Secondary sexual dimorphism and morphological diversity in two allopatric juniper species

Juniperus L. is a very diverse genus of dioecious or monoecious conifers distributed throughout the Mediterranean region. In addition to the complex taxonomic characteristics of the genus, sexual dimorphism leads to sex-specific differences in the morphology of juniper species, which further complicates the delimitation of species. Two of these species, Juniperus oxycedrus L., which occurs in the western part of the Mediterranean, and J. deltoides R.P.Adams, which occurs in the eastern part, have only recently been delimited as separate species. To further support the delimitation of the species, we examined the phenotypic traits of the cones and needles of both species for both sexes. Three populations from the western and three from the eastern part of the Mediterranean region were sampled and a total of 2400 needles, 1200 cones and 1200 seeds were measured and analyzed. Both needles and cones of J. oxycedrus were slightly larger, longer and wider than those of J. deltoides and also less variable. Sexual dimorphism was observed in most of the needle traits measured, with the majority of traits in J. oxycedrus being larger in females than in males. Although sexual dimorphism was confirmed based on needle morphology, no consistent pattern of diversity was observed between the two species. In addition, variability among populations of J. oxycedrus was higher than that of J. deltoides. Our results confirm the previous species delimitation and open the possibility for further exploration of sex-specific differences in adaptability, as well as the potential implications for differential management and conservation of individuals of both sexes.