This claims that warmth-adapted beetles stopped living in areas once spruce forests grew in. The phrase "open-ground" makes this tempting, because you might figure that beetles that thrive in open areas couldn't survive under a forest canopy. But the stimulus doesn't tell us what happened to the beetles after spruce forests arrived. All we know is the order in which things showed up in the sediments. What became of the beetles once the forests moved in isn't something the stimulus speaks to.

This gets the timeline backwards. Cold-adapted arctic beetles are found in the oldest sediments, the ones deposited during the coldest part of the period, before any warming began. Spruce pollen, on the other hand, only shows up in the newest sediments, after spruce forests had established themselves. And by the time spruce forests arrived, the arctic beetles had already been replaced by warmth-adapted beetles more than 500 years earlier.

This arguably contradicts the stimulus. We're told that ice masses "yielded to" spruce forests, meaning they retreated. Nothing here suggests ice continued to advance after the ice age ended. The 500-year gap between the two dates isn't evidence of ice advancing; it's evidence that two different indicators of warming (beetles and spruce forests) showed up at different times.

The stimulus says the arctic beetles were "replaced" in that location, not that they went extinct. The arctic beetles could easily have migrated to colder regions farther north that were still within their temperature range. "Replaced" describes what happened in the sediments being studied; it doesn't speak to whether the species survived somewhere else.

Supported by the 500-year gap. The warmth-adapted beetles showed up in an area, and then it took 500+ years for spruce forests to follow them in. The reason offered by (E), that beetles can colonize new terrain faster than soil changes and seed dispersion can establish a forest, fits this timing well. Beetles fly in and settle quickly; forests take centuries to grow. That's what the data supports.

Note that (E) doesn't have to be proven by the stimulus. It just has to be better supported than the other answers. And it is. No other answer fits the 500-year gap as cleanly as this one.