Scatter hoarding of seeds confers survival advantages and disadvantages to large-seeded tropical plants at different life stages.

Erin K Kuprewicz,Ben Bond-Lamberty

doi:10.1371/journal.pone.0124932

Abstract

Scatter hoarding of seeds by animals contributes significantly to forest-level processes, including plant recruitment and forest community composition. However, the potential positive and negative effects of caching on seed survival, germination success, and seedling survival have rarely been assessed through experimental studies. Here, I tested the hypothesis that seed burial mimicking caches made by scatter hoarding Central American agoutis (Dasyprocta punctate) enhances seed survival, germination, and growth by protecting seeds from seed predators and providing favorable microhabitats for germination. In a series of experiments, I used simulated agouti seed caches to assess how hoarding affects seed predation by ground-dwelling invertebrates and vertebrates for four plant species. I tracked germination and seedling growth of intact and beetle-infested seeds and, using exclosures, monitored the effects of mammals on seedling survival through time. All experiments were conducted over three years in a lowland wet forest in Costa Rica. The majority of hoarded palm seeds escaped predation by both invertebrates and vertebrates while exposed seeds suffered high levels of infestation and removal. Hoarding had no effect on infestation rates of D. panamensis, but burial negatively affected germination success by preventing endocarp dehiscence. Non-infested palm seeds had higher germination success and produced larger seedlings than infested seeds. Seedlings of A. alatum and I. deltoidea suffered high mortality by seed-eating mammals. Hoarding protected most seeds from predators and enhanced germination success (except for D. panamensis) and seedling growth, although mammals killed many seedlings of two plant species; all seedling deaths were due to seed removal from the plant base. Using experimental caches, this study shows that scatter hoarding is beneficial to most seeds and may positively affect plant propagation in tropical forests, although tradeoffs in seed survival do exist.

Highlights

Seed predation by animals negatively affects plant populations by limiting plant propagation and may influence forest community structure and plant distributions [1,2,3,4]
Hoarded seeds of all three palm species were protected from infestation by invertebrate seed predators whereas non-hoarded seeds suffered significantly higher levels of infestation by Coccotrypes beetles (A. alatum: t = -2.25, df = 10, P < 0.048; I. deltoidea: t = -4.45, df = 9, P < 0.002; S. exorrhiza: no statistical test needed for obvious difference between treatments, n = 10 depots; Fig 2A, 2B and 2C)
There was no evidence of infestation by Coccotrypes beetles or other seed-boring insects in any of the hoarded or non-hoarded D. panamensis fruits (Fig 2D)

Summary

Introduction

Seed predation by animals negatively affects plant populations by limiting plant propagation and may influence forest community structure and plant distributions [1,2,3,4]. In neotropical rain forests, many beetles in the family Bruchidae and subfamily Scolytinae attack and kill large seeds, contributing to high levels of seed mortality [5,6,7,8]. Neotropical rodents (e.g., agoutis, squirrels, rats) and ungulates (e.g., peccaries, tapirs) consume, and may potentially disperse, a variety of large seeds [9,10,11]. Seed predators negatively affect plant recruitment via seed consumption and destruction, mammals can positively affect seed survival and propagation by dispersing seeds away from source plants (e.g., [12,13,14]). Dispersal away from the parent plant may increase the likelihood of a seed escaping predation [15,16,17,18] and may enhance germination success if a seed is deposited in a favorable microhabitat and subsequently abandoned by the disperser [17, 19, 20]

Methods

Results

Conclusion