News

How variable are temperature effects on species interactions within a local community? Changes in global temperature regimes are expected to transform species interactions in natural communities. In theory, species should be adapted to their local temperature regimes, which might suggest a parallel shift across species interactions. But this may not hold if differences in traits (e.g., physiology or ecology) between sympatric species lead to concurrent differences in thermal responses. Zoey looked at 6 predators that all share a common prey but differ in various traits. Turned out there was a lot of variation in how per-capita consumption rates scaled with temperature, both in the magnitude and the shape of the response curve. Interestingly, all but one continued to increase with temperature to a point where both prey and predator started to die of heat stress. So we mostly did not see humped shaped relationship with temperature for biological relevant temperatures. Because of these differences across species, the hierarchy (ranking) of per-capita predation rates changes with temperature, indicating that temperature changes reshuffle relative differences in interaction strength in these food webs.

While temperature is well known to affect many life history traits of ectothermic organisms, any attempt to scale up these individual-level processes to population-level consequences must assume a relationship between temperature and the strength of per capita density dependence. Yet, theory has made contrasting predictions about this relationship, and we still need clear experimental tests to determine which relationship is realized in natural systems, especially in heterotrophs. Our start undergraduate Lillie in collaboration with former PhD student Zoey set up a big experiment to isolated and quantified the thermal response of density dependence from the population dynamics of the herbivore Daphnia pulex. (full disclosure, this was our second try at this, first trial had some kinks to work out). But, thanks to all the hard work of Lillie and team and counting thousands of Daphnia over weeks we got some pretty exciting results: We showed that the strength of negative density dependence increased linearly with temperature, doubling every 7C, while the intrinsic growth rate of increase showed a humped shape relationship. This difference caused a humped-shaped relationship of carrying capacity with temperature, with a dramatic 50% decline at the highest temperature. While warming temperatures may benefit the individual (via increased growth and reproduction), our results reveal that warming still can be a detriment to the population by strengthening density-dependent processes.

We are fortunate enough to secure some new funding to work on the role of time in shaping indirect interactions in food webs. Check out the news piece here

The best part of my job is to mentor and train the next generation of scientists. So while he will be very much missed, I'm very excited to see the new Dr. Hengxing Zou complete his outstanding PhD work and move on to his postdoc position at the Global Institute for Climate Change at the University of Michigan, and I can't wait to see what exciting new work he will do next!

The concept and term priority effect has been around for decades. Ultimately, it refers a scenario where the outcome of interactions are changed by the order of arrival of species. So in a sense, the term really just talks about the outcome, not the mechanism, except that the mechanism has to be tied to timing. Thus, it maybe is not surprising that over time, it has been used for a wide range of mechanisms. The issue with that, however, is that different mechanisms can lead to very different outcomes and operate at different time scales. As a consequence, there has been a disconnect between theory and empirical work, where for instance and experiment would cite theory on priority effects that is not actually relevant to the mechanisms described in the experiment. In a recent paper we talked about this disconnect and the wide range of different mechanisms and the different time scales at which they operate, and why it is important to differentiate between them to correctly predict the consequences and dynamic of the system. We also propose a general framework that suggest that we can group all these mechanisms in two ecologically distinct categories, trait-dependent vs. density-dependent mechanisms, and discuss how they can be quantified, when they are most likely to operate and how they can interact. You can read more about this in our recent perspective piece in TREE.

Predicting how species respond to climate change is without a doubt a big challenge for the 21st century. In many cases, these changes are based on statistical models (e.g. distribution patters) , rather then mechanistic models that incorporate the physiology and ecology of species. In collaboration with Chunsen Ma's lab, we combined a series of experiments with climate modelling to predict how the distribution of one of the most destructive global pests, the diamond back moth, could change in the future by allowing it to overwinter in areas that were previously too cold. Importantly, by allowing this species to overwinter, climate change is also likely to allow it to evolve up to 150 times higher pesticide resistance in those areas. This link between warming and evolution really highlights how climate change really poses a big problem for pest control and food security in the Anthropocene. A little news piece can be found here https://news.rice.edu/news/2021/crop-eating-moths-will-flourish-climate-warms

