Reproductive modes and genetic polymorphism in the tardigrade Richtersius coronifer (Eutardigrada, Macrobiotidae)

Allozymes were assessed by starch gel electrophoresis in 3 populations of a eutardigrade, Richtersius coronifer, with different reproductive modes. One population from Italy (with 2 sub‐populations) was amphimictic and 2 populations (1 from Italy and 1 from Sweden) were parthenogenetic. All populations, irrespective of their reproductive mode, were diploid with the same chromosome number (2n=12) and had bivalents in the oocytes. Of the 14 loci analyzed, only 3 were polymorphic. The amphimictic population had a higher degree of genetic variability (mean heterozygosity >0.25) than the parthenogenetic populations (mean heterozygosity of the 2 populations <0.01). In all female populations, allele frequencies at all 3 loci deviated from Hardy‐Weinberg equilibria due to heterozygote deficiency. These results support a hypothesis of automictic parthenogenesis in R. coronifer.