Hey, new paper by @cleggtom.bsky.social and me is just out in @pnas.org. This combines a lot of things that start with B: Biodiversity, Bipartite Networks, Bifurcations, Bacteria, ... www.pnas.org/doi/10.1073/... And yes, I know, Fig 1 looks like one of 'those' papers but please read on ... - ThreadSky

thilogross.bsky.social • 21 days ago

Hey, new paper by @cleggtom.bsky.social and me is just out in @pnas.org. This combines a lot of things that start with B: Biodiversity, Bipartite Networks, Bifurcations, Bacteria, ...

https://www.pnas.org/doi/10.1073/pnas.2425603122

And yes, I know, Fig 1 looks like one of 'those' papers but please read on ...

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thilogross.bsky.social•21 days ago

So this is about about crossfeeding, that is the exchange of molecules between bacteria. Think of this as a network where each node is a species of bacteria or a type of metabolite. Directed links indicate which metabolites are required by, or produced by the bacteria. ...

thilogross.bsky.social•21 days ago

So this becomes a directed bipartitie network, but if you want you can also think of it as a multilayer net or hypergraph.

What fascinates me is the algebraic structure: Bacteria in the system need ALL their requirements to be met, whereas metabolites need ONE of their producers to be present...

thilogross.bsky.social•21 days ago

So this becomes a percolation problem. The whole setup is captured by two nice eqs. Here c* is num of bacteria chance m^* is num of metabolites, and C, M, are the GFs for number of requirements, number of producers per metabolite ...

thilogross.bsky.social•21 days ago

For reasonable choices of parameters this system exhibits tipping points between a low and high diversity state ...

thilogross.bsky.social•21 days ago

Of course this is the classic two-folds scenario of tipping, so when we vary a second parameter (e.g. mean number of producers per metabolite), we find a nice Cusp bifurcation. This shows that the transition from high diversity to low diversity can occur by tipping/gradually depending on params...

thilogross.bsky.social•21 days ago

Why is this interesting: First, it shows why diversity tends to collapse in small samples. By missing some of the producers of metabolites we can cross the tipping point. In the equations we can model this effect of sampling as an attack on the network: We replace M(x)->M(A(x)).

bastikusch.bsky.social•21 days ago

Awesome! Will add to my train reading list!

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