Interactions among Shade, Caching Behavior, and Predation Risk May Drive Seed Trait Evolution in Scatter-Hoarded Plants

Abstract

Although dispersal is critical to plant life history, the relationships between seed traits and dispersal success in animal-dispersed plants remain unclear due to complex interactions among the effects of seed traits, habitat structure, and disperser behavior. We propose that in plants dispersed by scatter-hoarding granivores, seed trait evolution may have been driven by selective pressures that arise from interactions between seedling shade intolerance and predator-mediated caching behavior. Using an optimal foraging model that accounts for cache concealment, hoarder memory, and perceived predation risk, we show that hoarders can obtain cache-recovery advantages by placing caches in moderately risky locations that force potential pilferers to engage in high levels of vigilance. Our model also demonstrates that the level of risk needed to optimally protect a cache increases with the value of the cached food item. If hoarders perceive less sheltered, high-light conditions to be more risky and use this information to protect their caches, then shade-intolerant plants may increase their fitness by producing seeds with traits valued by hoarders. Consistent with this hypothesis, shade tolerance in scatter-hoarded tree species is inversely related to the value of their seeds as perceived by a scatter-hoarding rodent.

Rodent‐mediated plant seed dispersal: What happens to the seeds after entering the gaps with different sizes?

“…Data represented as mean ± standard error removed from the LG, as also found in previous studies Yang et al, 2016). The results clearly support the hypothesis tested in this study because the proportion of scatter-hoarded seeds did not increase significantly as the gap size increased, possibly because rodents must trade-off the risks of predation and pilferage by other animals (Lichti et al, 2020;Steele et al, 2015;Yang et al, 2016). A gap environment with large canopy openness increases the danger coefficient for the main seed disperser; they would rather scatter hoard to protect the seeds from pilfering rather than eat the seeds in dangerous gaps.…”

“…The seed fates might have varied between shrubs and open habitats because of differences in the activities and foraging behavior of rodents (Den Ouden et al, 2005; Perea et al, 2011; Perez‐Ramos & Maranon, 2008). The foraging behavior of mammals is associated with assessments of foraging costs and benefits, including time, energy, and the predation risk (Lichti et al, 2020; Schmidt & Ostfeld, 2003; Steele et al, 2015). The time spent on in situ eaten of seeds is usually longer than the time spent on removal, and the longer a seed disperser stays in the open, the higher the risk of predation.…”

“…Wang and Corlett ( 2017 ) found that scatter hoarders prefer caching larger and more nutritious seeds in shrubs than in the open habitats, and the selection of caching microhabitat by small rodents was relevant to seed traits. However, some studies found that small rodents favor open habitats when selecting cache sites (Lichti et al, 2020 ; Steele et al, 2014 , 2015 ) because less sheltered habitats reduce visits of other pilferers (Lichti et al, 2020 ; Steele et al, 2015 ). Canopy gaps are usually beneficial for seed dispersal.…”

Mast seeding promotes evolution of scatter-hoarding

“…On the other hand, variable seed production in synzoochorous plants was interpreted as an adaptation that enabled reducing seed mortality caused by animals that act as seed predators and only incidentally disperse seeds [39]. However, we suggest that the high CV of plants dispersed by scatterhoarders can also be linked to the caching behaviour of scatterhoarders (see also [86] for a model exploring the connection between caching behaviour and seed trait evolution).…”

Is Mus spretus a mutualistic species with oak species or does it parasitize previously established relationships with other rodents?

“…We again place the process of acorn dissemination as a key factor in the web of multiple processes that can affect the distribution of a woody species, but dissemination is a key process in the occupation of new territories. (Wang et al 2014a;Lichti et al 2015Lichti et al , 2020.…”