Evolution of leaf form correlates with tropical–temperate transitions in Viburnum (Adoxaceae)

Abstract

Strong latitudinal patterns in leaf form are well documented in floristic comparisons and palaeobotanical studies. However, there is little agreement about their functional significance; in fact, it is still unknown to what degree these patterns were generated by repeated evolutionary adaptation. We analysed leaf form in the woody angiosperm clade Viburnum (Adoxaceae) and document evolutionarily correlated shifts in leafing habit, leaf margin morphology, leaf shape and climate. Multiple independent shifts between tropical and temperate forest habitats have repeatedly been accompanied by a change between evergreen, elliptical leaves with entire margins and deciduous, more rounded leaves with toothed or lobed margins. These consistent shifts in Viburnum support repeated evolutionary adaptation as a major determinant of the global correlation between leaf form and mean annual temperature. Our results provide a new theoretical grounding for the inference of past climates using fossil leaf assemblages.

Causes of ecological gradients in leaf margin entirety: Evaluating the roles of biomechanics, hydraulics, vein geometry, and bud packing

“…These reconstructions accord with the demonstration by Schmerler et al (2012) of repeated transitions from entire to nonentire leaves, and vice versa, associated with latitude in a much smaller set of Viburnum species. Our fi ndings extend those results by showing how they are coupled to shift s in leaf thickness.…”

“…On the basis of the phylogeny and leaf thickness data for 81 Viburnum taxa presented by Chatelet et al (2013) and the leaf margin types scored by Schmerler et al (2012) for several dozen of these species, and by us for the remaining taxa (data sets available from the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad. h1d1b; Givnish and Kriebel, 2017 ), we found a signifi cant phylogenetically structured logistic regression relating leaf margin to leaf thickness, regardless of whether we pooled minutely toothed species with those having non-entire margins ( β = −10.14 ± 3.71 SE, α = 3.51, P < 0.007) or entire margins ( β = −7.81 ± 3.74, α = 6.62, P < 0.037) ( Fig.…”

A taxonomic reassessment of Viburnum (Adoxaceae) in the Azores

“…Traditionally, the genus has been subdivided into ten sections on the basis of morphological characters (Oersted 1861, Hara 1983. The monophyly of all sections was supported by morphological data and molecular studies, except sections Megalotinus and Odontotinus (Donoghue 1983, Baldwin et al 1995, Donoghue et al 2004, Winkworth & Donoghue 2005, Clement & Donoghue 2011, Schmerler et al 2012. Viburnum tinus Linnaeus (1753: 267−268), placed in section Tinus, is a morphologically variable taxon in which two to three subspecies have been recognised.…”

“…in Forbes & Hemsley (1888: 355), V. cinnamomifolium Rehder (1913: 31), V. atrocyaneum Clarke (1882: 7), V. calvum Rehder (1911: 310) and V. davidii Franchet (1885: 251), all native from China. Based on the results of Donoghue et al (2004) and Schmerler et al (2012) we selected the following outgroup taxa: V. acerifolium Linnaeus (1753: 268), V. flavescens Smith (1916: 139), V. edule (Michaux 1803: 180) Rafinesque (1808: 354), V. ellipticum Hooker (1833: 280), V. dentatum Linnaeus (1753: 268), V. farreri Stearn (1966: 22), V. lutescens Blume (1825: 655) and V. taiwanianum Hayata (1911: 137). The GenBank sequences for the outgroup taxa and additional taxa within section Tinus were from the studies of Donoghue et al (2004) and Clement & Donoghue (2011.…”

“…It was resolved as sister taxon to V. tinus subsp. tinus in studies by Clement & Donoghue (2011 and Schmerler et al (2012).…”