Interactions
Gastrocopta tappaniana (C.B. Adams, 1842) and Gastrocopta pentodon (Say, 1822) are two species that have similar morphologies, so much so, that at times it has been hard to distinguish between the two. In 1906, Vanatta and Pilsbry studied these two species and developed 53 drawings of their shells in order to show that there are two distinct species. These drawings showed a very subtle difference between the species but nonetheless, they identified the two as separate species. Debate still exists today over the idea of two species or one.
In a study conducted by Timothy A. Pearce many years later, he examined a sample of specimens collected from the Delmarva Peninsula in eastern United States, near the Atlantic coast. Pearce examined these specimens using morphometric methods to determine if there were two species co-existing in the same area and whether they prefer different moisture levels.
In their results, they concluded that Gastrocopta tappaniana tended to be larger, with a wider shell, wider whorl width, and taller body whorl than G. pentodon. G. tappaniana was found to have seven non-parietal teeth whereas G. pentodon had a varying number of teeth. Also, the majority of G. tappaniana were found in medium or wet areas. Gastrocopta pentodon was found in a variety of moisture ranges, and at times overlapped in habitats where G. tappaniana were found but, were primarily in drier areas. G. pentodon was found widespread throughout the peninsula except for the southeastern coast and barrier islands whereas G. tappaniana was found along the Atlantic in the southeastern coast and near major water bodies.
With these results, Pearce concluded that his observations were similar to the observations made by Vanatta and Pilsbry. Gastrocopta tappaniana and Gastrocopta pentodon were in fact, two distinct species as both species maintained their distinct morphologies in areas where they co-existed.
Information gathered from (Pearce, 2007)
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