Estimating the age of the polydnavirus/braconid wasp symbiosis.

Polydnaviruses are essential components mediating host-parasitoid relationships between some braconid wasps and their caterpillar hosts largely by suppressing or misdirecting the host immune systems. The polydnavirus-wasp relationship is an unusual apparent mutualism between viruses and eukaryotes and remarkably has evolved to the stage where the two entities no longer can be considered separate. Estimations of the age of the polydnavirus-bearing clade of braconid wasps based on separate calculations from the mitochondrial 16S rRNA and COI genes and the nuclear 28S rRNA gene, calibrated using fossil data, converge to indicate a date of origin of approximately 73.7 +/- 10 million years ago. This range provides an upper bound on the time during which these wasps and viruses have been functionally associated.