Many plant species produce fleshy fruits to attract vertebrate frugivores, which in turn can affect the condition of the seed and likelihood and timing of germination. Given that these interactions are common and likely important for plant demography, it is surprising that we lack a strong ability to predict the effects of gut passage by various frugivores on germination. Here, we review all known studies conducted on fleshy-fruited plant species (n=>200 studies representing >1300 separate plant-frugivore interactions) where the effect of gut passage is compared to a control treatment - either mechanically handled seeds or whole fruit, substantially increasing the number of studies relative to previous reviews. We first assessed knowledge gaps in terms of geography and taxonomy. Next, we conducted a meta-analysis to identify trends by study type, frugivore taxon, and geographic location. Finally, we consider these results in light of global change drivers affecting plants and frugivores listed on the IUCN red list or considered invasive in some regions of the world.
Results/Conclusions
We found that tropical areas are understudied relative to temperate areas, but there is not a difference in new world vs old world studies. Consistent with previous reviews, we found gut passage increases germination, with a larger effect size found in studies comparing gut passed seeds to whole fruit relative to studies comparing gut passed seeds to mechanically depulped seeds. We did not find significant differences in the effect of gut passage between tropical and temperate plant species, or mainland and island plant species. Reptiles, including birds, and primates are the most effective frugivores, whereas mammals other than primates, fish, and invertebrates had neutral to negative effects. We anticipate widespread potential effects of changing disperser communities on plant recruitment, and identify future research needed to develop a framework for predicting gut passage effects on plant recruitment.