Molecular evolution in Drosophila and the higher Diptera II. A time scale for fly evolution

Area of Science:

• Evolutionary biology
• Molecular evolution
• Genomics

Background:

• Assessing the constancy of molecular evolutionary rates is crucial for molecular dating.
• Drosophila larval hemolymph protein (LHP) is a suitable model for studying evolutionary rates due to its presence across diverse species.

Purpose of the Study:

• To investigate the steadiness of the evolutionary rate of LHP in Drosophila species.
• To develop and describe a method for calculating absolute rates of molecular evolution.
• To establish an evolutionary timescale for Diptera.

Main Methods:

• Quantitative microcomplement fixation assay to measure immunological distances.
• Statistical analysis of evolutionary rate variance.
• Calibration of LHP evolutionary rate against known divergence times.

Main Results:

• The evolutionary rate of LHP exhibits significant steadiness, with a variance comparable to or less than radioactive decay processes.
• No evidence of accelerated protein evolution was found in Hawaiian drosophilines.
• The mean evolutionary rate of LHP was calculated as 1.2 immunological distance units per million years, equivalent to a unit evolutionary period of 4 million years.
• This rate is comparable to that of mammalian hemoglobins.

Conclusions:

• The evolutionary rate of LHP is highly uniform across Drosophila species, similar to vertebrate proteins.
• A robust method for calculating absolute molecular evolutionary rates was established and validated.
• The calibrated LHP evolutionary rate provides a reliable timescale for Diptera evolution.