Eco-evolutionary dynamics of biotic-abiotic feedback
All organisms interact with their abiotic environment in some form. Ecologists invest a lot of effort in understanding how the abiotic environment affects organisms, shape community patterns and influence ecosystem services. But organisms also affect the environment by consuming abiotic resources and modifying their habitat. Such modifications could sometimes feed back to affect the survival and reproduction of the organism. These biotic-abiotic feedback are well documented in studies of ecosystem engineering and plant-soil feedbacks. Niche construction theory is a closely related topic which postulates that by modifying the environment, organims change the selection pressures they face, thereby extending the effects of biotic-abiotic feedback to evolutionary scales.
Using mathematical models I am describing both the ecological and eco-evolutionary consequences of biotic-abiotic feedback. First, I draw a distinction between conditionable abiotic factors like pH and temperature, and consumable resources like nitrogen and water by identifying how they vary in their effect on organisms and how they are affected in turn. This distinction leads to diverging effects on population dynamics, trait evolution and trait structure in communities. Second, I build trait- and system-specific models to illustrate the finer consequences of biotic-abiotic feedback.
Senthilnathan, Athmanathan and Sergey Gavrilets. "Ecological and eco-evolutionary dynamics of biotic-abiotic feedbacks". In Revision.
Niche theory for plant-soil feedbacks
Plant-soil feedbacks is an example of biotic-abiotic feedback with eco-evolutionary significance. Field studies from a wide range of biomes show that plants condition the soil directly by affecting edaphic properties and indirectly by selectively associating with soil microbes. These plant-soil feedback can be positive or negative and impacts plant community richness and ecosystem functioning. Theoretical models show the importance of negative soil feedback in maintaining plant diversity. However, we lack a trait-based understanding of plant-soil feedbacks due to the complexity of microbes plants interact with and the complex physical and chemical properties that are involved in these interaction. I model plant-soil feedbacks in a trait and soil explicit manner to describe the effects of trait-based plant-soil interactions. These models provide us with qualitative predictions for patterns of trait distribution and spatial compostition for different strength and direction of plant-soil feedback.
Understanding why species coexist has both basic and applied significance in ecology. Conditions for the coexistence of two species has long been studied using mathematical models and is an integral part of population biology. Most models consider the individuals of a species to be identical in their ability to interact with each other and their environment. However, differences between individuals (intraspecific variation) can affect population sizes and species interactions. I have been working on understanding the consequences of intraspecific variation to the two species coexistence problem, particularly when the variation is heritable and could change over generations. My approach is based on capturing the eco-evolutionary dynamics by extending the classical two-species population models to continuous traits.
Most modern human societies have persistent power struggles between different individuals or groups of individuals. This power dynamics has its basis in the conflict over resource distribution among the group. We modelled this as a public good game to explore the power dynamics based on rivalrous, excludable goods.
Collective animal movement is a charismatic phenomena which plays an important role in the ecology of several birds, fishes and mammals. Heterospecific bird flocks and ungulate foraging guilds are some common examples of heterogeneous animal groups moving together. Heterogeneity in conspecifics is also not uncommon due to individual differences in behaviour and movement traits. Field observations shows that conspecific animal group size distribution obeys a power law for several taxa. Theoretical models based on fission-fusion dynamics provides a neutral explanation for this pattern. These models assume groups randomly split and merge with other groups. Our goal is to extend this framework to understand heterogeneous groups.
We analysed the extended model analytically and using simulations. With the assumption that heterogeneous groups split more frequently than homogeneous groups, we found that large groups are typically heterogeneous.
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Preformatted
i = 0;
while (!deck.isInOrder()) {
print 'Iteration ' + i;
deck.shuffle();
i++;
}
print 'It took ' + i + ' iterations to sort the deck.';
