Does evolution predict more or fewer species?

[Nars_Glinley]

Does the theory of evolution lead to the conclusion that in the future, there will be more species than we currently have or less? Assuming that survival of the fittest is accurate, would we expect to see species that are more adapted to a smaller area or would we expect to see more “super-species” (and therefore fewer overall species) that have adapted to be dominant over a larger area?

I hope that makes sense. I’ll try to explain more if necessary.

[Telemark]

It depends.

To some degree speciation reflects changes in the environment and isolation of populations. If there are opportunities for species to develop they are likely to find ways to exploit the niche. If the environment is stable and uniform, you are more likely to get a few stable species.

[JasonFin]

Evolution has had enough time in which to act that we would expect the number of species to be in equilibrium over the long run. This doesn’t mean that various environmental or historical factors don’t cause the number of living species to fluctuate, but on average these should cancel out.

[Colibri]

Actually, biodiversity has increased enormously over time.

From here

Diversification and extinction in the history of life.

Benton MJ.

Department of Geology, University of Bristol, United Kingdom.

Analysis of the fossil record of microbes, algae, fungi, protists, plants, and animals shows that the diversity of both marine and continental life increased exponentially since the end of the Precambrian. This diversification was interrupted by mass extinctions, the largest of which occurred in the Early Cambrian, Late Ordovician, Late Devonian, Late Permian, Early Triassic, Late Triassic, and end-Cretaceous. Most of these extinctions were experienced by both marine and continental organisms. As for the periodicity of mass extinctions, no support was found: Seven mass extinction peaks in the last 250 million years are spaced 20 to 60 million years apart.

[Little_Nemo]

If evolution were the only factor at work, we would expect the number of species to grow. One species can split apart into two different species but two different species can never join together and become one.

[David_Simmons]

@Little Nemo

If evolution were the only factor at work, we would expect the number of species to grow. One species can split apart into two different species but two different species can never join together and become one.

Right. I think the theory would predict that species will occupy every environmental niche that will support live. And it looks like that is what happens.

[Little_Nemo]

The reason I specified “if evolution were the only factor at work” is because the total number of species is declining, albeit for reasons unrelated to evolution. But if that caveat wasn’t made, some evolution denier would turn this around and say, “evolution predicts the number of species will increase, but the number of species is declining, so that’s proof evolution isn’t true.”

[Colibri]

It might be pointed out that speciation is a positive feedback process for further speciation. It’s not just that species are adapting and specializing to new niches in the physical environment, but that species are adapting to each other. If an Amazonian tree speciates (forms one or more daughter species from an ancestral stock) then it’s possible that many of its original herbivores, pollinators, parasites, and commensals may speciate as well as they adapt to the new species. Also, as one species specilizes on a particular resource, it may force other species to specialize on other resources because they can no longer compete for the first resource.