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

Resumo

Adesmia bijuga Phil. is an endemic shrub in central Chile, classified as a critically endangered species of plant. After
more than 100 years since its original description by R. A. Philippi (1884), the species was rediscovered exclusively in
two locations of the Maule Region. One of them, Fundo San Pedro-Las Cañas, is close to extinction with a low number of
shrubs, occurring in a disturbed habitat due to plantations of Pinus radiata. This study examined the pollination biology
and breeding system of A. bijuga in order to explain their small number of shrubs. We estimated composition of pollinator
species attracted to flowers and visitation rates. In order to describe its breeding system in A. bijuga we used manipulated
treatments to estimate autonomous self-pollination, level of reproductive assurance and pollen limitation. The results of this
study indicate that only pollinators from the order Hymenoptera visit A. bijuga. The pollinator assemblage did not show
temporary variation during the flowering season, with Bombus dahlbomii as its most frequent visitor. A. bijuga showed a
mixed mating system that involves both cross- and self- pollination. The fruit set ranges from 20% to 60% in the absence or
presence of pollinators, respectively. This selfing ability would provide reproductive assurance when pollinators fail. The
taxon showed ability of asexual formation of seeds without the occurrence of fertilization by agamospermy. Supplemental
outcross pollen did not increase female reproductive success, suggesting that the species is not pollen limited. All these
factors may help to explain how this species has been able to survive over time in a small and isolated population. Finally,
this work discusses how the results of our study can be applied to future A. bijuga conservation measures.