How do mutations affect species diversity?

Mutations increase the amount of diversity within a population/species.

Mutations are the primary source of genetic diversity. By introducing new alleles into the population, the population becomes more heterogeneous.

For example, if you have all white shirts, you have no diversity in the color of your shirts. Then let's say you get a red shirt for your birthday and someone else gives you a blue shirt as a thank you gift. The diversity of your shirts has increased. You can choose whether you want to wear white, blue, or red. This is the same principle with mutations and populations different species.

****Note: if you mean "species diversity," which is defined as the number of species in a region and the abundance of each species, the answers differs.

A species with a higher mutation rate and therefore greater genetic diversity may do better than a species with lower diversity. The more diverse species may out-compete another, lowering the abundance of the second species and lowering the species diversity of the area.

For example, you have a population of turtles with high diversity and a population of birds with low diversity, and both species are hunted by humans. The genetic diversity of the turtles means that they have multiple ways of adapting to hunting, some work and some may not. The birds, with lower diversity, have one strategy to adapt to hunting, and it doesn't work very well.

Over time, the population of birds will drop but the population of turtles may stay the same or even increase, as those with successful adaptations survive and breed and their adaptations are passed on to offspring. The species diversity of the area may decrease because the number of birds dropped. However, species diversity is very complex and we still have much to learn.