Low Reproductive Success in Two Subspecies of Juniperus oxycedrus L.

Mature seed cone and seed production were studied in six populations of Juniperus oxycedrus (three of subspecies oxycedrus and three of subspecies macrocarpa). In both subspecies, seed cone abortion took place mainly just after the pollination period, and most of the remaining seed cones reached full size. Percentage of mature cones was significantly higher in subspecies oxycedrus than in macrocarpa. In both taxa, seed cones developed fully in the absence of filled seeds. Both the number of full-sized seeds per cone and the seed viability were low, and they were similar in both subspecies. However, seed potential was markedly higher in subsp. macrocarpa (mean 4.1 ovules/cone) than in subspecies oxycedrus (mean 2.8 ovules/cone), indicating a lower seed efficiency in subspecies macrocarpa. Results indicate that deficient pollination and site quality can be causes of low seed cone production and low seed viability in both subspecies of J. oxycedrus