How did researchers determine that there had been a leading edge expansion of black spruce populations after the last ice age?

Researchers determined that there had been a leading edge expansion of black spruce populations after the last ice age. This was possible by studying the level of heterozygosity in the mitochondrial genome and nuclear genome. It was found that the level of mitochondrial genome were much lower that the level of heterozygosity in nuclear genome.

A. southerners underestimated republicans eagerness to end slavery.