Leaf traits in parental and hybrid species of Sorbus (Rosaceae)

• Published in: American journal of botany 2012-09, Vol.99 (9), p.1489-1500
• Main Authors: Ďurkovič, Jaroslav, Kardošová, Monika, Čaňová, Ingrid, Lagaňa, Rastislav, Priwitzer, Tibor, Chorvát, Dušan, Cicák, Alojz, Pichler, Viliam
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Arias; atomic force microscopy; Biomass; Botany; Cell Wall - metabolism; Cell walls; Chlorophyll - metabolism; Dispersal; ecophysiology; Evolution; Evolution and Phylogeny; Flowers - anatomy & histology; Fluorescence; gas exchange; Gases - metabolism; Growth traits; Hybridity; Hybridization, Genetic; hybrids; hydraulic conductivity; intermediacy; Leaf area; Leaves; Mapping; Microscopy, Confocal; modulus of elasticity; Nonnative species; Phenotype; Phenotypic traits; plant communities; Plant Leaves - anatomy & histology; Plant Leaves - cytology; Plant Leaves - growth & development; Plants; Principal Component Analysis; Quantitative Trait, Heritable; reticulate evolution; Rosaceae; Sorbus; Sorbus - anatomy & histology; Sorbus - cytology; Sorbus - genetics; Sorbus aucuparia; Taxonomy; tracheary element; Tracheary elements; transgressive segregation; Xylem; Xylem - physiology
• ISSN: 0002-9122; 1537-2197
• DOI: 10.3732/ajb.1100593

• Premise of the study: 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.• Key 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.