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

Sandra Hervías-Parejo,Haldre S. Rogers,Isabel Donoso,Anna Traveset,Evan C. Fricke

doi:10.3389/fevo.2022.794481

Abstract

As the sole opportunity for most plants to move, seed dispersal influences the biodiversity and functioning of plant communities. Global change drivers have the potential to disrupt seed dispersal processes, affecting plant communities and ecosystem functions. Even though much information is available on the effects of seed dispersal disruption (SDD), we still lack a comprehensive understanding of its main causes at a global scale, as well as the potential knowledge gaps derived from research biases. Here we present a systematic review of biotic and abiotic SDDs to ascertain the global change drivers addressed, dispersal modes impacted, plant processes affected, and spatial focus of existing research on this topic up-to-date. Although there are many modes of dispersal and global change drivers in temperate and tropical ecosystems worldwide, research efforts have predominantly addressed the effect of alien species for biotic seed dispersal in temperate systems and oceanic islands as well as how defaunation of bird or mammal dispersers has affected seed removal in the Neotropics. SDD studies were also biased toward forest ecosystems, with few in shrublands or grasslands. Finally, the effects of climate change, ecological consequences at the whole community level, and evolutionary changes were largely unrepresented in SDD studies. These trends are likely due to a combination of true geographic and ecological patterns in seed dispersal and global change and bias in research focus. We conclude that increased research investment in the less-studied systems and a better understanding of potential synergies and feedback between multiple global change drivers will be important to forecast the threats to plant biodiversity and those ecosystem functions derived from seed dispersal in the Anthropocene.

Highlights

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, 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)
About two-thirds of studies have focused on the initial stages of the seed dispersal cycle—seed removal and seedling recruitment—while far fewer have dealt with the longer-term patterns demonstrated through plant community composition and evolutionary changes
We foresee that given the widespread nature of seed dispersal disruption (SDD) and its impacts on the early life history stages in plant populations, there will be increasingly more evidence for changes in plant community composition and evolution

Summary

Introduction

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). Besides moving seeds across the landscape, animals that ingest fruits and pass viable seeds through their digestive tracts can further play an important role in plant establishment as they can modify the rate of seed germination and seedling growth (Traveset and Verdú, 2002; Rogers et al, 2021b). Key dispersers include frugivores like primates and bats which disperse seeds primarily through endozoochory (Fuzessy et al, 2018), herbivores like deer and sheep which disperse non-fleshy fruits both through ectozoochory and endozoochory (Albert et al, 2015), and rodents which typically disperse seeds through scatter-hoarding (Gómez et al, 2019)

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