Macroecological questions. What patterns exist, and how are they determined by environment vs. history? How are ecosystems structured, and how is this structure shaped by evolution? What is the relationship between structure and function? What are the robustness and resilience properties of ecosystems and how are they shaped by evolution?

HOT features of ecosystems Organisms are constantly challenged by environmental uncertainties, And have evolved a diversity of mechanisms to minimize the consequences by exploiting the regularities in the uncertainty. The resulting specialization, modularity, structure, and redundancy leads to high densities and high throughputs, But increased sensitivity to novel perturbations not included in evolutionary history. Robust, yet fragile! Complex engineering systems are similar.

Uncertainty and Robustness Complexity Interconnection/ Feedback Dynamics Hierarchical/ Multiscale Heterogeneous Nonlinearity

Uncertainty and Robustness Complexity Interconnection/ Feedback Dynamics Hierarchical/ Multiscale Heterogeneous Nonlinearity

HomogeneousHeterogeneous Tight Loose coupling Ideal gas Internet Post office Turbulent Shear flows Power grid Organisms Ecosystems Telephone system Socio- economic systems

Internet Organisms Ecosystems HomogeneousHeterogeneous Tight Loose coupling Ideal gas Post office Turbulent Shear flows HOT Telephone system Power grid Socio- economic systems

Internet Organisms Ecosystems HomogeneousHeterogeneous Tight Loose coupling Ideal gas Post office Turbulent Shear flows Complexity Telephone system Power grid Socio- economic systems

Internet Organisms Ecosystems Ideal gas Post office Turbulent Shear flows Socio- economic systems Complexity Telephone system Power grid

Internet Organisms Ecosystems Ideal gas Turbulent Shear flows “Complexity” Telephone system All None design Phase transitions HOT

1dimension  All None design Control Theory Statistical Physics Dynamical Systems Information Theory Computational Complexity Theory of Complex systems?

Universal network behavior? demand throughput Congestion induced “phase transition.” Similar for: Power grid? Freeway traffic? Gene regulation? Ecosystems? Finance?

random networks log(thru-put) log(demand) Networks Making a “random network:” Remove protocols –No IP routing –No TCP congestion control Broadcast everything  Many orders of magnitude slower Broadcast Network

Networks random networks real networks HOT log(thru-put) log(demand) Broadcast Network

random designed HOT Yield, flow, … Densities, pressure,… The yield/density curve predicted using random ensembles is way off. Similar for: Power grid Freeway traffic Gene regulation Ecosystems Finance?

HOT Turbulence Log(flow) log(pressure drop) random pipes streamlined pipes

Ecosystems? random food webs real food webs HOT “through- put?” “density?”

random food webs real food webs HOT “throughput?” reproduction carbon biomass “density?” Genes Cells Neurons Organisms May: generic complexity destabilizes models but ecosystems are not random collections of organisms

HOT features of ecosystems Organisms are constantly challenged by environmental uncertainties, And have evolved a diversity of mechanisms to minimize the consequences by exploiting the regularities in the uncertainty. The resulting specialization, modularity, structure, and redundancy leads to high densities and high throughputs, But increased sensitivity to novel perturbations not included in evolutionary history. Robust, yet fragile!

Ecosystems and extinction 99.9% of all species which have ever existed are now extinct Extinction events have heavy tails. 5 major extinction events and numerous smaller ones. Currently in the sixth major extinction with the rate increasing orders of magnitude in the last 10,000 years. Observations

Ecosystems and extinction There is an ongoing debate about the cause of these extinctions. Biologists generally agree that they are due to catastrophic external events – meteor impacts –large scale geophysical phenomena. Advocates of SOC/EOC argue instead that they are due to SOC/EOC “co-evolutionary biological phenomena.” But while extinctions may be triggered by exogenous events, the distribution of extinctions for a given disturbance is a fairly structured, deterministic, and even predictable process.

Habitats terrestrial vs. marine island vs. continental tropical vs nontropical greater extinction vulnerability

Specialization Within a habitat, specialization offers short-term benefits. Evolution necessarily ignores events that don’t actually happen, even if they are catastrophic. (So do we.) Thus tails may be extra heavy. Specialization consistently correlates with extinction risk in large extinctions. For example, body size increases over time on average (both within and across species).

Specialization Large body size has been a risk factor in all major extinctions (although not always in marine animals). However, in the smaller late Eocene extinctions, large- bodied mammal species were not selected against. This highlights the role of external causes and the highly structured form of the response, because... The late Eocene extinctions were generally related to global cooling, which tends to favor large body size.

HOT Disturbance Evolution and extinction Specialization “density?” “through- put?”

Ecosystems and extinction There is an ongoing debate about the cause of the large extinctions that are known from the fossil record. Biologists generally agree that they are due to catastrophic external events – meteor impacts –large scale geophysical phenomena. Advocates of SOC/EOC argue instead that they are due to SOC/EOC “co-evolutionary biological phenomena.” But while extinctions may be triggered by exogenous events, the distribution of extinctions for a given disturbance is a fairly structured, deterministic, and even predictable process.

SOC/EOC HOT What’s at stake? If ecosystems are: EOC/SOC: Specie extinction, global warming, etc. are random fluctuations. Not to worry, nothing to do. Details don’t matter. HOT: Robust, but fragile. Details do matter.