Genetic Diversity and Population Structure in Cities Is Not Consistent Among Cosmopolitan Plant Species

Area of Science:

• Ecology
• Genetics
• Urban Ecology

Background:

• Urbanization leads to plant community homogenization.
• Genetic patterns of widespread plant species in urban environments are not well understood.

Purpose of the Study:

• To examine genome-wide genetic patterns in six widespread plant species across five US cities.
• To determine if urbanization, city-specific factors, or impervious surfaces drive genetic structure and differentiation.

Main Methods:

• Reduced-representation sequencing was used to analyze genetic variation.
• Assessed genetic structure, differentiation, isolation by distance (IBD), and isolation by environment (IBE).

Main Results:

• Most species showed limited population structure and high gene flow, with no significant genetic differentiation among cities.
• Exceptions included city-level differences in *Erigeron canadensis* (horseweed) and *Lactuca serriola* (prickly lettuce), particularly in Phoenix.
• *Erigeron canadensis* displayed stronger differentiation by city, temperature, and distance, while no species showed structure related to impervious surfaces.

Conclusions:

• Widespread plant genetic structure is influenced more by species traits and human-mediated dispersal than by urbanization itself.
• Cosmopolitan plant species largely maintain genetic homogeneity across urban landscapes due to high gene flow.