Neutral and adaptive genetic diversity in plants: An overview

Genetic diversity is a prerequisite for evolutionary change in all kinds of organisms. It is generally acknowledged that populations lacking genetic variation are unable to evolve in response to new environmental conditions (e.g., climate change) and thus may face an increased risk of extinction. Although the importance of incorporating genetic diversity into the design of conservation measures is now well understood, less attention has been paid to the distinction between neutral (NGV) and adaptive (AGV) genetic variation. In this review, we first focus on the utility of NGV by examining the ways to quantify it, reviewing applications of NGV to infer ecological and evolutionary processes, and by exploring its utility in designing conservation measures for plant populations and species. Against this background, we then summarize the ways to identify and estimate AGV and discuss its potential use in plant conservation. After comparing NGV and AGV and considering their pros and cons in a conservation context, we conclude that there is an urgent need for a better understanding of AGV and its role in climate change adaptation. To date, however, there are only a few AGV studies on non-model plant species aimed at deciphering the genetic and genomic basis of complex trait variation. Therefore, conservation researchers and practitioners should keep utilizing NGV to develop relevant strategies for rare and endangered plant species until more estimates of AGV are available.

This research was supported by grants from the National Institute of Biological Resources (NIBR) of the Republic of Korea (NIBR202206101 to MYC). KM was supported by the National Natural Science Foundation of China (grant numbers U20A2080, 31622015), while JL-P was also supported by the Spanish Ministerio de Ciencia e Innovación (PID2020-119163GB-I00 funded by MCIN/AEI/10.13039/501100011033).

1. Introduction 2. Estimation of neutral and adaptive genetic diversity 2.1. Neutral genetic diversity 2.2. Adaptive genetic diversity 2.2.1. Genetic diversity in quantitative traits 2.2.2. Identification of loci underlying local adaptation 2.2.3. Genetic diversity in single nucleotide polymorphisms, single genes, and genomic regions 3. Application of neutral genetic diversity to plant conservation 4. Application of adaptive genetic diversity to plant conservation 5. The relationship between neutral genetic diversity and adaptive genetic diversity 6. Controversy over the similarity between neutral genetic variation and adaptive genetic variation 7. Conclusion and a way forward Author contributions Funding Acknowledgments Conflict of interest Publisher’s note Supplementary material References