Trait differentiation across urbanized environments in invasive Centaurea melitensis is not predicted by the Plant Economic Spectrum
Urbanization imposes unique selective pressures on organisms, but connecting specific urban environmental differences to trait adaptation requires detailed characterization of environmental heterogeneity across urbanized landscapes and tests for adaptation to it, rarely done to date. The Plant Economic Spectrum (PES) predicts that plants invest in different life strategies according to resource…
Urban environments present distinct selective pressures on organisms, necessitating an understanding of trait adaptation in these settings. The Plant Economic Spectrum (PES) proposes that plants adopt different strategies based on resource availability, with an acquisitive strategy favoring rapid growth aboveground in resource-rich environments, and a conservative strategy favoring belowground investment in resource-poor areas.
To test whether the invasive annual plant Centaurea melitensis exhibits trait differentiation predicted by the PES in California's urbanized environments, researchers utilized a framework of Environmental Zones to categorize the mosaic of urban landscapes across the state. Seeds from 31 populations of C. melitensis were grown in greenhouses for two generations, and subsequent measurements of growth, reproductive, and phenology traits were taken to determine if genetic differentiation aligns with PES predictions.
The study revealed that variation across all genotypes was not structured along the multivariate trait axes predicted by the PES, indicating that no multi-trait strategies were present. While individual traits were observed to be associated with environmental variables, including impervious surface cover and tree cover, these associations partially followed some PES expectations.
The findings suggest that C. melitensis has undergone genetic differentiation across environments with varying features of urbanization. However, the absence of multi-trait strategies predicted by the PES implies that the plant's adaptation to urban environments may not be as complex or specialized as the spectrum suggests.
This research combines comprehensive knowledge of urbanized environments with rigorous testing of trait-environment relationships, highlighting how urbanization may select for specific traits in C. melitensis populations. The study underscores the importance of detailed characterization of urban landscapes and emphasizes the need for more nuanced models of plant adaptation in rapidly changing environments.
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