Maarten van Emmerik: Effect of Urban Heat Island on Germination of Common Dandelion

Radboud University

During this MSc internship, I studied urban dandelions in Amsterdam, Nijmegen, and Maastricht. The aim was to investigate adaptation to the Urban Heat Island (UHI) effect. This effect causes overheating of stony areas due to heat retention during sunny days. I sampled plants from the hot city center and compared these to plants in surrounding rural areas. To investigate adaptation, I first conducted germination experiments in climate chambers. And I sequenced heat resistance genes of a selection of different genotypes samples along urban-rural transects. I discovered that seed weight had a positive correlation with germination speed and -success. A gene lineage tree based on sequence diversity showed that clonal lineages on streets are nested within lineages from rural areas, indicating repeated colonization of the UHI by dandelions from outside cities. Of the 34 genes analyzed, a total of 5 genes showed fixation to certain nucleotides in city center plants, possibly due to adaptation to the UHI. In short, my internship indicated that urban dandelions adapt to the UHI but at what speed is not yet known.