Note: IBRG welcomes presentations given by visitors of our affiliated labs. Guest presenters are indicated by an asterisk (*) in the schedule below. Also, please note that on Oct. 19th (marked **) in addition to our regular IBRG speaker, Brian Sedio, all are welcome to attend Gordon Berman's talk at the Couzin Lab group meeting that same morning, at 11am. Gordon's talk will be in Guyot 301. Brian's will be held in Eno 209, as usual.
|David Sloan Wilson*|
|Gordon Berman (Couzin Lab Meeting)|
|Daniel Yasumasa Takahashi|
|No meeting due to fall break|
|No meeting due to Thanksgiving|
|No meeting due to job talks|
Collective decision making is ubiquitous in animal groups and plays an important part in social animals' life histories. Here, we investigate information transfer mechanisms that dictate the timing of individual decisions within groups. We expose groups of fish to two distinct environmental stimuli that closely mimic real-life situations (discovery of a source of food and attack by a predator). Strong reactions at the individual level allow us to extract the time points at which individuals show a response to the stimulus. Subsequently, we use Bayesian methods to investigate the support of our data for a number of candidate mechanisms for individual decision making. We find that for both stimuli the response time of individuals is likely to be influenced by the response times of other group members. Interestingly, our data supports different mechanisms for the two stimuli, suggesting that the mechanisms for social decision making in animals could depend on the context.Back to schedule
The collective behaviour that occurs in animal groups has been repeatedly shown to have an adaptive advantage, for example in making group decisions. Although collective motion is thought to facilitate avoiding attack from predators, this has not been shown directly due to difficulties in measuring and manipulating dynamic prey behaviour. We present a novel approach to this problem that exposes a projected simulation of moving prey to a live predatory fish, and show that coordinated collective motion reduces the risk of attack. We will then present a new experimental system under development that replaces the projected virtual prey with physical artificial prey that can be consumed by the predator. Real-time tracking of the predator will also allow its position and velocity to be fed back to the prey. The new system will allow examination of collective detection and information transfer in prey, and the predator’s attack success and subsequent learning over consecutive trials, none of which was possible in the original study.Back to schedule
This talk will analyze the latest round of controversy provoked by Martin Nowak, Ed Wilson, and others.Back to schedule
A primary impediment slowing our progress at quantitatively characterizing behavior is the lack of a language describing the movements of animals with the same richness and efficiency that base pair or amino acid sequences have for genetics or spike trains and firing rates have for neurobiology. As a result, most ethological experiments have focused largely on a restricted set of behaviors within the scope of a limited environment. Moreover, the set of behaviors to be examined is often user-defined, creating the potential for anthropomorphism and other biases. In this talk, I will describe our data-driven methodology for analyzing animal behavior, focusing on the fruit fly, Drosophila melanogaster, as a model system. Towards this end, we have built an imaging system that can track single flies as they move about a relatively unencumbered environment. Utilizing this capacity to generate large data sets of animal behavior, we have developed a method for automatically identifying behavioral states using techniques from image analysis, machine learning, information theory, and nonlinear dynamics. Identifying these states provides the starting point for many analyses, including characterization of stereotyped behaviors and finding subtle distinctions between closely related species.Back to schedule
Many tropical forests contain diverse assemblages of congeneric trees, which raises the question of how ecologically similar species can avoid competitive exclusion. Negative density-dependent fitness imposed by specialized natural enemies (i.e. the Janzen-Connell hypothesis) is a broadly accepted mechanism of species coexistence. Specialist herbivores, however, often specialize on a particular genus, not species, of plants. On the other hand, plant defenses can be quite divergent among closely related sympatric species. Herbivore-driven spatial overdispersion of such defense traits might allow a Janzen-Connell-like mechanism to facilitate coexistence within local assemblages. We examine the specificity of interactions between herbivorous insects and their host-plants among 21 sympatric species of the diverse tropical shrub genus Psychotria (Rubiaceae) on Barro Colorado Island (BCI), Panama. We employ next-generation DNA sequencing of plant and insect DNA barcodes to identify stomach contents of putative herbivores of Psychotria. This network of plant-insect associations is combined with profiles of Psychotria secondary compounds and mechanical leaf traits within the framework of a hierarchical Bayesian model to infer the degree to which particular defense traits predict the association between Psychotria and their herbivores. We address three principal questions: i) how specialized are the insect herbivores of a single, diverse plant genus? ii) do Psychotria defenses show evidence of evolutionary divergence? and iii) do Psychotria species assemblages reveal evidence of limited similarity in defense traits and/or herbivore affinity?
