Professor University of California, Davis Davis, California, United States
Abstract: Background/Question/
Methods:
Heterogeneity is a key facet of urban landscapes that may influence many ecological dynamics within cities. For plants, this heterogeneity may lead to intraspecific trait variation as populations respond to differing local environmental conditions across the city. Variation in morphological, phenological, and reproductive traits that are retained under common environmental conditions indicate that there are strong pressures driving trait divergence among sites.
This study explores whether landscape heterogeneity leads to increased plant trait variation in urban areas compared to non-urban areas, by asking the following questions: 1) In a controlled greenhouse environment, is the trait variation observed among urban sites greater than, less than, or equal to the trait variation observed among non-urban sites? 2) What explains more of the difference in plant traits – the specific site or whether the plants were collected from urban or non-urban landscapes? To answer these questions, we collected seeds of Italian ryegrass (Festuca perennis) from 10 urban sites and 10 non-urban sites. We grew 30 individuals from each site (600 total plants) throughout their lifespan in the greenhouse. Data on germination success, days to germination, aboveground biomass, reproductive biomass, and phenological stage at harvest was collected. To compare intraspecific variation among sites within and across urban and non-urban landscapes, we compared trait means and variance.
Results/
Conclusions:
We found significant differences in trait variance for aboveground biomass among urban sites (p < 0.01), but not among non-urban sites (p = 0.08) using a Levene’s test for homogeneity of variances. Comparing trait means using Welch’s ANOVA reveals that there are significant differences in mean aboveground biomass among urban sites (p < 0.001), while there are no significant differences among non-urban sites (p = 0.361). These results, though preliminary, indicate that the trait variation observed in urban landscapes may rival or exceed the variation observed in non-urban landscapes. This study demonstrates the importance of considering the effects of within-urban environmental heterogeneity suggesting that it may be fruitful to investigate the link between within-urban heterogeneity and plant trait expression.
