Those who are familiar with how habitats are being altered by human or natural activities also know that usually these alterations tend to be more harmful to some species and less harmful to other ones. As pollinators rely a lot on flower resources (that is pollen and nectar), an habitat alteration could target specific types of plants with some effects on pollinators too. To facilitate our understanding of how pollinators respond to habitat alteration we run an experimental test in which we removed several highly generalist plants from the plant community.
We found that removing these key plants had strong effects on the interactions between plants and pollinators. Earlier on, I presented some of the effects on pollinators (here) including how some insects preferred to go away rather than using local alternative flowers, and those who shifted flowers followed preferential flower types features. However, the pollinator responses also negatively impacted the ways pollinators interact with plants and the rate by which pollinators shifted to new plants. You will find all results at this link, or write me for more details.
Here below a “lay” summary presenting the paper in non-technical way, a requirement from the journal which I am not sure if was used eventually.
Field experiments reveal the alteration of plant and pollinator interactions when the generalist plants are removed
Paolo Biella, University of Milano-Bicocca, and colleagues
Species interact with each other in complex ways. Within these tangled systems, some species cover more prominent roles than others: in the case of plants and pollinators, some plants are highly abundant or provide very attractive floral resources to pollinators and thus they are highly visited. In this study we tested the effects, on pollinator richness and on the species interactions, generated by the experimental removal of these important plants from the system. In particular, we planned to remove 4 plant species from natural communities, one plant species at a time, based on the number of pollinators they had previously received. We discovered some important aspects of how a pollinator guild depends on the scenario set by the plant assemblage. We found that knocking out the most visited plants triggered the disappearance of many pollinators, and that these local extinctions were more in number than what expected from computer-based simulation models. On top of that, we discovered that the framework set by the interacting species changed towards more fragile states when the most visited plants were removed, which contrasts previous expectations that these multi-species systems are stable against species loss. Furthermore, the data showed that novel interactions were established after the important plant were lost. In particular, those generalist pollinators which visited both the plants targeted of removal and the non-target plants tended to establish novel links more often than the other pollinators. Additional interesting results from the experiment regard the emergence of opportunistic interactions established in a random fashion, and structural unpredictability of the network of species interactions when plants were removed. These latter aspects are fundamental because reveal that the framework of interactions set between plants and pollinators changed in their inner dynamics and rules of assembly. Overall, these findings supported the idea that generalist, highly visited, flowers play a key role in sustaining local pollinator guilds, and that otherwise the framework of interactions is perturbed. Nevertheless, our study indicates that some pollinators can find alternative resources by establishing novel links, a reorganizational ability that possibly buffers against even more dramatic effects of generalist plants loss.
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