Joe Brennan
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biologyjoe87.bsky.social
Joe Brennan
@biologyjoe87.bsky.social
Community ecology & theoretical population biology 🪴🧬 🧮
Ecological & evolutionary mechanisms of coexistence 🤝, community assembly ⬆️ , and community disassembly ⬇️
UC Davis Population Biology PhD Candidate 🐄

https://biologyjoe87.github.io/
@gcbias.bsky.social have you seen them yet?
November 15, 2025 at 9:58 PM
your reign of terror has spread across the entire fifth floor too… truly a horrifying moment when I tried it
November 5, 2025 at 5:35 AM
Excited to hear folks' thoughts! It is a project I have been really excited about and am glad to get out into the world. Please reach out with any questions, ideas, or feedback :D . (9/9)
October 2, 2025 at 6:16 PM
Lastly, we apply it to a model of keystone predation to demonstrate how the loss of a top predator can cause the secondary extinction of a prey species, paying homage to classic experiments of secondary extinction by Dr. Robert Paine. (8/X)
October 2, 2025 at 6:14 PM
We then apply our method to a grassland community with both facilitation and competition. We find several possible secondary extinctions and find that a mix of competition against the secondarily extinct species and facilitation for competitors against the secondarily extinct species. (7/X)
October 2, 2025 at 6:12 PM
We apply this to three different models to show its utility. We use an empirically-derived model from
@nathanjbkraft.bsky.social's lab to identify possible secondary extinctions in a fully competitive, annual plant community and demonstrate how these dynamics arise! (6/X)
October 2, 2025 at 6:06 PM
Once we identify when a secondary extinction occurs, we can understand why by asking (1) why the secondarily extinct species has a negative invasion growth rate at the disassembled community but (2) a positive invasion growth rate in a community containing the primarily extinct species (5/X)
October 2, 2025 at 6:00 PM
We use invasion growth rates to develop the "Community Disassembly Graph". Nodes represent coexisting communities and directed edges represent transitions from one community composition to another due to extinction. We can use this graph to identify possible secondary extinctions. (4/X)
October 2, 2025 at 5:55 PM
We apply recently-developed techniques from dynamical systems theory and modern coexistence theory to identify (1) WHEN and WHY secondary extinctions occur. We demonstrate that invasion growth rates (per capita growth rates of species when rare) can achieve these goals! (3/X)
October 2, 2025 at 5:51 PM
Coexistence outcomes often depend on the complex interplay of species interactions. Consequently in some cases, the extinction of one species can trigger the loss of another, a process known as secondary extinction, as explained by a plaque I came across at the Bronx Zoo. (2/X)
October 2, 2025 at 5:46 PM
COS 035 - COS - Modeling: Communities, Disturbance, Succession 2

Tue, Aug 12
8:00 – 9:30 AM EDT
BCC 344
August 11, 2025 at 1:56 PM