Note: IBRG welcomes presentations given by visitors of our affiliated labs. Guest presenters are indicated by an asterisk (*) in the schedule below.
|Frants Havmand Jensen * (WHOI) (Joint LabTea / IBRG)|
|Karpagam Chelliah *|
|Mark W. Moffett * (NMNH)|
|No meeting due to fall recess|
|Andre de Roos *|
|No meeting due to Thanksgiving|
|Andy Gersick *|
|Jake Peters * (Harvard)|
Group-living animals depend on signalling mechanisms to retain contact between individuals and prevent the group from losing its spatial and social coherence. Animals inhabiting areas of limited visibility, including underwater environments, preferentially use acoustic signals for this purpose. I use pilot whales as a model organism to develop methods for studying acoustic interactions and information flow within cohesive groups of animals to understand the social dynamics of toothed whale societies. Using acoustic and movement recording tags placed on individual short-finned pilot whales, I show that pneumatic call production is severely hindered by the high ambient pressure at typical foraging depths of 600-1000m. I show that the majority of calls produced below 500m of depth are too faint to be heard by conspecifics remaining at the surface, and that animals presumably lose acoustic contact with the social group while foraging. I show how complex tonal calls may allow individuals ascending from a deep foraging dive to re-establish contact with group members following periods of spatial separation from the social group during foraging. Determining the source of an acoustic signal, especially outside of a foraging dive when whales are close together, is still problematic. To overcome this difficulty, I will describe how I now tag multiple closely associated pilot whales to study social synchronization and flow of information within a cohesive group of animals. Preliminary data from long-finned pilot whales show how these animals coordinate their foraging dives to a remarkable degree, yet limit intragroup competition for resources by spreading out spatially during foraging. These animals employ multiple types of acoustic signalling mechanisms to mediate cohesion across varying spatial scales. Further studies of the underlying processes whereby toothed whales coordinate group behaviour and interact with conspecifics will ultimately lead to insight into the social structure and decision making of toothed whale societies.Back to schedule
Darwin was troubled by elaborate male traits observed in many species that are seemingly maladaptive for survival. To account for the evolution of apparently maladaptive traits he proposed the theory of sexual selection, wherein, traits that directly enhance mating success may be selected for, either through male-male competition for mates or through female-mate preference for elaborate male traits. Both male and female elephants in the proboscidean evolutionary radiation have had tusks that show extreme exaggeration in size and form. However, tusks in the Asian elephant (Elephas maximus) are sexually dimorphic, hinting that opposing selection (sexual selection advantage to males and natural selection disadvantage to females) may have driven this pattern of tusk expression. Intriguingly, tuskless males (male dimorphism with respect to tusk) also occur at fairly high frequencies in some Asian elephant populations. I explored sexual selection and artificial selection (selective poaching of tusked males for ivory) on elephant tusks as possible mechanisms leading to the observed patterns of tusk dimorphism in the elephants. Today’s talk is restricted to the role of tusks in male-male combats for mates and female mate choice.Back to schedule
Predation risk is long recognized to be a key force shaping ecological and evolutionary processes. However, it is only in recent decades that we have begun to understand the importance of the part of predation risk that scares but does not kill: the non-consumptive / non-lethal effects of predation risk are now recognized to be widespread in nature and cause significant impacts on many aspects of animal ecology. My Ph.D. work was centered on understanding the role of the non-consumptive effects of predation risk (NCPR) in influencing the relationships between forest birds and their habitat. In the tropical rainforest of lowland Sumatra and the long-leaf pine forest of Southeastern United States, I asked 1) whether forest habitat degradation could lead to NCPR by altering forest birds' perception of predation risk, and 2) what ecological impacts on forest birds could result from NCPR by way of increased perception of predation risk, in terms of birds' breeding habitat selection and reproductive performance. I will be presenting the major findings from my Ph.D. dissertation, and would like to have a discussion with the IBRG group about related topics.Back to schedule
The mate-finding behaviors of five species of butterflies in upstate New York span a range like that of vertebrates. The Ringlet cruises like 1950s teenagers, the Eyed Brown favors attractive domains in wet meadows, the Great Spangled Fritillary trap-lines for virgins, the Viceroy defends territories, and the Pearly Eye hangs out in singles’ bars. Behaviors like these can be generated by simple rules of response to simple environmental and social cues, and the different behaviors have different consequences for local demography.
