Related Experiment Video
Updated: Aug 10, 2026

Automated, Quantitative Cognitive/Behavioral Screening of Mice: For Genetics, Pharmacology, Animal Cognition and Undergraduate Instruction
Published on: February 26, 2014
Calibrating the molecular clock: estimates of ground squirrel divergence made using fossil and geological time
Abstract:
According to 5-Myr-old fossil evidence, ground squirrels within the genus Spermophilus had diverged into subgenera Spermophilus and Otospermophilus by late Miocene times. Radiometric dating has also provided a precise time for the sudden onset of a geological event, occurring 0.725 Myr ago, that initiated the complete and permanent reproductive isolation of two subspecies within the subgenus Otospermophilus. Since these two subspecies (S. beecheyi beecheyi and S. b. douglasii) readily hybridize with each other under laboratory conditions, allopatric subspeciation is unlikely to have occurred prior to 0.725 Myr ago. We employed Nei's model for estimating genetic distance in units which are linear in time, calibrated on the 0.725-Myr-ago date for initiation of S. b. subspeciation, to test its ability to generate a time scale for subgeneric divergence in keeping with the minimum estimate provided by the fossil record. This represents the most valid test to date of the utility of Nei's model for estimating genetic distance in units which are linear in time. Nei's model was found to underestimate this minimum time by 1 Myr, but it approximated this date after correcting values of D for variation in rates of evolution among loci.
More Related Videos
06:50The Use of Mouse Splenocytes to Assess Pathogen-associated Molecular Pattern Influence on Clock Gene Expression
Published on: July 24, 2018
07:59Alignment of Synchronized Time-Series Data Using the Characterizing Loss of Cell Cycle Synchrony Model for Cross-Experiment Comparisons
Published on: June 9, 2023
Related Concept Videos
Speciation Rates
Biological Clocks and Seasonal Responses
What is Evolutionary History?
The Fossil Record
Convergent Evolution
Evolutionary Relationships through Genome Comparisons