Additive genetic variance for lifetime fitness and the capacity for adaptation in an annual plant.

The immediate capacity for adaptation under current environmental conditions is directly proportional to the additive genetic variance for fitness, V (W). Mean absolute fitness, , is predicted to change at the rate , according to Fisher's Fundamental Theorem of Natural Selection. Despite ample research evaluating degree of local adaptation, direct assessment of V (W) and the capacity for ongoing adaptation is exceedingly rare.

Expression of additive genetic variance for fitness in a population of partridge pea in two field sites.

Despite the importance of adaptation in shaping biological diversity over many generations, little is known about populations' capacities to adapt at any particular time. Theory predicts that a population's rate of ongoing adaptation is the ratio of its additive genetic variance for fitness, , to its mean absolute fitness, . We conducted a transplant study to quantify and standing for a population of the annual legume Chamaecrista fasciculata in one field site from which we initially sampled it and another site where it does not currently occur naturally.

Detrimental effects of rhizobial inoculum early in the life of partridge pea, Chamaecrista fasciculata.

Premise Of The Study: Mutualistic relationships with microbes may aid plants in overcoming environmental stressors and increase the range of abiotic environments where plants can persist. Rhizobia, nitrogen-fixing bacteria associated with legumes, often confer fitness benefits to their host plants by increasing access to nitrogen in nitrogen-limited soils, but effects of rhizobia on host fitness under other stresses, such as drought, remain unclear.

Methods: In this greenhouse study, we varied the application of rhizobia (Bradyrhizobium sp.