Evidence from the field that multiple processes maintain hidden adaptive capacity to a novel environment in a wild daisy

Abstract

Populations often persist in novel environments despite predictions that adaptive capacity to such conditions should be limited by a lack of genetic variation. A leading hypothesis is that genetic variation for adapting to novel environments is maintained but remains hidden (or 'cryptic') under native conditions. However, direct evidence of mechanisms that maintain this adaptive potential in populations is scarce. We integrate data from four large-scale field experiments to test whether variation in selection across environments and life history, together with genetic architecture, maintains genetic variation important for adapting to novel environments. Using a quantitative genetic breeding design, we generated families of the Sicilian daisy, Senecio chrysanthemifolius (Asteraceae), and planted seeds and cuttings across native and novel elevations on Mount Etna. We tracked fitness across elevations, life stages, seasons and generations. Genotypes with higher survival and flowering success at the novel elevation increased adaptive potential, but were not strongly disadvantaged in the native environment. A negative genetic correlation in seedling survival across seasons indicated that different genotypes were favoured across temporal variation in native environments. Crosses between genotypes with low and high fitness in the novel environment revealed that genotypes that increased adaptive potential had heritable effects on plasticity and fitness across generations, but were partially recessive and likely to hide in heterozygotes. Together, these results provide rare field-based evidence that inefficient selection in native environments and dominance maintain cryptic adaptive potential for novel environments, while temporal variation in selection maintains genetic variation in fitness more broadly.