I love you all, but to get back to the original question, please look up the definition of "species" before sharing.
There is only one human species. By definition, that's all there can be. Our nearest past and present relatives, Neanderthal and chimps, are not members of our species, despite the fact that chimps share 99 percent of our DNA.
As far as we can tell in the real world, there is only one human species. Here's something to consider though. Are those advanced scanning device of the 24th century that can so easily differentiate a human from a Vulcan or a Klingon from a Cardassian tell the difference between a native of Beta III and a native of Eminiar VII? That's never specifically stated. In "Caretaker", when the whole crew was on the Array, Kim's tricorder was able to identify "a Vulcan and several humans", although Chakotay's Maquis cell was later established to include at least three Bajorans (one of whom turned out to be a Cardassian) and a Bolian.
I'm not suggesting something similar to the universe of Stargate where a lot of planets they visit are inhabited by "ancient offshoots" of humans courtesy of the Goa'uld. How big a role the Preservers and the ancient humanoids from "The Chase", though, is certainly worthy of speculation.
I address a few of these issues in one of my recent blog postings
, even reemphasizing that while Star Trek was a very low budget series in the 1960's, at least some "in-universe" explanation was provided for the Klingons of that era first hinted at in "Trials and Tribble-ations" and ironed out even more on ST:Enterprise.