Results indicate that the insect herbivores of Psychotria on BCI are not strict specialists. Nevertheless, while species of Psychotria that co-occur within 28 m2 plots are more closely related than by chance relative to the BCI species pool (i.e. are phylogenetically clustered), they are less similar with respect to secondary compounds and insect herbivores than random. Evolutionary divergence in defense may facilitate coexistence within assemblages of congeneric species by reducing herbivore overlap between close relatives.Back to schedule
How vocal turn-taking evolved, how it develops within individuals, and how it is mediated by neural circuits are open questions. We developed a computational model of marmoset monkey vocal production to make predictions about the mechanisms underlying vocal exchanges and their development. The model is based on the interactions among three neural structures (‘drive’, ‘motor’, and ‘auditory’) with feedback connectivity inspired by published physiological and anatomical data. We fitted our model to the temporal dynamics of spontaneous vocalizations produced by isolated marmosets. We then tested the model for its ability to predict the structure of vocal exchanges between two marmosets. Our results demonstrate that two, simple three-node models result in turn-taking behavior that is nearly identical to that seen in natural adult marmoset vocal exchanges. We simulated the development of the auditory node by gradual strengthening its connection with the drive node. This generated the prediction that, during turn-taking development, the maturation of the auditory system will lead to decreases in overlapping vocalizations and increases in alternating exchanges.Back to schedule
Traditionally approaches to primate behavioral ecology have avoided or ignored human impact except in the context of hunting or crop raiding. However, with many primate species, especially macaques (genus Macaca), this is an untenable approach, theoretically and practically. Macaques and humans share intertwined histories and ecologies. Research at multiple locations demonstrates that macaque behavior, population genetics, pathogen profiles, and ecology are integrated with anthropogenic ecosystems. The study of such systems can inform us not only about macaque-human co-ecologies but also add to the growing body of research on complex adaptive processes by nonhuman species in anthropogenic ecologies.Back to schedule
Ecologists of the 21st century are learning that top predators have surprisingly powerful effects on populations and communities that extend well beyond those directly attributable to the prey killed by predators. Some might even say that they are vital for ecosystem health. In this talk I consider migrations by salmon and sandpipers in British Columbia, describing work investigating how the threats posed by predators profoundly affects timing, routing, and behavioral details.Back to schedule
The Arctic contains some of the last intact wilderness ecosystems on the planet. The relatively simple food-webs of these systems are now facing the twin insults of rapid climate change and habitat modification through resource exploitation. There is an urgent need to understand what determines the dynamics of Arctic food webs,particularly as they will provide broad insights into what will happen when climate change eventually impacts temperate and tropical systems. This talk will (inevitably) focus on host-parasite systems in caribou and I will present a mixture of empirical evidence and mathematical models that examine whether interactions between botflies and lemmings cause long-term population cycles in caribou. I will then briefly consider how robust these interactions (and this slightly heretical notion) are to climate change, and whether botflies, and other parasites, are important in movement behavior of caribou.Back to schedule
I study ecosystems and climate, mostly using numerical models that show up in climate simulations. At a cocktail party once, someone naively asked me how the monkeys fit into the model, and I had to explain "Oh no, there are no animals in these models!" Since then I realized it's nearly a tautology in Earth system science that animals don't play a part in the big picture of climate and biogeochemistry, and it's been a sideline to investigate those parts of the earth system where animals have unquestionably been crucial to their functioning. Here I'll present two studies I've worked on.