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

The role of timing in intraspecific trait ecology

Olivia L. Cope, Laura A. Burkle, Jordan R. Croy, Kailen A. Mooney, Louie H. Yang and William C. Wetzel


Intraspecific trait variation has tremendous importance for species interactions and community composition. A major source of intraspecific trait variation is an organism’s developmental stage; however, timing is rarely considered in studies of the ecological effects of intraspecific variation. Here, we examine the role of time in the ecology of intraspecific trait variation, focusing on plants and their interactions with other organisms. Trait variation due to differences in developmental timing has unique features and dynamics, distinguishing it from variation due to genes or the environment. When time is considered in studies of intraspecific trait ecology, the degree of variability in timing within a population becomes a key factor structuring trait-mediated ecological interactions and community processes.

Trends in Ecology and Evolution (TREE)

Timing of a plant-herbivore interaction alters plant growth and reproduction

Nick L. Rasmussen and Louie H. Yang


Phenological shifts have the potential to change species interactions, but relatively few studies have used experimental manipulations to examine the effects of variation in timing of an interspecific interaction across a series of life-stages of a species. While previous experimental studies have examined the consequences of phenological timing in plant-herbivore interactions for both plants and their herbivores, less is known about their effects on subsequent plant reproduction. Here, we conducted an experiment to determine how shifts in the phenological timing of monarch (Danaus plexippus) larval herbivory affected milkweed (Asclepias fascicularis) host plant performance, including effects on growth and subsequent effects on flower and seed pod phenology and production. We found that variation in the timing of herbivory affected both plant growth and reproduction, with measurable effects several weeks to several months after herbivory ended. The timing of herbivory had qualitatively different effects on vegetative and reproductive biomass: early-season herbivory had the strongest effects on plant size, while late-season herbivory had the strongest effects on the production of viable seeds. These results show that phenological shifts in herbivory can have persistent and qualitatively different effects on different life stages across the season.



Different factors limit early- and late-season windows of opportunity for monarch development

Louie H. Yang, Karen Swan, Eric Bastin, Jessica Aguilar, Meredith Cenzer, Andrew Codd, Natalie Gonzalez, Tracie Hayes, August Higgins, Xang Lor, Chido Macharaga, Marshall McMunn, Kenya Oto, Nicholas Winarto, Darren Wong, Tabatha Yang, Numan Afridi, Sarah Aguilar, Amelia Allison, Arden Ambrose-Winters, Edwin Amescua, Mattias Apse, Nancy Avoce, Kirstin Bastin, Emily Bolander, Jessica Burroughs, Cristian Cabrera, Madeline Candy, Ariana Cavett, Melina Cavett, Lemuel Chang, Miles Claret, Delaney Coleman, Jacob Concha, Paxson Danzer, Joe DaRosa, Audrey Dufresne, Claire Duisenberg, Allyson Earl, Emily Eckey, Maddie English, Alexander Espejo, Erika Faith, Amy Fang, Alejandro Gamez, Jackelin Garcini, Julie Garcini, Giancarlo Gilbert-Igelsrud, Kelly Goedde-Matthews, Sarah Grahn, Paloma Guerra, Vanessa Guerra, Madison Hagedorn, Katie Hall, Griffin Hall, Jake Hammond, Cody Hargadon, Victoria Henley, Sarah Hinesley, Celeste Jacobs, Camille Johnson, Tattiana Johnson, Zachary Johnson, Emma Juchau, Celeste Kaplan, Andrew Katznelson, Ronja Keeley, Tatum Kubik, Theodore Lam, Chalinee Lansing, Andrea Lara, Vivian Le, Breana Lee, Kyra Lee, Maddy Lemmo, Scott Lucio, Angela Luo, Salman Malakzay, Luke Mangney, Joseph Martin, Wade Matern, Byron McConnell, Maya McHale, Giulia McIsaac, Carolanne McLennan, Stephanie Milbrodt, Mohammed Mohammed, Morgan Mooney-McCarthy, Laura Morgan, Clare Mullin, Sarah Needles, Kayla Nunes, Fiona O’Keeffe, Olivia O’Keeffe, Geoffrey Osgood, Jessica Padilla, Sabina Padilla, Isabella Palacio, Verio Panelli, Kendal Paulson, Jace Pearson, Tate Perez, Brenda Phrakonekham, Iason Pitsillides, Alex Preisler, Nicholas Preisler, Hailey Ramirez, Sylvan Ransom, Camille Renaud, Tracy Rocha, Haley Saris, Ryan Schemrich, Lyla Schoenig, Sophia Sears, Anand Sharma, Jessica Siu, Maddie Spangler, Shaili Standefer, Kelly Strickland, Makaila Stritzel, Emily Talbert, Sage Taylor, Emma Thomsen, Katrina Toups, Kyle Tran, Hong Tran, Maraia Tuqiri, Sara Valdes, George VanVorhis, Sandy Vue, Shauna Wallace, Johnna Whipple, Paja Yang, Meg Ye, David Yo, Yichao Zeng


Seasonal windows of opportunity are intervals within a year that provide improved prospects for growth, survival, or reproduction. However, few studies have sufficient temporal resolution to examine how multiple factors combine to constrain the seasonal timing and extent of developmental opportunities. Here, we document seasonal changes in milkweed (Asclepias fascicularis)–monarch (Danaus plexippus) interactions with high resolution throughout the last three breeding seasons prior to a precipitous single-year decline in the western monarch population. Our results show early- and late-season windows of opportunity for monarch recruitment that were constrained by different combinations of factors. Early-season windows of opportunity were characterized by high egg densities and low survival on a select subset of host plants, consistent with the hypothesis that early-spring migrant female monarchs select earlier-emerging plants to balance a seasonal trade-off between increasing host plant quantity and decreasing host plant quality. Late-season windows of opportunity were coincident with the initiation of host plant senescence, and caterpillar success was negatively correlated with heatwave exposure, consistent with the hypothesis that late-season windows were constrained by plant defense traits and thermal stress. Throughout this study, climatic and microclimatic variations played a foundational role in the timing and success of monarch developmental windows by affecting bottom-up, top-down, and abiotic limitations. More exposed microclimates were associated with higher developmental success during cooler conditions, and more shaded microclimates were associated with higher developmental success during warmer conditions, suggesting that habitat heterogeneity could buffer the effects of climatic variation. Together, these findings show an important dimension of seasonal change in milkweed–monarch interactions and illustrate how different biotic and abiotic factors can limit the developmental success of monarchs across the breeding season. These results also suggest the potential for seasonal sequences of favorable or unfavorable conditions across the breeding range to strongly affect monarch population dynamics.

Ecology and Evolution

Open Access PDF