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УДК 502.753, 57.022
Juan-Vicedo J., Mateo G., Zidorn C.
TAXONOMICAL, PHYTOCHEMICAL AND ECOLOGICAL ANALYSIS OF THE IBERIAN DIVERSITY OF HIERACIUM L. AND PILOSELLA HILL.: AN OUTLINE ON THE INTEGRATED STRATEGY FOR EX SITU CONSERVATION AND FURTHER REVALORISATION
Jorge Juan-Vicedo, PhD, Research Collaborator, Department of Pharmaceutical Biology, Christian-Albrechts-University of Kiel, Germany: echinops83@hotmail.com;
Gonzalo Mateo, PhD, Associate Professor, Botanical Garden-University of València, Spain;
Christian Zidorn, PhD, Associate Professor, Department of Pharmaceutical Biology, Christian-Albrechts-University of Kiel, Germany
In this contribution we briefly review the state of knowledge on the diversity, ecology and conservation of Iberian Hieracium and Pilosellaspecies. We also discuss its implications for an integrated strategy of revalorization and sustainable exploitation,with focus on its conservation, using biotechnological approaches.
Keywords: Hieracium, Pilosella, taxonomy, conservation, phytochemistry, in vitro cultures, bioactivities.
Historically, Hieracium L. and Pilosella Hill. were usually treated as two subgenera of one genus, Hieracium s.l. Hieracium L. and Pilosella Hill. are members of the tribe Cichorieae (Asteraceae) and comprise more than 850 wild species and subspecies, and over 10000 micro-species distributed in the temperate areas of the world, excluding Australasia (Heywood, 1993). A limited number of taxa have been introduced into North America and New Zealand, some of those are invasive weeds (Mateo, 2007; Wilson, 2006). An innumerable number of subspecies, varieties and forms affiliated to both basic and intermediate species have been described. This diversity could have either originated by mutations or hybridization processes. Pilosella and Hieracium display an almost universal ability of both interspecific and intersectional hybridization having produced hundreds of the above mentioned intermediate taxa (Mateo, 2007). The huge diversity of intermediate taxa in Hieracium and Pilosella as a result of hybridization and polyploidization with apomixis indicates an active process of evolution occurring within these genera. This makes Hieracium and Pilosella a unique group of plants. Specifically, the outstanding taxonomical architecture within the genus makes Hieracium one of the most diverse genera in the entire plant kingdom becoming a very challenging group of plants not only for botanists and scientists in general, but also for conservationists. A diversity of more than 300 species has been estimated for the Iberian Peninsula (Mateo, 2007, Mateo and del Egido, in press and references therein). Traditionally, Hieracium was considered sensu lato by most of scientists, whereas
A
only a minority regarded Pilosella as a separate genus (Mateo, 2007). However, in recent treatments the idea of dividing European taxa into two genera has been picked up again. From the chemical point of view, Hieracium and Pilosella are firmly nested within the Cichorieae and thus share the main phytochemical features of this tribe: occurrence of various types of phenolic acids, flavonoids and flavonoid glycosides, simple coumarins, glycosylated sesquiterpene lactones, and triterpenes (Zidorn, 2008). Some of these substances (e.g. sesquiterpenoids) appear as very promising chemosystematic markers that are still not studied in these genera. Furthemore, all these substances display interesting properties that might be industrially exploited. Naturally occurring antioxidants play an important role in inhibiting both free radicals and oxidative chain reactions within tissues and membranes both as a protection for the plants producing them as for human health when taken up in vegetables or food supplements (Nsimba et al., 2008). Flavonoids and phenolic acids occurring in Hieracium and Pilosella also exhibit such activities. Sesquiterpenoids exhibit a wide range of bioactivities including anti-inflammatory activity (LyB et al., 1998) and cytotoxicity (Johrer et al., 2012).Sesquiterpene lactones are so far the most interesting compounds from the Cichorieae tribe concerning bioactivities (Zidorn, 2008). In a few previous studies, sesquiterpene lactones have also been found in the genus Hieracium (Fig. 1). However, a deeper research is needed to know the presence and abundance of these substances in Iberian taxa, as well as the bioactivities that they might present.
Nr. Ri R2 R3 Source species
A-1 a HD DßDOGlc CH2 H Hieraciumintybaceum All.
A-2 a HDD ßDOGlc aDCH3, ßDH H Hieraciumintybaceum All.
A-3 O CH2 H Hieraciumintybaceum All.
A-4 O aDCH3, ßDH H Hieraciumintybaceum All.
A-5 O CH2 O-Ac HieraciumirasuenseBenth.
B-1 a H DDßDOGlc CH2 CH3 Hieraciumintybaceum All.
