Common microgeographical selection patterns revealed in four European conifers

Area of Science:

• Evolutionary Biology
• Genomics
• Ecology

Background:

• Microgeographical adaptation, where selection persists despite gene flow, leads to adaptive divergence at specific genetic loci.
• The prevalence and strength of selection driving these microgeographical adaptations remain largely unknown.
• Understanding adaptation at fine spatial scales is crucial for predicting species' responses to environmental change.

Purpose of the Study:

• To investigate microgeographical patterns of genomic divergence in four diverse European and Mediterranean conifer species.
• To quantify the strength of selection acting at the microgeographical level.
• To determine if selection maintains within-population genetic diversity in heterogeneous environments.

Main Methods:

• Genomic data screening of geographically close forest stands along ecological gradients.
• Application of divergence outlier detection, demographic modeling, and Approximate Bayesian Computation.
• Development of a novel method for estimating microgeographical selection coefficients (Ns).

Main Results:

• Strong selection was detected in all four species (Abies alba, Cedrus atlantica, Pinus halepensis, Pinus pinaster) at the microgeographical scale.
• Selection affected distinct loci in each species, with a fraction of 0.1%-1% of genome loci showing clear signatures.
• Estimated microgeographical selection coefficients (scaled by population size, Ns) ranged from 2 to 30.

Conclusions:

• Selection actively maintains within-population genetic diversity in spatially heterogeneous environments at microgeographical scales.
• This genetic diversity serves as a vital reservoir for adaptive potential, enabling populations to cope with environmental fluctuations.
• The findings highlight the importance of microgeographical adaptation in evolutionary processes and species resilience.