Drafting a book with the above title and content has been on the back burner for nearly thirty years. It is now on the front burner, thanks to new insights into butterfly vision and new agent-based models of ranging and mate-encounter. I seek IBRG’s help in testing the coherence and strength of the whole story.Back to schedule
In the societies of most vertebrates, each member must recognize every other member as an individual. This typically limits societies to 100 members, and never more than 200. Numerous and diverse identity labels substitute for such knowledge in humans, and were a necessary precursor before our societies could grow more populous. How did a capacity for using labels arise? The rule of parsimony indicates that, at least as far back as their divergence from the chimpanzee line, our ancestors would have never lived in strict family groups or in any other compact societies offering regular face-to-face interaction. Nor did they form open networks. They were fission-fusion species that evolved, by simple steps, from having societies bounded by the recognition of individuals to societies differentiated by labels. I propose that this transition, ignored before now, occurred well before language by a shift in signals resembling those employed by chimpanzees today. Free from usual size limits, societies at first reached into the multiple hundreds. But agricultural settlements would be able to grow larger still in part through the improved stabilization of the labels associated with each society. This lecture expands upon the author's review in the September 2013 issue of Human Nature, Human Identity and the Evolution of Societies.Back to schedule
Understanding the structure of food-webs is central to ecology. Bob May's early work at Princeton created a classic dilemma by showing that food webs with greater that 5 species were highly unlikely to be stable. How do we resolve this general theoretical insight with the empirical observation that large complex food webs do exist in places like Serengeti, Yellowstone and the coastal salt marshes of California?
In this talk I'll report on three (maybe four) pieces of work that describe how we assemble and visualize food-webs and species interactions for Serengeti and Yellowstone, illustrate how adding parasites makes food webs even more complex and then briefly describe recent theoretical work that partly resolves Bob May's original insight on the relationships between stability and complexity.
It will then be time for soccer and a cold beerBack to schedule
Please join Virginia Riddle Pearson on Friday, November 15, 3PM in Guyot 100 as she talks about her lifetime of research with elephants. She will fascinate you with insight into the secret lives of elephants , sentient beings so similar to humans, and tell you about her current research to help find a cure for the lethal elephant herpesviruses. She has traveled to Africa four times over the past 4 years searching for the African origins of this devastating disease in elephants. She asks why these Probosciviruses, which have coevolved along with the elephants for 100 million years, are unexpectedly lethal, especially to the Asian elephant, while herpesviruses in general, ubiquitous and species-specific in most mammals, many birds, reptiles, fish and even mollusks, rarely cause death to the host species. And she will tell you that elephants are facing imminent extinction due to the ivory poaching crisis. When she began studying elephants nearly half a century ago, there were 1,300,000 elephants alive. Today, fewer than 400,000 elephants remain, the last remnants of the ancient lineage of Proboscidea. Come on Friday, November 15, 3PM, and learn of one women’s volunteer quest to save the elephants.
Virginia Riddle Pearson is a Guest Researcher in the Enquist Laboratory, Department of Molecular Biology at Princeton University and an Honorary Associate in Vertebrate Zoology at the Academy of Natural Sciences of Philadelphia. She collaborates on the elephant herpesviruses research with colleagues at The Johns Hopkins School of Medicine in America, Save The Elephants in Kenya and South Africa, and Elephants Without Borders in Botswana.Back to schedule
Andre de Roos' IBRG lecture is the final part of a week-long workshop and seminar on stage-structured modeling (you should already have received an email or two from Anieke about this - let me know if you need it resent!). The workshop can be view as an in-depth background for the IBRG seminar, and it has the following title and topics:
Dr. de Roos' IBRG seminar will provide the theoretical and mathematical background of the derivation of a stage-structured biomass model from a continuously structured population model.Back to schedule
Sexual selection is widely understood through the lens of the peacock’s tail – as the evolutionary driver shaping elaborate courtship displays and signals. Less studied is the influence of sexual selection on cognitive abilities or behaviors that allow individuals to regulate how they use those signals. Prevailing theory suggests, for example, that courting males always present their sexually selected signals at maximum intensity and thus exhibit their capacity to bear the associated signaling costs. Yet many social creatures face shifting competitive contexts that would reward more flexible control over signaling behavior. Humans, for example, conduct courtship within complex networks of potential eavesdroppers, many of whom may have an interest in our sexual signaling efforts. Humans also engage in flirtation - a distinctively subtle category of courtship signaling. I propose that flirtation may be just one example of an adaptive response to the shifting competitive pressures that surround courtship in a social group. I will discuss experiments with another social class of animals with a sophisticated communication system — songbirds — demonstrating that humans' flexible signaling is far from unique.Back to schedule
Social insect colonies often exhibit fine control of the microclimate in their nests, allowing them to thrive in habitats that undergo large climate fluctuations. Regulation of the nest microclimate by many social wasps, ants and termites arises from continuous modification of complex nest structures (such as chimneys and thermosiphons) that promote passive ventilation. In contrast, honeybee colonies occupy pre-existing cavities and must rely on a robust and adaptable active ventilation system. When temperature or CO2 concentrations inside a honeybee nest are too high, individuals respond locally by fanning their wings to generate small air currents. Individuals then align with one another to form fanning chains that propagate large-scale airstreams. I am studying the mechanisms by which local interactions among individuals scale up to produce colony-level solutions to complex ventilation challenges. My investigations of this system require a unique marriage of biomechanics and collective behavior.Back to schedule