title: Climate determines vascular traits in the ecologically diverse genus Eucalyptus.
abstract: Current theory presumes that natural selection on vascular traits is controlled by a trade-off between efficiency and safety of hydraulic architecture. Hence, traits linked to efficiency, such as vessel diameter, should show biogeographic patterns; but critical tests of these predictions are rare, largely owing to confounding effects of environment, tree size and phylogeny. Using wood sampled from a phylogenetically constrained set of 28 Eucalyptus species, collected from a wide gradient of aridity across Australia, we show that hydraulic architecture reflects adaptive radiation of this genus in response to variation in climate. With increasing aridity, vessel diameters narrow, their frequency increases with a distribution that becomes gradually positively skewed and sapwood density increases while the theoretical hydraulic conductivity declines. Differences in these hydraulic traits appear largely genotypic in origin rather than environmentally plastic. Data reported here reflect long-term adaptation of hydraulic architecture to water availability. Rapidly changing climates, on the other hand, present significant challenges to the ability of eucalypts to adapt their vasculature.
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Pfautsch
authors.affiliation: Faculty of Agriculture and Environment, University of Sydney, 1 Central Avenue, Eveleigh, NSW, 2015, Australia.
authors.forename: Marco
authors.initials: M
authors.lastname: Harbusch
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Anita
authors.initials: A
authors.lastname: Wesolowski
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Renee
authors.initials: R
authors.lastname: Smith
authors.affiliation: CSIRO Land and Water Flagship, Floreat, WA, 6014, Australia.
authors.forename: Craig
authors.initials: C
authors.lastname: Macfarlane
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Tjoelker
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.|Department of Forest Resources, College of Food, Agricultural, and Natural Resource Sciences, University of Minnesota, St. Paul, MN, 55108, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Reich
authors.affiliation: Faculty of Agriculture and Environment, University of Sydney, 1 Central Avenue, Eveleigh, NSW, 2015, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Adams
mesh_terms: D001315:Australia; D002980:Climate; D005052:Eucalyptus / Q000033:anatomy & histology*; D014934:Wood / Q000033:anatomy & histology*
keywords: Anatomy; angiosperm tree; aridity; conduit diameter; hydraulic conductivity; vessel frequency distribution; water availability; wood density; xylem