New Mutualisms at New Ecosystems: Seed Dispersal Assessment of Invasive Shrubs by Native and Non-Native Mammals

Abstract

Biological invasions are a significant driver of global biodiversity decline in the Anthropocene. The success of plant invasions often depends on mutualistic relationships, such as animal-mediated seed dispersal. While the role of birds in dispersing invasive plants is well documented, the involvement of mammals in new ecosystems remains largely unclear. In the mountains of Central Argentina, Pyracantha species are among the most prominent invasive plants, and their seed dispersal by birds has been extensively studied. In this study, we assessed the role of mammals within a novel assemblage (comprising native, invasive, and domestic species) in the seed dispersal process of invasive Pyracantha angustifolia and P. crenulata shrubs. Specifically, we identified which mammal species are legitimate seed dispersers, evaluated their impact on seed germination, and determined where they deposit the seeds using a combination of observational and experimental approaches. Through camera traps and faecal analyses, we identified the following mammals consuming Pyracantha fruits: (1) domestic species: cattle and horses; (2) native species: grey fox, common hog-nosed skunk, and collared peccary; and (3) invasive species: European hare, wild boar, and invasive deer (red or spotted deer). We included two additional native mammals (i.e., collared peccaries and brown brocket deers) to perform germination trials due to their presumably frugivorous behaviour. The germination experiment revealed that seed ingestion by captive horses, grey foxes, collared peccaries, brown brocket deer, red deer and exotic deer enhanced seed germination. Principal Component Analysis indicated no specific association between mammal species and seed deposition sites, suggesting non-directed dispersal. This research highlights the emergence of new mutualisms in anthropogenic systems that may influence plant community structure through the promotion of plant invasions. Understanding these novel mutualisms is crucial for predicting community rearrangements and improving management actions against plant invasions.