Southern-Summer School on Mathematical Biology

In nature, ecosystems are full of ecological interactions. The ecological interactions could occur between two or more species and will be an interchange of services or resources between them. The outcome of ecological interactions can be positive, neutral or negative for each of the involved species. The combination of the outcome for each species is how we classify the type of ecological interaction. For instance, mutualism are interactions in which all interacting partners benefit from the interaction like seed dispersal and others. But, when one species benefit, as a predator, and the other species has a loss, as the prey, this is an antagonism.

Pollination is usually considered a mutualistic interaction. The reason is that most plants need to transfer pollen from its own flowers to other's individuals flowers to successfully reproduce, and the animals do this in the pollination process. On the other hand, animals benefit from eating part of the pollen or nectar that they acquire while interacting. In this scenario, both the flower and the pollinator gain from the pollination process. However, relationships can be more complicated; interactions do not happen in isolation. Some animals can cheat, acquiring the resources from flowers by alternative ways. Some bees, for example, are able to cut a hole in the side of the flower large enough to access the nectar (nectar robbers, as shown in the figure).

The presence of nectar robbers in plant-pollinator interactions hamper our understanding of the interaction. Even though robbers will always benefit from the interaction, plants and pollinators could be positively, negatively or remain unaffected by interacting with robbers. Nectar robbers could be costly to plants as they obtain pollen and nectar without providing pollination. Moreover, nectar robbers could damage ovary or other structures of the flowers not allowing reproduction, or could else interact aggressively with the pollinators, startling them, or even make the robbed flowers unattractive to pollinators. However, some studies point out that we may not be catching all plant-pollinator-robber dynamics. Zhang et al (2007) proposed that nectar robbing could indirectly affect plant reproduction, by changing pollinators' behavior or frequency of visitation, bringing even positive consequences for the plants. If the presence of robbed flowers changes pollinators behavior, making pollinators visit more flowers, it could improve pollen flow and out-crossing. Varma & Sino (2019) observed that the behaviour of the pollinator could change because of the presence of cheaters, indicating a higher foraging efficiency of pollinators.

The interplay between distinct interacting partners could elucidate the underlying mechanism that regulates interaction species dynamics. Build a mathematical model with the mechanisms that could modulate plant-pollinator-robber interactions to enables us to deepen our knowledge about the interaction dynamics.

• How could the population proportions of each group (pollinator, plants, robbers) or even the interaction frequencies modulate the persistence and dynamics of the interaction?

• In which scenarios robbers could act as mutualistic or as antagonistic partners to plant-pollinators?

Varma & Sino, 2019. Nectar robbing in bellflower (Sesamum radiatum) benefited pollinators but unaffected maternal function of plant reproduction

Zhang et al 2007. Effects of nectar-robbing on plant reproduction and evolution