Since brown widows are a relatively young species and their

Since brown widows are a relatively young species and their dispersal is expected to be fairly recent (in evolutionary terms) – which segment of their mitochondrial DNA should we be looking at - a gene that is critical for aerobic respiration - or some intergenic region that probably codes for nothing critical or indeed - nothing at all ( i.e. so called non-coding DNA)?

Solution

The answer is - gene in mitochondrial DNA which is critical for aerobic respiration (mitochondrial cytochrome oxidase subunit I)

Reason - DNA sequencing of the mitochondrial cytochrome oxidase subunit I gene of the brown widow show minimum genetic divergence. Hence, this fact supports that the brown widow is a relatively young species.