Pollination and breeding system in Adesmia bijuga Phil. (Fabaceae), a critically endangered species in Central Chile

Abstract

Adesmia bijuga Phil. is an endemic shrub in central Chile, classified asa critically endangered species of plant. After more than 100 yearssince its original description by R. A. Philippi (1884), the species wasrediscovered exclusively in two locations of the Maule Region. One ofthem, Fundo San Pedro-Las Canas, is close to extinction with a lownumber of shrubs, occurring in a disturbed habitat due to plantations ofPinus radiata. This study examined the pollination biology and breedingsystem of A. bijuga in order to explain their small number of shrubs. Weestimated composition of pollinator species attracted to flowers andvisitation rates. In order to describe its breeding system in A. bijugawe used manipulated treatments to estimate autonomous self-pollination,level of reproductive assurance and pollen limitation. The results ofthis study indicate that only pollinators from the order Hymenopteravisit A. bijuga. The pollinator assemblage did not show temporaryvariation during the flowering season, with Bombus dahlbomii as its mostfrequent visitor. A. bijuga showed a mixed mating system that involvesboth cross- and self- pollination. The fruit set ranges from 20% to60% in the absence or presence of pollinators, respectively. Thisselfing ability would provide reproductive assurance when pollinatorsfail. The taxon showed ability of asexual formation of seeds without theoccurrence of fertilization by agamospermy. Supplemental outcross pollendid not increase female reproductive success, suggesting that thespecies is not pollen limited. All these factors may help to explain howthis species has been able to survive over time in a small and isolatedpopulation. Finally, this work discusses how the results of our studycan be applied to future A. bijuga conservation measures.