While cannibalism is wide spread and ubiquitous in nature, it's also heavily understudied. In fact, we know very little about why the rate of cannibalism varies not only across species, but also within populations. To fill this gap, we started to think about what factors should actually limit the evolution of cannibalism and a few years ago we developed new theory which predicts that the spatial structure of population could be a key driver. When dispersal is limited, kin selection should select against cannibalism bc it increases the relatedness of individuals that interact with each other. In collaboration with group of Mike Boots, we tested this theory experimentally by using a clever method Mike developed in the indian meal moth system. Specifically, we can manipulate the viscosity of the medium which limits how far the larva can move. Consistent with predictions, we did indeed found that limiting dispersal selected against cannibalism and measured strong changes within just a few generations.

There is nothing better than seeing your students succeed! Covid delayed this moment by almost two years, but Dr Shannon Carter finally got to wear the official outfit and get her hood! While this wasn't in the usual setting, the outdoors venue probably is a much better fit for an Ecologists. Congratulations Shannon, I'm proud of you!

In biodiversity research, the focus is often at the species level or higher, e.g. we ask what happens when species or functional groups are lost from an ecosystem. But, this approach ignores the diversity within populations! Because of changes in the ecology of individuals during their development (a.k.a. ontogenetic niche shifts), differences between developmental stages of the same species can even exceed differences between species (check out some of our earlier work demonstrating this). In our newest work, we manipulated ontogenetic diversity within predator populations and simulated species loss to examine how different levels of diversity interact with each others. We found that this diversity within species can often buffer diversity loss at the species level. This emphasizes the importance of within species diversity and again calls for an approach to biodiversity research that doesn't simply focus on the cursed "latin binomial".

One of the coolest experiments we ever did is now published! Alternative stable states can lead to dramatic regime shifts in nature. While perturbations that initiate regime shifts are well documented, mechanisms upholding alternative stable states are often unknown or appear highly complex. Using combination of theory and experiments we show that alternative states could arise from a simple & ubiquitous feature of life: developmental (ontogenetic) change. When put into a community context, this population level processes allows for complex feedbacks that can lead to alternative states. For longer "blog" on this, check out the thread on my twitter

Many years back, at a Predator-Prey Gordon conference I got lucky to be part of a great group of scientist who were interested in similarity and differences between the role of fear in predator-prey vs host parasite systems. Both predators and parasites elicit defensive responses in individuals, but how to they differ? Over the years, this common interest lead to a great synthesis paper lead by Dave Daversa that proposes a conceptual framework on how to answer this question, revealing key differences and similarities. This framework makes some clear predictions, and while some limited data in amphibians provides some support, we really need a lot more experiments to learn more. Lots of food for thought!

We're always excited to host great undergraduates and they have shown time after time again what great work they can do. Sasha Figel is a great example. She's worked with us for several years while being an undergraduate at Rice. After helping us with our work, she embarked on her own independent research project together with our former post doc Ben Toscano. Sasha and Ben conducted a clever lab experiment that imposed different harvest/mortality regimes on replicate daphnia population that targeted either small life stages, or reproductive adults and examined how this affected long-term population dynamics. This was a experimental test of theory that suggested that differences in energetic needs across life stages can often lead to counterintuitive response in natural population, like overcompensation in response to mortality (i.e. mortality results in larger population). Interestingly, they did find strong stage specific population regulation, but populations showed compensatory response instead. Nevertheless, the study demonstrates how important accounting for stage structure is to predict how they respond to harvesting and environmental change.

March: Parasites rarely come alone. Indeed, co-infections (multiple parasites infecting a single host) are ubiquitous in most ecosystems. Importantly, this allows pathogens to interact within hosts, either directly or indirectly. For his PhD work Patrick has demonstrated that the timing of these interactions within hosts have important consequences for the ecology and evolution of hosts and pathogens. You can check out his awesome papers under publications, but his newest paper & capstone project is just out now in Royal Proceedings B. Using a combination of simulated epidemics in Daphnia and models, he revealed how we can scale up interactions between pathogens within a single hosts from the lab to predict patterns of epidemics of each pathogens in entire populations. You can find a little news piece of this exciting work here.

