Conversion loss among strobili, conelets, and cones and its impact on effective population size: a case study in Cedrus libani

Taurus cedar ( Cedrus libani A. Rich.), also known as cedar of Lebanon, is a target species in the Turkish National Tree Breeding and Seed Production Program. It is valued for its wood and non-wood products and sociocultural significance and occurs naturally across 580,515 ha, primarily in the Taurus Mountains of Türkiye. Conversion from strobili to the mature cone in Taurus cedar can take 24–26 months. The conversion, impacted by many abiotic and biotic factors, is essential for the sustainability of the species. In this case study, the production of female and male strobilus, conelets, and cones, their variation and conversion, and correlations among the characteristics, fertility variation, and linkage parameters (i.e., effective number of parents and gene diversity) were examined on 50 individual trees sampled from a natural population in southern Türkiye. Average numbers of female and male strobilus, conelets, and cones were 179, 653, 35, and 28, respectively, although individual trees showed large variations in characteristics. Conversion ratios of female strobili to conelets and mature cones, and from conelets to mature cones, were 21.7, 17.9 and 81.6%, respectively, despite the large differences among trees in the conversions. For instance, from the conversion of conelets to mature cones ranged from 48.6 to 100.0% among trees. The ratios of female to male strobilus, conelets, and cones changed. However, cone production was only significantly ( p < 0.01 ) related to number of conelets ( r = 0.943, R 2 = 0.89). The result showed that conelet production was a better indicator of cone production in Taurus cedar. Fertility variation was lower in female strobili (1.20, 42% of trees), conelets (1.17, 43%), and mature cones (1.20, 42%) compared to zygotic fertility (2.90, 35%) and male strobili (2.08, 24%). Female, conelet, and cone fertility pathways thus showed greater consistency across the sampled population than zygotic fertility and male strobilus production. Effective population size was about 48% larger in strobili than mature cone stages.