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Jeff Arnoldi (CNRS)

February 6 @ 13:00 - 14:00

Title : Linear Functional Ecology – Rethinking species contributions to ecosystem functions

Abstract :

Ecosystem functions describe processes like biomass production, respiration, or nutrient cycling, that can be key to the livelihood of humans and other life forms.
These functions are collectively performed by the many species that constitute an ecosystem; trees is a forest, plants in a grassland, or bacterial strains in a microbiome.
Here, I will use linear algebra to show that generically, there is a sense in which a rare species can have as much importance as an abundant one.
The reason why this claim is not obvious comes from the fact that in functional ecology, under the mass ratio hypothesis, species contributions should be well predicted by their traits and abundance. I will illustrate using soil-microbiome data that this is indeed true, even for complex functions related to nutrient cycling. Yet the mass-ratio hypothesis has an awkward corollary: functions are typically performed by just a few dominant species, so that most of an ecosystem diversity appears useless. This a description of the state of the system, but says nothing of its dynamics. To understand why rare species can be important, one has to take a perturbative approach, looking at the sensitivity of a function to say, added mortality (a pathogen) on a given species. In doing so, we reveal a completely different picture than the one the mass-ratio hypothesis depicts. Via direct and indirect interactions between them, species can have large impacts on a given function, even if those species are rare or if they do not possess traits that relate to the function.

The seminar will take place in Room S08 at the Faculty of Sciences.

Details

Date:
February 6
Time:
13:00 - 14:00
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