Flat Tree Oyster
Isognomon alatus (Gmelin, 1791)
Family Isognomonidae (Tree Oysters or Toothed Oysters)
Isognomon alatus, also called the Mangrove Oyster, forms large compact colonies or "oyster bars" on dock pilings and cement seawalls in the Florida Keys (here on a PVC piling at Ramrod Key). The extreme flatness of the isognomonid shell valves has been interpreted as an adaptation that minimizes resistance to strong water flow. The family Isognomonidae is known since the Permian Period, is represented by 2 living genera and ca. 20 species, distributed worldwide in shallow subtropical and tropical seas, from shallow to abyssal depths. Isognomon alatus is eaten in Jamaica as a substitute for the dwindling populations of harvestable oysters (Ostreidae). Isognomonids are often called “tooth pearl shells” because of their prominent multivincular ligaments and nacreous interior shell surfaces.
Evolution on the Half Shell...
The Assembling the Tree of Life: Bivalvia project (BivAToL) is a part of the Assembling the Tree of Life initiative, a large research effort sponsored by the National Science Foundation. Its goal is to reconstruct the evolutionary origins of all living things.
Jetsam & Flotsam
Some of the BivATOL team met in early May at the Mote Marine Laboratory’s Tropical Research Station at Summerland Key, FL for a combined collecting trip and coding workshop. Both activities are essential to our project’s goal of determining the phylogenetic relationships among the bivalve families.
After collection, many of the species’ visible and molecular characteristics must be compared and “coded,” after which the phylogenetic computer analyses will be run to produce the final “tree” from which a hypothesis of relationships can be made. Below is an example of a portion of such a phylogenetic tree. Families that are on nearby branches are more closely related to each other than those further away.