Pollinators and plants as ecosystem engineers: post‐dispersal fruits provide new habitats for other organisms

Abstract

Ecosystem engineering consists of a ubiquitous and fundamental class of interactions where some organisms promote state changes in biotic and abiotic materials which indirectly affect others. Since the concept was created as a counterpoint to traditional flux‐based models, pollinators have never been considered to promote ecosystem engineering because they modulate the supply of resources used by seed/fruit consumers. However, dry fruits may persist in the environment for long periods after seed dispersion as empty structures that are an additional alternative for occupancy. These increase the realized niche of some organisms, being a clear example of biogenic habitats. Here, we demonstrate how pollination may boost ecosystem engineering using an illustrative case study based on a specialized interaction between a bee and an orchid with characteristic capsular fruits. We demonstrate that the orchid is fully dependent on the pollinator to set fruits. Post‐dispersal fruits are voluminous and remain attached to the plant for several years. By investigating the occupation patterns of arthropods, we show that post‐dispersal fruits are highly suitable for occupants when compared to pre‐dispersal and dispersing fruits. Only 13.3% of post‐dispersal fruits were never occupied, 33.3% had organisms inside and 53.3% showed signs of previous occupation. We propose that pollinators are allogenic engineers and plants autogenic, since they promote state changes through their actions and their own physical structure, respectively. Thus, pollination is a case of cooperative ecosystem engineering whereby the effects of the interaction between two or more species expand habitat suitability. Since most plants rely on pollination to set fruits, we suggest that pollination‐mediated engineering constitutes a widespread phenomenon. This offers a new perspective about the effects of pollination in nature, highlighting the importance of pollinators and opening new avenues of investigation of ecosystem dynamics and biodiversity maintenance.