Seed fate and decision‐making processes in scatter‐hoarding rodents

Abstract

A mechanistic understanding of seed movement and survival is important both for the development of theoretical models of plant population dynamics, spatial spread, and community assembly, and for the conservation and management of plant communities under global change. While models of wind-borne seed dispersal have advanced rapidly over the past two decades, models for animal-mediated dispersal have failed to make similar progress due to their dependence on interspecific interactions and complex, context-dependent behaviours. In this review, we synthesize the literature on seed dispersal and consumption by scatter-hoarding, granivorous rodents and outline a strategy for development of a general mechanistic seed-fate model in these systems. Our review decomposes seed dispersal and survival into six distinct sub-processes (exposure, harvest, allocation, preparation, placement, and recovery), and identifies nine intermediate (latent) variables that link physical state variables (e.g. seed and animal traits, habitat structure) to decisions regarding seed allocation to hoarding or consumption, cache placement and management, and deployment of radicle-pruning or embryo excision behaviours. We also highlight specific areas where research on these intermediate relationships is needed to improve our mechanistic understanding of scatter-hoarder behaviour. Finally, we outline a strategy to combine detailed studies on individual functional relationships with seed-tracking experiments in an iterative, hierarchical Bayesian framework to construct, refine, and test mechanistic models for context-dependent, scatter-hoarder-mediated seed fate.

Effects of nitrogen deposition on reproduction in a masting tree: benefits of higher seed production are trumped by negative biotic interactions

“…Reproduction of many large‐seeded plant species relies on seeds that are dispersed and buried by scatter‐hoarding birds and mammals, but are not recovered under certain conditions (Theimer ; Vander Wall ; Jansen et al . ; Lichti, Steele & Swihart ; Pesendorfer et al . ; Zwolak, Bogdziewicz & Rychlik 2016; Zwolak et al .…”

“…; Zwolak & Crone ). The fate of scatter‐hoarded seeds is often determined by one or more seed traits (reviewed in Lichti, Steele & Swihart ). For example, larger seeds are cached more often than smaller ones (Theimer ; Jansen, Bongers & Hemerik ; Steele et al .…”

Effects of fragmentation on the seed predation and dispersal by rodents differ among species with different seed size

“…Seed size has been demonstrated to play an important role in mediating rodent foraging behavior upon seeds (Wang & Chen 2009;Vander Wall 2010;Lichti et al 2017). In our study, the 2 large-seeded species Q. acutissima and C. mekongensis were more likely to have their seeds being removed and cached and transported to a further distance than the small-seeded species, C. echidnocarpa and C. hystrix (Figs 1 and 2).…”

“…In this study, we have mainly discussed the effects of seed size, but other seed traits, such as germination schedule, nutrition level and secondary metabolites, could also influence seed predation and dispersal by rodents (Vander Wall 2010;Lichti et al 2017;Zhang et al 2017). Most of these traits differed among our study species, but there was no apparent relationship between seed size and any of these traits (Table 2).…”

“…A second source of variation may result from differences in seed characteristics of tree species studied at each site, as rodents predate seeds differently based on their characteristics. Numerous studies have demonstrated that seed size can significantly influence rodent foraging preference and, thus, seed fate (Moore et al 2007;Wang & Chen 2009;Vander Wall 2010;Lichti et al 2017). Most previous studies have targeted a single plant species in their experiments (Xiao et al 2013;Mendes et al 2016;Zhang et al 2017).…”