TY - JOUR T1 - Assortment of flowering time and defense alleles in natural <em>Arabidopsis thaliana</em> populations suggests co-evolution between defense and vegetative lifespan strategies JF - bioRxiv DO - 10.1101/131136 SP - 131136 AU - Shirin Glander AU - Fei He AU - Gregor Schmitz AU - Anika Witten AU - Arndt Telschow AU - J. de Meaux Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/06/19/131136.abstract N2 - The selective impact of pathogen epidemics on host defenses can be strong but remains transient. By contrast, life-history shifts can durably and continuously modify the balance between costs and benefits of immunity, which arbitrates the evolution of host defenses. Their impact, however, has seldom been documented. Here, we show with a simple mathematical model how the optimal investment into defense is expected to increase with increasing lifespan. We further document that in natural populations of the model plant Arabidopsis thaliana, the expression levels of defense genes correlate positively with flowering time, which in annual species is a proxy for lifespan. Using a novel genetic strategy based on bulk-segregants, we partitioned lifespan-dependent from lifespan–independent defense genes and could demonstrate that this positive co-variation can be genetically separated. It is therefore not explained by the pleiotropic action of some major regulatory genes controlling both defense and lifespan. Moreover, we find that defense genes containing variants reported to impact fitness in natural field conditions are among the genes whose expression co-varies most strongly with flowering time. In agreement with our model, this study reveals that natural selection has likely assorted alleles promoting higher expression of defense genes with alleles that increase the duration of vegetative lifespan in A. thaliana and vice versa. This is the first study documenting the pervasive impact of life history variation on the maintenance of diversity in host immunity within species. ER -