Biology subjects

Rivkin, L. R.

Publications and source records attributed to Rivkin, L. R..

3 recordsLinked to original sources

bioRxiv2020

Road to ruin: Herbivory in a common tropical weed (Turnera subulata) along a rural-urban gradient

Urbanization is associated with numerous changes to the biotic and abiotic environment, many of which degrade the environment and lead to a loss of biodiversity. Cities often have elevated pollution levels that harm wildlife; however, the increased concentration of some pollutants can fertilize urban plants, leading to corresponding positive effects on herbivore populations. Increases in herbivory rates may lead to natural selection for greater defence phenotypes in plants. However, evidence supporting increased herbivory leading to the evolution of plant defence in urban environments is contradictory, and entirely absent from tropical regions of the world. To address these research gaps, we evaluated herbivory on Turnera subulata, a common urban wildflower, along an urbanization gradient in Joao Pessoa, Brazil. We predicted that higher rates of herbivory in urban areas would lead these populations to evolve cyanogenesis, a chemical defence found in a closely related Turnera species. We assessed herbivory and screened for cyanogenesis in 32 populations along the urbanization gradient, quantified by the Human Footprint Index. Our results show that urbanization is significantly associated with increased herbivory rates in T. subulata populations. Despite elevated herbivory, we found no evidence for the evolution of cyanongenesis in any of the populations, suggesting that the fitness effects of leaf herbivory are not extreme enough to select for the evolution of plant defence in these populations. Habitat loss, predator release, and nutrient enrichment likely act together to increase the abundance of herbivorous arthropods, influencing the herbivory patterns observed in our study.

ecology↗

bioRxiv2020

Urbanization alters ecological and evolutionary interaction between Darwin's Finches and Tribulus cistoides on the Galapagos Islands

Emerging evidence suggests that urbanization shapes the ecology and evolution of species interactions. Islands are particularly susceptible to urbanization due to the fragility of their ecosystems; however, few studies have examined the effects of urbanization on species interactions on islands. To address this gap, we studied the effects of urbanization on interactions between Darwins finches and its key food resource, Tribulus cistoides, in three towns on the Galapagos Islands. We assessed the effects of urbanization on seed and mericarp removal, mericarp morphology, and finch community composition using natural population surveys, experimental manipulations, and finch observations. We found that both seed and fruit removal rates were higher in urban compared to non-urban populations in the natural and experimental populations, and that urbanization modified selection on mericarp size and defense. Urban environments supported smaller and less diverse finch communities than non-urban environments. Together, our results suggest that urbanization can dramatically alter ecological interactions between Darwins finches and T. cistoides, leading to modified selection on T. cistoides populations. Our study demonstrates that urban development on islands can have profound effects on the ecology and evolution of trophic interactions.

evolutionary biology↗

bioRxiv2019

Multivariate phenotypic divergence along an urbanization gradient

A growing body of evidence suggests that natural populations can evolve to better tolerate the novel environmental conditions associated with urban areas. Invariably, studies of adaptive divergence in urban areas examine only one or a few traits at a time from populations residing only at the most extreme urban and nonurban habitats. Thus, whether urbanization is driving 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, and grew them up to measure multiple phenotypic traits in a common garden. Overall, urban populations had later phenology and germination, larger flowers, thinner stolons, reduced cyanogenesis, greater biomass, and were more attractive to pollinators. Pollinator observations revealed near complete turnover between urban and nonurban sites, which may explain some of the observed divergence in floral traits and phenology. Our results suggest that adaptation to urban environments involves multiple organismal traits.

evolutionary biology↗