Orthalicus Reses - Taxonomy

Taxonomy

Orthalicus reses is a species within the genus Orthalicus, a group of large, arboreal pulmonate snails in the family Orthalicidae. The genus Orthalicus occurs primarily in Central and South America. Two species occur in North America, Orthalicus reses and Orthalicus floridensis Pilsbry, both of which are restricted to South Florida. The Stock Island tree snail (Orthalicus reses) was first described by Thomas Say in 1830, based on a snail which was probably collected in Key West. That specimen was lost, and the species was later redescribed by Henry Augustus Pilsbry in 1946 using a snail collected from Stock Island.

Orthalicus reses has two subspecies:

• Orthalicus reses reses (Say, 1830) - Stock Island tree snail
• Orthalicus reses nesodryas Pilsbry, 1946 - Florida Keys treesnail

It is generally thought that the two subspecies of Orthalicus reses do not interbreed due to anatomical incompatibility. However, Emmel and Perry (2004) recommended that if the two Orthalicus reses subspecies prove to be as genetically invariant as was observed in their study, the groups should be considered a single taxon or taxonomic unit. In that case, the nominate form, Orthalicus reses reses, would prevail, and Orthalicus reses nesodryas would be demoted to a synonym instead of a valid subspecies. Emmel and Perry (2004) however asserted that the taxa “should continue to be considered as independent units for management purposes”.