Finding the nectar robbers....

Robbers, larcenists, illegitimate visitors, parasites, exploiters… all these terms are used for animals which sometimes display a particular behaviour: they open and use a hole in the flowers to get to the nectar within. Far from being a rare event, nectar robbing is a common behaviour in several animal groups (including insects, birds and mammals) and it has been recorded in many angiosperms. However, not all nectariferous plants in a certain locality suffer similar frequency of robbing, and also animals that commonly behave as nectar robbers in some plants usually pay ‘legitimate’ visits to the flowers of other species. Therefore, it is likely that some traits of plants and animals are responsible for triggering this behaviour. To answer this question we study the frequency of nectar robbing in plants of temperate and tropical regions and examine its association with plant traits.

This study brought up new and interesting points about the global distribution of nectar robbing and its ecological implications. We found that nectar robbing was present at all sampling sites regardless of the biogeographical region, altitude and sampling effort. This reveals that nectar robbing is not only taxonomically and geographically widespread, but that it probably occurs in all plant communities containing nectariferous plants with morphological restrictions for illegitimate visitors. These limitations will be overcome by those animals with the behavioral and physical capacity to rob.Nectar robbing is more frequent in species having long corollas, abundant nectar production and an energy offer densely distributed. On the contrary, a high aggregation of flowers within plants and the presence of long calyxes and bracts are associated to low robbing rates by insects and to a lesser extent by birds.

Consequently, besides the morphological constraints that operate on a single flower basis, nectar robbing is a phenomenon dependent upon the density of energy rewards reflecting implications at higher ecological scales.

This paper is a part of our work devoted to disentangle the complexity of plants-pollinators-larcenists interactions. We also aim to understand the consequences for nectar robbed plants. Initially it was thought that the effect of nectar robbing would be negative for the fitness of plants. However, we now know that this is not always the case. We are currently working in this line of evidence. You can see, if interested, the progress of our work in this video that we made using 3D animation techniques:

https://www.youtube.com/watch?v=YnZjvr9m2qU.