I live in southern Ohio, an area referred to geologically as unglaciated, meaning that the ice sheets from the last ice age did not reach here. I am a bit of a reptile buff. In reading I have done about the distribution of reptiles in Ohio, I frequently run into range discussions that mention species that are found in the glaciated area and not the unglaciated, or vice versa. I am simplistically dividing Ohio in glaciated and unglaciated regions, but it’s a little more complicated than that.
Thinking about those glaciers led me to the following thoughts. If most of Ohio was covered by ice during the last ice age, then reptiles, amphibians and insects must have been entirely absent. The unglaciated areas would probably have been too cold for exothermic species to survive as well.
So my questions. When did the glaciation that covered most of Ohio end? I have done a bit of internet reading and have not seen a firm answer on this question. Maybe a firm answer is not possible. Whenever it may have been, does that mean that all of the species of insects, reptiles and amphibians found in Ohio now migrated here since then?
Per this site, the last retreat of glaciers from Ohio started about 18,000 years ago, and they had retreated to the north of Lake Erie by about 14,000 years ago.
Pretty much all of the exothermic species now found in Ohio would have moved into the area after the glaciers were gone and the non-glaciated areas had warmed up enough so they could survive. However, note that some cold-blooded creatures can survive fairly close to glaciers if the summers are long enough…
Thanks, Colibri. One species that interests me in light of your answer is the spotted turtle, which is found only in the glaciated part of the state. It’s basically a coastal plain species south of the Potomac River, but ranges from New England all across southern New York and all of Pennsylvania over to northern Indiana and southern Michigan. It’s a pretty weird distribution, especially given that the species is not generally found in river habitats, but prefers ponds and bogs.
Your link leads to this thread. I know that you answered my timing question, but I suspect that you did not intend for your post to be your cite.
That suggests to me that it might have colonized the Great Lakes area via the large postglacial melt lakes that formed sin the area. Also, areas with glacial pothole lakes might be particularly suited to it.
I think that due to the relatively brief time period involved, what we are looking at in the previously glaciated areas is reoccupation, not speciation. So the northern part of the range of the spotted turtle makes sense if the lakes were a vector for colonization, even if they are not found in the current lakes. Here is a range map for the spotted turtle. This one shows a gap in Pennsylvania in the mountains. The one in my phone app did not.
I meant different species as in the habitats are more suitable for different species rather than different species evolving. As they reoccupied the area they found the niches that best fit them.
I grew up in South Dakota on the Missouri River. Dad had land on both sides. East River had glaciers and the terrain and soil are different . The wildlife is different with whitetail deer, badgers, gophers, and ducks & geese in the sloughs. West River had no glaciers and it has antelope, grouse, prarrie dogs, and rattle snakes with few natural lakes or sloughs. A little further south, some of the East River land didn’t have glaciers and is more similiar to West River.
