| Genetic Diversity of Humpback
Chub (Gila cypha) Within the Colorado River Ecosystem
Project Officer: Dana Winkelman
Project Start Date: 06/19/01
Expected Completion Date: 01/01/05
Introduction:Interrelationships among populations of the endangered Gila cypha are being assessed through analysis of mitochondrial and nuclear DNA. We are evaluating the distinctiveness of mainstem Colorado River (MCR) individuals and their relationship with other chub populations within Grand Canyon (GC). To gain a basin-wide perspective on diversity for this endangered species, five populations from the Upper Colorado River basin will be analyzed. Information derived from this project will be used to make recommendations on how to adaptively manage Gila cypha in the aquatic ecosystem of Grand Canyon.
Objectives: (1) Obtain additional series of spatial and temporal samples by coordinating with Grand Canyon Monitoring and Research Center (CGMRC)-sponsored monitoring and research programs. (2) Assess genetic diversity within groups of G. cypha from selected areas of GC, with particular emphasis on 3-Mile, Little Colorado River (LCR), Shinumo Creek, Middle Granite Gorge, and Western Grand Canyon. (3) Infer interrelationships among individuals of G. cypha within GC. (4) Examine relationships among G. cypha populations in the entire Colorado River basin. (5) Discern if recruitment arises locally or is instead a product of reproduction in the LCR. (6) Delineate conservation units based upon findings. (7) Provide recommendations for adaptive management of G. cypha in GC.
PROGRESS: Sufficient numbers of individuals were obtained during previous years for most populations and no additional samples were collected during 2004. However, samples from the Cataract Canyon population are still not available. DNA extraction has been completed for all available samples to date. Mitochondrial (mt) DNA genes were amplified and sequenced for a subset of samples. Preliminary analyses of mtDNA sequence data were completed. Microsatellite data across 20 loci have been generated for all populations. Intron loci with species-diagonstic differences have been identified, but must now be screened on larger datasets to confirm lack of within-species variation.
RESULTS/PRODUCTS: Preliminary analyses of mitochondrial DNA sequences revealed that the majority of Humpback Chub haplotypes are basin- or population-specific, supporting a hypothesis of reduced gene flow. However, shared ancestral polymorphism also indicates that lineage sorting in these populations is incomplete. More detailed analyses are needed to assess historic and contemporary levels of gene flow. Microsatellite DNA analysis revealed sufficient levels of genetic diversity to address fine-scale questions of gene-flow and population structure. However, microsatellite allele patterns appear to be quite complex and require additional time for accurate scoring. A one-year extension was thus requested. Interim reports were submitted. Manuscripts will be submitted to major journals for peer-review at close of project.