Low seed viability and germination in Polylepis flavipila hinder forest restoration: The role of seed mass and maternal effects

Seed physiological quality is usually determined by the interaction between genetics and the mother tree's environment, as well as by intrinsic characteristics, such as seed mass. In the Andean highlands, massive sapling production for forest restoration projects is constrained by seed availability and quality. There, species of the genus Polylepis dominate the remnant forests. The associations of seed viability with seed mass and maternal effects were evaluated in P. flavipila, a threatened tree species endemic to the Peruvian Andes. The characteristics and environments of 18 mother trees from two sites were measured, and seed quality was assessed in three tests. Seed mass was 3.49 ± 1.76 mg (range: 0.5–16 mg) and showed the greatest variability within mother trees, followed by variability among trees and among sites. Viability rates, standard germination and greenhouse germination (2.06 ± 1.35 %, 0.59 ± 0.89 % and 0.64 ± 1.11 %; respectively) were low at both sites. These results were attributed to the presence of seeds with non-viable or absent embryos. Seed viability increased with seed mass and mother tree height, and was positively associated with number of seedlings (r = 0.56). The deficient seed viability and germination found in P. flavipila are the lowest reported for the genus. The low seed physiological quality detected is a risk factor that exacerbates the species' degree of threat, posing a challenge for sapling production. The reported associations of P. flavipila seed viability with seed mass and maternal characteristics and environment may guide the selection of better seed quality and serve as a basis for future studies on the challenges and limitations of the reproductive biology of this species.