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RESEARCH

I am broadly interested in the ways organisms respond to urbanization, a significant and growing aspect of global change. My research takes an integrative approach to understand if and how species adapt to urban habitat modification. I focus on the neotropical lizards in the genus Anolis, but tropical organisms and reptiles & amphibians in particular are both understudied in the urban realm and are also particularly sensitive to the pressures of urbanization.

Urban Evolution

Urban environments are dramatically different from exurban areas. They are typified by elevated temperatures, open habitat, anthropogenic structures, reduced tree cover, and increased impervious surface cover. The ecological dynamics of these environments are altered, generating novel conditions in the city for plants and animals to adapt too. Because many cities globally are modified in the same way, urban environments provide a natural experiment to study evolution as it unfolds before our eyes on our city streets. 

Anole lizards

Lizards in the neotropical genus Anolis (called anoles) are an emerging model organism for evolutionary biology. They have an evolutionary history of rapidly diversifying across the Caribbean to take advantage of unique microhabitats, resulting in convergent trait-environment relationships known as “ecomorphs”. Relationships between environmental and trait variation are well-studied, and there is evidence that changes to the environment such as increased temperatures or shifts in vegetation structure lead to rapid adaptive trait shifts.

Herpetology

Reptiles and amphibians face many additional challenges as our world becomes increasingly impacted by human activities. As small-bodied ectotherms, many find the fragmented habitat of the city and the elevated temperatures difficult to deal with. Yet many species are extremely resilient, expanding their niches to exploit human spaces and resources in novel ways. Understanding how and why taxa respond differently to the pressures of urbanization can help us build cities more sustainably and work towards conservation objectives.

research areas

CONVERGENT RESPONSES TO URBANIZATION

Urban environments are modified in similar ways globally. The replicated nature of the structural and climatic environment provides ideal conditions for convergent adaptive responses. A major theme of my current research is investigating how predictable adaptive responses to urbanization are within species (across populations) and across species. In other words, if two species exploit urban environments, do they follow similar adaptive evolutionary trajectories? If not, what factors influence the variation in responses?

I am presently addressing this question in Caribbean anoles. My initial findings from the islands of Hispaniola, Jamaica, Bahamas, and Puerto Rico are forthcoming, and I have additional field trips planned (currently delayed because of COVID-19) to explore this theme in the anoles of the Lesser Antillean islands. An initial study from this research theme was recently published (Falvey et al. 2020), documenting convergent shifts in claw morphology across five species of anoles, consistent with shifts in structural habitat use.

ENVIRONMENT — PHENOTYPE — FUNCTION

The urban environment generates novel selection pressures for urban organisms. Depending on how species use the urban habitat space, the relationship between traits and environment may be altered resulting in phenotypic shifts at the population level. By investigating the function of these trait shifts under urban conditions, we can gain insight into the mechanisms of natural selection in producing adaptive evolutionary responses. With this phenotype – performance – fitness paradigm in mind, a major theme in my research is connecting ecological variation to phenotypic variation, and then investigating the fitness consequences of phenotypic shifts by measuring performance under experimental conditions replicating urban environments.

I am presently addressing this question by examining habitat use, morphology, and performance across several species of anoles. In the spring of 2020, the next phase of this research was planned to explore functional morphology more extensively in urban anoles — this research has been postponed until 2021 because of COVID-19. I am also exploring variation in trait-environment relationships in anoles more generally using museum specimens, with results from this work forthcoming. re

GENOMICS OF URBAN ADAPTATION

Patterns of genomic variation can shed light on the nature of adaptive responses. Adaptability may be influenced by patterns of gene flow: local adaptation may be overrun by extensive movement between populations, or alternatively, genetic diversity may be insufficient for natural selection to act if populations are small and isolated. Adaptation may also be better understood at the genomic level by identifying the genetic bases of trait shifts and by exploring regions of the genome under selection.

The genomics of urban adaptation is a developing area of my research. As I explore convergence in phenotype and function in other anole species, I am also exploring convergence at the genomic level. Forthcoming are results from a study of genomic signatures of selection across multiple populations of Anolis cristatellus, and recently published is a study on the genetic underpinnings of adaptive shifts in thermal physiology (along with collaborator Shane Campbell-Staton).