Multivariate phenotypic divergence along an urbanization gradient

Abstract

Evidence suggests that natural populations can evolve to better tolerate the novel environmental conditions associated with urban areas. Studies of adaptive divergence in urban areas often examine one or a few traits at a time from populations residing only at the most extreme urban and nonurban habitats. Thus, whether urbanization drives divergence in many traits simultaneously in a manner that varies with the degree of urbanization remains unclear. To address this gap, we generated seed families of white clover ( Trifolium repens ) collected from 27 populations along an urbanization gradient in Toronto, Canada, grew them in a common garden, and measured 14 phenotypic traits. Families from urban sites had evolved later phenology and germination, larger flowers, thinner stolons, reduced cyanogenesis, greater biomass and greater seed set. Pollinator observations revealed near-complete turnover of pollinator morphological groups along the urbanization gradient, which may explain some of the observed divergences in floral traits and phenology. Our results suggest that adaptation to urban environments involves multiple traits.

The effect of temperature and invasive alien predator on genetic and phenotypic variation in the damselfly Ischnura elegans: cross-latitude comparison

“…This approach is particularly important for organisms with complex life cycles whose development through different developmental stages strongly depends on the environmental conditions [ 14 ]. Some studies have also incorporated human-related factors and provided evidence for their effects on phenotype, such as selection for different wing shapes along an urbanization gradient in mosquitoes [ 15 ] and pollutant-based selection for body size and mass in beetles [ 16 ]; similar studies were also conducted in crustaceans [ 17 ] and in plants [ 18 ].…”

Ecological consequences of urbanization on a legume–rhizobia mutualism

“…Mutualisms can be important for community and ecosystem stability, and disruptions to these interactions caused by urbanization may be particularly problematic for maintaining ecosystem functions. For example, pollinator abundance, diversity and composition often change with urbanization (Harrison et al 2018, Santangelo et al 2020), which can shift the balance of the benefits conveyed between interacting plants and pollinators (Irwin et al 2014, Rivkin et al 2020, Santangelo et al 2020). As another example, plant–microbe interactions are important for community assembly and nutrient cycling (van der Heijden et al 2008), and urbanization can affect these interactions through altered soil chemistry mediated by pollution and nutrient deposition (Grimm et al 2008, Stevens et al 2018).…”

Urbanization and a green corridor do not impact genetic divergence in common milkweed (Asclepias syriaca)

“…These environmental conditions can also impose indirect impacts by restructuring species interactions such as antagonisms (e.g., predator/prey, including herbivory) and mutualisms (e.g., plant-pollinator and plant-microbe) [9][10][11] . In response, individuals and ultimately populations have experienced trait changes associated with growth, reproduction, defense/damage, morphology, and behavior, a process indicative of intraspecific phenotypic divergence [12][13][14][15][16] . Despite the recent rise of studies documenting phenotypic divergence among urban and rural populations, few have distinguished the degree to which evolution and phenotypic plasticity drive these patterns.…”

“…Several studies have investigated the basis of phenotypic divergence in plants [27][28][29][30] , yet few include multiple traits, or traits from diverse ecological functions such as reproduction, defense/damage, and growth. Thus, we have a poor understanding of how urbanization affects divergence in the multivariate phenotype but see 16 . Individual responses to environmental change often involve multiple correlated traits 31,32 , and excluding traits from major categories (e.g., defense) complicates the detection of shifts in life history strategies, including trade-offs, or the lack thereof.…”