The structure and dynamics of a hybrid population of Anigozanthos manglesii D. Don and A. humilis Lindl. (Haemodoraceae)

Abstract

The structure of a hybrid kangaroo paw population (Anigozanthos Labill.) in the shire cemetery at Gingin, Western Australia, was analysed from multivariate morphometric, pollen fertility and floral colour data. A. manglesii D. Don. comprised 87% of the population of 9547 flowering individuals in 1976, and occupied the lower, wetter areas of the cemetery to the exclusion of A. humilis Lindl. A. humilis (11 % of the population) occurred at the greatest density on the higher, drier areas. The intervening ecotonal regions were occupied by both species, and by the majority of F1 hybrids (0.5 % of the population) and backcrosses (c. 2%). Census data documented a threefold increase in the number of A. manglesii individuals, a slight increase in the number of F1 hybrids, and a decrease in the number of A. humilis by a third over a 3-year study period. These data suggest the occurrence of a limited amount of introgressive gene exchange in the face of potent barriers to interspecific hybridization.