Repeated evolution of dioecy from androdioecy in Acer

GLEISER, G.; VERDÚ, M.

NEW PHYTOLOGIST

WILEY-BLACKWELL PUBLISHING, INC

Año: 2005 vol. 165 p. 633 - 640

0028-646X

The evolution of breeding systems was studied in the genus Acer, with specialattention to the origin of androdioecy and dioecy, using a phylogenetic approach.Parsimony and maximum-likelihood techniques were used to infer the ancestralcharacter state and trends in the evolution of breeding systems. Information onbreeding systems was obtained from the literature, and phylogenetic relationshipswere taken from three published phylogenies.Although a general trend from duodichogamy to dioecy through heterodichogamyhas been proposed for the genus Acer, our results show that a general trend is notdetected when phylogenetic relationships are taken into account. Dioecy appearedas a derived state that evolved at least three times and never reversed towardsother states.Three different paths to dioecy have been followed in the genus Acer:from heterodichogamous androdioecy; from heterodichogamous trioecy; and fromdichogamous subdioecy. Therefore, although the best documented cases of evolutionof androdioecy indicate that this breeding system evolves from dioecy, in thegenus Acer the opposite situation occurs (androdioecy leading to dioecy). Here wediscuss the role of inbreeding avoidance and sexual specialization as selective forcesdriving the evolution of dioecy in the genus Acer.