title: Leaf traits in parental and hybrid species of Sorbus (Rosaceae).
abstract: OBJECTIVE
  Knowledge of functional leaf traits can provide important insights into the processes structuring plant communities. In the genus Sorbus, the generation of taxonomic novelty through reticulate evolution that gives rise to new microspecies is believed to be driven primarily by a series of interspecific hybridizations among closely related taxa. We tested hypotheses for dispersion of intermediacy across the leaf traits in Sorbus hybrids and for trait linkages with leaf area and specific leaf area.
  
  
  METHODS
  Here, we measured and compared the whole complex of growth, vascular, and ecophysiological leaf traits among parental (Sorbus aria, Sorbus aucuparia, Sorbus chamaemespilus) and natural hybrid (Sorbus montisalpae, Sorbus zuzanae) species growing under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to characterize the topography of cell wall surfaces of tracheary elements and to map the reduced Young's modulus of elasticity.
  
  
  RESULTS
  Intermediacy was associated predominantly with leaf growth traits, whereas vascular and ecophysiological traits were mainly parental-like and transgressive phenotypes. Larger-leaf species tended to have lower modulus of elasticity values for midrib tracheary element cell walls. Leaves with a biomass investment related to a higher specific leaf area had a lower density. Leaf area- and length-normalized theoretical hydraulic conductivity was related to leaf thickness.
  
  
  CONCLUSIONS
  For the whole complex of examined leaf traits, hybrid microspecies were mosaics of parental-like, intermediate, and transgressive phenotypes. The high proportion of transgressive character expressions found in Sorbus hybrids implies that generation of extreme traits through transgressive segregation played a key role in the speciation process.
authors.affiliation: Department of Phytology, Technical University, 960 53 Zvolen, Slovakia. jaroslav.durkovic@tuzvo.sk
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Durkovic
authors.forename: Monika
authors.initials: M
authors.lastname: Kardosová
authors.forename: Ingrid
authors.initials: I
authors.lastname: Canová
authors.forename: Rastislav
authors.initials: R
authors.lastname: Lagana
authors.forename: Tibor
authors.initials: T
authors.lastname: Priwitzer
authors.forename: Dusan
authors.initials: D
authors.lastname: Chorvát
authors.forename: Alojz
authors.initials: A
authors.lastname: Cicák
authors.forename: Viliam
authors.initials: V
authors.lastname: Pichler
mesh_terms: D000704:Analysis of Variance; D002473:Cell Wall / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D035264:Flowers / Q000033:anatomy & histology; D005453:Fluorescence; D005740:Gases / Q000378:metabolism; D006824:Hybridization, Genetic; D018613:Microscopy, Confocal; D010641:Phenotype; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000166:cytology / Q000254:growth & development; D025341:Principal Component Analysis; D019655:Quantitative Trait, Heritable; D031994:Sorbus / Q000033:anatomy & histology* / Q000166:cytology / Q000235:genetics*; D052584:Xylem / Q000502:physiology
chemical_list: D005740:Gases; D002734:Chlorophyll