Oak morphological traits: Between taxa and environmental variability

Abstract

The seven oak species present in Lebanon show taxonomic ambiguity partly due to their great morphological variability among and within species. Very few investigations were conducted on oaks in Lebanon despite the presence of endemic species, and none tried to discriminate these according to their morphology, nor to determine subspecies or identify eventual hybrids. In this study 1328 leaves and 550 fruits were collected covering the whole range of oak species over the Lebanese territory; 24 leaf and 6 fruit traits were recorded and analyzed in order to differentiate among species, to define missing gaps for certain subspecies and to discriminate eventual hybrids and their possible parents. Environmental conditions were attributed in each sampling location to study the effect of selected environmental factors on leaf traits. PCA results showed that several leaf and fruit traits differ significantly among species, and that species leaf characteristics override the environmental influence. The interval between central nerve and apical leaf nerve, interval between apical and basal lobes, scale length and cupule diameter are the main contributors to differentiation among taxa. Oak species were grouped according to the 3 subgenus sections and species and subspecies were discriminated mainly according to fruit traits variance. Three potential hybrids were identified, with intermediate morphology or closer to one of their parents. Variation of morphological traits were discerned according to biogeographical gradients, and varied from one species to another.