Consequences of intraspecific variation in seed size: does the presence of small seeds reduce predation on large ones?

Abstract

Seeds produced by individual plants often vary substantially in size. Typically, larger seeds produce seedlings that have higher chances of establishment and survival relative to seedlings produced by smaller seeds. However, larger seeds are also preferred by granivores due to larger caloric content. While choosing the patch to forage, granivores might avoid the ones with smaller, less preferred seeds. We tested a novel hypothesis that the production of different size seeds by a plant may be a strategy to decrease predation by granivores. We conducted a 3-year seed removal experiment. We presented Quercus robur acorns in forests in three configurations: large acorns alone, medium acorns alone, and large acorns mixed with small ones. The impact of seed size on seed survival was inconsistent: in the first year of the study, survival probability for seeds in the mixed treatment was significantly higher than survival probability of large seeds alone, supporting our hypothesis. However, in the following years, results were non-significant, probably because of reduced granivore selectivity in poor seed crop years. Our study demonstrated that the impact of neighbourhood of different size seeds seed survival varied over time in Q. robur. This provides limited evidence that intraspecific variation in seed size could evolve to shift the interaction between trees and scatter hoarders away from predation and towards mutualism.

Behaviour, body mass and sex: How intraspecific variation influences seed dispersal by a scatter‐hoarding rodent

“…Seed‐granivore interactions are highly context‐dependent (Celebias & Bogdziewicz, 2023; Lichti et al., 2017; Ostoja et al., 2013). Several factors, such as the quality of the patch (Caccia et al., 2006), population size of granivores (Janova et al., 2016; Zwolak et al., 2021) and the availability of alternative food sources (Van Baalen et al., 2001), shape the decisions granivores make regarding encountered seeds.…”

Intraspecific variation of Quercus ilex L. seed morphophysiological traits in Tunisia reveals a trade-off between seed germination and shoot emergence rates along a thermal gradient

“…Many studies have revealed that among-population variation in germination response to environmental conditions resulted in different responses to climate change within species, which could mitigate the species' vulnerability to changing climate and provide opportunities for species adaptation and conservation (Chamorro et al 2017(Chamorro et al , 2018Cochrane et al 2015a). The sensitivity of germination to climate variability depends on the species' phenotypic plasticity, local adaption, and geographic distribution (Cochrane et al 2015b;Nicotra et al 2010).…”