1. Persistence-based Selection - Most contemporary biologists characterize natural selection as heritable variation in fitness. Furthermore, they interpret and measure fitness in terms of differential reproduction: the fitness of an entity corresponds to its capacity to produce offspring. In this part of the project, we examine another (complementary) interpretation of fitness in terms of differential persistence, i.e., fitness as the capacity of an entity to survive. This view (so-called “persistence-based selection”) recasts units of selection as spatiotemporal continuous processes or lineages rather than individuals or groups of contemporary individuals. By so doing, it offers a promising framework to understand selection on complex systems such as multi-species microbial communities, clades, and biogeochemical cycles. Persistence-based selection also expands multilevel selection theory (MLST), one of the pillars of contemporary evolutionary biology.

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2. Multi-Level Selection and Ecology - In this part of the project, we make use of multilevel selection theory (MLST) to study ecological processes and alternative mechanisms of dispersal (i.e., non-selective random migration) in ecological communities and metapopulations. We are currently considering two new investigations related to MLST. The first is a “global evolution model” that extends a standard metapopulation model to include feedback between populations and the global environment. The objective is to provide a concrete example of evolution without reproduction (i.e., the evolution of a single entity) in the context of MLST. The second is a metacommunity model intended to mimic a system in which the process carried out by a community (e.g., cross-feeding) evolves independently of species composition. These are both intended to provide support through modeling of ITSNTS theory.

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3. “It’s the song, not the singer” (ITSNTS) - This theory was developed to legitimize and supplant claims that we and our microbiomes (“holobionts”) – or complex communities more generally (maximally, the biosphere) – are units of selection (“Darwinian individuals”). ITSNTS holds that it is the processes implemented, not the implementing taxa (individually or collectively) that are the relevant units, evolving through differential persistence and recruitment of implementing taxa, not differential reproduction. ITSNTS engages and challenges traditional philosophical concerns about individuality, function, causation, emergence and hierarchy, is increasingly relevant biomedically (as in the new discipline of “microbiomics”), and should provide a much-needed and novel theoretical underpinning for evolutionary biology and ecology. 

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4. Darwinizing Gaia - We are trying to re-formulate understandings of evolution by natural selection (ENS) in ways that Charles Darwin himself, and contemporary philosophers and biologists who are Darwinians, might accept. The goal is to legitimize attributions of “adaptation” and selected-effect function to community, ecosystem and biosphere-level activities. Approaches, which would require that differential persistence as well as differential reproduction be recognized as legitimate outcomes or mechanisms of ENS, include “It’s the Song, not the Singer” (ITSNTS) theory, modifications to David Hull’s replicator interactor framework, and recognition of clade selection for complex clade-level adaptations. These efforts will be accompanied by appropriate modeling studies and integration with existing biogeographic and metagenomic data. 

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