December: As individuals grow and develop, most of their traits (body size, morphology, habitat use, etc.) change. As a consequence, the majority of organisms go through a change in their ecological "niche" during the development, also called ontogenetic niche shift. Yet, we know surprisingly little on how this niche shift looks like across species, in part because measuring shift in multi-dimensional niche space is inherently complicated. In a recent paper I proposed one way to quantify a shift in the trophic position based on stable isotopes in a wide range of species in pond communities. This fun project revealed some surprising patterns, but also generalities & hopefully will inspire a lot more work in other systems. You can read more about it here in Freshwater Biology.

August: What better reason to reunite the lab than to celebrate our newest graduate, Dr. Shanon Carter who did an outstanding job defending her thesis. We all learned a lot about the role of phenological shifts in structuring species interactions and communities. We are very proud of you! You will be missed, but at least your new job is not far. (Note special guest Raul Costa-Pereira who came from Brazil just to celebrate with us ;-)

June: The planet is slowly warming with & one of the key challenge in the 21st century is to predict the consequences of these temperature changes on species. In this new paper in Global Change Biology with an all star team of collaborators we show that behavioral thermo-regulation is key to predict temperature effects on the fitness of species. Indeed, the model suggest that this can lead to a behavioral rescue effect where this adaptive behavior can prevent species extinction, but the potential for this effect depends on the spatial heterogeneity in a given habitat. Check out the paper online here and a little news piece as well following this link.

August: Climate change is shifting phenolgies of species worldwide, but what are the likely long-term effects. In this new paper in Ecology Letters we provide a modeling and theoretical framework to link phenological shifts to species coexistence to better understand how current timing of species' phenologies affect coexistence of species, and what happens when phenologies change over time.

Intraspecific variation is ubiquitous, but what happens when it changes? In our new paper in the American Naturalist we propose and test a conceptual framework explaining why ecological effects changing intraspecific diversity often appear context dependent

March: Congratulations Dr. Clay! Patrick defended his PhD, giving an great talk ending his excellent PhD work. He will be moving to Michigan for Post doc with Meg Duffy. You will be missed Patrick!
This also earned him two awards: Outstanding PhD Thesis Award & Outstanding Graduate Publication Award. Well deserved

January: Co-infections can lead to unexpected changes in parasite prevalence in host populations. Check it out at Oikos

December: Timing matters: Check out our new paper on how priority effects alter coexistence of co-infecting pathogens at Am Nat.

September: Our collaboration with our Brazilian friends is out, showing how and why predator-prey size relationships vary across natural communities and size of predators.

July 2018: Patrick is the 2017-2018 recipient of the "Joe Davies Prize for Outstanding service as a Teaching Assistant", and another one, the "BioScience Leadership Award". Together with his best student talk award, he's been getting them all! Well done Patrick!

June 2018: Lots more cool papers coming out: Discover why variation in the phenology of species matters for interactions here, and what are the ecological drivers of individual niche variation here.

June 2018: Check out our new paper on how changes in the distributions of phenologies reshape interactions in nature and increase power to detect directional long-term shifts.

May 2018: Shannon gets a well deserved award for best Graduate Student Paper.

May 2018: Social context matters for spread of diseases, check out our new paper and a news piece on it here.

April 2018: Lots of good news. Nick Keiser gets tenure track faculty job at University of Flordia! Ben Toscano moves on to Assistant professor position at Trinity College! Well done Nick & Ben, you'll be missed!

April 2018: The awards keep coming! Shannon was awarded the highly competitive American Society of Naturalists Graduate Student Research Award!

January 2018: Good start in the new year. Ben wins Don Abbott Award for best talk at the ASN meeting!

October 2017: Check out our new paper lead by Ben T. on cannibalism and alternative states in the American Naturalist.

September 2017: What's cooler than cannibalism or diseases? Cannibalism & diseases; check out our new synthesis paper on how both interact in the American Naturalist and a little news piece on it here.