Diet complementation as a frequency‐dependent mechanism conferring advantages to rare plants via dispersal

Abstract

We used an agent‐based model to test the hypothesis that diet complementation by frugivores can promote the persistence of rare plant species in communities (DCH). Models simulated bird movement, frugivory, seed dispersal and plant recruitment on landscapes that differed in their degree of fragmentation and in their degree of fruiting species mixing at the scale of frugivores’ foraging decisions. Diet complementation promoted the dispersal of rare species without the need of a priori preference from birds. The effects of landscape structure on the dispersal of rare plants were small (<5%) compared to positive effects of diet complementation because birds tracked the nutrients contained in rare fruits to balance their diets. However, resource‐tracking of rare fruits increased foraging costs up to 20% of net energy intakes. During postdispersal stages, density‐dependent mortality only conferred advantages to rare plants when located within heterospecific plant patches. Still, thanks to rare‐biased dispersal, rare plants showed the highest seed dispersal effectiveness irrespectively of landscape configuration. Our theoretical approach presents a behavioural mechanism by which fruit choice can act as a frequency‐dependent mechanism conferring rare species advantages as important as classic postdispersal density‐dependent processes. We hope that this study stimulates future work aimed at evaluating the importance of diet complementation in structuring the composition and spatial patterning of plant communities. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13152/suppinfo is available for this article.

Can network metrics predict vulnerability and species roles in bird‐dispersed plant communities? Not without behaviour

“…Similarly, accounting for fruit handling behaviours (Simmons et al ), or the suitability of habitat of seed deposition (González‐Castro et al ) will result in more accurate estimates of frugivores’ contribution to recruitment. Maybe more crucially, we need a better understanding of seed retention times, and of how bird physiology influences fruit choice (Morán‐López et al ). Once available, this information can be easily incorporated into our model by modifying forbidden links and weighing interactions by their effectiveness.…”

How does avian seed dispersal shape the structure of early successional tropical forests?

“…It is still possible that the seed rain patterns of the Bird treatment match the fruit availabilities of an intermediate spatial scale between our Local and Landscape scales. However, this is unlikely because the anti‐apostatic biases in the dispersal of rare plant species remain constant given that plant species that are rare at the Local and Landscape scale will also be rare at intermediate spatial scales (Morán‐López et al, ).…”

“…In addition, nutritional qualities of fruit may influence frugivore behaviour (Levey & Martinez del Rio, ) to include a wider array of fruiting species compared to what would be expected from plant relative abundances (Carlo & Morales, ). Thus, interactions of frugivores with rare plant species can be surprisingly common and function as an equalizing mechanism in plant communities where a few species are common while many are rare (Carlo & Morales, ; Morán‐López, Carlo, Amico, & Morales, ). Still, we need a fuller understanding of how these processes combine to create structural attributes in plant communities.…”

Species activity promote the stability of fruit-frugivore interactions across a five-year multilayer network

“…This stability suggests that not only birds from different modules tend to have distinct fruit preferences, but these preferences tend to be temporally consistent and independent of fruit abundance. Indeed, some abundant plant species were rarely dispersed (e.g., Arbutus unedo), suggesting that birds likely select fruits based on other intrinsic traits such as their nutritional composition (Schaefer et al 2003;Yang et al 2013;Morán-López et al 2018). Incorporating "historical interaction information" for module detection minimizes the influence of transient species roles and allows the detection of long-lasting modules which may be highly informative for conservation efforts (Blonder et al 2012).…”