The roles of genetic drift and natural selection in quantitative trait divergence along an altitudinal gradient in Arabidopsis thaliana

Abstract

Understanding how natural selection and genetic drift shape biological variation is a central topic in biology, yet our understanding of the agents of natural selection and their target traits is limited. We investigated to what extent selection along an altitudinal gradient or genetic drift contributed to variation in ecologically relevant traits in Arabidopsis thaliana. We collected seeds from 8 to 14 individuals from each of 14 A. thaliana populations originating from sites between 800 and 2700 m above sea level in the Swiss Alps. Seed families were grown with and without vernalization, corresponding to winter-annual and summer-annual life histories, respectively. We analyzed putatively neutral genetic divergence between these populations using 24 simple sequence repeat markers. We measured seven traits related to growth, phenology and leaf morphology that are rarely reported in A. thaliana and performed analyses of altitudinal clines, as well as overall Q ST -F ST comparisons and correlation analyses among pair-wise Q ST , F ST and altitude of origin differences. Multivariate analyses suggested adaptive differentiation along altitude in the entire suite of traits, particularly when expressed in the summer-annual life history. Of the individual traits, a decrease in rosette leaf number in the vegetative state and an increase in leaf succulence with increasing altitude could be attributed to adaptive divergence. Interestingly, these patterns relate well to common within-and between-species trends of smaller plant size and thicker leaves at high altitude. Our results thus offer exciting possibilities to unravel the underlying mechanisms for these conspicuous trends using the model species A. thaliana.

Parallel adaptive evolution of geographically distant herring populations on both sides of the North Atlantic Ocean

“…Identification of the genetic basis for ecological adaptation is a fundamental goal in evolutionary biology (7), and current technological advances in population-scale high-throughput sequencing provide powerful tools to explore these processes at a genomic scale (8). However, many adaptive traits are expected to have a highly polygenic background (9) in which genes of small effect are hard to detect with traditional genome scans, and adaptive changes can often be confounded with demographic history effects such as population structure and genetic drift (10), making the dissection of such genetic differentiations challenging.…”

A Single Nucleotide Deletion in Gibberellin20-oxidase1 Causes Alpine Dwarfism in Arabidopsis

“…In the array of accessions used here, only one accession carried the dwarfing allele of ga5-184, suggesting that the variation in plant height across all accessions is complicated by other factors. A decrease in plant height with altitude is expected if altitudinal selection led to trait divergence; however, it is also consistent with a role of genetic drift (Leinonen et al, 2013;Luo et al, 2015). Indeed, analyses of a fitness proxy, total seed number, revealed that accessions did not generally perform better at an altitude close to their altitude of origin.…”

“…Spray et al, 1996;Peng et al, 1999;Monna et al, 2002). Dwarfism and dwarfing alleles have also been reported in natural Arabidopsis accessions (Barboza et al, 2013), and other recent studies have shown evidence of population differentiation and climatic adaptation along altitudinal gradients in this model plant (Montesinos et al, 2009;Méndez-Vigo et al, 2011, 2013Montesinos-Navarro et al, 2011;Pico, 2012;Suter et al, 2014;Luo et al, 2015). In this study, we have investigated plant dwarfism in natural Arabidopsis accessions collected in left) and SAO (right) in the greenhouse.…”

Natural variation in life history strategy of Arabidopsis thaliana determines stress responses to drought and insects of different feeding guilds

“…In line with this observation, an increase of summer annuals with increasing altitude in Spain (400–1700 m) and the Swiss alps (600–2700 m) has been reported (Pico ; Luo et al . ). It is interesting that a decrease in grasshopper abundance is correlated with a decrease in resistance of plants to chewing insect herbivores (Descombes et al .…”