopus ID: 2-s2.0-85213267560OAI: oai:DiVA.org:du-49953DiVA, id: diva2:1925385
Available from: 2025-01-08 Created: 2025-01-08 Last updated: 2025-10-09
In thesis
1. Epistasis, Pleiotropy, Robustness, and Evolvability: Insights into Evolutionary Dynamics
Open this publication in new window or tab >>Epistasis, Pleiotropy, Robustness, and Evolvability: Insights into Evolutionary Dynamics
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study of evolutionary dynamics requires a comprehensive understanding of how genetic interactions shape adaptation, particularly through the interplay of epistasis, pleiotropy, robustness, and evolvability. Despite significant advances in evolutionary modeling, existing frameworks often oversimplify genetic architectures, assuming fixed interactions and static environments. However, epistasis and pleiotropy are not static properties; they evolve over time, continuously reshaping the adaptive landscape. This dissertation addresses these limitations by developing a computational framework that extends the classic NK fitness landscape model through indirect encoding. This key innovation decouples epistasis and pleiotropy from landscape ruggedness, allowing these fundamental properties to evolve and to be studied independently. To systematically quantify genetic interactions, this research uses an Interaction Matrix (IM) as a tool, which captures the strength and distribution of genetic dependencies. This enables a structured approach to measuring epistasis (the degree of gene-gene interaction) and pleiotropy (the extent to which a single gene influences multiple traits). Furthermore, the study integrates Gene Regulatory Networks (GRNs) to explore how these interactions change over evolutionary time, providing insights into the role of genetic sparsity in shaping adaptive potential. The key question in evolutionary biology is how epistasis and pleiotropy influence the balance between robustness and evolvability. While robustness–the ability to maintain function despite mutations–ensures stability, evolvability–the capacity to generate beneficial variation–is crucial for long-term adaptation. The interplay between these properties is complex and widely debated. To explore this interplay, I focus on the Survival of the Flattest (SoF) phenomenon, where populations in high-mutation environments favor flatter fitness peaks over higher narrower peaks. This raises fundamental questions: How can populations remain on higher fitness peaks for extended periods? What mechanisms enable successful transitions between peaks, avoiding the SoF trap? In what scenarios does evolvability provide an advantage, and when is robustness more beneficial? I use the SoF model as a framework to investigate the role of epistasis and pleiotropy in this context. This dissertation provides new insights into these evolutionary challenges, offering a refined perspective on how populations navigate rugged landscapes, escape local fitness traps, and dynamically balance stability with adaptability. To further investigate these evolutionary dynamics, a dynamic fitness landscape is developed, allowing the study of how populations respond to changing environments. Unlike static models, the experimenter sets the velocity at which the landscape changes independently from other parameters, such as the ruggedness or the mutation rate. By varying key parameters such as ruggedness (K) and environmental change rate (V), the study examines their effects on genotype-phenotype (GP) mapping. To further validate the findings, real-world datasets were incorporated, bridging the gap between theoretical models and empirical data. The findings have broad implications beyond evolutionary biology, offering valuable insights for genetic engineering, synthetic biology, and evolutionary computation, where understanding and harnessing genetic interactions can drive innovations in biotechnology and artificial life systems. By providing a refined approach to studying how genetic architectures evolve and persist over time, this work lays a foundation for future research into the fundamental principles governing adaptive complexity. All complex systems are composed of interacting components, inherently shaped by epistasis and pleiotropy. While our model is not a literal replication of any single system, it captures these fundamental properties, allowing us to probe general principles that can illuminate the behavior of complex, real-world evolutionary dynamics. 

Place, publisher, year, edition, pages
Borlänge: Dalarna University, 2025
Series
Dalarna Doctoral Dissertations ; 45
Keywords
epistasis, pleiotropy, ruggedness, evolvability, NK fitness landscape, gene regulatory networks, interaction matrix, mutational robustness, survival of the flattest, genotype-phenotype mapping, dynamic fitness landscapes
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:du-50615 (URN)978-91-88679-96-3 (ISBN)
Public defence
2025-08-29, room B301, campus Borlänge and online, 13:00 (English)
Opponent
Supervisors
Available from: 2025-06-16 Created: 2025-05-19 Last updated: 2025-10-09Bibliographically approved

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Mehra, PriyankaHintze, Arend

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