Beyond the Bites: Rethinking seed-dispersal networks in plant-frugivore studies

Abstract

In recent years, the use of ecological networks to understand the roles of species in plant-frugivore relationships and their evolutionary significance has increased significantly. However, the accuracy of these networks can vary based on construction methods, and there is limited discussion about the true functional roles of species. In this review, I critically evaluate the methodologies and approaches used in 65 studies to construct seed dispersal networks, with a focus on distinguishing between frugivory and effective seed dispersal. In general, I found that most of the studies built the interaction networks based on direct observations of animals eating seeds/fruits (n = 23 studies, 35.38%) and by sampling of scats (n = 18, 27.69%). Data from datasets and by using complementary methods (e.g., DNA-barcoding) accounted for 33.85% (n = 22 studies). Surprisingly, only two studies (3.08%) confirmed seed viability (i.e., if the viability of the dispersed seeds were experimentally confirmed or the microhabitat where the scat had been dropped). This highlights a critical issue: many studies fail to assess all stages of the seed dispersal process (i.e., seed consumption, transport, deposition, and germination). The potential misapplication of the term “seed-dispersal networks” could lead to significant misunderstandings about the true functionality and coevolutionary dynamics of these interactions. Consequently, I advocate for more rigorous methodologies and detailed discussions to improve accuracy about the true functional roles of species within these networks.