Balancing selection on electrophoretic variation of phosphoglucose isomerase in two species of field cricket: Gryllus veletis and G. pennsylvanicus

• Published in: Genetics (Austin) Vol. 147; no. 2; pp. 609 - 621
• Main Authors: Katz, L.A. (Smith College, Northampton, MA.), Harrison, R.G
• Format: Journal Article
• Language: English
• Published: Bethesda Genetics Soc America 01.10.1997; Genetics Society of America
• Subjects: ADN; ALLELES; ALLOENZYMES; ALLOZYME; ALLOZYMES; ALOZIMAS; AMINO ACID SEQUENCES; AMINO ACID SUBSTITUTIONS; Amino acids; CAROLINA DEL NORTE; CAROLINE DU NORD; CHEMICAL COMPOSITION; COMPLEMENTARY DNA; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; CONNECTICUT; DNA; ELECTROFORESIS; ELECTROPHORESE; ELECTROPHORESIS; ENZYME POLYMORPHISM; Enzymes; GENE; GENE FREQUENCY; GENES; Genetic markers; Genetics; GLUCOSA 6 FOSFATO ISOMERASA; GLUCOSE 6 PHOSPHATE ISOMERASE; GRYLLUS; GRYLLUS PENNSYLVANICUS; Heterogeneity; Insects; Investigations; MITOCHONDRIA; mitochondrial DNA; MITOCHONDRIE; MITOCONDRIA; NATURAL SELECTION; NEW YORK; NORTH CAROLINA; NUCLEOTIDE SEQUENCE; nucleotide sequences; NUEVA YORK; PGI GENE; POLIMORFISMO ENZIMATICO; POLYMORPHISME ENZYMATIQUE; Proteins; restriction fragment length polymorphism; RFLP; SECUENCIA NUCLEOTIDICA; SELECCION NATURAL; SELECTION NATURELLE; SEQUENCE NUCLEOTIDIQUE; VERMONT; VIRGINIA; VIRGINIE; North Carolina; Vermont; New York; Virginia; Connecticut
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/147.2.609

Two species of crickets, Gryllus veletis and G. pennsylvanicus, share six electrophoretic mobility classes for the enzyme phosphoglucose isomerase (PGI), despite evidence from other genetic markers that the two species are not closely related within eastern North American field crickets. Moreover, the frequencies of the two most common PGI electrophoretic classes (PGI-100 and PGI-65) covary in sympatric populations of these species in the eastern United States, suggesting that PGI may be subject to trans-specific balancing selection. To determine the molecular basis of the electrophoretic variation, we characterized the DNA sequence of the Pgi gene from 29 crickets (15 G. veletis and 14 G. pennsylvanicus). Amino acid substitutions that distinguish the electrophoretic classes are not the same in the two species, and there is no evidence that specific replacement substitutions represent trans-specific polymorphism. In particular, the amino acids that diagnose the PGI-65 allele relative to the PGI-100 allele differ both between G. veletis and G. pennsylvanicus and within G. pennsylvanicus. The heterogeneity among electrophoretic classes that covary in sympatric populations coupled with analysis of patterns of nucleotide variation suggest that Pgi is not evolving neutrally. Instead, the data are consistent with balancing selection operating on an emergent property of the PGI protein.