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Population Genetics of Cerion incanum in the Florida Keys Open Access

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Cerion is a genus of terrestrial snails. They are endemic to islands of the tropical Western Atlantic region, ranging from the Florida Keys in the north to the Dutch West Indies in the south. There are around 600 species that have been identified thus far, all based on morphological characteristics. Cerion incanum (Leidy, 1851), the species endemic to the Florida Keys, is the subject of this study. Not only are the patterns of dispersal and the distribution of genetic variations of interest, but also the special case of hybrids found at one of the collection sites. Hybrid specimens were found on the southeastern coast of Bahia Honda Key, the descendants of the deliberate introduction of the Bahamian species, Cerion casablancae Bartsch, 1920, by Paul Bartsch in the early 20th century (Bartsch, 1920). The purpose of this study was to analyze the genetic variation among and within populations of C. incanum occurring throughout the Keys and determine if it is correlated to the geological history of the Florida Keys Formations. To do this, two mitochondrial genes, the protein-coding Cytochrome c oxidase subunit 1 (CO1) gene and the ribosomal 16S rDNA were utilized. Being mitochondrial genes, both have a high rate of mutation. COI in particular has an even higher relative rate of mutation, being a protein-coding gene. It is a useful tool to differentiate between closely related individuals who have undergone recent genetic changes. Due to geological processes by which the Florida Keys were formed, it is expected that the Key Biscayne (KB) populations are the oldest, and include the oldest genotype. As the archipelago that is the Florida Keys was formed during the Pleistocene by extension from the northeast (KB) to the southwest (KW), the range of Cerion incanum expanded in a southwesterly direction, population the new islands as they were formed. The genetic relatedness among the populations of the various keys is expected to reflect this linear pattern.

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