The genetical and environmental determination of phally polymorphism in the freshwater snail Bulinus truncatus

In some species of self-fertile pulmonate snails, two sexual morphs co-occur in natural populations: regular individuals and aphallic individuals that cannot transmit sperm to other snails. Purely aphallic populations therefore reproduce obligatorily by selfing. Understanding the evolution of aphall...

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Bibliographic Details
Published inGenetics (Austin) Vol. 142; no. 1; pp. 217 - 225
Main Authors Doums, C, Bremond, P, Delay, B, Jarne, P
Format Journal Article
LanguageEnglish
Published United States Genetics Society of America 01.01.1996
Subjects
Animal reproduction
Animals
Biological Evolution
Bulinus - genetics
Environment
Female
Genetic Variation
Genetics
Genetics, Population
Investigations
Male
Mollusks
Polymorphism, Genetic
Reproduction - genetics
Sex Characteristics
Temperature
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Summary:In some species of self-fertile pulmonate snails, two sexual morphs co-occur in natural populations: regular individuals and aphallic individuals that cannot transmit sperm to other snails. Purely aphallic populations therefore reproduce obligatorily by selfing. Understanding the evolution of aphally and selfing in these snails requires a precise knowledge of phally determination. In this paper, we investigate the genetic and environmental determination of aphally in Bulinus truncatus by a survey of the family (offspring) aphally ratio of 233 individuals originating from seven natural populations and a study of the reaction norm of the family aphally ratio to temperature using 60 individuals from 10 selfed lineages of one population. Our results indicate a high genetic variability for the determination of aphally between populations and within some populations, associated with a high level of genetic determination. Our second experiment indicates a significant temperature and lineage effect though no interaction between these two effects. We discuss our results in the framework of threshold models developed for dimorphic traits with polygenic inheritance. We propose that the sexual morph of an individual at a given temperature is determined by a temperature threshold value depending on both the individual genotype and probabilistic processes.
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ISSN:0016-6731
1943-2631
1943-2631
DOI:10.1093/genetics/142.1.217