Are the Orange Beetles Sexier?

Author: John Monczunski

Maybe it’s that lady Jamaican click beetles see the guy beetles with the orange lights as more their type, or maybe it’s that the bats who dine on them have trouble finding the orange fireflies. Whatever the reason, Notre Dame biologist Jeffrey Feder and graduate students Uwe Stolz and Sebastian Velez have strong genetic evidence that natural selection is occurring in the Jamaican click beetle population. Beetles that glow orange at night appear to be winning over the ones who glow green or yellow-green.

Jamaican click beetles are unique among bioluminescent insects because their light organs vary widely in color from green to yellow-green on the top and yellow-green to orange on the bottom. Because the genetic basis for the color variation is known— it involves certain amino-acid variations in the enzyme luciferase, which is used in the chemical reaction that produces the light —it is possible to reconstruct a relative evolutionary timeline based on where the variation occurs in the sequence of proteins that comprise the gene.

Feder and his graduate students gathered click beetles at three different locations on the island from east to west. Based on their analyses of luciferase sequence variation, they demonstrated an evolutionary trend from green to orange light among the beetles. Genetic evidence suggests that the orange characteristic emerged first in an isolated population of click beetles in eastern Jamaica, where the highest concentration of “orange lights” was observed, and appears to be sweeping westward across the island.