Time for a brief aside from my reports on nereid plants. A discussion on Sigmund Nastrazzurro's Furaha website has touched on the idea of exactly how many species is sufficient for a "complete" speculative world; it's a difficult number to pinpoint because it depends on so many different factors, not the least of which being the amount of work a speculator is willing to put into the project. I thought I'd put together a blog explaining some of the creative process I go through early in my speculations and how I decide how many species to put in an ecosystem. Some other factors I could think of include:
- Diversity of the planet: How many different biomes of the planet do you want to explore/detail? Generally speaking, a planet that supports life as we know it will have several biomes, but if you're only interested in one or two you can largely ignore the others.
- Size of the biome: How much area does the biome cover? Obviously a water world will have many more aquatic creatures than land-based, and a biome that occurs in only a small corner of the world will not have room for much diversity.
- Biodiversity of the biome: How varied is life in each biome? You typically find more species in a tropical biome than you will in a desert. I chose to reflect this difference in my Nereus project, and you may wish to do so as well.
- The complexity of the food web: Who eats whom? When you're doing an overview of the biome's ecosystem you want to reflect the different trophic levels: producers, eaten by herbivores, eaten by carnivores. Obviously the process isn't always that cut and dried (both carnivores and omnivores can occupy several levels within the food web), but those three levels make for a good starting point.
For my own project I chose a rather large number of species (200 in total) because, in addition to well rounded ecologies, I wanted to show cladistic diversity and evolutionary radiation. That's a lot species for a project, of course, but if you want to do a project that's "complete" you could go through the following steps:
- Each ecology should include one apex predator, which means that a pyramid of species would sit underneath it in the food web. With two "lesser" predators underneath, and at least one herbivore for each predator you have six species of animals (if desired, you could throw in three or four plant species for good measure.
-Say there are three biomes you want to highlight. In order to reflect differing biodiversity of the largest one you could double the amount of species present and divide them up into groups of, say, six herbivores, three predators that consist of both carnivores and omnivores, two predators that prey on those species and an apex predator that pretty much eats what it wants. Or you could divide the biome species into two distinct ecosystems of six (for north and south continents, perhaps) and build them independently. Either way you're reflecting the broader biodiversity of the planet.
- In total, with three biomes (one of them twice the size of the other two) you've got 24 species to think up, and nine to twelve more if you add some plant species. If 36 seems like too much for your purposes you can always adjust your numbers accordingly. Perhaps highlighting only one herbivore, two carnivores, and a major plant for each biome will be enough, totalling to twelve species for the entire project. Of course there are more species on the planet than this, but you're not trying to show it all.
Well that's what I have to say on the matter; in the end it turned out to be longer than I expected and I'm glad I didn't post such a huge thing in Furaha's guestbook. If you think there's anything to add or a creative approach that serves you better let me know!