title: Scalariform-to-simple transition in vessel perforation plates triggered by differences in climate during the evolution of Adoxaceae.
abstract: Background and Aims Angiosperms with simple vessel perforations have evolved many times independently of species having scalariform perforations, but detailed studies to understand why these transitions in wood evolution have happened are lacking. We focus on the striking difference in wood anatomy between two closely related genera of Adoxaceae, Viburnum and Sambucus, and link the anatomical divergence with climatic and physiological insights. Methods After performing wood anatomical observations, we used a molecular phylogenetic framework to estimate divergence times for 127 Adoxaceae species. The conditions under which the genera diversified were estimated using ancestral area reconstruction and optimization of ancestral climates, and xylem-specific conductivity measurements were performed. Key Results Viburnum, characterized by scalariform vessel perforations (ancestral), diversified earlier than Sambucus, having simple perforations (derived). Ancestral climate reconstruction analyses point to cold temperate preference for Viburnum and warm temperate for Sambucus. This is reflected in the xylem-specific conductivity rates of the co-occurring species investigated, showing that Viburnum lantana has rates much lower than Sambucus nigra. Conclusions The lack of selective pressure for high conductive efficiency during early diversification of Viburnum and the potentially adaptive value of scalariform perforations in frost-prone cold temperate climates have led to retention of the ancestral vessel perforation type, while higher temperatures during early diversification of Sambucus have triggered the evolution of simple vessel perforations, allowing more efficient long-distance water transport.
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.
authors: Frederic
authors: F
authors: Lens
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.
authors: Rutger A
authors: RA
authors: Vos
authors: INRA, University of Bordeaux, UMR EGFV, F-33450 Talence, France.
authors: Guillaume
authors: G
authors: Charrier
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.|School of Life Sciences, University of Kwazulu-Natal, P. Bag X01, 3209, Scottsville, South Africa.
authors: Timo
authors: T
authors: van der Niet
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.
authors: Vincent
authors: V
authors: Merckx
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.
authors: Pieter
authors: P
authors: Baas
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.|Institute for Biodiversity and Ecosystem Dynamics, Computation Geo-Ecology, University of Amsterdam, Amsterdam, The Netherlands.
authors: Jesus
authors: J
authors: Aguirre Gutierrez
authors: Section Ecology, Evolution and Biodiversity Conservation, KU Leuven, Belgium.
authors: Bart
authors: B
authors: Jacobs
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.
authors: Larissa
authors: L
authors: Chacon Dória
authors: Naturalis Biodiversity Center, Leiden University, P.O. Box 9517, 2300RA Leiden, The Netherlands.|Section Ecology, Evolution and Biodiversity Conservation, KU Leuven, Belgium.
authors: Erik
authors: E
authors: Smets
authors: INRA, University of Bordeaux, UMR BIOGECO, F-33450 Talence, France.
authors: Sylvain
authors: S
authors: Delzon
authors: Botanic Garden Meise, Nieuwelaan 38, BE-1860 Meise, Belgium.
authors: Steven B
authors: SB
authors: Janssens
keywords: 
            Sambucus
          ; 
            Viburnum
          ; Adoxaceae; Baileyan wood trends; ancestral area and climate reconstruction; molecular dating; vessel perforation plate transition; wood anatomy