Single Type of Organism In Isolated Eco system 'Very Very Rare'?

I'm perplexed by a couple of comments released alongside a recently published (and reasonably reputable looking) paper here. (Comments and feedback most welcomed).

Microbes living in a toxic volcanic lake could hold clues to life on Mars:

(The perplexing comment is emboldened below).

Quote:

Researchers at the University of Colorado Boulder have discovered microbes living in a toxic volcanic lake that may rank as one of the harshest environments on Earth. Their findings, published recently online, could guide scientists looking for signs of ancient life on Mars. ... To search for living organisms in this "fringe" environment, the researchers scanned samples of lake water for DNA. In research published this month in Astrobiology, they found the signature of one species of bacteria belonging to the genus Acidiphilium—a group of microbes that scientists have previously seen in toxic drainage from coal mines and other harsh locations. "It's not uncommon to find an environment with no life, say in a volcano that's self-sterilizing," Hynek said. "But to find a single type of organism and not a whole community of organisms is very, very rare in nature." If life did evolve on Mars, Hynek said, it would likely have survived in ways similar to the lake's bacterium—by processing the energy from iron- or sulfur-bearing minerals. Hynek has spent much of his career searching for places on Earth today that look like Mars did nearly four billion years ago, when liquid water was plentiful on the surface. It's a hard task: Rampant volcanism during that period created volatile and mineral-rich pools of water, giving rise to "Yellowstones all over Mars," Hynek said. In 2020, NASA is planning to send the Mars 2020 Rover to the Red Planet to hunt for fossil evidence of life. Hynek said that they should look first at these "Yellowstones."

All interesting stuff, however the section I've emboldened above, I think, is a very interesting and a very unexpected comment to come from a research scientist(?)

Firstly, in a relatively thermodynamically (and chemically) isolated, resource constrained eco-system, surely the organism type most suited to that environment, will outcompete all others .. so finding a single niche filling species should come as no real surprise at all?

Secondly, finding an environment on Earth with 'no life' whatsoever, and claiming that's 'not uncommon', is also difficult to accept at face value?

via International Skeptics Forum https://ift.tt/2FCJKOj