Endozoochorous dispersal by herbivores and omnivores is mediated by germination conditions

Abstract

Background: Vertebrate-mediated seed dispersal is probably the main long distance dispersal mode. Through endozoochory, large mammals act as mobile links between habitats within and among forest patches. Along with other factors, their feeding regimes do affect their contribution as dispersal vectors. We conducted a cross-species comparative experiment involving two herbivores, red deer and roe deer; and two opportunistic omnivores, wild boar and brown bear, all occurring in the forest and steppe-forest ecotone habitats of the southeastern Caspian region. We compared their role as endozoochorous seed dispersal agents by monitoring seedling emergence in their dungs under greenhouse and natural conditions. Results: In total, 3078 seedlings, corresponding to 136 plant taxa sprouted from 445 paired dung sub-samples, under greenhouse and natural conditions. Only 336 seedlings, corresponding to 36 plant taxa, emerged under natural conditions, among which five taxa did not appear under greenhouse conditions. Graminoids and forbs composed 91% of the seedlings in the greenhouse whereas shrubs were more abundant under natural conditions, representing 55% of the emerged seedlings. Under greenhouse conditions, first red deer and then wild boar dispersed more species than the other two mammals, while under natural conditions brown bear was the most effective vector. We observed remarkably higher species richness and seedling abundance per dung sub-sample under buffered greenhouse conditions than we did under natural conditions. Conclusions: The four sympatric mammals studied provided different seed dispersal services, both in terms of seedling abundance and species richness and may therefore be regarded as complementary. Our results highlight a positive bias when only considering germination under buffered greenhouse conditions. This must be taken into account when planning management options to benefit plant biodiversity based on the dispersal services concluded from greenhouse experiments.

Seed traits matter—Endozoochoric dispersal through a pervasive mobile linker

“…With this controlled feeding experiment, we provide fundamental advances in understanding the potential impacts of mobile linkers as seed dispersers. Hitherto our understanding of the efficiency of smaller mammals and their potential impacts on plant communities and recruitment was limited, as most of the literature focuses on rather large mammals with more extensive home ranges (Albert, Mårell, et al, 2015 , Karimi et al, 2020 , Mouissie, Vos, et al, 2005 , but see, e.g., Lessa et al, 2019 , Naoe et al, 2019 , Yang et al, 2019 ). Our feeding experiment demonstrates that 32 out of 42 species that germinated in the control group also survived the gut passage of hares and germinated afterward.…”

Seed recovery and germination rate after gut passage by Korean water deer (Hydropotes inermis argyropus)

“…Seeds also encounter seedling competition within or between species (Milotić and Hoffmann, 2017). Additionally, after endozoochorous seed dispersal, the germination in natural conditions might also affect the seed germination success (Milotić and Hoffmann, 2016a; Karimi et al, 2020). Meanwhile, the seedlings had a higher increase in biomass and height, as dung can supply the nutrients (e.g.…”

Seed germination of a myrmecochorous plant endemic to the Brazilian semiarid region: the wolf is not so bad

“…Although poorly documented, seeds of some myrmecochorous plants can also be used as food by vertebrates, especially when the elaiosome represents a great energetic reward (Calviño-Cancela et al 2008;Souza & Fagundes 2017;Snell et al 2019). The passage of these propagules through the vertebrate digestive tract can eliminate external seed appendages, such as the elaiosome, and/or break dormancy through chemical or mechanical scarification, thereby increasing seed germinability (Traveset et al 2007;Farias et al 2015;Karimi et al 2020). Finally, the elimination of seeds in fecal cakes can also provide some shelter from predators and greater availability of organic matter for the initial development of seedlings (Farias et al 2015).…”

“…Finally, the elimination of seeds in fecal cakes can also provide some shelter from predators and greater availability of organic matter for the initial development of seedlings (Farias et al 2015). Thus, vertebrates are important and effective long-distance seed dispersers in most ecosystems (Nathan & Muller-Landau 2000;Levine & Murrel 2003), although some studies indicate that seed ingestion by vertebrates may have neutral or negative effects on seed germination for some plant species (Schupp et al 2010;Karimi et al 2020).…”