Milksnake taxonomy

One great thing about science is that as knowledge is gained, it is put to good use to improve science.  Discoveries are made and older understandings are fine-tuned, or corrected, or completely overhauled.  Science makes progress (which is a statement that can be read in at least two ways — can you see them both?).

One challenging thing about these progressive practices is that it makes taxonomy a bit harder to keep up with.  Taxonomy is the classification of living things into, well, taxa: species, genera, and so on in larger and more encompassing groups.  And herp taxonomy has been changing in the last few decades, to some degree because of techniques for classifying animals based on their genetic relationships.  This leads to a reorganization of how we understand which animal belongs to which species, and how those species are related to others.

One recent-ish (2013) major taxonomic revision took place in milksnakes.  There had been one species of milksnake — Lampropeltis triangulum — that contained two dozen subspecies:

abnorma, amaura, andesiana, annulata, arcifera, blanchardi, campbelli, celaenops, conanti, dixoni, gaigae, gentilis, hondurensis, micropholis, multistrata, nelsoni, oligozona, polyzona, sinaloae, stuarti, smithi, syspila, taylori, and triangulum.

Many of these are common in captive collections: L. t. campbelli -- the Pueblan Milksnake; L.t. hondurensis -- the Honduran Milksnake.  Others are not: L.t. smithi, for example.

But as of 2013, there are six species of milksnakes (though be sure to hang on until the end for another interesting twist, since in one sense milksnakes no longer exist at all).  

Lampropeltis abnorma is the species that contains the former L.t. abnorma (Guatemalan Milksnake), L. t. blanchardi (Blanchard’s Milksnake), L.t. hondurensis (Honduran), L.t. oligozona (Pacific American), and L.t. stuarti (Stuart’s).

Lampropeltis annulata contains all the L.t. annulata (Mexican Milksnake) that are not from central Texas, as well as L.t. dixoni (Dixon’s Milksnake).

Lampropeltis gentilis took on many former subspecies: those L.t. amaura (Louisiana Milksnake) from western Texas, southeastern Oklahoma, Louisiana west of the Mississippi River, and southern Arkansas; those L.t. annulata (Mexican Milksnake) from central Texas; L.t. celaenops (New Mexico Milksnake); L.t. gentilis (Central Plains Milksnake); L.t. multistrata (Pale Milksnake); those L.t. syspila (Red Milksnake) from Nebraska, Kansas, and Oklahoma; L.t. taylori (Utah Milksnake)

Lampropeltis polyzona is now the name of a few former subspecies you might know, and a few you likely don’t: L.t. arcifera (Jalisco Milksnake); L.t. campbelli (Pueblan Milksnake); L.t. conanti (Conant’s Milksnake) in part; L.t. nelsoni (Nelson’s Milksnake); L.t. polyzona (Atlantic Central American Milksnake) in part; L.t. sinaloae (Sinaloan Milksnake); L.t. smithi (Smith’s Milksnake).  

Lampropeltis micropholis is the species name of some of the physically largest of the milksnakes: L.t. andesiana (Andean Milksnake); L.t. gaigeae (Black Milksnake); and L.t. micropholis (Ecuadoran Milksnake).

Lampropeltis triangulum is comprised of those L.t. amaura (Louisiana Milksnake) from northeastern Louisiana (specifically La Salle Parish); those L.t. syspila (Red Milksnake) from Alabama, Indiana, Iowa, Illinois, Kentucky, Missouri, Mississippi, Tennessee, and possibly Arkansas north of the Arkansas River; and L.t. triangulum (Eastern Milksnake).

One interesting observation is that some milksnakes that have been (mostly) kept separate in captive breedings are now the same species: Pueblan and Nelson’s Milksnakes, for example, are now all Lampropeltis polyzona.  I’m not sure we have a common name ready for them.

But that’s OK, since we should continue to keep them separate.  Consider that the snake formerly known as Red Milksnake (L.t. syspila) is now split into two species; if a Red Milksnake from, say, Missouri had been crossed with one from Kansas, the offspring would be hybrids.  The fact that taxonomy is always improving provides a reason to breed locale-specific herps whenever possible, and not just to cross two because (we think) they are the same species.

I mentioned that there would be a twist.  Here it is:

This is a ‘species tree’ that indicates the relations between species.  Look at the middle of the right column: see that L. gentilis and L. annulata derive from a shared point? That means that those two species share a common ancestor with each other — 1.7 million years ago. A little further to the left (back in time), that ancestor shared an earlier ancestor (3 MYA) with L. triangulum.  

The twist is that when we trace back to find the last common ancestor of all the snakes we tend to call ‘Milksnakes’, we find that there are eight species that we usually call ‘Kingsnakes’ attached to the tree”:

L. elapsoides (Scarlet Kingsnake)
L. zonata (California Mountain Kingsnake)
L. knoblochi (Chihuahua Mountain Kingsnake)
L. pyromelana (Arizona Mountain Kingsnake)
L. webbi
L. ruthveni (Ruthven’s Kingsnake)
L. mexicana (Mexican Kingsnake)
L. alterna (Gray Banded Kingsnake)

This means that a group that contains both the Pueblan Milksnake and the Eastern Milksnake also contains the seven kingsnake species listed above.  In scientific terms, milksnakes are “paraphyletic”.   In another way of thinking, milksnakes, like fish, don’t exist.





Ruane, Sara & Bryson Jr, Robert & Pyron, R & Burbrink, Frank. (2013). Coalescent Species Delimitation in Milksnakes (Genus Lampropeltis) and Impacts on Phylogenetic Comparative Analyses. Systematic biology. 63. DOI:10.1093/sysbio/syt099. link to PDF

https://iere.org/do-fish-technically-exist/

https://en.wikipedia.org/wiki/Category:Paraphyletic_groups