Introduction

The Rise, Fall, and Rise Again of Metacommunity Ecology

Prospectus

1. Traditional perspectives of community ecology, including species interactions, coexistence, and biodiversity, have focused on local-scale processes and have met with a great deal of controversy and disagreement.

2. The recognition of the importance of spatial (and temporal) processes has risen dramatically in recent years, although threads of ideas (importance of dispersal) and controversies (stochasticity vs. determinism) are evident throughout the history of ecology.

3. Metacommunity ecology, by explicitly incorporating scale as a critical feature of the outcomes of coexistence and biodiversity, among other variables, has the potential to unify what seems like a largely unresolved field.

4. This unification will require explicitly incorporating spatiotemporal heterogeneities, dispersal, the interactions between stochasiticity and determinism, and a number of complicating variables (e.g., food webs, evolution).

The major weakness of traditional community ecology, and why it has so conspicuously failed to come up with many patterns, rules and workable contingent theory, is its overwhelming emphasis on localness.

— Lawton (1999)

Community ecology is the study of how species interact with each other in ways that determine patterns in the distributions and abundances of different species. It represents the nexus at which individual traits, fitness, and population dynamics scale up to influence the distribution and coexistence among species on local to biogeographic scales and from months to millennia. It influences the role that species play in ecosystems and how they evolve. And it plays a critical role inunderstanding the destruction and conservation of biodiversity, as well as its restoration, as the human footprint becomes more pervasive. Unfortunately, community ecology has not yet fully lived up to its potential (Lawton 1999, Ricklefs 2008).

Are there any broadly applicable concepts and approaches that can help to resolve the clear limitations of community ecology as much of it continues to be practiced? Elton (1927) suggested four important ones — the niche, the food web, body size relations, and the trophic pyramid — that still serve as key concepts of community ecology (Chase and Leibold 2003). Lotka (1925) introduced the idea that energy relations and the laws of physics (thermodynamics) and chemistry (stoichiometry) could serve as a foundation for biology in general, and although these ideas fell largely silent, their core aspects have been championed in putative "unified" ecological theories of neutral coexistence (Hubbell 2001), metabolism (Brown et al. 2004), and stoichiometry (Sterner and Elser 2002), as well as mathematical principles such as body-size relations (Ritchie 2010), maximum entropy (Harte 2011), and neutrality (Hubbell 2001). Attempts have even been made to unify the unified theories (McGill 2010, 2011). Despite these efforts, there does not seem to be a strong sense that any one of these perspectives is able to adequately address the full scope of the questions at hand.

In this book we argue that we already know many of the key aspects of community ecology but that we do not have a framework that adequately links these in an appropriate context. We argue that the missing link that can provide this context is the combination of spatial and interaction processes that characterize metacommunity ecology. To us, the metacommunity approach allows one to explicitly transit from fitness and population dynamics to community- and ecosystem-level processes, as well as from smaller to larger scales, without the need to artificially designate where one community ends and another begins. Our goal for this book is to motivate others to share this vision of metacommunity ecology as a "synthetic hub" for understanding community and ecosystems ecology. We aim to contribute to a synthesis that is akin to the modern synthesis achieved many decades ago in evolutionary biology, which embraced the multiple roles of selection, drift, mutation, and gene flow.

Some elements of this synthesis have already been vetted. For example, Vellend (2010, 2016) developed an important conceptual connection between the major drivers of diversity in community ecology — niche selection, ecological drift, speciation, and dispersal — and the major drivers of diversity in population genetics — natural selection, genetic drift, mutation, and gene flow. In some ways, our goal is to more deliberately "look under the hood" of the relatively simple framework described by Vellend to identify just how niche selection, stochastic drift, speciation, and dispersal interact with eco-evolutionary processes (Hendry 2016), geometric scaling processes (McGill 2010, 2011), and constraints of energy flow and conservation of matter (Loreau 2010) to influence pattern and process at multiple spatial and temporal scales. We use this framework to discuss and synthesize numerous levels of organization ranging from pairwise interactions, to guilds of multiple competing taxa across scales of space and time, to micro- and macroevolutionary processes, to macroecological patterns, to food webs and ecosystems-level processes and patterns.

1.1 THE INDELIBLE INFLUENCE OF SCALE

Before we begin exploring the advantages of the metacommunity approach, it is useful to first ask, what is a community? When we talk of what a community is, we usually think of an idealized case in which multiple species have populations that interact by affecting each other's birth and death rates at a particular place and time (Fig. 1.1). A great deal of effort has been aimed at understanding the patterns of species composition, relative abundance, and diversity within such communities, as well as the processes leading to those patterns (e.g., the role of interspecific interactions, spatial effects, and environment). And many would argue that the field of community ecology with this focus has gained considerable insight into the patterns and processes by which species interact and coexist (Morin 2011, Mittelbach 2012).

Unfortunately, the definition of community is always qualified by some phrase like "at a particular place and time" (also "in the same geographic area," "in the same location," "coexist together," etc.). Such qualification is not easily...