The Species

Zelkova sicula Di Pasquale, et Garfi Quézel has been discovered and described as a new species in 1991. It is a rare endemic species unique to south-eastern Sicily, a relict of Tertiary flora, belonging to an entirely extinct throughout continental Europe following the Quaternary glaciations.Up to 2009 was known only one population of Z. sicula, , consisting of about 230 plants confined to a single site extended less than 0.4 hectares, within the SIC ITA090022 "Bosco Pisano," Hyblaean Mountains (south-eastern Sicily). At the end of 2009 was unexpectedly discovered a second population on the same mountain range. As above, it is represented by some hundreds of plants distributed in an area of ​​approximately 0.8 hectares, the environmental conditions are very similar. In both cases, the two populations are confined along the bed of a small watershed, where the characteristics of water in relation to this particular situation micro-topographical probably play an essential role in the survival of the species, constituting an underground reservoir where plants can draw especially during the summer season.Because of its extreme rarity, the species included in the IUCN Red List of threatened species, in the category 'Critically Endangered' extinction (CR - Critically Endangered) (IUCN 2010. IUCN Red List of Threatened Species. Version 2010.1.  Downloaded on June 14, 2010) and selected as one of the "Top 50 Mediterranean Island Plants at the risk of extinction" . Nevertheless, until now has not yet been undertaken no measure of legal protection.Several surveys have shown that Z. sicula survives in a habitat that, in general terms, appears to deviate significantly from a bioclimatic optimum condition. Moreover, in this sense, recent surveys on climate change outline future scenarios certainly not encouraging. Water stress in summer periodically causes the death of the weaker plants, extremely scarce and episodic fruiting, probable gamete sterility dependent probably on its karyological state (triploidy), the heavy and prolonged human disturbance and the lack of specific protection measures are the main critical points for the conservation of the species. In addition, the long geographical isolation and small size of the two populations are particularly drastically reduced gene flow, promoting a rapid loss of genetic variability at intra-specific.In a biogeographical point of view, gender Zelkova is included in the family of Ulmaceae and is currently represented by 4 -6 species, distributed into two disjoint groups: one in the Mediterranean-Pontica region and the other in the Far East Asia. For its ecological requirements Z. sicula is very different from other species, which are generally related to climate perimid conditions without summer drought, from this general situation partially deviates only Cretean Z. abelicea, but shows a temperament much less thermophilic of the Sicilian specie, living in the Mediterranean-mountain habitat.The quota flora hygro-mesothermal which  the genus Zelkova belongs was very common in the lush forests of the Tertiary in the whole Europe. From the Pleistocene, the climate change which have appeared with the onset of glaciation, caused his rarefaction from north to south. In the alternation of glacial-interglacial cycles, the Italian peninsula has played a fundamental refuge role for flora hygro-mesotermica, allowing the survival of some taxa, including Zelkova, which remained in the more southern latitudes and in Mediterranean. Zelkova has persisted in central Italy until 31,000 years ago, time which the remains date from latest pollen are attribuible to gender. After that date the genus Zelkova is considered extinct by the entire continental Europe. Only in the two Mediterranean islands of Crete and Sicily, where the effects of glaciation have been less severe, the two species Z. abelicea and Z. sicula have survived until today, more or less effectively adapting to the characteristics of typical aridity of Mediterranean climate. But although both endemic wrecks of the respective islands, Z. abelicea is however relatively widespread on the main mountain ranges of Crete, while Z. sicula is extremely rare, being now represented by only two small scattered populations, which have a total of only a few hundred individuals.Both populations of Z. sicula have a spatial distribution to groups or scattered plants, small impluvia concentrated along the length of which is respectively of about 200 m and 250 m in ZS1 in ZS2. In ZS1 all plants show a shrub (height exceptionally up to 2.5 m) and a rather poor general state of conservation. Many plants are stunted because of the difficult environmental conditions and the long-age human disturbance (grazing, fires, overexploitation) is responsible for a substantial degradation of its habitat. Moreover, the absence of sexual renewal makes particularly critical the specie survival prospects. Overall, even in ZS2 can be observed  very similar conditions, although the individual status seems slightly better and many plants try to assume a posture of small tree with a height of up to 6 m. In relation to the latter aspect, it should also remark that some plants grown in ex-situ environmental conditions much less restrictive (no water stress, warmer temperatures, partial shade), have revealed a potential of growth of real trees.