Plant-insect interactions have played a pivotal role in the development of modern coevolutionary theory, beginning with Darwin's initial insights into reciprocal adaptation between plants and pollinators. When Ehrlich and Raven published their now classic study of coevolution between butterflies and plants in 1964, the link between the development of coevolutionary theory and plant-insect interactions was cemented. Since this time, numerous studies of plant-insect interactions have revealed an important role for coevolution, even as the perceived importance of coevolution for the overall structure of plant-insect communities has waxed and waned. Currently, much of the research on the ecology and evolution of plant-insect interactions, both mutualistic and antagonistic, is expanding from simpler two-species frameworks to consider coevoluton in the context of multispecies communities.
The Geographic Mosaic Theory:
The geographic mosaic theory focuses on how spatial variability in the abiotic and biotic environment shapes ecological and evolutionary dynamics of interspecific interactions. The geographic mosaic theory explicitly identifies coevolution as the driving force underlying the ecological dynamics and structure of biological communities. Much of the empirical work motivated by the geographic mosaic theory has focused on quantifying patterns of trait matching or local adaptation in interacting species, with plant-insect interactions representing several of the best studied cases. A general result that has emerged from this work is that species interactions exhibit a complex mix of local adaptation, local maladaptation, trait matching, and trait mismatching as predicted by the verbal theory. A substantial body of mathematical theory has been developed to elucidate whether these patterns are consistent with a geographic mosaic process, and if so, whether such a process is more likely than other simpler processes. The development of a robust mathematical framework for the geographic mosaic is essential for interpreting existing data and designing future empirical studies.
Community genetics focuses on the role the genetic structure of component species plays in shaping the ecological structure and dynamics of biological communities. Thus, community genetics represents a marriage of the traditional disciplines of quantitative genetics, population genetics, and community ecology. As it is usually articulated, community genetics does not explicitly integrate the process of coevolution, although its potential importance is generally acknowledged. Empirical studies of community genetics have relied heavily on interactions between insects and plants. For instance, the long running studies of interactions between cottonwoods and insects conducted by Thomas Whitham and colleagues have clearly demonstrated that host genetics strongly influence the community of associated insect species. A wide variety of other studies, conducted in a diverse array of taxa, support the basic argument of community genetics - that integrating the genetic structure of the interacting species is important for any cohesive theory of community ecology. From a theoretical perspective, work in community genetics has been somewhat piecemeal, although excellent models have been developed and analyzed to address particular topics (e.g., see Neuhauser et al. for a particularly nice collection of examples). The development of a general theoretical framework for community genetics is an important goal, and essential for interpreting rapidly accumulating empirical data.
The importance of evolutionary history:
A third area receiving increased attention recently has been the exploration of the role of evolutionary history in the assembly of communities and in the evolution of plant defense against insects, and insect adaptations. To date, there have been a few studies examining co-diversification of plants and insects. (Futuyma, Becerra, Funk), and ants and fungi (Mueller). Another set of studies explores the role of host plants in sympatric speciation and host shifts (Nosil, Feder); yet a third group examines multivariate trait space to understand constraints and tradeoffs in the evolution of defense under different biotic and abiotic conditions. The degree to which phylogenetic history predicts host use by insects varies among systems, and may benefit from broader theoretical approaches to this question.
Neutral theory suggests that how communities are assembled is largely agnostic to evolutionary processes. In contrast, strong evidence for coevolution between interacting species flies in the face of such approaches. We seek to understand how complex biological communities are assembled, what factors contribute to their stability or instability, and why the structure of such communities is often spatially variable. Discussing profitable avenues for the development of a mathematical framework which unifies multiple approaches to understanding the interplay between coevolution and community assembly will be an important focus of this workshop. An additional focus will be the development of statistical tools that can be used to evaluate the importance of reciprocal selection and ongoing coevolution for the composition, structure, and stability of plant-insect communities.
Goals of the Workshop: