Publications scientifiques
Christian Bellec
Philippe Jarne
Luc Finot
Bernard Delay
Journal of Molluscan Studies
Uniparental reproduction in the tetraploid hermaphrodite species Bulinus truncatus has been suggested to occur via self-fertilization, on the basis of cytological and genetic studies. However, recent analyses of population genetic structure by protein electrophoresis indicated the occurrence of multi-banded phenotypes referred to as ‘fixed hetero-zygosity’. Although intrapopulation and geographical variation of multibanded phenotypes occur, many populations bear only one type of such patterns. This led to the suggestion that parthenogenesis may well be the mating syste in B. truncatus. However, such fixed heterozygosity patterns are expected in some tetraploid species in which double disomic inheritance of alleles occurs. It is therefore not possible to determine from population genetic structure analysis alone whether segregation occurs or not. Here, we investigate the stability of such patterns over one generation of uniparental reproduction among four populations. We also present results of crossing experiments between individuals from two populations, using two diagnostic loci to analyse their offspring. Our results clearly indicate Mendelian segregation of alleles, and confirm sexual reproduction by self-fertilization and cross-fertilization. We interpret the multibanded patterns observed in populations as the product of both diploid loci of the tetraploid genome when they are monomorphic for different alleles. Our study also allows us to suggest that partial selfing may be the regular mating system in B. truncatus.
