Evolutionary relationships of functional trait and environmental variation: Gene expression variation across the range of a plant species
Understanding both environmental and genetic mechanisms underlying locally adaptive trait variation across a species’ range is critical for predicting how species will respond to changing climate. In this study, we performed a common garden experiment with a South African shrub, Protea repens, displaying diverse phenotypes along strong environmental gradients. We grew plants from seeds collected at 19 populations spanning the species’ range, and sequenced the transcriptomes of these plants to reveal gene pathways associated with potentially adaptive trait variation. We related patterns of co-expressed gene networks to trait phenotypes measured in the common garden, to source population climate, and to traits of the maternal plants measured in the wild.
We found that expression in gene networks correlated strongly with source-population environment and with plant traits. In particular, gene networks enriched for growth related pathways correlated strongly with source site minimum winter temperature and with leaf area, stem diameter and maternal plant specific leaf area. Other gene networks with enrichments for gluconeogenesis correlated with source-site precipitation. Our results strongly suggest that there is heritable control of gene expression in the common garden shaped by source population site climate, and reflected in traits both in the common garden seedlings and mother plants in the wild.