Hierarchical levels of seed predation variation by introduced beetles on an endemic Mediterranean palm.

Marta Rodríguez,José Mª Fedriani,Miguel Delibes,Suzannah Rutherford

doi:10.1371/journal.pone.0109867

Marta Rodríguez, José Mª Fedriani + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0109867

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Abstract

Seed predators can limit plant recruitment and thus profoundly impinge the dynamics of plant populations, especially when diverse seed predators (e.g., native and introduced) attack particular plant populations. Surprisingly, however, we know little concerning the potential hierarchy of spatial scales (e.g., region, population, patch) and coupled ecological correlates governing variation in the overall impact that native and introduced seed predators have on plant populations. We investigated several spatial scales and ecological correlates of pre-dispersal seed predation by invasive borer beetles in Chamaerops humilis (Arecaceae), a charismatic endemic palm of the Mediteranean basin. To this end, we considered 13 palm populations (115 palms) within four geographical regions of the Iberian Peninsula. The observed interregional differences in percentages of seed predation by invasive beetles were not significant likely because of considerable variation among populations within regions. Among population variation in seed predation was largely related to level of human impact. In general, levels of seed predation were several folds higher in human-altered populations than in natural populations. Within populations, seed predation declined significantly with the increase in amount of persisting fruit pulp, which acted as a barrier against seed predators. Our results revealed that a native species (a palm) is affected by the introduction of related species because of the concurrent introduction of seed predators that feed on both the introduced and native palms. We also show how the impact of invasive seed predators on plants can vary across a hierarchy of levels ranging from variation among individuals within local populations to large scale regional divergences.

Highlights

The degradation of ecosystems has altered the strength, pattern, and outcomes of many plant-animal interactions because of modifications such as habitat fragmentation, species introduction, and defaunation [1,2,3]
For example, the dynamics of native plant populations and even communities are altered by the combined impact of native and introduced seed predators limiting plant recruitment [4,5,6]
We know little concerning the potential hierarchy of spatial scales and coupled ecological correlates governing variation in the combined effect of introduced and native seed predators on plant populations

Summary

Introduction

The degradation of ecosystems has altered the strength, pattern, and outcomes of many plant-animal interactions because of modifications such as habitat fragmentation, species introduction, and defaunation [1,2,3]. The only native Arecaceae in continental Europe, the Mediterranean dwarf palm (Chamaerops humilis), often coexists with many ornamental palm species introduced together with their respective seed predators and pests [23,24] especially at the interface between natural and humanaltered habitats ([25], Authors unpublished data). We investigated several levels of spatial variation in the intensity of seed predation by introduced and native beetles on C. humilis seeds across the Mediterranean Spain.

Results

Conclusion