Phylogeny and evolution of alternative genetic systems in insects

摘要

The ancestral and most frequent genetic system in insects is dioecious, diplodiploid sexuality, in which every individual is either male or female and both meiosis and syngamy occur in every organismal generation. From this system there have been repeated origins of alternative genetic systems that fall into two major classes. One is thelytoky and the other is arrhenotoky. In thelytoky (often called 'parthenogenesis'), males are absent and all individuals are anatomically female. The simplest, mostextreme, and most frequently arising form of thelytoky is obligate apomixis. in which meiosis and syngamy are completely absent from the life cycle and oocytes are produced mitotically. Other forms of thelytoky are in some way intermediate between apomixis and obligate sexuality; these include various forms of automixis, pseudogamy, cyclic parthenogenesis, and facultaive parthenogenesis.