Rolling in the Isles: Michigan Land Snail Distribution Influenced by Past Glaciers
Featuring Tim Pearce, Carnegie Museum of Natural History
When: Monday, May 12, 2025, 12:00 – 1:00 p.m.
Where: Earth Theater and online via Zoom
Tickets: This lecture is free. Museum admission is not required.
Learn about scientific discoveries directly from the experts in the field. Carnegie Museum of Natural History’s scientific research staff and invited speakers discuss their latest findings on numerous scientific topics at the R.W. Moriarty Science Seminar series.
Click here to register to attend virtually via Zoom. Registration is not necessary to attend in person. Museum admission is not included with the lecture. Visitor Services staff can direct you to Earth Theater on arrival.
Abstract
Does past glacial history influence modern species distributions?
During field work on islands in northern Lake Michigan, Dr. Tim Pearce found that snails were more similar to those in the Upper Peninsula than they were to the nearby adjacent Lower Peninsula. He initially wondered if this pattern could be explained by currently operating ecological principles such as predation or microhabitat. Applying my training in paleontology, he then wondered if past events could have influenced modern distributions.
To study the glacier hypotheses, he compared occurrences of the four largest and best studied land snail species in three areas: the (1) Upper and (2) Lower Peninsulas and (3) the 13 islands adjacent to the Lower Peninsula. This comparison showed that all four species occur only on the Lower Peninsula but two of them occur in all three areas, with minor exceptions.
The two species that occur in all three areas appear to be more cold-adapted. In contrast, the two species restricted to just the Lower Peninsula are consistent with warm-adaptation.
This talk examines whether smaller snails show the same distribution patterns as these larger snails. Are smaller cold-adapted species more ubiquitous while smaller warm-adapted species are more confined to the Lower Peninsula?
The current distributions of land snails are consistent with a glacial history scenario where 11,500 years ago, a glacier covered the area and eliminated the land snails. Then 9,500 years ago, the glacial retreat exposed a land bridge from the mainland to the proto-islands. Then with more climate warming, cold-adapted snails dispersed northwards on the heels of the glacier and crawled to the proto-islands. Subsequent lake level rise isolated the islands from the mainland, so when the warm-adapted snails migrated into the Lower Peninsula, their island vacations were stymied.
About Dr. Pearce
Timothy Pearce is Assistant Curator of Mollusks at Carnegie Museum of Natural History, where he conducts research on land snails and cares for and promotes use of the huge research collection of snails and clams (1.4 million specimens). His MS in snail paleontology and his PhD in snail ecology give him a valuable perspective on how time has affected the makeup of modern snail communities.
Pearce received his PhD (1994) and MS (1991) in biology from the University of Michigan. His post-doctoral work at SUNY–Stony Brook from 1995–1996 focused on Madagascar’s land snails. He received his MA in paleontology from the University of California–Berkeley in 1988 and his BS in marine biology from Evergreen State College in 1979.
Prior to his appointment at Carnegie Museum of Natural History in 2002, he was Assistant Curator of Mollusks at the Delaware Museum of Natural History from 1997–2001.
Pearce’s research focuses on ecology and systematics of mollusks, especially terrestrial snails and slugs in the northeastern United States. He also pursues the biogeography of land snails on islands in the Great Lakes, distribution and ecology of land snails on California islands, and systematics of North American land snails.
Pearce has published more than 55 peer-reviewed scientific papers on mollusks. He has been known to tell snail jokes.
