Based on their hypothetical origin in lava tubes, what characteristics of hypothetical Martian lava tube microbes can we reasonably extrapolate? Could we theorize how different microbe species might interact with one another?
It's really hard to answer this with any kind of real credibility, as we haven't actually detected any life on Mars, but... The most significant obstacle to life on Mars is the UV radiation on the surface due to the lack of atmosphere, and to a lesser extent magnetic field.
There have been a number of studies that look in to this. These will be protected from the harsh radiation that would kill most life that we know of on the surface. These look primarily at cold lava tubes on Earth and theorize how that would affect things on Mars.
On Earth, life in cold lava tubes is primarily found on ice. One interesting thing is that life has thrived in these locations without access to sugars, and instead has relied on Iron for energy, which of course is commonly found on Mars.
Bottom line, the most likely characteristics would be pockets concentrated around ice and some minerals that are commonly found on Mars and have some energy content.