Would a dominant species of a planet generally consist of a single species, or multiple species?

Question

I'm working on a planet wherein the dominant species isn't humanoid (in this case, mantids.)

However, I'm unsure as to whether or not it'd make more logical sense for the dominant species to be comprised of a single species of mantis, or multiple species of mantises. Mantises, after all, are an order, not a species. There are thousands of mantis species, and hundreds of genera.

I know that humans are classified as a single species with multiple races/ethnic groups. Would that be how the mantis planet would develop, or would it make more sense for it to be comprised of multiple mantis genera or species?

Answer 1

As you said humans are one species. But we also have the other great apes, Chimpanzees, Gorillas, orangutans, etc. We also have other farther monkey species. Though there were several other homids that got wiped out, such as Neanderthal and Denisova, who died out with some cross breeding. So either they died out or were absorbed depending on interpretation.

So you'd more likely have something like that. species that are 'similar' but not the same. You might even still have some of species that are separate branches, maybe there was enough separation that one didn't dominate and wipe out the others (yet). If each one was locked on a continent, it is possible that there might be multiple species. But you'd have to keep them mostly separate for a long time.

Answer 2

No

A niche is an N-dimensional hypervolume the dimensions are spatial as well as environmental variables and resources. Species compete when they overlap the overlapping hyperspace is ceded to one or the other or divided up. If the niches overlap completely or by too much one of the species goes extinct. (or you get symbiosis)

On Earth there is a kind of old world monkey that is such a generalist that it's niche literally overlaps with that of every bit of macro life on the planet. This could be a special case and on Mantvald the mantids species are all specialists with non-overlapping niches. Some only eat Craykits
others are Vegetarians, fisher-mantids etc. If there is no competition between the species then there is no reason for them to compete with each other.

There is a paradox that emerges that on the individual level a crayket-eater would have less to fear from a fisher-mantid than from his own species as there is no resource to fight over.

If you mantid's niches are non-overlapping there is no reason that there cannot be any number of sentient species especially if sentience is an ancestral trait. I.e. the common ancestor was sentient.

Answer 3

If you looking at a technologically advanced species, one thing you need to consider is the significant difference between the physical evolution and the technological evolution. The differences between these makes it possible that two sapient species could evolve at the same time.

As a species, Homo sapiens came into being 200-500 thousand years ago. This means that if you had a time machine and brought a young child from then to our time, they would be able to fit into modern society¹.

We know that agriculture has been around for at least 10 thousand years. So it took over 90% of our existence as a species so far in order to develop agriculture. Agriculture has allowed us to live in much larger groups. Living in large groups, we have the ability to systematically destroy any threat that consists of only small groups. This is why reaching the milestone of agriculture means dominance over non-agricultural threats.

So now, what about that window of 190 thousand years? What if another species capable of developing technology evolved during that period? It would be a race to develop agriculture, with the winner being the species that developed it first. This means that it is very unlikely that there could be multiple dominant species unless the two species did not have to compete with each other.

Consider the dog. According to the first result of a quick Google search, there are around half a billion dogs in the world. Most people would agree that they are not dominant, but dogs are clearly doing well as a species without any level of technology at all. They were able to attain this status by being capable of things that we can't do and helping us.

Over time, dogs have been bred to emphasize the traits that we find useful. One result of this is that most dogs have been bred to be more obedient. As such, dogs have proliferated by not even trying to be the dominant species anymore.

So what needs to happen to have multiple dominant species? They can't be in competition, or else the first to agriculture will likely wipe out the other. Also, they should be of roughly the same level of intelligence, with other features to distinguish between them. For example, suppose one species is stronger and the other is quicker. This would allow for interesting ways that the two species could work together—predators against which the stronger species has a distinct advantage, and others against which the quicker species has the advantage.

Another possibility is, as others have mentioned, physical separation. Suppose that instead of being different races, Africans and Europeans had been separate species. By the time of the "Age of Discovery", European society had advanced enough to no longer be immediately concerned about survival. The Europeans would likely have still chosen the slave trade over extermination. The slave trade may have lasted longer with the Africans being a different species, but as society continued to progress it would still be eliminated. It still would not have been enough time for intelligence to be bred out of the African species, allowing them to join the European species as dominant.

_{1. Assuming that the child did not have mental disability due to malnutrition during their mother's pregnancy, diseases that we no longer have to worry about, etc.}

Answer 4

Humans have been fighting for resources for 10's of thousands of years. Some homids are known to be lost to history. This fighting is still going on today. However one could easy argue that we are getting more similar as we cross breed. Also our technology is reducing the radical responses to our visual and cultural differences.

So to answer the question ...

If the mantids could not interbreed then over a long time the most adaptable/advanced group of mantids would dominate the most habitable regions of their planet leading to enslavement / extinction of the weaker/less adaptable groups. This may leave mantid groups acting like horses or bullocks or maybe like pets cats dogs?

If however they could interbreed then there would more assimilation's into the most adaptable/advanced/numerable group of mantids leading to that group's dominance.