Cascading Impacts of Seed Disperser Loss on Plant Communities and Ecosystems

Abstract

Seed dispersal is key to the persistence and spread of plant populations. Because the majority of plant species rely on animals to disperse their seeds, global change drivers that directly affect animals can cause cascading impacts on plant communities. In this review, we synthesize studies assessing how disperser loss alters plant populations, community patterns, multitrophic interactions, and ecosystem functioning. We argue that the magnitude of risk to plants from disperser loss is shaped by the combination of a plant species’ inherent dependence on seed dispersers and the severity of the hazards faced by their dispersers. Because the factors determining a plant species’ risk of decline due to disperser loss can be related to traits of the plants and dispersers, our framework enables a trait-based understanding of change in plant community composition and ecosystem functioning. We discuss how interactions among plants, among dispersers, and across other trophic levels also mediate plant community responses, and we identify areas for future research to understand and mitigate the consequences of disperser loss on plants globally. Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 52 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Drivers of Ecological and Evolutionary Disruptions in the Seed Dispersal Process: Research Trends and Biases

“…The movement of seeds away from the mother plant allows them to colonize specific microsites and new areas, reduces sibling competition and attack by natural enemies (e.g., herbivores, pathogens), and determines the potential area of recruitment, acting as a template for the subsequent stages of plant growth as well as the plant spatial patterns (Howe and Smallwood, 1982;Howe and Miriti, 2004;Jordano, 2014;Traveset et al, 2014;Rogers et al, 2021a). The dispersal vectors can be both biotic (i.e., transported in the digestive tracts, fur, plumage or feet of animals) or abiotic (i.e., transported by wind, water, or gravity).…”

“…Animals play an important role as seed dispersers for more than half of the plant species around the globe (Levey et al, 2002;Dennis et al, 2007;Rogers et al, 2021a), thus contributing to numerous ecosystem functions. Birds, mammals, lizards, fish and invertebrates are common dispersers, although their relative importance varies across habitat types (Fleming and John Kress, 2011;Albert et al, 2015;Correa et al, 2015;Gómez et al, 2019;Anjos et al, 2020;Araujo et al, 2021;Rogers et al, 2021a).…”

“…Animals play an important role as seed dispersers for more than half of the plant species around the globe (Levey et al, 2002;Dennis et al, 2007;Rogers et al, 2021a), thus contributing to numerous ecosystem functions. Birds, mammals, lizards, fish and invertebrates are common dispersers, although their relative importance varies across habitat types (Fleming and John Kress, 2011;Albert et al, 2015;Correa et al, 2015;Gómez et al, 2019;Anjos et al, 2020;Araujo et al, 2021;Rogers et al, 2021a). Within studies involving avian frugivores, most research has focused on those species dispersing fleshy-fruited plants, but many birds can serve as dispersers including waterbirds which move many wetland species (Green et al, 2016(Green et al, , 2021.…”

“…Habitat loss, land use change, overhunting, and invasive species are key threats underlying animal seed disperser population declines, extinctions, and range reductions (McConkey et al, 2012;Dirzo et al, 2014). The disruption of plant-seed disperser interactions have shown to have serious consequences for plants, which can cascade to affect other species, as well as the whole community and ecosystem (reviewed in Rogers et al, 2021a). Widespread rapid changes in seed disperser assemblages-which likely translate into changes in the seed dispersal process-have occurred since prehistoric times, when humans started colonizing new regions, strongly modifying landscapes and defaunating ecosystems by hunting mainly largebody animals, leading to many megafaunal extinctions in the Pleistocene (Janzen and Martin, 1982;Malhi et al, 2016;Galetti et al, 2018).…”

“…Islands mostly lack megafauna, but the pattern of greater threat to larger-bodied animals holds true on islands as well, where large-bodied birds, bats, and lizards are those suffering the largest declines (Traveset et al, 2012;Pérez-Méndez et al, 2016;Kingston et al, 2021). It is important to recognize that small-bodied bird and mammal dispersers tend to be less threatened although they also have experienced declines (Davidson et al, 2009;Rosenberg et al, 2019), which could cause imperceptible but pervasive impacts on seed dispersal (Rogers et al, 2021a).…”