Genetics
In a recent genetic sequence study of the 16S ribosomal RNA gene, the lacy elimia was found to be very similar to the compact elimia (Elimia showalteri). Despite their apparent close genetic relationship, the authors made no suggestion that the two species represented a single species. Upon review of Lydeard et al. (1997), Dillon suggested that additional genetic studies were needed to demonstrate the genetic uniqueness of the lacy elimia. However, the Lydeard et al. (1997) genetic study addressed only one small genetic character of the genome (entire genetic make-up of an individual) of these species, and other characters strongly support the taxonomic status of the lacy elimia.
The two species are allopatric (do not overlap in distribution - the compact elimia occurs in the Cahaba River, whereas the lacy elimia is found in the Coosa River drainage), and are strikingly different in size, appearance, and behavior. The compact elimia has a large, robust, smooth shell boldly colored brown and/or green, whereas the lacy elimia has a small, delicate, darkly colored, and ornamented shell.
The lacy elimia is one of the few elimia snails in the Basin that does not exhibit clinal variation. In addition, compact elimia are found grazing individually throughout shoal habitats, whereas the lacy elimia is usually found in tight clusters or colonies on larger rocks within a shoal. Allopatry, morphology, and behavior are strong characters supporting the species status of the lacy elimia.
Read more about this topic: Lacy Elimia