The family Atyidae is large and cosmopolitan in distribution, including both surface (epigean) and cave dwelling (stygobytic) forms. The majority of atyid species are epigean and are tropical and sub-tropical in distribution. North America is home to four recognized species of Atyidae:Syncaris pacifica, S. pasadenae, Palaemonias alabamae, and P. ganteri. Historically, only two named species, the Kentucky Cave Shrimp (Palaemonias ganteri) and the Alabama cave shrimp (P. alabamae) were known from the southeastern United States. Recently however, an undescribed third species (Palaemonias sp.) of cave shrimp was discovered from two localities in Alabama. Genetic comparison of this new population to known populations of P. alabamae revealed significant genetic differences and indicate an absence of gene flow between these populations. Similarly, genetic comparisons of specimens of Syncaris pacifica from various drainages revealed the presence of multiple mitochondrial haplotypes.
A recent collaboration with an international group of colleagues resulted in a 2012 publication in Molecular Phylogenetics and Evolution [63: 82–96]. This multi-gene based global phylogenetic hypothesis of the Atyidae revealed some interesting patterns including multiple subterranean invasions and indicated some trans-oceanic dispersal of the ancestors of these freshwater shrimps.