Thesis Title

Using Mitochondrial Cytochrome C Oxidase Subunit I Sequence To Resolve The Springsnail Species Complex: Pyrgulopsis Micrococcus

Date of Graduation

Summer 2001


Master of Science in Biology



Committee Chair

Hsiu-ping Liu

Subject Categories



The freshwater springsnail genus Pyrgulopsis (Hydrobiidae: Nymphophilnae) is the largest genus of freshwater mollusks in North America, with over 130 extant species currently recognized. Most species are locally endemic, occurring in a single drainage, a few however, occur in multiple drainages. Pyrgulopsis micrococcus, a widespread species found in three distinct river systems, displays morphological and ecological variation. To evaluate if P. micrococcus is a single species, or a species complex a 621 base pair fragment of the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene was sequenced from 1-6 individuals from thirteen populations, in three river systems in the Death Valley region. Outgroups included regional congeners P. amargosae, P. guilani, P. neritella, P. owensensis, P. turbatrix, P. wongi, and used P. stearnsiana to root the tree. Intra-population sequence divergence was low, between 0-0.8%. Inter-population sequence divergence ranged from 0-12.2%. Maximum-parsimony and maximum likelihood analyses produced trees with similar topology, with five clades of P. micrococcus being consistently resolved. These clades were more closely related to outgroup species (3.2-10.3%), than to other clades of P. micrococcus (3.4-12.2%), suggesting the presence of multiple species of polyphyletic origin. At least five species were identified using mtCOI, and four populations were identified as at least evolutionary significant units.


© Shannon Jennings