Variation in ant-mediated seed dispersal along elevation gradients.

Israel Del Toro,Relena R Ribbons

doi:10.7717/peerj.6686

Abstract

Ant-mediated seed dispersal, also known as myrmecochory, is a widespread and important mutualism that structures both plant and ant communities. However, the extent to which ant functional types (e.g., granivorous generalists vs. myrmecochorous ants) across environmental gradients affect seed removal rates is not fully understood. We used a replicated, standardized seed removal experiment along elevation gradients in four mountain ranges in the southwestern United States to test predictions that: (1) seed removal rates would be greater at lower elevations, and (2) seed species identity influences seed removal rates (i.e., seeds from their native elevation range would be removed at higher rates than seeds outside of their native elevation range). Both predictions were supported. Seed removal rates were ∼25% higher at lower elevation sites than at higher elevation sites. The low elevation Datura and high elevation Iris were removed at higher rates in their respective native ranges. We attribute observed differences in dispersal rates to changes in ant community composition, functional diversity, and abundance. We also suggest that temperature variation along the elevation gradient may explain these differences in seed removal rates.

Highlights

Myrmecochory—ant-mediated seed dispersal—is an ecologically important and ubiquitous mutualistic interaction that exists between ants and plants (Ness & Bressmer, 2005), occurring in over 11,000 species, and across 70 plant families (Lengyel et al, 2010)
Consistent with our first prediction, seed removal rates were higher at low elevations (1,600 and 2,200 m; Fig. 1)
Datura seed removal was highest at the low elevation sites, with no differences between the mid and high elevation sites

Summary

Introduction

Myrmecochory—ant-mediated seed dispersal—is an ecologically important and ubiquitous mutualistic interaction that exists between ants and plants (Ness & Bressmer, 2005), occurring in over 11,000 species, and across 70 plant families (Lengyel et al, 2010). Ants influence the dispersal capacity of a seed by making seeds unavailable to other potential seed predators (Leal, Leal & Andersen, 2015) and disperse non-elaiosome bearing seeds through seed harvesting or granivory (Christianini et al, 2007; Taber, 1999). In both cases antmediated seed dispersal plays a key role in shaping vegetation community structure (Del Toro, Ribbons & Pelini, 2012; Ghobadi et al, 2015), as ants may serve as seed dispersers or predators depending on the context.

Methods

Results

Discussion

Conclusion