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Current research

My current research is about phenology and mutualisms. This started with a previous investigation about the role of temporal overlaps on the structure and dynamics of mutualistic networks.

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Phenological mismatches between resources and consumers

Global warming is causing the phenologies of many species to advance towards earlier dates, but at different rates. Thus, some interactions can weaken and others can intensify. Consumer-resource interactions involve feedbacks that can affect the abundances of the resources (top-down effects) and the consumers (bottom-up effects). I considered these feedbacks in a model where consumers and resources recruit during specific seasons of the year, interact, and produce the propagules (seed and/or eggs) that will recruit in the next year.

[FIG: Phenology]

If consumers recruit too early or too late relative to the resources, sure they will go extinct. If they recruit very close in time with the resources, they avoid extinction, but they will not attain high densities. This is because increased temporal overlap between consumers and resources causes overexploitation and scarcity in future times.

[FIG: Abundance vs mismatch]

Higher consumer abundances occur when recruitment happens few weeks before or after the resource. This result also applies, with appropriate modifications, in community modules of three species. For example, two consumers can coexist with a single common resource if one recruits before, and the other recruits after the resource, but the earliest recruiter becomes more numerous because it can eat during more days. Thus, predictions about future consequences of phenological changes due climate change must consider top-down controls in addition to seasonal availability of food (bottom-up control).

Phenological shifts and habitat destruction in mutualistic networks

Phenology is an important structuring factor of mutualistic networks. There is concern that global climate change will disrupt the temporal schedules of interactions between plants and their pollinators and/or seed dispersers, making ecological communities more vulnerable to other threats, for example habitat destruction or fragmentation. We developed a spatially-explicit meta-community model to explore the effects of habitat destruction and phenological changes on the mutualistic networks.

Habitat destruction causes the gradual erosion of local diversity, leading to global meta-community collapses. Restoration of meta-communities, by recovering destroyed sites back to habitable, can be difficult due to hysteresis.

[FIG: Diversity vs phenological shift and site destruction]

Shifts in phenologies (e.g. 10, 20, 30 days earlier, on average) can weaken mutualistic interactions, enabling meta-community collapses by lower amounts of habitat destruction. We found that the combined effects of phenological shifts and habitat destruction can re-inforce each other synergistically, i.e. their joint detrimental effects are larger than the sum of their effects.

Effects of population structure on mutualisms

In many systems mutualism occur only during very specific life-stages, such as the adult phase of an insect. We developed a plant-pollinator model where the pollinator is divided into adults and larva. By consuming nectar, the adults give pollination services to the plants. Changes in the life-cycle of the insect, caused by climate change or pesticides for example, will alter the balance between servicing adults and useless larvae, affecting the quality of the service for the plants.

This model predicts that large plant abundances are positively related with large adult to larva ratios, and that for plants that strongly depend on pollination services, decreases in adult:larva ratios could lead to a sudden drop in plant abundances.

[FIG: Plant abundance vs adult:larva ratio]

If other life-stages are actually harmful, such as herbivorous larvae, changes in population structure can even change the net sign of the interaction. To demonstrate this, we considered a model where the larvae consume the tissues of the same plant pollinated by the adults. This model can develop oscillations like many predator-prey models. An important detail of these oscillations is that the plant population can cycle above and below its carrying capacity (in some cases entirely above) thanks to the positive effects of pollination. Essentially, the dynamics can display a periodic alternances between antagonism (larvae in control) and mutualism (adults in control).

[FIG: Plant-pollinator oscillations]

Functional and numerical responses in mutualistic interactions

The exchange of resources such as nectar or nutrients, or services such as pollination, requires the existence of structures or organs, such as fruits and flowers. These are usually short lived compared with dynamics of interacting populations. We considered these structures in an interaction model.

[FIG: Flower dynamics and pollination]

Since flowers or fruits are ephemeral, we consider that their numbers attain a steady state very rapidly. This allows a mechanistic derivation of functional and numerical responses in plants and pollinators. For the plants for example, the "handling time" of a plant turns out to be proportional to the amount of time required to produce a new flower.

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Mutualism, competition and adaptation

Predators can promote prey coexistence by preying more on abundant preys and less on rare preys. In contrast, if pollinators tend to pollinate the most common plants, this can make common plants more common and rare plants more rare. I am investigating this kind of mutualistic driven apparent competition using simple community modules, e.g. 2 plants + 2 pollinators.

[FIG: Plant -- Pollinator module]

Using optimal foraging theory, we can understand better how adaptation in pollinators and seed dispersers can affect plant diversity.

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Past research

I investigated topics such as resource competition between juvenile and adult stages and the coexistence and stability conditions under intra-guild predation. During my doctorate I worked on the dynamics of multispecies resource competition. I also did research that concerns human health, like the characterization of the mortality of disease vectors, or the hypothetical use of viruses against other viruses.

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