Mass Effects

by

Jani Heino, Luis Mauricio Bini

• LAST REVIEWED: 21 April 2021
• LAST MODIFIED: 21 April 2021
• DOI: 10.1093/obo/9780199830060-0234

Introduction

In the last two decades, community ecology has matured to consider biotic communities as a product of both local and regional processes. Therefore, local communities are currently thought to be connected by the dispersal of organisms, thereby forming a metacommunity. A metacommunity is organized by multiple processes, including environmental filtering, biotic interactions, dispersal, and ecological drift. Thus, spatial variations in local diversity (i.e., alpha diversity) and community composition (i.e., beta diversity) result from the relative roles of these major processes. In turn, these processes are mediated by organisms’ characteristics, environmental heterogeneity, and the connectivity between localities in a metacommunity. For a given environmental gradient, the role of environmental filtering is likely to be dependent on the dispersal rates shown by organisms. Unsuitable habitat patches (i.e., sinks), in terms of biotic and abiotic characteristics, may be occupied by different species due to high dispersal rates from suitable habitat patches (i.e., sources). Thus, mass effects occur when species are established at localities where their populations cannot be self-maintained. Even though it may be difficult to prove the action of mass effects per se, given the complex interactions between different mechanisms shaping biotic communities, there is some empirical evidence supporting their importance in nature. In addition, high dispersal rates that lead to mass effects may have important implications for biomonitoring and biodiversity conservation. This is because species occurring at sites beyond their niche requirements may provide false information about a site’s ecological quality or result in misleading plans to conserve species at sites where they cannot persist in the absence of continuous influx of propagules.

General Overviews

Mass effects have been explicitly considered in ecology after the seminal paper by Shmida and Wilson 1985, where the authors propose that mass effects lead to the occurrence of species at localities where their populations cannot be self-maintained without a recurring influx of immigrants from nearby localities. Thereafter, the concept of mass effects has been embraced in the field of metacommunity ecology, with Mouquet and Loreau 2003; Leibold, et al. 2004; Urban 2006; and Logue, et al. 2011 providing summaries of mass effects as one of the original four metacommunity archetypes, as also discussed by Cottenie 2005; Holyoak, et al. 2005; Brown, et al. 2017; and Leibold and Chase 2018. The works described in this section are key theoretical references in this research field. In addition, applied work building on the concepts of metacommunity dynamics and mass effects is receiving increasing attention (Bengtsson 2010), as has been emphasized in reviews on biological assessments and ecosystem monitoring (Heino 2013).

• Bengtsson, J. 2010. Applied (meta)community ecology: Diversity and ecosystem services at the intersection of local and regional processes. In Community ecology: Processes, models and applications. Edited by H. A. Verhoef and P. J. Morin, 115–130. Oxford: Oxford Univ. Press.

  In this overview, the author discusses how the concepts and ideas developed in metacommunity ecology should be incorporated in applied research on biodiversity and ecosystem management.

• Brown, B. L., E. R. Sokol, J. Skelton, and B. Tornwall. 2017. Making sense of metacommunities: Dispelling the mythology of a metacommunity typology. Oecologia 183.3: 643–652.

  An interesting review article criticizing the simplistic view of the four metacommunity archetypes. The penultimate section of the paper provides an insightful list of six strategies to improve the usefulness of variation partitioning analysis in metacommunity studies, one of the main statistical tools in this research field.

• Cottenie, K. 2005. Integrating environmental and spatial processes in ecological community dynamics. Ecology Letters 8.11: 1175–1182.

  The author tested the prevalence of the four original metacommunity paradigms. The author used a variation partitioning approach in the context of multivariate ordination analysis to tease apart the relative roles of environmental and spatial factors on community composition. Most of the 158 data sets analyzed were structured by species sorting, followed by a combination of species sorting and mass effects.

• Heino, J. 2013. The importance of metacommunity ecology for environmental assessment research in the freshwater realm. Biological Reviews 88.1: 166–178.

  Building on the concepts and ideas from metacommunity ecology, the author proposes that biological assessments of ecosystem condition cannot be based on the niche-based perspective alone. The author thus argues that multiple mechanisms, including mass effects, should be better integrated in environmental assessment and ecosystem monitoring programs.

• Holyoak, M., M. A. Leibold, and R. D. Holt. 2005. Metacommunities: Spatial dynamics and ecological communities. Chicago: Univ. of Chicago Press.

  This is a multiauthored book that covers different facets of metacommunity ecology, including core concepts (where the reader will find a basic description of mass effects), empirical patterns about specific groups (e.g., butterflies, beetles, and zooplankton), and theoretical and further perspectives.

• Leibold, M. A., and J. A. Chase. 2018. Metacommunity ecology. Monographs in Population Biology 59. Princeton, NJ: Princeton Univ. Press.

  This book goes beyond the four archetypes described in Leibold, et al. 2004. The authors argue that metacommunity ecology provides a key link between smaller-scale processes (e.g., births and deaths, biotic interactions, environmental selection, and stochasticity) with larger-scale features (e.g., dispersal and habitat heterogeneity). These ideas are also directly associated with the conditions for and prevalence of mass effects in nature.

• Leibold, M. A., M. Holyoak, N. Mouquet, et al. 2004. The metacommunity concept: A framework for multi-scale community ecology. Ecology Letters 7.7: 601–613.

  In this seminal paper, the authors define the field of metacommunity ecology, its boundaries and underlying theories. It focuses heavily on the four major paradigms (or archetypes) of metacommunity processes, including neutral, patch dynamics, species sorting, and mass effects.

• Logue, J. B., N. Mouquet, H. Peter, H. Hillebrand, and Metacommunity Working Group. 2011. Empirical approaches to metacommunities: A review and comparison with theory. Trends in Ecology & Evolution 26.9: 482–491.

  The authors provide a review of the empirical approaches (both observational and experimental) used to test the so-called (and now outdated) metacommunity paradigms. They argue that species sorting and mass effects were the most supported paradigms in empirical studies. More importantly, they also emphasize that many studies indicated that the patterns observed in metacommunities can be potentially associated with more than one paradigm.

• Mouquet, N., and M. Loreau. 2003. Community patterns in source-sink metacommunities. American Naturalist 162.5: 544–557.

  In this theoretical study, the authors evaluate how changing dispersal rates shape species richness, relative abundances, and community-level functional properties at local and regional scales. They found that local (alpha) diversity is maximal at intermediate dispersal rates, while between-community (beta) diversity and regional (gamma) diversity decline with increasing dispersal rates owing to increased homogenization of species composition among sites in the metacommunity.

• Shmida, A., and M. V. Wilson. 1985. Biological determinants of species diversity. Journal of Biogeography 12.1: 1–20.

  In this seminal paper, the authors define mass effects as “the establishment of species in sites where they cannot be self-maintaining.” Therefore, this idea refers directly to the relative importance of environmental conditions and high dispersal rates affecting biological communities, with implications for alpha, beta, and gamma diversity in metacommunities.

• Urban, M. C. 2006. Maladaptation and mass effects in a metacommunity: Consequences for species coexistence. The American Naturalist 168.1: 28–40.

  In this simulation study, the author evaluated how evolution changes species richness of a mass effects-driven metacommunity. The simulations showed that few species were dominant over the landscape, with many sink populations and a negative effect of community isolation on both genetic and species diversity.