Nathan Rank Sonoma State University Local adaptation in montane leaf beetles Geographic variation in enzyme polymorphisms (Page 2 of 4) Introduction & Collaborators Enzyme polymorphisms Environmental Gradients & Stress Proteins Study Objectives Research Home See also research summary. Background Different forms of the enzyme phosphoglucose isomerase are found in beetle populations living in different drainages. Allele 1 predominates in the northern drainage Rock Creek (p = 0.9), and it is the most common allele in Bishop Creek (p = 0.7), but it is relatively rare in Big Pine Creek (p = 0.2). The unusual pattern at PGI succests that natural selection acts on it. In Bishop Creek, allele 1 has increased in frequency since 1988, supporting the hypothesis that PGI is under natural selection. Four of 8 beetles in Big Pine Creek are homozygous for PGI allele 4 and four are heterozygotes with Allele 1. Seven of 11 beetles from Bishop Creek are homozygous for PGI allele 1 and four are heterozygotes with allele 4. All six beetles from Rock Creek are homozygous for PGI allele 1 Variation in PGI-1 frequencies. Because PGI-4 is the only other common allele, it decreases in frequency as PGI-1 increases. For example, in BPC, the frequency of PGI-4 is 0.8, while in RC it is 0.1. Spatial and Temporal PGI variation We collected1600 beetles in 1988 and 1300 beetles in 1996 and screened them at five polymorphic enzymes. PGI-1 predominated in RC, but was rare in BPC. PGI-4 was rare in RC but predominated in BPC. PGI frequencies did not change in BPC and RC during the 8 years between samples. In BC, PGI-1 frequencies increased by 15%. Evidence for selection on PGI in Bishop Creek PGI-1 increased in frequency at all four sites between 1988 and 1996. No other enzyme showed a consistent increase in frequency of a single allele. This indicates that PGI-1 was selectively favored between 1988 and 1996.   PGI-1 frequencies in BC, shown for each site in the drainage. Previous Page Next Page Research Home|Nathan Rank's Homepage |Department of Biology | Sonoma State University January 23, 1999 NER