Goals and Objectives:

The objective of the project is to document genetic diversity, population structure, the extent of gene flow, and historical connections between populations of the Iowa Pleistocene Snail (Discus maccklintocki).

Progress:

Due to issues with the quality of the DNA obtainable from the FTA cards we were not able to use the microsatellites that were developed to survey the populations of D. macclintocki. We instead used three different genes (one mitochondrial, and two nuclear) to assess genetic variation across populations.

Conclusions and Recommendations:

Phylogenetic analysis of each of the three gene portions (not shown) all indicate that D. macclintocki is a monophyletic group and distinct from other species of Discus. Results of the analysis of haplotypes revealed 44 different haplotypes distributed across the 17 IPS sites sampled. Only one of these haplotypes was widespread and was sampled from 12 different sites. Three other haplotypes were shared between two different sites, and the remaining 41 haplotypes were unique and were recovered from a single site only. The relative few shared haplotypes and the large number of unshared haplotypes is consistent with an absence of gene flow between many of the sites.  The few shared haplotypes are possibly indicative of past connections between sites, when the environment was cooler and D. macclintocki was more widespread. This interpretation is supported by the large number of inferred nucleotide substitutions between clusters of haplotypes which indicates the divergence between these clusters is most likely quite ancient. Taken together, these results indicate that IPS sites do appear to represent distinct populations of snails. The conservation implications of these results are that sites occupied by snails should be managed as distinct entities even if these sites reside with the same algific slope. The genetic divergence between the southern and northern sites implies that additional efforts should be made to preserve these more southern sites as they represent genetically distinctive lineages of D. macclintocki. Similarly, IPS 30 appears to represent a phylogenetically distinct lineage of D. macclintocki despite its proximity to other sites and should be protected as an evolutionarily distinct entity.

Funding Organization: Iowa Department of Natural Resources (IDNR)

Duration: 09/30/2012 to 09/15/2016

Principal Investigator(s): Dr. Kevin Roe