The curious case of the variable kingsnake

Background Information Variable Kingsnakes (Lampropeltis mexicana) live in the northern segments of the Sierra Madre Oriental, mostly in the Mexican states of Nuevo Leon and Tamaulipas although they are found also in extreme eastern Coahuila. These snakes are found on both the western (drier) and eastern (wetter) sides of the Sierra Madre. See the next 2 slides if you are unfamiliar with the geography of Mexico. Find the area we’re talking about.

Color Schemes For reasons that we can only hypothesize about, Variable Kingsnakes are found in 3 main color phases – leonis, tricolor, and black. Within those main color phases, there are even more variations in background color (from white to orange to gray to brown) and band count (the number of black or reddish bars on the body of the snake. The next 3 slides will show you examples of the color phases.

Leonis Phase Note the narrow bands with the lighter background color.

Tricolor Phase Note the bands of red, black, tan or more equal width than in the leonis phase animals.

Black Phase In this phase the pattern underneath, which can be leonis or tricolor phase, is covered up by the black coloration.

> > The Genetics of it all Scientists aren’t sure about the exact genetics of the Variable Kingsnake and why they have so many varieties, but we know that leonis phase dominates tricolor phase and tricolor phase dominates black phase. It is NOT incomplete dominance. > >

So why all the colors The leonis phase lives mostly on the western (drier) side of the Sierra Madre. It shares its habitat with the mottled rock rattlesnake, and perhaps is a successful mimic of the rattlesnake. These snakes are nocturnal, and orange looks dark at night.

So why all the colors The tricolor phase lives on the easter (wetter) side of the Sierra Madre. It shares its habitat with the coral snake, and may be a successful coral snake mimic.

So why all the colors No one knows what purpose the black coloration serves. One hypothesis is that these populations live at higher altitudes where temperatures are colder and the dark coloration soaks up more of the sun’s heat.

So now you should be ready to do the worksheet about the curious case of the variable kingsnake. Remember that this is to help you practice your genetics work for your quiz next class