Geographic variability of terpene composition in Abies cephalonica Loudon and Abies species around the Aegean: hypotheses for their possible phylogeny from the Miocene

Summary Cortical oleoresin composition of lateral shoots (mono- and sesquiterpenes) was analysed by gas chromatography on 18 Mediterranean fir populations grown in experimental fields in southern France: 13 Abies cephalonica Loudon provenances and one A. borisii regis Mattfeld provenance from Greece, 2 A. alba Miller provenances from Romania and Bulgaria, 1 Abies bornmuelleriana Mattfeld provenance and 1 A. equi trojani Ascherson and Sintenis provenances from Turkey. Terpenes with the highest between-provenance variability were limonene, -pinene, longifolene, -cadinene and -humulene. Both similarity in terpene composition of all the firs studied and paleogeographical data demonstrated the possible existence of a unique Eastern Mediterranean tertiary ancestor for present-day Aegean species. The Pliocene marine transgression of the Aegean basin could have caused this geographical disjunction. According to this hypothesis, A. alba would have appeared in the Northern part of the Aegean and then colonized all of Europe while A. bornmuelleriana would have appeared in its Eastern part. Frequent Pleistocene contacts between the two species could have contributed to the individualization of A. equi trojani and given rise to the particular morphology of the south-eastern ecotypes of A. alba. In the western part of the basin, A. cephalonica populations would have appeared. Southern migrations of A. alba during the Ice Age and contact with A. cephalonica in refugia probably led to the development of A. borisii regis hybrid populations. Evidence for an A. alba gene flow can be found in the southernmost A. cephalonica populations.