Cone and seed variability in Serbian spruce – indicators of population endangerment

Serbian spruce (Picea omorika (Pančić) Purk., Pinaceae) is a tertiary relict and one of the rarest, most endangered, and protected conifer species in Europe. Alarmingly, many studies report a continuous decline in its population and vitality. In response to this concerning trend, the present research aims to better understand the reproductive potential of this species by analysing cone and seed characteristics, as well as intra- and inter-population variability — the critical factors for designing effective in situ and ex situ conservation strategies. To achieve this, cones were collected during the 2022/23 season (autumn/spring) from 111 trees across seven natural populations and one urban population in Bosnia and Herzegovina. Immediately after collection, cones were measured and processed, seeds were extracted, and germination tests were conducted in April–May 2023. The analysis revealed significant differences among trees and populations for all cone traits. Notably, the level of intra-population variability observed closely resembles the patterns previously identified in genetic studies of the same populations, suggesting a consistent underlying diversity structure. However, the overall germination results point to very low seed viability, 57.03% on average, with 26.85% of seeds being empty. Population-level differences were pronounced: germination rates ranged from 20.40% to 81.14%, while the proportion of empty seeds ranged from 8.10% to 59.60%. Overall, our results suggest that small and endangered populations are particularly vulnerable, producing smaller cones with a higher proportion of empty seeds and significantly lower germination success. This highlights an urgent need for conservation action — to protect the species and support natural regeneration in situ, and to establish ex situ plantations beyond its natural range.