Female ligers and tigrons are often fertile, this after a few million years of evolution. The horse-donkey split is of comparable age. Clearly then, 100,000 years isn't long enough to make full speciation particularly plausible.
The chlorine worlds would be universally corrosive to oxygen breathing life, and vice versa (in the absence of oxygen there would be much more use of nitrogen compounds, which are often unstable against water) but the precursors wouldn't be settling humans on those worlds, only on the planets with a near compatable sugar/protein/DNA based biosphere.
The stars move, of course, affecting the jump points. The precursors are recent enough that this doesn't matter, but during earlier periods of stellar travel the sun's neighbours will have been different. Empires from those periods will have become disconnected, with isolated remants in the solar neighbourhood.
Some of these empires probably also transferred interesting lifeforms to new planets, the same as the precursors - a dozen worlds may have terran grasses - but because of stellar motion the transfers will look near. Two planets a hundred light years apart may both have true cats, and none of the worlds in between.
The chlorine worlds would be universally corrosive to oxygen breathing life, and vice versa (in the absence of oxygen there would be much more use of nitrogen compounds, which are often unstable against water) but the precursors wouldn't be settling humans on those worlds, only on the planets with a near compatable sugar/protein/DNA based biosphere.
The stars move, of course, affecting the jump points. The precursors are recent enough that this doesn't matter, but during earlier periods of stellar travel the sun's neighbours will have been different. Empires from those periods will have become disconnected, with isolated remants in the solar neighbourhood.
Some of these empires probably also transferred interesting lifeforms to new planets, the same as the precursors - a dozen worlds may have terran grasses - but because of stellar motion the transfers will look near. Two planets a hundred light years apart may both have true cats, and none of the worlds in between.