Welcome Jolene!

Jolene A. Saldivar will be completing her Ph.D. in Plant Biology at UC Riverside this June before starting as a UC Davis Chancellor’s Postdoctoral Fellow in our lab later this summer. Jolene also received an NSF Postdoctoral Research Fellowship in Biology, which she has deferred for a year. Jolene is interested in documenting plant-butterfly interaction networks across a management gradient, using isotopes to learn about the migratory ecology of painted lady butterflies, and developing species distribution models for butterflies and their host plants.

Welcome Melanie and Annalee!

Melanie is a third-year Environmental Science and Management major, working primarily with Tracie on her Pacific Northwest beetle project. Annalee is a first-year Wildlife, Fish, and Conservation Biology major with experience at the UCD Stable Isotope Facility and an interest in butterflies. Annalee will be helping us with a variety projects while developing her research interests.

Predator-driven behavioural shifts in a common lizard shape resource-flow from marine to terrestrial ecosystems

Oriol Lapiedra, Nina Morales, Louie H. Yang, Darío Fernández-Bellon, Sozos N. Michaelides, Sean T. Giery, Jonah Piovia-Scott, Thomas W. Schoener, Jason J. Kolbe, Jonathan B. Losos


Foraging decisions shape the structure of food webs. Therefore, a behavioural shift in a single species can potentially modify resource-flow dynamics of entire ecosystems. To examine this, we conducted a field experiment to assess foraging niche dynamics of semi-arboreal brown anole lizards in the presence/absence of predatory ground-dwelling curly-tailed lizards in a replicated set of island ecosystems. One year after experimental translocation, brown anoles exposed to these predators had drastically increased perch height and reduced consumption of marine-derived food resources. This foraging niche shift altered marine-to-terrestrial resource-flow dynamics and persisted in the diets of the first-generation offspring. Furthermore, female lizards that displayed more risk-taking behaviours consumed more marine prey on islands with predators present. Our results show how predator-driven rapid behavioural shifts can alter food-web connectivity between oceanic and terrestrial ecosystems and underscore the importance of studying behaviour-mediated niche shifts to understand ecosystem functioning in rapidly changing environments.

Ecology Letters


Complexity, humility and action: a current perspective on monarchs in western North America

Louie H. Yang


Recent studies have continued to shed light on the ecology of monarch butterflies (Danaus plexippus) in western North America. These studies have documented a declining overwintering population over several decades, punctuated by unexpected variability in recent years. Understanding this variability will require grappling with the spatial and temporal heterogeneity of resources and risks presented to western monarchs throughout their annual life cycle. Recent changes in the western monarch population further illustrate how interacting global change drivers can create complex causes and consequences in this system. The complexity of this system should inspire humility. However, even recognizing the limits of our current understanding, there is enough scientific common ground to take some conservation actions now.

Current Opinion in Insect Science


Thermal asymmetries influence effects of warming on stage and size-dependent predator–prey interactions

Adam Pepi, Tracie Hayes and Kelsey Lyberger


Climate warming directly influences the developmental and feeding rates of organisms. Changes in these rates are likely to have consequences for species interactions, particularly for organisms affected by stage- or size-dependent predation. However, because of differences in species-specific responses to warming, predicting the impact of warming on predator and prey densities can be difficult. We present a general model of stage-dependent predation with temperature-dependent vital rates to explore the effects of warming when predator and prey have different thermal optima. We found that warming generally favored the interactor with the higher thermal optimum. Part of this effect occurred due to the stage-dependent nature of the interaction and part due to thermal asymmetries. Interestingly, below the predator and prey thermal optima, warming caused prey densities to decline, even as increasing temperature improved prey performance. We also parameterize our model using values from a well-studied system, Arctia virginalis and Formica lasioides, in which the predator has a warmer optimum. Overall, our results provide a general framework for understanding stage- and temperature-dependent predator–prey interactions and illustrate that the thermal niche of both predator and prey is important to consider when predicting the effects of climate warming.

Theoretical Ecology


Tracking phenological distributions and interaction potential across life stages

Calvin M. Carroll, Daniel Saenz, and Volker H. W. Rudolf


Climate change is shifting the phenological timing, duration, and temporal overlap of interacting species in natural communities, reshaping temporal interaction networks worldwide. Despite much recent progress in documenting these phenological shifts, little is known about how the phenologies of species interactions are tracked across different life history stages. Here we analyze four key phenological traits and the pairwise interaction potential of nine amphibian species for the adult (calling/breeding) and subsequent larval (tadpole) stage at eight different sites over six years. We found few strong correlations among phenological traits within species, but the strength of these correlations varied across species. As a consequence, phenological trait combinations of both stages varied substantially across species without clear signs of multidimensional clustering, indicating a distinct and diverse range of species-specific phenological strategies. Despite this considerable variation in the phenologies across species, the temporal overlap between species was largely preserved through the two life history stages. Further, we also detected significant correlations among the duration and temporal overlap of interactions with other species across stages in five species, demonstrating that temporal patterns of species interactions are mirrored across life history stages. For these species, these results indicate a strong tracking of phenologies and species interactions across life history stages even in species with complex life cycles where stages occupy completely different environments. This suggests that phenological shifts in one stage can impact the temporal dynamics and structure of interaction networks across developmental stages.




Critical thermal limits and temperature-dependent walking speed may mediate coexistence between the native winter ant (Prenolepis imparis) and the invasive Argentine ant (Linepithema humile)

Rebecca A. Nelson, Dylan J. MacArthur-Waltz and Deborah M. Gordon


Comparing the thermal tolerance and performance of native and invasive species from varying climatic origins may explain why some native and invasive species can coexist. We compared the thermal niches of an invasive and native ant species. The Argentine ant (Linepithema humile) is an invasive species that has spread to Mediterranean climates worldwide, where it is associated with losses in native arthropod biodiversity. In northern California, long-term surveys of ant biodiversity have shown that the winter ant (Prenolepis imparis) is the native species best able to coexist with Argentine ants. Both species tend hemipteran scales for food, and previous research suggests that these species’ coexistence may depend on seasonal partitioning: winter ants are active primarily in the colder winter months, while Argentine ants are active primarily in the warmer months in northern California.

We investigated the physiological basis of seasonal partitioning in Argentine and winter ants by a) measuring critical thermal limits, and b) comparing how ant walking speed varies with temperature. While both species had similar CTmax values, we found differences between the two species’ critical thermal minima that may allow winter ants to remain functional at ecologically relevant temperatures between 0 and 2.5 °C. We also found that winter ants’ walking speeds are significantly less temperature-dependent than those of Argentine ants. Winter ants walk faster than Argentine ants at low temperatures, which may allow the winter ants to remain active and forage at lower winter temperatures. These results suggest that partitioning based on differences in temperature tolerance promotes the winter ant’s continued occupation of areas invaded by the Argentine ant.

Journal of Thermal Biology