Study On The Variation In Leaf Morphology Of Quercus Aquifolioides Rehd. Et Wils. And Quercus Spinosa David Ex Franch.Using Geometric Morphometric Methods

Leaves are the main photosynthetic organs of plants,and their morphology affects a series of important physiological processes and consequently plant fitness.Based on Simple Sequence Repeats(SSR)molecular markers,we attempt to quantify leaf morphology variation between and within species of two species(Quercus aquifolioides and Q.spinosa),and explore leaf morphology variation caused by genetic,geographical and climatic factors.Based on SSRs,we analyzed the genetic structure of Q.aquifolioides and Q.spinosa,and their individuals were divided into different genetic lineages with Q = 0.8 as the threshold(Q.aquifolioides: WSP-HDM and Tibet lineages;Q.spinosa: East and West lineages).We characterized their leaves in terms of 13 landmarks.Leaves morphology was digitally captured in the two-dimensional coordinates of 13 landmarks,then divided into leaf size and asymmetric and symmetric components of leaf shape by generalized Procrustes analysis.Three sets of morphological data,symmetric component,asymmetric component and leaf size,were used to study leaf variation of Q.aquifolioides and Q.spinose.It was found that there were significant differences in leaf morphology between Q.aquifolioides and Q.spinose.Within species,there were significant differences in leaf symmetric component and leaf size between different genetic lineages,but no significant difference in the asymmetric component.We used tleaf morphology to discriminant individuals and found that 75% of the individuals of Q.aquifolioides and 80% of those of Q.spinose can be correctly identified.Within species,80% WSP-HDM individuals and 87% Tibet individuals can be correctly identified respectively.The East and West lineages of Q.spinose can be correctly identified in 75% and 74% of individuals,respectively.This indicates that it is difficult to distinguish some morphologically similar individuals only by leaf shape,and it may be necessary to use other characteristics of leaves,such as whether there are hairs or not,and the distribution of hairs.We found that the symmetric component and size of leaves were mainly related to genetic factors,and influenced by geographic and climatic factors by distance-based redundancy analysis(db RDAs).The asymmetric component was only affected by geographic factors.This indicates that the influence of environment on leaf morphology is not negligible,so leaf morphology as an indicator of species discrimination should be cautious.This study provided new insights for the ecology and evolution of the taxa.