Demographic fluctuations and selection during host-parasite co-evolution interactively increase genetic diversity.

Area of Science:

• Evolutionary biology
• Ecology
• Genetics

Background:

• Host-parasite interactions drive demographic changes and selection, potentially limiting genetic diversity and adaptation.
• Recent research suggests interactions between demography and selection may enhance genetic diversity for adaptation.

Purpose of the Study:

• To experimentally test how demography, selection, and their interaction affect genetic diversity in a host-parasite system.
• To disentangle the independent and combined effects of demographic fluctuations and virus-induced selection on algal host populations.

Main Methods:

• Utilized 12 experimental populations of the alga Chlorella variabilis, subjected to distinct conditions: constant size, demographic fluctuations, selection, or combined fluctuations and selection.
• Conducted whole-genome sequencing after 50 days (~50 generations) to analyze genetic variation within each population.
• Measured genetic diversity and compared it against expected values based on population sizes.

Main Results:

• Populations experiencing both demographic fluctuations and selection exhibited higher genetic diversity than those with separated processes.
• Experimentally measured diversity in combined populations surpassed theoretical expectations for their population sizes.
• Eco-evolutionary feedbacks were shown to positively influence genetic diversity.

Conclusions:

• The interplay of demographic fluctuations and selection enhances genetic diversity, contrary to expectations that these processes reduce variation.
• These findings provide crucial empirical data for refining theoretical models of adaptation in co-evolutionary contexts.
• Eco-evolutionary feedbacks are vital for maintaining and potentially increasing genetic diversity, facilitating host adaptation.