Resurrection ecology in Viola arvensis

Premise of the study: As part of global change, climate warming and
pollinator decline are expected to affect plant phenology and
plant-pollinator interactions. This paper aims at characterizing rapid
evolution of life history traits and floral traits over two decades in the
wild pansy (Viola arvensis), a common weed in agrosystems. Methods: We
used a resurrection ecology approach with genotypes sampled in 1991 and
2012 from a population in Burgundy (France). The species has a mixed
mating system (hereafter: mixed selfer) and presents a floral
polymorphism. In order to correct for maternal effects, plant traits were
measured in the second generation in a common garden (after a refreshing
generation) to characterize plant evolution during the two decades. In
addition, historical population selfing rates in the 1991 and 2012 were
inferred from microsatellites markers through heterozygote deficiency and
identity disequilibrium. Key results: Phenotypic data revealed a
significant advance in flowering date, reduced flower sizes and a higher
propensity of plant to set seed by autonomous selfing. Moreover, we
detected a change in color morph frequency with an increase of the pale
morph frequency. In accordance with phenotypic data, the neutral genetic
data revealed in increase in historical selfing rates from s=0.68 in 1991
to s=0.86 in 2012. Conclusions: Taken together, such data suggest that the
wild pansy, as mixed selfer, is evolving a selfing syndrome that may be
the consequence of reduced pollinator activity in agrosystems.