Pollen quality limitation in the Iberian critically endangered genus Pseudomisopates (Antirrhinaceae)

Abstract

Pollen limitation occurs when sexual reproduction is decreased due to inadequate pollen receipt. Limitation is usually associated with the quality and the quantity of pollen; still, most studies do not discriminate between the two. We used hand-pollination experiments and observations of floral visitors to determine the mating system and limitations to seed production of the Spanish endangered species Pseudomisopates rivas-martinezii. We tested for agamospermy, autogamy, obligated autogamy, cross-pollination and supplementation. The response variables considered were fruit set, seed set and viable seed set. Previous studies indicated that (i) the species exhibits extensive clonal growth, (ii) plants flower profusely in summer, (iii) seeds showed to be highly unviable, and (iv) no seedlings were observed in the field. We found that P. rivas-martinezii is predominantly self-incompatible, has an unexpected generalized pollination system considering its occluded corolla, and is limited by qualitative rather than quantitative pollen limitation. These results indicate that, in addition to other presumed environmental factors, the low seed viability of this self-incompatible species is due to pollen quality limitation as a result of reduced mate availability.