Axial variation in the threespine stickleback: relationship to Hox gene expression

Area of Science:

• Evolutionary developmental biology
• Genetics
• Zoology

Background:

• Developmental regulator genes, like Hox genes, are implicated in macroevolutionary changes.
• Few studies link variation in these genes to population-level phenotypic variation.

Purpose of the Study:

• To investigate the functional significance of Hox gene expression variation in generating population-level differences.
• To compare Hox gene expression domains in two morphologically distinct populations of the threespine stickleback (Gasterosteus aculeatus).

Main Methods:

• Examined and compared expression domains of three Hox gene homeobox sequences in stickleback embryos.
• Analyzed skeletal morphology differences between populations.

Main Results:

• Found within-population variation in anterior expression limits of 5' Hox genes.
• Observed significant differences in skeletal morphology between populations.
• Did not find a correlation between phenotypic variation and Hox gene expression variation.

Conclusions:

• Hox gene expression patterns do not appear to directly account for the observed skeletal differences between stickleback populations.
• The combinatorial Hox code may buffer development in fluctuating environments.
• Population and quantitative genetic perspectives are crucial for understanding Hox gene function and evolution.