Supergenes in polymorphic land snails. II. Partula suturalis.

Area of Science:

• Genetics
• Molluscan Biology
• Evolutionary Biology

Background:

• Shell morphology, including color, banding, and coiling, are key phenotypic traits in gastropod species.
• Understanding the genetic basis of these traits is crucial for evolutionary and population genetics studies.

Purpose of the Study:

• To elucidate the genetic control of shell color and banding in the land snail Partula suturalis.
• To investigate the genetic basis of shell coiling direction in Partula suturalis.
• To determine the relationship between the genes controlling shell color/banding and coiling.

Main Methods:

• Analysis of shell phenotypes in Partula suturalis populations.
• Genetic crosses and examination of offspring phenotypes to infer allelic interactions and dominance hierarchies.
• Segregation analysis to assess linkage between shell color/banding and coiling loci.

Main Results:

• Shell color and banding are controlled by a single locus (M) with at least six alleles exhibiting a complex dominance hierarchy (MX > MF1 > MF2/MA > MC > MS).
• A unique heterozygous phenotype (bisecta) was observed for the MF2MA genotype, differing from both homozygotes.
• Shell coiling direction is controlled by a separate locus (H), with sinistrality (HS) dominant to dextrality (HD), and expression is maternally influenced with a one-generation delay.

Conclusions:

• The Partula suturalis shell color and banding locus (M) is likely complex, potentially involving multiple closely linked genes or complex allelic interactions.
• The genetic architecture of shell coiling (H locus) demonstrates maternal inheritance effects on phenotype.
• The shell color/banding locus (M) and coiling locus (H) are not linked, indicating independent assortment of these traits.