Does late-acting self-incompatibility (LSI) show family clustering? Two more species of bignoniaceae with LSI: Dolichandra cynanchoides and Tabebuia nodosa

By means of hand pollination experiments and fluorescence microscopy the breeding systems and pollen tube growth were studied in Dolichandra cynanchoides and Tabebuia nodosa, two bignoniaceous species of the Chaco woodland of NE Argentina. Both species abscised all selfed pistils within 4-8 d although self pollen tubes grew successfully to the ovary and penetrated many ovules. Both species therefore show 'late-acting self-incompatibility' (LSI) or 'ovarian sterility' (OS) type control of selfing. LSI-OS has been reported in 17 species of the Bignoniaceae, and is also clustered in families such as the Bombacaceae-Sterculiaceae, Fabaceae and Myrtaceae. The implications of such family clustering are discussed, with regard to current hypotheses for the action of LSI-OS phenomena. (C) 1999 Annals of Botany Company.