The Delray Beach, Florida, colony of Cerion (Paracerion) tridentatum costellata Pilsbry, 1946 (Gastropoda: Pulmonata: Cerionidae): Evidence for indirect Cuban origins
A large colony of Cerion has recently been reported from Delray Beach, Florida, far north from the ranges of both native and introduced species of Cerion. Specimens correspond morphologically to the type series of Cerion (Paracerion) tridentatum costellata Pilsbry, 1946, which no longer survives at its type locality (Fort Jefferson, Garden Key, Dry Tortugas, Florida.) Historical data indicate that this taxon is a hybrid of two or more of the five Cuban species of Cerion introduced to Fort Jefferson by Bartsch in June, 1924. Museum records document that a propagule of this hybrid taxon was transplanted to Boynton Beach in the late 1940s and proliferated to give rise to the Delray Beach colony. Partial cytochrome c oxidase I sequences reveal the Delray colony to be monophyletic, and of exclusively Cuban ancestry. Limited sampling confirms the presence of mitochondrial genes from two (C. tridentatum and C. sculptum marielinum) of the five Cerion taxa introduced to Fort Jefferson in 1924. A larger sample size, together with data from nuclear genes, will be needed to rule out the presence of rare alleles from other taxa. Transplantation of this newly formed hybrid propagule to an area distant from either parent population has allowed it to evolve in isolation and provides a unique opportunity to study the origins and persistence of genetic diversity within the genus Cerion.
