SEX AND EUKS. “Given that sexual reproduction is pervasive and extant in all of the major super groups of the eukaryotic tree of life, it is hypothesized the sex emerged once in an ancestral eukaryote and has been preserved and conserved throughout the eukaryotic tree of life. Thus, one can think of the ability to undergo sexual reproduction as a synapomorphy for the eukaryotes.”
http://www.mycologia.org/content/105/1/1.full