Coccothrinax argentata (Arecaceae) occurs in southern Florida, both on the mainland and in the islands of the Florida Keys. However, the palms from the mainland and Keys display morphological differences that led taxonomists to recognize them as distinct species in the past. They are now treated as a single, polymorphic species, but the question remains: Are the morphological differences best explained by genetics or environment? In 1999, seedlings grown from seeds collected from different populations were planted in a common garden in a randomized plot design. In 2007, the first research was published comparing genetics based on ISSRs to morphological measurements. The research from 2007 showed evidence for a genetic explanation, but with poor resolution. Here, we present new genetic data using microsatellite regions (SSRs), in combination with morphological data from more mature palms. The results support the recognition of two taxa, which we propose at the rank of subspecies.