One method of figuring out when prehistoric events occurred relies on modern DNA evidence. The idea is to find a stretch of DNA that can act as a molecular “clock.” This type of DNA works a bit like a timer: every mutation, or change in the DNA, represents a certain amount of time. So if every mutation represents one million years, a lineage with six mutations in that stretch of DNA would be six million years old.
Chelsea studied the DNA of different Costaceae lineages to figure out about how many mutations each had accumulated and used molecular clocks to figure out how old the lineages were. Then she calculated the rate of speciation for those lineages. She found that lineages that evolved specialized pollination syndromes had higher speciation rates than generalist lineages. The evidence supported Chelsea’s hypothesis: lineages that evolved specialized pollination syndromes do seem to have experienced a surge of speciation events. So, are “jacks-of-all-trades” better off if they specialize? Well, in this group of plants (and in terms of speciation rates), the answer seems to be “yes.”
Find out more about molecular clocks.
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