Characterization and distinction of two subspecies of Eryngium duriaei J. Gay ex Boiss., an Iberian endemic Apiaceae, using flow cytometry and essential oils composition

Eryngium duriaei (Apiaceae) is an endemic taxa from Iberian Peninsula. Some doubts exist in the literature about the taxa relationships, especially among Iberian populations at different altitudes. Also, as other Apiaceae, this species presents a large potential for essential oil production. Considering all this, a multidisciplinary study comprising taxonomic, cytological (using flow cytometry and chromosome counts) and chemical (essential oils) analyses was performed with the objective to morphologically characterize this species and to evaluate the cytotaxonomical and chemical diversity of E. duriaei Portuguese populations. FCM and chromosome counts have shown that every individual presented the same ploidy level, i.e., 2n = 2x = 16 chromosomes. However, flow cytometric analyses revealed that individuals of E. duriaei from higher altitudes (A >> 1,700 m) presented a significantly higher genome size than those belonging to E. duriaei populations below 1,700 m (2C = 6.20 +/- A 0.04 vs. 2C = 5.52 +/- A 0.05 pg). Moreover, the essential oils analyses revealed that most chemical constituents were sesquiterpenes, but relevant differences in the main components were observed: alpha-neocallitropsene (28-53 %), beta-betulenal (8.5-15.8 %) and 14-hydroxy-beta-caryophyllene (5.8-13.7 %) were the main compounds of Eryngium duriaei oil below 1,700 m, whereas caryophyllene oxide (47 %) and E-caryophyllene (6 %) were the major compounds of E. duriaei oil of higher altitude populations. The results provide important evidences to support the taxonomic separation of E. duriaei in two taxa: E. duriaei J. Gay ex Boiss. subsp. duriaei and E. duriaei subsp. juresianum (M. Lainz) M. Lainz, as previously considered by this author.