Genetic evidence for parthenogenesis in small carpenter bee, Ceratina dallatoreana in its native distribution area

Abstract

Arrhenotoky is typical mode of reproduction for Hymenoptera - females originate from fertilized eggs, males from unfertilized eggs. However, some lineages of Hymenoptera have switched to thelytoky, where diploid females originate instead from unfertilized diploid eggs. In the contras with some other hymenopteran lineages, thelytoky is generally very rare in bees. Here, we examined reproduction in the small carpenter bee Ceratina dallatoreana, which is assumed to be thelytokous. We compared genotype of microsatellite loci between mothers and their offspring. Offspring were genetically identical with mother in all cases. We did not detect any male offspring. Therefore, we conclude that parthenogeny is the prevailing, and perhaps obligate, mode of reproduction in C. dallatoreana. Offspring were clones of their mother with no observed decrease of heterozygosity. Thus the cytological mode of parthenogenesis is apomixis, or automimic with central fusion and extremely reduced or non-existing recombination. Ceratina bees are originally facultatively eusocial, therefore thelytoky may influence social evolution by causing extremely high within-colony relatedness. However, to date no multifemale nests have been recorded in C. dallatoreana.