Geographic variation in Chromosome III inversion types of Drosophila pseudoobscura

Standard (ST) is most common at sea level on the West Coast, and declines inland. Arrowhead (AR) is common in inland populations, which tend to be at higher altitudes. Pike's Peak (PP) is common in desert environments. Chiricahua (CH) is uncommon in the US Southwest, but is the most frequent type on the Mexican plateau (not shown).