Abstract
Pre-dispersal seed predation (PDSP) is commonly observed in woody plants, and recognized as a driver of seed production variability that is critical for successful regeneration. Earlier studies on PDSP and its determinants were mostly species specific, with community-level PDSP rarely estimated; and the interactions between the temporal variability of seed production and PDSP remain elusive. In this study, the community seed rain of woody plants in a mixed evergreen-deciduous broadleaf forest was monitored for seven years. We examined predation on collected seeds and analyzed the determinants of PDSP. PDSP was recorded in 17 out of 44 woody plant species, and three-quarters of PDSP was due to insect predators. Annual seed production varied substantially at community level, reversely linked with the temporal variation of PDSP rate. The PDSP rate was biased regarding fruit types, and being significantly correlated with seed mass when using phylogenetic independent contrasts (PICs) or without taking into account phylogenetic relations, especially for nuts. PDSP rate was also negatively correlated with seed density, showing a threshold-related predator satiation effect. The community-level PDSP rate was primarily determined by tree height, fruit type, and interannual variation of seed production and seed mass. Our analysis revealed a causal link between seed production and the dynamics of PDSP rate at the community level. The predator satiation effect was primarily contributed by the dominant species, whereas the rare species seemed to apply a distinct “hide-and-seek” strategy to control the risk of PDSP. The mechanistic difference of seed production between the common and rare species can shed new light on species coexistence and community assembly. Long-term monitoring of both seed rain and seed predation is required for understanding the ecological and evolutionary implications of species regeneration strategies in a species-rich forest community.
Highlights
Seed predation has long been a central topic in population and community ecology [1, 2]
pre-dispersal seed predation (PDSP) has been commonly observed in various vegetation types [7,8], and the intensity of PDSP substantially differs among plant species due to the phenotypic characteristics of plants such as phenology [9,10,11], number of flowers [12,13], seed size and density [14, 15], as well as the body size of predators [16]
We explored the correlation between pre-dispersal predation rate and seed density using quantile regression, which facilitates analysis from the minimum to maximum response rather than the mean or median [36], and provides a more complete picture of the relationships between variables missed by other regression methods [37]
Summary
Seed predation has long been a central topic in population and community ecology [1, 2]. By reducing seed density around conspecific individuals [3], pre-dispersal seed predation (PDSP) can modify the species composition and spatial patterns of effective seed dispersal [4,5,6], regulating the coexistence of plant species in the community [7]. PDSP has been commonly observed in various vegetation types [7,8], and the intensity of PDSP substantially differs among plant species due to the phenotypic characteristics of plants such as phenology [9,10,11], number of flowers [12,13], seed size and density [14, 15], as well as the body size of predators [16]. HoweverOn the other hand, plants can reduce seed predation by developing physical barriers and chemical defenses [20], and can minimize seed loss through a predator satiation effect produced by mast seeding [21, 22]
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