B-2 a H DDßDOGlc aDCH3, ßDH CH3 Hieraciumintybaceum All.
B-3 O CH2 CH3 Hieraciumintybaceum All.
B-4 O aDCH3, ßDH CH3 Hieraciumintybaceum All.
C - - - Hieraciummurorum (L.) L.
Figure 1. Sesquiterpene lactones from various Hieraciums.l. species
The Iberian Peninsula represents one of the main centers of speciation for Hieracium s.l. in the world, along with the Alps and the Balkan Peninsula. However, the mentioned taxonomical complexity as well as the kind of habitat the plants inhabit (e.g. pastures and rocky places in high mountains, Table 1) make Hieracium s.l. quite unknown to the public and even a neglected group for most not specialised botanists (DYCs = damned yellow composites). This could be one reason why so far no practical applications for this botanical resource, besides the historic medicinal use of the widespread Pilosella officinarum Vaill., have been reported. In the same manner, these challenges probably let to an insufficient effort in their conservation needs for the whole Europe in general, and in the Iberian Peninsula in particular.
Table 1. Percentages of Hieracium L. and Pilosella Hill. species in regard to the environment where they grow
Environment Hieracium L. Pilosella Hill.
Alpine-steppes 2.86 6.25
Dry and/or sunny
areas 8.56 43.75
Exclusively
pastures or
grasslands 0.00 31.25
Exclusivelyrocky
places 42.85 43.75
Forests and
associatedvegetation 20.00 12.50
Rocky places and
grasslands 17.15 0.00
Shadedareas 5.72 0.00
Wide range of
environments 2.86 6.25
of these taxa are rare with narrow distribution areas (Mateo and del Egido, in press) and 20 taxa have been included in different categories in the Spanish Red Data Listsuch as H. queraltense, H. recorder, H. texedense and H. vinyasianum, which are listed as CR (Moreno et al., 2008). However, a complete lack of practical ex situ conservation strategies focused on Hieraciums.l. is remarkable. In fact, the presence of seeds or tissue cultures in Spanish and Portuguese genebanks and botanical gardens is almost lacking (http://www.jbotanicos.org/). Moreover, there is not any publication on conventional or in vitro propagation of plants from these genera, nor for highly endangered taxa, unlike in other mega-diverse European genera with economical and conservation interests (e.g. Narcissus, Thymus,'etc.).
Proportion of endemic plants in the Iberian Peninsula (%) HieraciumL fftoMflaHHL
OWijHji yc endem sm
□ Ex:lu live Iber ei ertJamam
BNy rowings ifidemism
Figure 2. Proportion of endemic plants of the genera Hieracium and Pilosella in the Iberian Peninsula based on Mateo and del Egido (in press). Percentages of each type of endemic plant are classified as follows: non-endemic (e.g. distributed along the whole Mediterranean or Eurosiberian Region), wide-range endemism (e.g. distributed along the Iberian Peninsula and some of the Mediterranean Islands), exclusive Iberian endemism (e.g. distributed in some regions of the Iberian Peninsula), and narrow-range endemism (restricted to one particular biogeographic unit, e.g. the Pyrenees)
Hieracium-Pilosella significantly contributes to the endemic flora of this territory and some species are included in local Red Data Lists of threatened vascular plants such as Hieracium harzianum in Germany (listed as Critically Endangered, CR), H. lucidum in Italy (CR), or H. eriophorum in France (Vulnerable) (Schnittler et al., 2001). In the Iberian Peninsula, almost 50% of the listed species are endemic to this territory (Fig. 2). Most
The richness in certain chemical compounds makes these genera worth to be deeply studied not only for taxonomical purposes, but also for a possible usage as medicinal plants. In addition, they might be used as ornamentals; for instance, as alpine plants. For all these reasons, the development of usual biotechnological approaches (e.g. in vitro cell cultures) could be applied both for conservation purposes as well as to sustainably
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propagate medicinally interesting materials. In vitro cultures can be valuable tools for both the ex situ conservation of endemic, rare, and threatened species as well as an important tool for mass-propagation of selected genotypes to be used as novel medicinal plants. Micropropagation is the true-to-type propagation of a selected genotype using in vitro techniques (Debergh and Read, 1991; Werbrouck and Debergh, 1996). The use of the available in vitro techniques (such as micropropagation) is a suitable strategy for both commercial mass-propagation (Winkelmann et al, 2006) and/or conservation of plant germplasm (Tasheva and Kosturkova, 2013). These techniques can be employed for the conservation of genetic resources such as threatened plants, species with recalcitrant seeds or with vegetative propagation, and of plant genotypes of outstanding interest such as their attractive structures or colours for gardening or the production of secondary metabolites (Tasheva and Kosturkova, 2013).
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