1. Max R. Bangs*; Marlis R. Douglas**^; Michael E. Douglas**^
Utilization of Molecular Markers to Examine Potential Hybridization in Bluehead Suckers (Catostomus discobolus) in the Weber River, UT
Max R. Bangs*; Marlis R. Douglas**^; Michael E. Douglas**^
*Graduate Student of the Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701
**Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701
^Illinois Natural History Survey, University of Illinois, Urbana/Champaign, IL 61820
Introduction
Fishes of the desert Southwest face numerous anthropogenic threats including introduction of invasive species, habitat modifications, and recent climate change driven drought. Continuous monitoring of threatened taxa provides important data to develop management plans. However, accurate assessments can be inhibited if species identifications are ambiguous due to hybridization. Level of admixture (e.g., hybridization or introgression) is generally difficult to quantify without employing molecular genetic techniques.
Douglas et al. screened over 1,500 samples of Catostomus spp. throughout the Southwest using 18 microsatellite loci and two mitochondrial genes. Several of these samples were identified as having admixed ancestry, however, whether these hybrids are introgressing or potentially sterile could not be accurately accessed.
We designed a database using three biallelic nuclear loci along with two mitochondrial genes in order to determine if samples identified as putative hybrids were first generation hybrids (a result of two pure parents of different species mating) or introgressed hybrids (a result of a hybrid backcrossing with a parental species).
Here we present a study of how this database can be used on the Bluehead Sucker (Catostomus discobolus) in the Weber River, UT (Bonneville Basin), where the species is of conservation concern and hybridization with Utah Sucker (C. ardens) has been recognized as an issue.
Methods
Samples identified as putative hybrids (n=13) in the Weber River, UT, were screened to determine if introgression is occurring.
PCR Amplification:
- mtDNA ATPase 6 and 8 genes (842 bps)
- three nDNA loci (415, 211, and 323 bps)
Direct Sequencing of PCR Products
Sequences edited (Sequencher v4.1), aligned (BioEdit), and compared to representative samples of several other sucker species that could be the source of introgressed material.
Results
We successfully obtained ~1 kb of nDNA sequence across three loci. Of this, there were 66 polymorphic sites with 46 of these sites being diagnostic between species. (Tables 2, 3 ,and 4)
All individuals were heterospecific across all three loci, indicating first generation crosses.
Coupled with the mtDNA sequence, we were able to characterize the parental species involved as being Utah Sucker female x Bluehead Sucker male 64% of the time and Bluehead Sucker female x Utah Sucker male 36% of the time.
uitfwd.com
Conclusion
Bluehead Sucker and Utah Sucker are hybridizing in the Weber River, UT.
No introgression into either parental species was found, suggesting hybrid sterility.
No parental bias, thus both types of female/male crosses can produce hybrids.
Due to lack of introgression into parental species, management suggestions are for the identification and removal of hybrids.
Table 1: Haplotypes for Utah Sucker (UTS) and Bluehead Sucker (BHS) of the three nuclear loci used. Polymorphic sites are to be read vertically. A (.) represents a match to the top haplotype. Fixed differences between species are shown in red.
UTS 1 G A A T G G T T G G T T A G C T G C T G T A A T
UTS C
BHS 1 A C . C A A . G T C C
BHS 2 A C . C A A A . G T C C
BHS 3 A C . C A A G T C C
UTS A A G G T G G T C G T
UTS A . . .
UTS A .
UTS 4 G
BHS G A T G A A
BHS G A T G A T A
BHS G A T G A . . A . A
UTS 1 G T T G T C C A G T G C C A C T C T G G T T T G T - G
UTS T
UTS G T
UTS T T T G . . .
UTS
BHS 1 T A A A C T T T G C A
BHS 2 T A A A C T T T C A
Future Goals
Determine the range and severity of hybridization between these two species in the Bonneville Basin.
Determine if there is a correlation between environmental factors (e.g. anthropogenic causes) and occurrence of hybridization.
Examine other hybrid events within Catostomus throughout the Southwest.
Figure 1: Putative hybrid of a Bluehead Sucker (C. discobolus) from the Weber River, UT. (Picture curtsey of Paul Thompson)
Goals
Develop a database for screening Catostomus spp. for introgressive hybridization
Determine if Bluehead Sucker x Utah Sucker hybrids are introgressing
Characterize the parental species involved in admixture
Acknowledgements
Numerous agencies contributed field expertise, specimens, technical assistance, collecting permits, funding or comments for the completion of this study. First and foremost, we like thank Paul Thompson, Aaron Webber, Cassie Melon and Krissy Wilson from Utah Department of Natural Resources, who initiated this study. Thanks also goes to their team at UDNR, in particular P. Martin, S. Jones, K. Beidinger, M. Breen, T. Hedrick., S. McKay, and C. Walker. Thanks also go to natural resource agencies in Arizona, Colorado, New Mexico, Utah and Wyoming as well as the National Park Service and U.S. Bureau of Reclamation. We are also in debt to the students, postdoctorals and faculty who contributed to the development of our research: A. Albores, W. Anthonysamy, P. Brunner, T. Dowling, R. Cooper, J. Cotter, M. Davis, E. Fetherman, M. Hopken, M. Kwiatkowski, S. Mussmann, A. Reynolds, J. Reynolds, C. Secor, and P. Unmack. Sampling procedures were approved under IACUC permit R (Arizona State University) and A-01 (Colorado State University). Funding was provided by a grant from UDNR.
Figure 2: Drainage map of Utah. Only major drainages are shown. Circle shows location of Weber River.