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L. Llorens et al. / Biochemical Systematics and Ecology 56 (2014) 246e254  253

           Fig. 4. CCA joint biplot of compounds and localities, and relationships to the bioclimatic indices. A, p-cymene chemotype; B; b-bisabolene chemotype.

           These findings may be correlated with factors other than genetic determinants, as the biosynthetic pathway for terpenoids
        may change during plant development, under herbivore pressure (Sturgeon, 1979), or because of environmental factors Boira
        and Blanquer, 1998; Delazar et al., 2011; Robles and Garzino, 2000).
           Having little and bimodal rainfall, and subtropical dry summers characterize western and central Mediterranean climates.
        However, because of geomorphological conditions, variability and interrelations among climatic factors can determine the
        climatic conditions in particular regional and local (microclimate) locations.
           Quantitative differences between chemotypes in the studied populations were related to soil and bioclimatic factors
        (temperature and water).
           The Bosnian populations (Konjic and Borci) were characterized by growing in a temperate or humid Mediterranean
        microclimate, especially during summer. The essential oils of these populations were related to Valencia populations (Safor)
        by the high content of aromatic monoterpenes (p-cymene). The Konjic, Borci and Valencia areas have a higher average rainfall
        than those of the other studied populations. The Safor population (750 m asl) occurs on a small island (4 km ) where the
        rainfall reaches 900 mm annually, and is surrounded by a vast area where the rainfall does not exceed 550 mm. The presence
        of significant amounts of g-terpinene, a differential compound for chemotype A (Valencia and Bosnia), was positively related
        to ETP, Ttv and IG (availability of water in summer months) (Fig. 4).
           The occurrence of b-bisabolene, germacrene-D and carvacrol (compounds characteristic of chemotype B) was related to
        positive values of Io. These conditions are common in Ibiza and Sicily, and these parameters reach higher levels in Majorca.
           The presence of the phenol chemotypes (g-terpinene, p-cymene, camphene and 1-terpinene-4-ol) in Thymus spp.
        occurring outside areas having xeric climate conditions seems to be related to the chemical characteristics of the soil
        (Martonfi et al., 1994).
           The populations of Majorca, Ibiza and Marettimo grow in limestone dolomitic rocks, in crevices and cracks on almost
        vertical rock surfaces (chasmophytes). The Konjic, Borci and Safor biotypes occur on incipient soils (soils characterized by
        stony rendosol with a poorly developed B horizon) on gentle slopes, and are closely associated with dolomitic bedrock in
        initial stages of soil development (Table 1).
           The data for the volatile components of the various Thymus richardii populations analyzed showed that although most
        were phenol precursors related to the monoterpenoid fraction, the main differences involved the sesquiterpenoid fraction,
        with b-bisabolene being the most representative compound for this species.
           The adaptation of the Majorca population to extreme climatic and edaphic conditions of the mountain of Puig Major wasn't
        associated with a decrease in the amount of phenolic compounds or an increase in non-phenolic monoterpenoids. In this case
        we found a major increase in the sesquiterpenoid fraction (mainly b-bisabolene).
           Comparison of the more xeric populations and those from an environment having a damper climate and deeper soils
        (Safor, Konjic and Borci) indicated two trends: (a) precursors of phenolic compounds predominated in Safor, Konjic and Borci
        samples, whereas the phenolic compounds formed from the precursors were evident to a greater extent in the other wild
        populations; (b) the Konjic, Borci and Safor (mainly) populations had greater amounts of non-phenolic monoterpenoids. In
        relation to the distribution of chemotypes of T. vulgaris described by Thompson et al. (2003), both trends are consistent with
        previous reports (Bruneton, 1995; Kukelanova et al., 1996) of the relationship between typical Mediterranean environments
        and the occurrence of phenolic compounds.
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