Missouri's Icy Past

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Published on: Dec. 2, 2001

Last revision: Nov. 10, 2010

from a soap-like substance in its roots. Only one kind of insect, the yucca moth, can pollinate yucca flowers. Once the yucca moth provides this service, it lays its eggs in a seed case, providing a ready food source for its larvae. Some of the seeds survive to produce the next generation of plants.

Skeleton weed, also found here, has tiny leaves, giving it a bare, almost skeleton-like appearance. The plant has numerous small, roundish growths on its stem. These galls-sometimes mistaken for fruits-are formed when a small wasp or fly lays its eggs on the plant's stem. These and other plants more typically found on the Great Plains give Missouri's loess hill prairies their unique character.

Glacial Effects in the Ozarks

Evidence of glacial effects in the Ozarks is more subtle. Glaciers never extended as far south as the Missouri Ozarks, but they did affect this region indirectly. The Ozarks climate was colder and moister during glacial events, providing hospitable conditions for plants and animals that moved in from areas farther north and northeast. Some of these plants and animals survive today in caves, springs and other isolated damp, cool areas.

After glaciers retreated, conditions became warmer and drier. However, cool, wet conditions still occur on some north-facing bluffs, in springs and in bog-like areas, called fens. These sites provide relatively small, secluded places that moderated the more extreme conditions in surrounding areas.

Northern wildlife species, such as wood frogs and four-toed salamanders, survive in these isolated places, providing living evidence that glaciers widely influenced Missouri's natural history. Biologists call these species, "glacial relicts," but they are part of the modern day mosaic of Ozarks life. Four-toed salamanders live along spring-fed creeks in scattered sites in southeastern Missouri. Predators grasping this salamander by its tail may not get a full meal. The appendage easily breaks off next to its body, giving the animal a chance to escape.

Wood frogs favor cool, north-facing wooded hillsides. Males call between early February and late March, depending on weather conditions. They have a short breeding period, and their calling occurs only at select breeding ponds and lasts only a few nights. In his book, "The Amphibians and Reptiles of Missouri," Tom Johnson describes their call as being similar to the quacking of a duck. This sound may be overpowered by choruses of spring peepers calling at the same time.

Northern bedstraw, harebell and northern white violet are plants found only on moist, shaded ledges and in crevices along narrow ravines and streams.

Snake-mouth orchid, green twayblade orchid, queen of the prairie and marsh bellflower survive in fens. Here, groundwater seeping from underlying bedrock into overlying soils provides the cool, moist conditions that have allowed these plants to survive over centuries.

The northern brook lamprey, channel darter and mottled sculpin are fish species which live mainly north and northeast of Missouri, but have outlying populations in Ozark streams. In his book, "The Fishes of Missouri," Bill Pflieger reported that all three species are thought to have survived in the Ozarks as glacial relicts.

Relict insect species in the Ozarks include two species of stonefly and at least two kinds of caddis flies living in the cool waters of large Ozark springs.

Glaciation had a lasting effect on Missouri. Look around at the relict species of animals and plants living in the Ozarks. Marvel at the boulders and pebbles carried into the northern part of the state from distant landscapes. They, along with the loess hills and the dramatically altered courses of river channels in northwest Missouri, are all links to an icy past.

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