Eastern Range Extensions of Western Fauna on Xeric Limestone Prairies

I wrote an article a few years ago about roadrunners (Geococcyx californiannus). (See: https://markgelbart.wordpress.com/2016/08/05/pleistocene-roadrunners-geococcyx-californianus/ ) I noticed roadrunners ranged into Arkansas–a curious eastern range extension–and I wondered why.  A few weeks ago, a scientist sent me a box of science books, and I found the answer to my question in 1 of them.  Xeric limestone prairies in Arkansas and Missouri provide excellent habitat for 3 species of western fauna including roadrunners, collared lizards (Crotophytus collaris), and Texas brown tarantulas (Aphonopelm hentzi).  Xeric limestone prairies are openings in woodlands that are created naturally but may be maintained with or without human influence.  Dry shallow soils, not more than 3 feet deep, on a bed of limestone or dolomite, favor the growth of grass over trees. Little bluestem grass dominates xeric limestone prairies, but Indian grass, side oats gramma, and big bluestem also grow on them with the summer annual grass, poverty dropseed, on areas with even shallower soils.  Grazing and fire help maintain these openings, but the dry shallow soils high in calcium can remain open without these influences.  Nevertheless, in the absence of fire or grazing woody encroachment can occur.  Juniper, blackjack oak, and black hickory may invade some xeric limestone prairies.

 Xeric Limestone Prairie in West Virginia.

Roadrunners primarily are a western species, but they have an eastern range extension into Arkansas because they like limestone prairies.

Texas brown tarantulas also range into limestone prairies in Arkansas.

Dry limestone prairies provide habitat for an eastern range extension of the collared lizard.

Reptiles like to sun themselves on the limestone rocks scattered throughout these prairies, and this attracts roadrunners that prefer open areas with lots of the insects, reptiles, and rodents they prey upon.  Collared lizards are 1 of the reptiles that like to sun themselves on rocks, and they may become prey for roadrunners,  but they are also predators that hunt insects and other lizards in this habitat..  Collared lizards are cannibalistic.  Texas brown tarantulas, yet another western species extending their range east on limestone prairies, are large spiders reaching 6 inches in length with a 4 inch leg span.  They can weigh as much as a McDonald’s quarter-pounder.  Their venom is not harmful to humans unless the person is allergic.  But their fangs are large and can cause a painful bite that may get infected.

Other species of animals common on xeric limestone prairies in Arkansas include 6-lined race runners, southern coal skinks, fence lizards, slimy salamanders, leopard frogs, box turtles, Bachman’s sparrows, field sparrows, prairie warblers, cerulean warblers, Kentucky warblers, painted buntings, brown thrashers, hawk wasps, and numerous species of grasshoppers.

Xeric limestone prairies are not confined to Arkansas and Missouri but are also found in parts of West Virginia, Alabama, Tennessee, Georgia, Indiana, Illinois, Ohio, and Pennsylvania.  However, limestone prairies in those states don’t host as many species of western fauna as those in Arkansas and Missouri.  The Mississippi River must be too big an hurdle for them.

Reference:

Cartwright, Jennifer and William Wolfe

“Insular Ecosystems of the Southeastern United States: A Regional Synthesis of Support Biodiversity Conservation in a Changing Climate”

U.S. Geological Survey Professional Paper 1828 2016