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Greenback Cutthroat Trout Morphology Study

Morphology Study

A Summary and Introduction to the Morphology Study of the Cutthroat Trout Populations in Colorado by Allyn Kratz

Phenotype predicts genotype for lineages of native cutthroat trout in the Southern Rocky Mountains Bestgen, K. R., K. B. Rogers, and R. Granger. 2013.

Greenback-1.1_2Oct15This study was initiated due to the surprising findings in the genetic study – Metcalf 2012 that showed that previous conclusions made about the distribution of the various Subspecies of the Cutthroat Trout. These conclusions were based on the Phenotype displayed in the morphology of the various subspecies and the location as to where the samples were collected. The genetic study and records search showed that Cutthroat trout had been moved around the state to a very great extent to make many of the conclusions drawn from the location of the collected sample suspect.
This study using the distribution information provided by the genetic study compared the morphology, the physical structures, of the various subspecies both within the subspecies and to each other in order to determine ways of differentiating between the subspecies.

The Colorado River cutthroat

The Colorado River cutthroat

The difficulty of the previous morphology studies was due to the lack of information on the extent the subspecies had been moved around the state. As a result scientist were attempting to find a phenotypic standard to identify a Greenback trout, as example, from a Colorado River Cutthroat Trout when they may have actually collected the “Greenback” samples from a stream on the Eastern Slope that had been stocked with Colorado River Cutthroat 75 years ago.

rio-grande-cutthroat

Rio-grande-cutthroat

This study was able to find phenotypic structures within the subspecies consistent with the genotype. The authors of this study were not comfortable concluding that the “Green” trout is a new subspecies and recommended addition samples collected and tested with additional genetics tests as well as morphology studies. Said samples should be collected from greater distances in an attempt to insure that the “Green” trout is indeed separate from the Colorado River Cutthroat Trout.
Link to the full study.