Hydrobiid snails, or hydrobiids, are the largest group of freshwater molluscs, which includes clams and mussels. Hundreds of species of hydrobiids are found in North and South America, Europe, and Africa. Hydrobiids are beautiful little creatures with shell lengths of less than a quarter of an inch, and with a closeup camera lens can be highly photogenic. They serve as food for many other animals in the freshwater springs or streams where they occur. In Australia, they are often the most abundant organism present.
Phylogeny refers to the evolutionary relationships among a group of plants or animals.
The phylogeny of interest in this case is the snail family tree. Biogeography is a determination to help explain why a certain group of organisms is distributed around the world in a certain pattern. For one thing, because of their abundance, they serve as the food base for many fish and other aquatic organisms. For another, they are confined to restricted areas, often small springs or streams. Their limited distribution makes them highly vulnerable to extinction from human activities that alter habitat, water supply, or water quality.