The maintenance of genetic variation in mutualism-related traits is key for understanding mutualism evolution,yet the mechanisms maintaining variation remain unclear.We asked whether genotype-byenvironment(G3E)interac...The maintenance of genetic variation in mutualism-related traits is key for understanding mutualism evolution,yet the mechanisms maintaining variation remain unclear.We asked whether genotype-byenvironment(G3E)interaction is a potential mechanism maintaining variation in the model legume–rhizobia system,Medicago truncatula–Ensifer meliloti.We planted 50 legume genotypes in a greenhouse under ambient light and shade to reflect reduced carbon availability for plants.We found an expected reduction under shaded conditions for plant performance traits,such as leaf number,aboveground and belowground biomass,and a mutualism-related trait,nodule number.We also found G3E for nodule number,with83%of this interaction due to shifts in genotype fitness rank order across light environments,coupled with strong positive directional selection on nodule number regardless of light environment.Our results suggest that G3E can maintain genetic variation in a mutualism-related trait that is under consistent positive directional selection across light environments.展开更多
基金NSERC Canada for funding that supports our science,Megan Frederickson,Art WeisHelen Rodd for comments on our workBill Cole and Thomas Gludovacz for horticultural assistance。
文摘The maintenance of genetic variation in mutualism-related traits is key for understanding mutualism evolution,yet the mechanisms maintaining variation remain unclear.We asked whether genotype-byenvironment(G3E)interaction is a potential mechanism maintaining variation in the model legume–rhizobia system,Medicago truncatula–Ensifer meliloti.We planted 50 legume genotypes in a greenhouse under ambient light and shade to reflect reduced carbon availability for plants.We found an expected reduction under shaded conditions for plant performance traits,such as leaf number,aboveground and belowground biomass,and a mutualism-related trait,nodule number.We also found G3E for nodule number,with83%of this interaction due to shifts in genotype fitness rank order across light environments,coupled with strong positive directional selection on nodule number regardless of light environment.Our results suggest that G3E can maintain genetic variation in a mutualism-related trait that is under consistent positive directional selection across light environments.
