Assortative mating may have facilitated rapid evolution of locally adaptive phenologies during a biological invasion

Research suggests that assortative mating may have played a crucial role in the rapid evolution of locally adaptive flowering times during the invasion of the purple loosestrife (Lythrum salicaria) in eastern North America. Scientists grew 600 individuals from 20 populations across a 10-degree latitudinal gradient in a common garden setting.

They found that flowering schedules were less synchronized in the mixed garden population compared to the locally adapted populations, with synchrony decreasing towards higher latitudes of origin. The study also examined assortment potential, which varied by population but was not consistently negatively correlated with flowering synchrony (s) as predicted.

This discrepancy was attributed to among-individual fitness variation in the common garden. The researchers conclude that the combined effects of fitness variation and asynchrony associated with locally adapted phenology can mitigate the detrimental impacts of maladaptive gene flow, thereby accelerating the rate of adaptive evolution during the invasion process.