Food Webs
30 Ontological Micro-Realms · Interconnected Chains, Connectance, Trophic Interactions & Web Stability
The 30 Ontological Nodes of Realm 20
Ultra-Crisp 2-to-5-Word Architectural Portals
Food Web Concept
- Charles Elton 1927 Food-Cycle
- Interlocking trophic network
- Realistic multi-prey architecture
- Replaces isolated linear-chains
Interconnected Food Chains
- Anastomosing trophic pathways
- Polyphagous consumers cross-link-chains
- Multiple energy avenues
- Prevents single-point failure
Nodes & Directed Links
- Nodes (S): trophic species
- Lumped identical-prey/predator guilds
- Links (L): feeding arrows
- Directed graph (digraph) math
Basal, Intermediate & Top
- Basal (B): zero prey
- Intermediate (I): prey-and-predators
- Top (T): zero predators
- Scale-invariant B:I:T proportions
Paine's Three Web Types
- Robert Paine 1980-classification
- 1. Connectedness topological web
- 2. Energy-flow bioenergetic web
- 3. Functional interaction web
1. Connectedness Web
- Binary presence-absence links
- All arrows weighted-equally
- Maps complete diet-breadth
- Overemphasizes rare-meals
2. Energy-Flow Web
- Quantifies kcal/m²/yr flux
- Arrow thickness equals-volume
- Highlights dominant biomass-conduits
- May miss low-biomass-keystones
3. Functional Web
- Revealed by removal-experiments
- Measures per-capita interaction-strength
- Identifies critical keystone-nodes
- True community regulation-map
Terrestrial Food Web
- Grass-shrub-tree producer base
- Insects rodents rabbits-deer
- Spiders frogs lizards-snakes
- Hawks foxes tigers-top
Marine Food Web
- High size-structured omnivory
- Pelagic plankton-fish-cetacean web
- Benthic filter-detritus web
- Coupled by vertical-migrators
Green & Brown Webs
- Green: living plant-based-web
- Brown: soil detritus-based-web
- Root-Craswell multichannel coupling
- Asynchronous energy stabilization
Parasites in Food Webs
- Kevin Lafferty 2006-discovery
- Parasites comprise >50%-links
- Predator-eat-parasite concomitant predation
- Doubles food-web connectance
Food-Web Complexity
- Species richness (S)
- Linkage density (L/S)
- Directed connectance (C)
- Mean chain length
Linkage Density (L/S)
- Average links per-species
- Measures dietary generalization
- Briand-Cohen constant-scaling debate
- Increases in rich-webs
Directed Connectance (C)
- Realized vs possible-links
- Or C = L / [S(S-1)/2]
- Typical empirical C ≈ 0.10–0.15
- Tracks network saturation
Small-World Topology
- Two-degrees of separation
- Short path-length between-nodes
- Highly connected hub-species
- Rapid perturbation propagation
Four Core Sub-Web Motifs
- 1. Tri-trophic linear chain
- 2. Omnivory (IGP) triangle
- 3. Apparent competition V-motif
- 4. Exploitative competition Λ-motif
Direct vs Indirect Effects
- Direct: pairwise A→B-contact
- Indirect: mediated via-third-species
- Enemy of my-enemy-is-friend
- Often outweigh direct-effects
DMII vs TMII (Fear)
- Density-Mediated (DMII): lethal-killing
- Trait-Mediated (TMII): behavioral-fear
- Wolves scare elk-from-willows
- Non-consumptive predator effect
Keystone & Apparent Modules
- Diamond keystone-predation module
- Predator targets dominant-competitor
- Frees subordinate prey-species
- Sustains basal diversity
Wasp-Waist Control
- Rich base rich-top
- Single mid-trophic bottleneck
- Anchovies sardines or-krill
- Controls predators top-up-and-down
Compartmentalization
- Semi-isolated sub-web modules
- Dense links inside-compartments
- Sparse links between-compartments
- Quarantines disturbance shocks
MacArthur Diversity–Stability
- Robert MacArthur 1955-index
- Shannon-entropy energy pathways
- Alternative prey buffers-crashes
- Tropical vs Arctic-stability
May's Complexity Paradox
- Robert May 1972-theorem
- Random complex webs-unstable
- High S-C-i triggers-collapse
- Real webs non-random!
Weak-Link Stabilization
- Kevin McCann 1998-solution
- Skewed toward weak-interactions
- Dampens strong consumer-oscillations
- Resolves May's paradox
Allometric Mass Ratios
- Ulrich Brose 2006-discovery
- Predators 10–100x larger-than-prey
- Slower predator metabolic-rates
- Stabilizes multi-trophic webs
Prey Switching (Type III)
- Holling Type-III S-curve
- Predators target abundant-prey
- Spare rare declining-prey
- Density-dependent prey refuge
Network Robustness (R50)
- Jennifer Dunne robustness-metric
- Resilient to random-loss
- Fragile to hub-removal
- Secondary extinction avalanches
Web Simplification & Unraveling
- Apex truncation and-overfishing
- Invasive species rewiring
- Homogenized agro-monoculture webs
- Loss of portfolio-buffering
Food-Web Synthesis
- Master blueprint of-coexistence
- Integrates GFC DFC-PFC
- Complexity with weak-link-order
- Bridge to Realm-21
Core Ontological Distinctions
1. Connectedness vs. Energy-Flow vs. Functional Food Webs (Paine, 1980)A Connectedness (Topological) Web shows all feeding links equally, regardless of how much is eaten. An Energy-Flow Web weights links by the quantity of energy/carbon transferred ($kcal/m^2/yr$). A Functional Web weights links by their dynamic importance to community stability (revealed by removal experiments)—showing that a low-energy link (like a keystone predator) can be the most functionally decisive link in the entire web.
2. Linkage Density ($L/S$) vs. Directed Connectance ($L/S^2$)Linkage Density ($d = L / S$) is the average number of feeding links per species. Directed Connectance ($C = L / S^2$) is the fraction of all possible feeding links in a network of $S$ species that are actually realized.
3. Elton–MacArthur Stability vs. May's Paradox & McCann's ResolutionElton & MacArthur observed that complex natural food webs are more stable than simple Arctic/agricultural chains because predators can switch prey. Robert May (1972) proved mathematically that randomly assembled complex webs become unstable when $i\sqrt{SC} > 1$. McCann et al. (1998) resolved the paradox by showing that real food webs are not random: they are packed with weak interactions, compartmentalized modules, and allometric body-size ratios that dampen wild oscillations.
Realm 20 Complete
All 30 nodes of **Realm 20: Food Webs** (`20.01` to `20.30`) are forged. Next in the **World B** sequence is **Realm 21: Ecological Productivity** (`[021 / 266]`).