Clinal variation over species boundaries?: A morphological analysis of the Mediterranean ‘Gall Oaks’, Quercus subsectio Galliferae (Spach) Guerke (Fagaceae)
(English)Manuscript (preprint) (Other academic)
The distribution ranges of many so-called Tertiary relict taxa in western Eurasia are disjunct and reflect historical processes of area disruptions and shifts. In woody angiosperms (trees), such taxa have variously been treated as species or infraspecific taxa. Here, we revised a group of morphologically well-defined western Eurasian white oaks (Quercus Group Quercus) belonging to the subsection Galliferae, with a disjunct distribution in the western and eastern parts of the Mediterranean Basin. Based on previous extensive molecular studies, there is no clear pattern of genetic differentiation among members of this group. In our analysis we used 72 quantitative and qualitative morphological characters measured on more than 2000 leaves, twigs, cupules and acorns to assess the variability of the taxa and their systematic relationships. The results indicate a clear gap between the western species Q. canariensis and the remaining five taxa of the group. The latter are best accommodated within a single species Q. faginea with a disjunct distribution in the Western and Eastern Mediterranean. This disjunction appears to be young. Fossils with strong affinities to Q. canariensis and eastern Mediterranean populations of Galliferae are known from the (early) Pliocene of Italy. This may suggest that the disruption of the formerly homogeneous distribution range of Galliferae began about 5.3-3.6 million years ago and is in agreement with the very weak molecular differentiation within the subsection.
Quercus, morphology, interspecific variability, intraspecific variability, quantitative analysis, species delimitation, taxonomy, biogeography
Research subject Plant Morphology; Plant Ecology
IdentifiersURN: urn:nbn:se:su:diva-62713OAI: oai:DiVA.org:su-62713DiVA: diva2:444092