7970

• UCREFRP Catalog Number: 7970
• Author: Dowling, T. E. and W. L. Minckley.
• Title: Genetic Diversity Of Razorback Sucker As Determined By Restriction Endonuclease Analysis Of Mitochondrial DNA.
• USFW Year: 1994.
• USFW - Doc Type: Bureau of Reclamation, # 0-FC-40-09530-004,
• Copyright Material: NO

and among existing populations. Synthesis of information from both data sets will allow
assessment of degree of past isolation among and levels of variation retained by remnant
stocks, information essential for formulation of sound management strategies. It is important
to no*e that this report does not provide such a synthesis, but is limited to evaluation of
razorback suckers using mtDNA data. Thus, we assign no value to specific populations.
Monte Carlo simulations indicated that frequencies of specific haplotypes differed among
samples; however, the proportion of variation differentiating populations (as estimated by 8
and nucleotide divergence) was small, indicating that populations were not divergent.
Phylogenetic and phenetic analysis also indicated a lack of population differentiation, as
indicated by low estimates of sequence divergence among haplotypes and their failure to
cluster as distinct geographic lineages in networks. Taken together, these analyses of mtDNA
restriction site data indicate that existing populations of razorback sucker have been
interconnected by considerable gene flow or have become isolated so recently that mtDNA
differences have yet to accumulate.
While divergence among regions was limited, levels of variation within some
populations were high. The sample from Lake Mohave was especially variable, exhibiting
estimates of h and nh as high as any org;utism examined to date (Avise et al., 1989). Such
high diversity indicates surviving individuals were produced by a large number of females,
likely more than exist in the region today. This high diversity and lack of appreciable
differentiation of existing populations is consistent with considerable interconnection of
regions (including extirpated populations like those from the vast Gila River). Most
razorbacks we examined were old individuals that aze likely remnant offspring of a single,
essentially panmictic population that previously occupied the entire Colorado River basin.
Samples of razorbacks from the Little Colorado River and ponds near Grand Junction are
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