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Nancy Dammann Davis

Living in the Edge: Community Based Management of the Terrestrial Aquatic Interface in the Peruvian Amazon

Community based management has been widely heralded as a successful conservation tool even in highly dynamic, connected, and mobile systems such as the Amazon. Little rigorous effort has been made, however, to analyze the ecological effects of such efforts nor to place them in a regional or landscape context. Given the length of the river (>6,400 km), the high levels of biodiversity (150-300 tree spp/he), and the extremes of the flooding regime (up to 20 meters annual variation), the Peruvian Amazon presents one of the most dynamic contexts available in which to test these ideas. I posit that community based management of the aquatic terrestrial interface represents one human adaptation to increase stability and resiliency of the system. In order test this hypothesis, I ask the following three questions. When, under what circumstances, and in what ways do community based efforts to manage the terrestrial aquatic interface lead to positive ecological outcomes. What are the factors that drive community based management decisions, and how can we understand these community based efforts and their effects (both social and ecological) when place them in their landscape or regional context. Initial results, based on study of the community based management of the fisheries, found that community managed floodplain lakes had slightly higher species richness (44 species/lake vs. 36), greater productivity (as represented by kilos caught per hour, 13.06 vs 7.9), and slightly larger average body sizes of the most commercially valuable species. The presentation outlines initial findings regarding both the fishery and drivers of community decision making and proposes a plan to examine the effects of management on the broader interface area.

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Heather Leslie

Hotspots of barnacle reproduction associated with nearshore ocean conditions

Coastal marine ecosystems provide important ecosystem services to human populations worldwide. Understanding the contexts that generate 'good habitats' (e.g. those where a given species has markedly higher reproductive output) is vital for effective management and conservation of these valuable and highly impacted systems. We documented reproductive hotspots, i.e., larval source sites, for an ecologically significant benthic marine invertebrate, the barnacle Balanus glandula. Greater production of offspring was associated with higher primary productivity in the adjacent nearshore ocean in Oregon (USA). B. glandula has served as an important model species for marine ecologists for >100 years in part because its life history is similar to that of most marine species. Consequently, the documentation of B. glandula reproductive hotspots is relevant to broader issues in marine conservation. Specifically, our results highlight the importance of particular places in the marine environment, and provide a mechanistic basis for evaluating the relative contributions of different sites. Such differences in the ecological functioning of benthic habitats reinforce the importance of network approaches when designing marine reserves and other area-based management strategies.

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Adi Livnat

The Evolution of Intergenerational Discounting: New directions for research

Intergenerational effects occur when an individual's actions affect not only its own survivorship and reproduction but also those of its offspring and possibly later descendants. Many intergenerational effects exist and are well documented. Interestingly, it follows from intergenerational effects that some strategies are better in the short term and others are better in the long term. What then do we expect to see in nature? Normally in life history theory, people assume that long term measures of success are the relevant ones. But that conclusion stems from work that was based on phenotypic analysis and that did not include evolutionary dynamics. What does it mean for an individual to invest in far future descendants, when those descendants are necessarily going to carry traits different than their ancestor's, due to evolutionary change such as mutation, Mendelian segregation, and recombination? We studied this with the help of analytical models and computer simulations. It turns out that the faster a trait evolves, the less it will invest in future generations. One can think of this as extending the inclusive fitness approach over the time dimension. Our theoretical models demonstrate this result for the clutch size trait as well as for the total reproductive effort trait. We are now trying to extend the principle to dispersal, and I would very much like to get some feedback on that point. There are many other ways to extend the theoretical work and, importantly, there are ways in which it could be tested empirically.

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Nikolay Strigul

Stable social groups, consumption and homophilous imitation behavior

Social norms play a fundamental role in developing and maintaining societal structures. Using individual-based models, we consider two problems 1) the coexistence of stable social groups and 2) the role of social norms in mediating human consumption patterns. In contrast with traditional models of social norms, we do not apply game theoretical approach and ignore pay-offs. In the consideration of the two-party coexistence problem, our results are based mostly on the recently published paper by Durrett and Levin (2004). We assume that individuals change their opinions based on their similarity with the other individuals (homophilous imitation). The symmetrical structure of interactions between individuals leads to random drift, but also to the development of stable social groups. The structure and dynamics of stable social groups in homogeneous and spatially-distributed societies are investigated by means of statistical modeling and analytical techniques.

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Drew Purves

Directed seed dispersal and metapopulation dynamics: simple theory, a Brazilian water hyacinth, and Spanish Oaks

Seed dispersal is often directed toward locations with particular characteristics, particularly where seeds are moved by animals. I begin with a simple extension of the classical Levins metapopulation model, that includes directed dispersal, and see how this affects metapopulation response to changes in habitat cover and disturbance rates. I then apply this simple model to the Brazilian water hyacinth Eichhornia paniculata. This suggests that directed dispersal from waterfowl is key for the persistence of this species. Next, we're off to Sunny Spain, where I've fit a metapopulation model for the Oaks in Castile La Mancha, to survey data. This model includes a heterogeneous environment, local dispersal, and directed dispersal reflecting non-random acorn movements by the European Jay. We can estimate the importance of local dispersal, and directed dispersal, in determining current abundances, species-environment correlations, and spatial structure. Finally, we can estimate the potential importance of directed dispersal for the species response to perturbations, using model simulations under altered habitat cover, drought length and fire frequency. These examples suggest that the behavior of seed-dispersing animals may be a key factor determining the response of fragmented plant populations to anthropogenic disturbances.

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Last updated 09/07/04
pulliam@princeton.edu