Producers, grazers, and the shape of a food web

Five ways to make a living

Every organism, real or speculative, solves the same basic problem: where does my energy come from? Ecology sorts the answers into a handful of roles, and SpecEvo uses five:

• Producers make their own food from sunlight or chemistry: plants, algae, and the chemosynthetic mats around deep-sea vents. They are the base everything else rests on.
• Herbivores eat producers, mowing algae, grazing plankton, cropping plants.
• Carnivores eat other animals. The hunters.
• Decomposers eat the dead, recycling detritus back into the system. The cleanup crew, without which everything would bury itself in its own waste.
• Generalists eat a bit of everything, the opportunists that hedge their bets.

These roles are not fixed for a lineage forever. Under the right pressure a generalist can drift toward pure hunting, or a grazer can be pushed to scavenge. But at any moment, every creature has one.

Where you live decides who you meet

A role is only half the story. A carnivore on the seabed floor and a swimmer in the open water above never interact, however hungry. So SpecEvo also places every species in a zone, a broad slice of the world: aerial, canopy, surface, underground, shallows, open water, and the floor or depths. Most worlds use only a few of them.

A frozen ocean moon, for example, has life clinging to the under-ice ceiling, drifting in the open water, and crowded around the seabed vents far below: three separate communities that rarely mix. Two species only count as neighbours if they share a zone.

How roles and zones build a web

Put roles and zones together and a food web falls out on its own. Within a single zone, a carnivore preys on the herbivores and generalists smaller than it. Two herbivores compete for the same producers. A producer feeds the herbivores and, when it dies, the decomposers. Remove the producers and the whole column starves; remove the top carnivore and its prey runs rampant. These are the relationships that drive the most interesting evolution: the arms races, and the scramble for unclaimed niches.

In SpecEvo

Diet type and zone are not just labels. They are the structured facts the engine reads to decide who your creature actually evolves against. When you found a species you choose both, and from then on every evolution adapts to the real neighbours they create. For how that plays out in practice, see your creatures evolve against their neighbours.