BIOCHEMICAL GENETICS OF MOSQUITOFISH. IV. CHANGES OF ALLELE FREQUENCIES THROUGH TIME AND SPACE.

Area of Science:

• Ecology
• Population Genetics
• Evolutionary Biology

Background:

• Understanding population genetic structure is crucial for conservation and evolutionary studies.
• Gambusia affinis (mosquitofish) is a widely distributed species often used as a model organism.

Purpose of the Study:

• To investigate temporal and spatial patterns in the population genetic structure of Gambusia affinis.
• To assess genetic variation across different scales within the Savannah River drainage.

Main Methods:

• Analysis of gene frequency data from 76 localities of Gambusia affinis.
• Sampling across multiple years (1971, 1977, 1979) in the Par Pond system.
• Calculation of genetic differentiation (FST) and gene diversity (GST), and spatial autocorrelation analysis.

Main Results:

• Allelic frequencies were generally stable over time, except in areas with thermal effluent.
• Significant spatial genetic subdivision was observed at both microgeographic and regional scales (mean FST = 0.051 within Par Pond, 0.196 across drainage).
• Most genetic diversity was found within populations, with low between-habitat diversity, suggesting limited role of differential selection.

Conclusions:

• Gambusia affinis populations in the Savannah River drainage exhibit significant spatial structuring.
• Genetic and geographic distances showed a general lack of concordance, with some exceptions.
• Spatial autocorrelation supported an isolation-by-distance model, indicating limited gene flow among proximate populations.