Genetic population structure and breeding systems in arionid slugs (Mollusca: Pulmonata)

Abstract

Accepk-d for publication Jub 1981Electrophoresis and biochemical staining were used to analyse genetic variation in enzymes in nine species of terrestrial slugs of the genus Arion from 58 localities in the British Isles. The species fall into three categories on the basis of the genetic structure of their populations and their breeding systems. Anon lusitanicus, A . hortcnris, A . distinctus and A . owmii are highly polymorphic and heterozygous, and apparently reproduce predominantly, if not completely, by outcrossing. Arion c i r m r i p h , A . silvaticus, and A . intmedius consist of one or a few monogenic strains. Their monogenicity apparently results from an automictic mode of reproduction, most probably self-fertilization. Asion a& and A . s u b f u r c u r consist of both a polymorphic, heterozygous form and a monogenic strain, between which hybridization occurs. The monogenic strain and the polymorphic form of A . subficus occur in pure populations only in Ireland and England, respectively, but each has been introduced throughout the British Isles. In both A . a h and A . subfurcur, hybrid populations show a marked deficiency of heterozygotes as a result of self-fertilization. The genetic structures and breeding systems of populations of the species of Arwn introduced to North America are similar to those of native populations in Britain.

Large scale patterns of genetic differentiation at enzyme loci in the land snails Cepaea nemoralis and Cepaea hortensis

“…The correlation between electromorphs at the Lap-i locus depends on a single locality, and is not compelling evidence of a common agent of natural selection. There is, however, some evidence at selection acting at an Lap locus in the mussel Mytilus (Koehn et a!., 1976(Koehn et a!., , 1980 and Foltz et a!. (1982) describe an unusually high level of geographic differentiation for Lap in four species of slugs.…”

Allozyme diversity in slugs of the Carinarion complex (Mollusca, Pulmonata)

“…The three species are widely distributed in Europe and North America (Chichester & Getz, 1969;Kerney et a!., 1983) and their population genetics has been dealt with in two major allozyme surveys. McCracken & Selander (1980) reported that in North America each species consists of a single homozygous strain, whereas in Ireland Foltz et al (1982) observed one homozygous strain of A. circumscriptus and two of A. silvaticus. These data were interpreted as suggesting that: (i) Caninarion spp.…”

“…are selfers; (ii) the single strain structure of American populations is not the result of a loss of genetic variation (e.g. founder effects) caused by their introduction from more variable European populations (Selander & Ochman, 1983; *Correspondence E-mail: tbackeljau@kbinirsnb.be 1997 The Genetical Society of Great Britain, 445 homozygous strains, population genetics, Foltz et al, 1984); and (iii) the three taxa involved deserve species rank because of their low mean genetic identities, respectively I = 0.65 between the three species (McCracken & Selander, 1980) and I = 0.74 between A. circumscriptus and A. silvaticus (Foltz et a!., 1982).…”

“…However, Foltz et aL (1982) did not consider A. fasciatus (which was the most intensively studied species in North America) and did not investigate continental populations of both other species.…”

Population genetics: Using recombination to detect sexual reproduction: the contrasting cases of Placozoa and C. elegans

“…In these populations (Abbott and Gomes, 1988;Berge et al, 1998), the high selfing rates inferred (about 98-99%) support greenhouse observations that plants readily selffertilise. However, Northern Europe is a region where selection during the recolonisation after the most recent ice age has probably favoured selfing (Foltz et al, 1982), since densities of animals and plants were probably often low. Populations elsewhere in the world may have higher outcrossing rates.…”