Esterase polymorphism in the butterfly Hemiargus isola: stability in a variable environment.

Area of Science:

• * Population genetics
• * Evolutionary biology
• * Entomology

Background:

• * Esterase enzymes (Es-d) in lycaenid butterflies display considerable electrophoretic variation.
• * This variation is observed across natural populations in Texas.

Purpose of the Study:

• * To investigate the genetic basis and population-level variation of a dimeric esterase in lycaenid butterflies.
• * To identify the factors maintaining isozyme polymorphism in natural populations.

Main Methods:

• * Electrophoretic analysis to detect esterase isozyme variation.
• * Allele frequency estimation in sampled butterfly populations.
• * Examination of genetic variation across different ecological conditions and time points.

Main Results:

• * A high degree of isozyme variation was detected, controlled by multiple alleles at an autosomal locus (Es-d).
• * Each population harbored 9-14 alleles, with two predominant alleles (Es-d(100) and Es-d(80)) constituting approximately 84% of the gene pool.
• * Frequencies of the predominant alleles remained stable despite ecological variability and the butterflies' dispersal capabilities.

Conclusions:

• * Environmental heterogeneity within local habitats is the likely primary factor sustaining the observed esterase polymorphism.
• * The study highlights the complex genetic structure and adaptive potential within lycaenid butterfly populations.