Systematic and ecological wood anatomy of NeotropicalSchefflera(Araliaceae), with an emphasis on theDidymopanaxgroup

Abstract

Wood anatomy has been investigated from 35 species belonging to the Neotropical clade of the polyphyletic genus Schefflera (Araliaceae), representing three of the five subgroups (Didymopanax, Crepinella and Sciodaphyllum). The species examined are rather uniform in their wood structure, sharing the presence of scalariform and simple perforation plates, septate fibres and scanty paratracheal axial parenchyma. The observed variation in many wood characters showed statistically significant differences relative to latitude, climate and, especially, vegetation types. In particular, the intervessel pits are larger in species from higher latitudes and in seasonally dry habitats than those from lower latitudes and rainforests. Latitudinal and ecological trends in the variation of vessel element lengths, bar numbers on perforation plates, intervessel pit sizes and ray widths may be at least partially explained as effects of adaptation to drier environments in the course of dispersal outside the Amazonian region and diversification in the Atlantic Forest subclade and the Savannic subclade within the Didymopanax group. The occurrence of a granular annulus on the intervessel pit membranes in S. chimantensis and S. sprucei (both of the Crepinella group) is the first record of this feature in Araliaceae. In comparisons of Neotropical Schefflera with the other major clades of Schefflera sensu lato, wood anatomical diversity is consistent with the polyphyly of this genus based on molecular phylogenetic analyses. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 452–475.

Wood and bark of Buddleja: uniseriate phellem, and systematic and ecological patterns

“…Such a weak response could result from a considerable functional effect of even minor changes in this trait, as water conductivity increases to the fourth power of vessel diameter (Tyree & Zimmermann 2002). Additionally, the shortening of vessel elements and fibres in drier habitats has been reported as an environmental trend in several other genera (Baas 1973;Van der Graaff & Baas 1974;Van Den Oever et al 1981;Baas 1986;Noshiro & Baas 2000;Lens et al 2003;Kotina et al 2013). The length of tracheary elements is linked to the size of cambial fusiform cells, but the adaptive or functional significance of these parameters remains obscure (Noshiro & Baas 2000).…”

“…The length of tracheary elements is linked to the size of cambial fusiform cells, but the adaptive or functional significance of these parameters remains obscure (Noshiro & Baas 2000). As for the size of intervessel pits, variation in this trait in different taxa can show opposite responses to drought and precipitation seasonality (Sonsin et al 2012;Kotina et al 2013). The functional and adaptive effects of this character cannot be assessed separately from the estimation of other wood characters, such as the density of bordered pits on vessel walls, the area of pit membranes on vessels, the sectoriality of long-distance transport in the stem, and especially the thickness and porosity of pit membranes (Orians et al 2004;Wheeler et al 2005;Ellmore et al 2006;Hacke et al 2006;Tixier et al 2014;Schenk et al 2015;Li et al 2016).…”

Asterids

“…Oskolski et al . () present wood anatomical analyses of Neotropical Schefflera J.R.Forst. & G.Forst.…”