Cryptic speciation in the freshwater invertebrate, Lecane luna, from isolated waters of the Chihuahuan Desert

Rotifers take part in the ecological functions of aquatic habitats and are important indicators of water contamination.  Phylogenetic research of rotifer species can benefit in maintaining the integrity of aquatic habitats.  Rotifer species were once thought to have cosmopolitan distribution.  This is due to their capability of dispersing long distances through diapausing embryos.  In addition, rotifer populations of different geographic regions are indistinguishable morphologically. Using molecular markers, it has been found that many cosmopolitan rotifer species are actually complexes of cryptic species. We investigated whether Lecane luna has shown cryptic speciation in isolated aquatic habitats in the Chihuahuan Desert. DNA was extracted from individuals from eight geographically isolated populations and then the ribosomal internal transcribed spacer (ITS) region and cytochrome c oxidase subunit 1(COI) were sequenced.  Sequences were aligned using ClustalW and input into PAUP* for estimating genetic distances and phylogenetic reconstruction. Using the neighbor-joining algorithm, a distance analysis was done of L. luna from eight sites, including defined outgroups (L. bulla, L. elsa, L. leotina). Sequences for L. elsa and L. leotina were obtained from GenBank.  Each gene/region was analyzed separately.  For ITS, most populations had negligible genetic differentiation; the maximum distance between populations was 1% between the Campagna and Balmo Rhea isolates.  More variation was found among populations using the COI gene. Genetic distances ranged from 6-11% from three isolates while differences from outgroup species ranged from 15-18%.  As of yet, there does not seem to be any clear indication of cryptic speciation among the L. luna populations.