Structured Generalization: evolutionary dynamics at fine spatial scales in a generalist system (StruGen)

Specialization and generalization are key concepts in evolutionary biology that has been object of intense debate, but controversy yet persists concerning their role in the ecology and evolution of pollination systems. Generalization has been traditionally considered a non-adaptive state maintained by spatial/temporal fluctuations in the interaction with selective agents and by the absence of any trade-off in the selective pressures exerted by pollinators. However, contrary to the theoretical expectancies, generalization is quite frequent in natural pollination systems and vary at population and individual levels.

In pollination generalist systems, all plant genotypes in a population are assumed to interact with random subsets of the overall pollinator pool. We think that the generalization degree of a given plant could be non random, but related with some intrinsic and extrinsic factors, such as its microenvironment, its spatial location in the population, and most important, its phenotype and genotype. Plants exhibiting different values for those factors would attract different subset
of pollinators, and plants showing different values of those traits would share similar subgroups of pollinators. These inter-individual differences could promote a structured pattern of interaction among the plant and its pollinators, a phenomenon that we call structured generalization. We propose that structured generalization occurs when there are non-random inter-individual differences in generalization and the intraspecific pollination and mating networks at population level are divided in subgroups of plants sharing similar pollinators (i.e., network is clustered).

The main aim of this project is to explore the occurrence of pollinator-mediated structured generalization, the factors favouring or cancelling it, and their potential evolutionary and functional consequences. Using our previous experience working with the extremely generalist crucifer Erysimum mediohispanicum, we will carry out observational and experimental approaches to evaluate the relative importance of the spatial structure, the micro-environment and the genotype/phenotype in shaping the generalization degree of plants belonging to the same population. We will assess the structure and clustering pattern of the pollination and mating intraspecific networks emerging from those interactions and we will also analyse how individual differences in the degree of generalization affect plant fitnesses. We will extend the network analytical approach widely used in community ecology to understand the ecological and genetic factors driving generalization differences among individuals within populations and will analyse their evolutionary outcomes. Finally, we will test our hypothesis setting up an experimental population and controlling for the main factors affecting individual generalization.

This research project is financed by a grant from the spanish Ministry of Science and Innovation.

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