Theoretical Ecology Lab Tea

The Theoretical Ecology Lab Teas are informal meetings where members of affiliated lab groups give talks on their current research and receive feedback from their audience. The talks are 30 minutes (20 minutes of presentation and 10 minutes of questions) and are scheduled generally on Wednesdays at 12:30 pm. All talks this semester will be held in Eno 209 unless stated otherwise.

This semester, talk schedules and email lists will be maintained by Kaz Uyehara and Matt Grobis. Please contact one of us to have your name added to the labtea email list so that you can receive reminders about upcoming meetings.

Spring 2015 schedule

Date and time Speaker
Pawel Romanczuk
Allison Dedrick
Verónica Miró Pina
Matt Grobis
Emily Klein
No lab tea: Spring break
Emma Fuller
Phil Hannam & Andrew Tilman
Alex Washburne & Jacob Socolar
Ken Haste Andersen * (Technical University of Denmark)
Charlotte Chang
Efrat Shefer
George Hagstrom

Note: Priority is given to graduate students. A symbol next to the speaker's name means that approval is pending for a week and graduate students can still claim the slot.

Titles and abstracts

Death by a thousands cuts: Cooperative hunting of sailfish Pawel Romanczuk

Group hunting allows predators to catch prey more efficiently. Sometimes this involves long chases and the gradual exhaustion of prey through repeated injuries before the final kill. However, this form of hunting is mostly reported in terrestrial predators (such as wolves and wild dogs) and is usually required for killing prey larger than the predator. Here we investigate a highly unusual form of group hunting. Sailfish, Istiophorus platypterus, use a turn taking strategy to repeatedly injure and exhaust their schooling prey, sardines, Sardinella aurita. During attacks individual sailfish approach the sardine school and insert their rostrum into the school to injure and subsequently capture prey. On average, 2 sardines were injured for every attack, whereas only a small fraction of attacks resulted in prey capture. This resulted in the proportion of injured prey fish rapidly increasing in the shoal with the number of attacks. Hence, it appears that each sailfish that attacks produces a mutualistic benefit for others by injuring more fish than it can capture, thereby increasing the future capture probability for conspecifics. To answer why a group-hunting strategy is beneficial for individuals in these groups, we built an individual-based stochastic model of the hunt. We found that group hunting is only beneficial for individuals in groups when hunting time is limited. The predicted optimal group site is approximately 5 sailfish per group but grouping benefits are expected for groups of up to 15-20 individuals. This unique form of group hunting raises some important issues regarding predators cognitive abilities, social organisation and predatory-prey arms races.

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Developing a spatial framework for quantifying the interactions among ocean acidification, temperature change, and fishing Allison Dedrick

Ocean acidification (OA) and changing temperatures could change the spatial distribution and persistence of marine invertebrate populations through their effects on the survival, growth, and development of invertebrate larvae, particularly those that calcify. For exploited populations, changes in population structure will also alter the spatial pattern and intensity of fishing. This project develops a framework to explore and quantify the interactions among OA, temperature change, and fishing at the population level.

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The waiting time to parapatric speciation Verónica Miró Pina

Biodiversity is based on a dynamic equilibrium between two forces: speciation and extinction. In most of the models used so far to infer the history of species diversification, speciation and extinction are seen as spontaneous events, independent of the ecological or genetic context of the species. Therefore, the process of speciation is still poorly understood. In order to understand how ecological and genetical dynamics (dispersal, recombination, genetic drift) affect speciation, I propose a microscopic model of speciation, in the presence of gene flow. This model is able to predict the effects of mutation, migration and population size on the waiting time to speciation and the spatial patterns that are most stable.

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Quantifying a self-organized antipredator response Matt Grobis

Many fish species exhibit a "startle" behavior in response to predators, a reflexive burst of swimming away from the stimulus. These startles can propagate across a group, enabling the entire shoal to quickly respond to threats. However, despite the strong selective pressure on many fish species to be coordinated when a predator is present, very little research has examined how fish self-organize in the shoal to best coordinate responses to predators. I will present preliminary analyses on golden shiner shoal behavior and information propagation in the laboratory in an effort to uncover how fish shoals deal with predation risk.

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Tell Me About It! The value of qualitative information for quantitative approaches Emily Klein

Narrative, anecdotal, or qualitative information can seem outside the realm of theoretical and quantitative approaches to ecological questions. However, such information can be deeply insightful, for example by helping to shape driving questions and useful hypotheses as well as providing additional lines of evidence. Both lines of inquiry can be essential, especially as we focus on complex questions of coupled natural-human systems. I will discuss two examples to make this point. First, briefly, the importance of narrative in providing secondary evidence for quantitative findings in my previous work. Second and in more detail, how recent interviews with West coast fishing communities have dramatically altered both model structure and driving questions for current research on the motivations of common pool resource users’ behavior and social networks construction.

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Ecosystems, species interactions and behavior: how to put it all together? Emma Fuller

Species eating species are the most basic building block of ecosystems. We've known this for a long time, and it is the root of some very famous ecological disagreements, i.e. green world versus trophic cascades. Understanding these species interactions can inform these foundational ecological disagreements, and help us manage ecosystems better. Take fisheries for example: we want biomass, and we want it from the top of a food web as much as possible (jellyfish are gross). The consequences of fishing are very different if the system is primarily regulated from the top down versus from the bottom up. The key then is understanding how the abundance of one species translates into the abundance of another. In this talk I'll review how we tend to model these interactions and what might be missing. I'll end with some next steps about how I hope to integrate behavioral and population level dynamics in the commercial fisheries ecosystem on the US west coast where I work.

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"Race to the Bottom”? Does Chinese competition mean the collapse of World Bank environmental standards? Phil Hannam & Andrew Tilman

As the Asian Infrastructure Investment Bank (AIIB) - created in 2013 under China’s leadership - rises in international prominence, there are concerns the institution will become a dominant financier of coal power infrastructure globally and also have weak social and environmental safeguards. This comes at a time when many established development institutions - most reputably the World Bank - have been trying to improve safeguards and also eliminate carbon-intensive investments from their portfolios. Does competition between AIIB and the World Bank lead to a “race to the bottom” in environmental standards, and what would be the consequences for the climate and power sector trajectories in developing countries? We analyze this situation with a simple game theoretic model where two competitors with different interests compete to maintain their political clout in recipient countries. We explore the impact of unilaterally strengthening environmental safeguards and the importance of recipient country preferences. We motivate the model with a historical example of strategic interaction shaping the World Bank's policy in hydropower, and also provide a political analysis. The topic has important implications for our understanding of the resilience and efficacy of development norms in the power sector, and for the future of energy governance in a world with competing rule structures.

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A quantitative Janzen-Connell alternative to Hubbell’s neutral theory Alex Washburne & Jacob Socolar

In a strict mechanistic sense, Hubbell’s neutral theory is wrong, but it lays out an important challenge for community ecologists. If stabilizing mechanisms are causally important for maintaining species diversity, then neutral theory is a null hypothesis that coexistence theories must falsify. However, alternative models have struggled to balance parsimony and realism both in their treatment of interspecific competition and in their handling of physical space. Among the most prominent alternatives to the neutral theory is the Janzen-Connell hypothesis, which posits that predators and pathogens act in a distance-dependent fashion to limit tree recruitment near conspecific adults. Studies at small spatial scales resoundingly confirm the operation of this mechanism. We take the Janzen-Connell mechanism as a given, and use it as the basis for a parsimonious forest simulator. We ask two principal questions: Should we expect neutral and Janzen-Connell dynamics to yield dramatically different species-abundance distributions? Inasmuch as the distributions are different, and given that we know Janzen-Connell dynamics occur, what else happens in tropical forests to yield neutral-like species-abundance distributions?

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The size- and trait-based approach to model fish and fisheries Ken Haste Andersen

Introduction of the ecosystem approach to fisheries management requires models to make impact assessment of fishing. I will introduce the size- and trait-based approach to designing models of intermediate complexity of entire fish communities. In the models, individuals are characterized by size, and their interactions by the simple rule: big fish eat smaller fish. As an example of an impact assessment I illustrate the potential conflict between yield and rent optimization in a fish community.

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How might multi species hunting lead to different outcomes than single species hunting? Charlotte Chang

Overhunting is one of the gravest threat to mammals, birds, and herpetofauna, particularly in the tropics. Traditional management of natural resource extraction has focused on single species bio-economic models, which generally hold that harvesting a species to extinction is economically inviable due to the rising cost of exploiting collapsed stocks. However, when multiple species can be harvested simultaneously, the costs of harvest could be more diffusely spread. It is also possible that extractors may shift to more common, resilient species rather than targeting rare and declining prey. I will discuss the background for these two possible outcomes, very preliminary results, and directions for continued research.

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Sustainable silvopastoral solutions can prevent the collapse of the tropical nitrogen cycle Efrat Shefer

Warm and moist tropical forests are many times rich in soil nitrogen and can therefore offer ideal habitat for agricultural land-uses such as crops and pastures. However, this nitrogen-rich state appears to be related to the existence of dinitrogen (N2) fixing trees. Deforestation, and forest conversion to agricultural land-uses, often leads to a gradual decline in the availability of soil nitrogen until agricultural productivity is no longer profitable. At this stage either anthropogenic nitrogen (fertilizer and manure) is added or degraded farmland is abandoned, and substituted by clearing additional forest area. My work aims at understanding: (1) how forest conversion to agriculture can lead to the collapse of the nitrogen cycle? and (2) are there alternative management schemes, for example silvopastoral pasture systems, that can provide a sustainable solution? I am using a model of the local nitrogen cycle to evaluate how forest conversion to different land-use systems (pasture, silvopasture, coffee plantations and crops) influences both the local nitrogen budget and nitrogen exports from the system. I will (eventually) compare model predictions to empirical data of the nitrogen budgets in forests, pastures and silvopastoral systems in Amazonian Colombia.

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Predicting phytoplankton stoichiometry using sub-cellular compartment models with an application to biogeochemical cycling George Hagstrom

Recent measurements of particulate organic matter in the ocean indicate that phytoplankton communities significantly deviate from the Redfield ratio. I will present a mechanistic model of a phytoplankton based on allocations to different sub-cellular compartments. This model will predict plankton stoichiometry as a function of environmental conditions, and the predictions will be compared with data. As an application, we will use the model to study the effects of non-Redfield stoichiometry on ocean biogeochemical cycles.

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Links to previous schedules

  1. Fall 2000
  2. Spring 2001
  3. Fall 2001
  4. Spring 2002
  5. Fall 2002
  6. Spring 2003
  7. Fall 2003
  8. Spring 2004
  9. Fall 2004
  10. Spring 2005
  11. Fall 2005
  12. Spring 2007
  13. Fall 2007
  14. Spring 2008
  15. Fall 2008
  16. Spring 2009
  17. Fall 2009
  18. Spring 2010
  19. Fall 2010
  20. Spring 2011
  21. Fall 2011
  22. Spring 2012
  23. Fall 2012
  24. Spring 2013
  25. Fall 2013
  26. Spring 2014
  27. Fall 2014