Cool things you didn't know - 3 - Temperatures affect dragonfly wings

Whitetail dragonflies.  Center:  female.  Corners:  male.  (right one isn't my photo).

Whitetail dragonflies are fairly common, one of the most ubiquitous in North America.  They live in all Canadian provinces and all US states in North America.  Their range is reduced in arid climates but they are still present where freshwater bodies exist.  As you can imagine, the variation in habitats over that range would likely affect the insect's phenotype (outward genetic expression).  One of the big drivers of adaptation and selection is temperature.

As you can see from the above image, male and female whitetailed dragonflies do not look the same; mature adult males have a pronounced white abdomen (juvenile adult males do not) while females have white markings on theirs.  Another difference is in the wings, where the males' are relatively shorter, requiring more effort but also allowing greater manoeuvrability.  This comes in handy when they are defending their claimed territory from other dragonflies that encroach upon it.  But it doesn't stop there.

Males have darker and larger bands on their wings.  The darkness of these bands varies geographically, as hotter climates create genomes producing lighter bands.  It seems that the males, who expend a great deal of energy defending territory, have a greater need to expel heat.  The darker bands make this more difficult in hot environments.  It seems that adaptation and selection have caused whitetailed males in these areas to have lighter "dark" bands.

Keeping in mind that dragonflies do not cross the country and therefore mix genes with other populations, it is likely that population differences will arise over time.  Studies have shown that there is about a 2% variation in the genetics across the continent and results in subtle changes in wing and body colour.  Local environmental factors no doubt play a role in this.

Thanks for reading.

Eric Svendsen     www.ericspix.com