AbstractPremiseSexual dimorphism in dioecious plant species is often not obvious or is absent. Dioecious species populations also often exhibit deviations from expected sex ratios. Previous studies on members of the Salicaceae family have shown strong, partial, and no sexual dimorphism. Some studies have shown sex-biased ratios in severalSalixspp., however,S. purpureahas never been examined for evidence of sexual dimorphism or for the presence of sex-ratio bias, and therefore a comprehensive phenotypic study is needed to fill this knowledge gap.MethodsThis study examined a suite of morphological, phenological, physiological and wood composition traits from multi-environment and multi-year replicated field trials in a diversity panel of unrelatedS. purpureaaccessions and in full-sib F1and F2families produced through controlled cross pollinations to test for sexual dimorphism and sex ratio bias.Key ResultsSignificant evidence of sexual dimorphism was found in vegetative traits with greater means for many traits in male genotypes compared to females across three populations ofS. purpurea, measured across multiple years that were highly predictive of biomass yield. Male plants exhibited greater nitrogen accumulation under fertilizer amendment as measured by SPAD in the diversity panel, and males showed greater susceptibility to fungal infection byMelampsoraspp in the F2family. There were also consistent female-biased sex ratios in both the F1and F2families.ConclusionsThese results provide the first evidence of sexual dimorphism inS. purpureaand also confirm the prevalence of female-biased sex ratios previously found in otherSalixspecies.
