Research

Please see my PUBLICATIONS page for complete work and to request PDF reprints.

Biodiversity through Justice, Equity, Diversity, & Inclusion: Environmental conditions – whether physical, temperature, chemical, sounds, or otherwise – are heterogeneous and vary across space and time. Recent work I co-led with Chris Schell and colleagues synthesizes the diverse ways that social inequality – particularly systemic racism and classism – are the strongest drivers of environmental heterogeneity, especially in urban areas. We provide a framework for continuing to study how social inequality impacts the ecology and evolutionary biology of the organisms and ecosystems we study. More importantly, we highlight how social and environmental justice is essential for effect biodiversity and conservation. As conservation biologists, how do we bring ourselves to advocate not only for the organisms and environments we strive to protect, but also the people? My colleagues and I also outline how conservation biologists – especially predominantly white, settler-colonizer biologists – can be for a place. We outline the approaches biologists can take to advance effective conservation efforts while simultaneously promoting the needs and knowledge of Indigenous and other marginalized communities.

Systemic biases in the form of structural racism and classism underlie most environmental variation in urban ecosystems and, ultimately, shape ecological and evolutionary processes in cities. Conservation and ecological restoration is therefore inherently intertwined with social and environmental justice. Figure from Schell et al. (2020).

Evolving Urban Conservation: Much of my current work is centered on understanding if and how developed, urban landscape and associated aquatic pollution impede different amphibian species from persisting and thriving in our cities and suburbs. Myself and many collaborators are using innovative field experiments, genomics, and analytical chemistry in both natural and stormwater ponds in the greater Portland and Seattle areas to test whether some amphibian species can rapidly evolve to tolerate a diversity of pollutants. Our research is directly feeding into active population and habitat management in these urban landscapes.

This work builds out of a growing theoretical framework built by my Dr. Colin Donihue, myself, and collaborators around the world to understand whether wildlife can rapidly evolve to live in cities. We first posed this question in 2015 in large part to use cities as natural experiments to understand evolution in real time. We are now actively working to understand who evolution in and because of cities means for conserving and managing urban biodiversity. In large part, if species are evolving in cities, conservation and management become a moving target and we have to ‘adapt’ our techniques to these changing species.

Conceptual framework for considering how evolutionary biology fits into conservation and management decisions in cities. From Lambert & Donihue (2020): Urban biodiversity management using evolutionary tools. Nature Ecology & Evolution.

This research is supported by the Smith Fellowship from the Society for Conservation Biology.

Sexual Diversity as Biological Diversity…and Global Change: I try to understand what turns tadpoles into male or female frogs. Like humans, frogs have sex chromosomes and genes that set the baseline for determining their expressed sex. But, features of the environment, like chemicals or temperature, can influence the way testes and ovaries develop. Sometimes this can cause sex reversal where a frog’s functional, expressed sex is opposite its genetic sex. Specifically, a genetically female frog can develop testes that produce working sperm or a genetic male can develop ovaries and lay viable eggs.

Historically, biologists believed sex reversal was a natural part of amphibian biology. But in the past twenty years, many biologists now believe sex reversal is strictly a consequence of human contamination. My research teases apart the natural, evolutionary history of sex reversal in amphibians with the effects of environmental pollution. I have combined careful field surveys, laboratory experiments, and genomics to reveal that sex reversal is predominantly a natural process in amphibians. Although experiments suggest that human contaminants can cause sex reversal, the extent to which this occurs in the wild relative to natural levels of sex reversal may be more limited than we previously thought. Additionally, conditions like “amphibian intersex” where male frogs have egg cells in their testes, also appear to be a relatively natural condition and not necessarily a response to human contaminants. My emerging research suggests that temperature may actually be a key regulator of amphibian sexual development. This work shifts our understanding of the evolution of sex determination in amphibian and provides critical insight for how we understand human land use and contamination. Our next steps are to understand whether sex reversal is an adaptive versus a random process.

Read this op-ed I wrote with Dr. Melina Packer in the Washington Post about how gendered language can misguide entire fields of biology, including frog sex reversal research. (Link & Lambert_Packer_gendered_language_washington_post_op_ed)

Both genetic females and genetic males sex reverse into the opposite expressed, phenotypic sex. This is a natural process and appears to be minimally impacted by human contaminants. Photos by Geoffrey Giller and Dan Field, respectively.

Urban Turtles: Urban and suburban areas, with fast-moving traffic and abundance of predators like cats and raccoons, pose a serious threat to wild turtles. At the same time, because we often directly ponds and lakes in urban landscapes, urban areas can also be hotspots for successful turtle conservation. My research has focused on understanding how competition with non-native turtles and impacts from urban pressures and urban conservation efforts influences native turtle species. Much of my work has focused the western pond turtle (Emys marmorata) and the red-eared slider turtle (Trachemys scripta elegans). While western pond turtles are one of the few aquatic turtles in California and a species currently undergoing review for listing under the U.S. Endangered Species Act, red-eared sliders are one of the world’s most invasive species because they are commonly released as former pets. Using both observational studies and experiments with wild populations, I have found that native pond turtles and non-native sliders use very different habitats in the same urban waterway and that sliders may not be a direct competitor. However, because sliders are released in very high numbers, their extraordinary densities can take a toll on native turtles.

I am currently collaborating with multiple colleagues to understand the large-scale impacts of roads, urbanization, and climate change on the demography (sex ratios, age structure, etc.) of turtles, in particular, but also reptiles more broadly. Check back soon for results!

The UC Davis Arboretum where I’ve studied impacts of urban habitat and non-native species on threatened western pond turtles. Inset is a native western pond turtle (left) and non-native red-eared slider turtle (right) basking together at the Arboretum. Photo by Max Lambert.

White Sands izards – a living laboratory for evolution: In 2018, I excitedly joined Dr. Bree Rosenblum’s lab at UC Berkeley as an NSF post doctoral researcher. As part of my work, I have been studying the evolution and population biology of three lizard species which have convergently evolved to live in the stunning landscape of White Sands National Monument (check out this amazing video). I have been using whole genome resequencing to understand the underlying genomic architecture associated with these lizards evolving to a brilliantly divergent new habitat. In collaboration with Dr. Simone Des Roches, we are also using capture-mark-recapture data to understand how natural selection proceeds or breaks down at the in ‘ecotone’ where the White Sands environment meets the dark soils of the surrounding Chihuahuan Desert.

The bright, white gypsum dunes at White Sands National Monument in New Mexico and one of its lizard denizens. Only three species of lizard have managed to colonize this intense landscape but they have done so in very similar ways.