Urban environments are warmer, have higher levels of atmospheric CO2 and have altered patterns of disturbance and precipitation than nearby rural areas. These differences can be important for plant growth and are likely to create distinct selective environments. We planted a common garden experiment with seeds collected from natural populations of the native annual plant Lepidium virginicum, growing in five urban and nearby rural areas in the northern United States to determine whether and how urban populations differ from those from surrounding rural areas. When grown in a common environment, plants grown from seeds collected from urban areas bolted sooner, grew larger, had fewer leaves, had an extended time between bolting and flowering, and produced more seeds than plants grown from seeds collected from rural areas. Interestingly, the rural populations exhibited larger phenotypic differences from one another than urban populations. Surprisingly, genomic data revealed that the majority of individuals in each of the urban populations were more closely related to individuals from other urban populations than they were to geographically proximate rural areas – the one exception being urban and rural populations from New York which were nearly identical. Taken together, our results suggest that selection in urban environments favors different traits than selection in rural environments and that these differences can drive adaptation and shape population structure.
Bibliographical noteFunding Information:
We thank Jim Lewis for help with collecting in NYC, Jeremy Yoder, Ruth Shaw, Amanda Gorton, Liana Burghardt, David Moeller, and Jennifer Powers for discussion and comments that improved the research and presentation and NSF (DDIG Award 1401222) for funding.
© 2016 John Wiley & Sons Ltd
- isolation by distance
- local adaptation