A survey of seed and seedling characters in 1744 Australian dicotyledon species: cross-species trait correlations and correlated trait-shifts within evolutionary lineages

Abstract

Seedling traits have been described across 1744 species of Australian plants. Six traits were coded as binary alternatives: (1) phanerocotyly vs cryptocotyly; (2) first leaf scale-like vs leaflike; (3) first leafsingle vs paired; (4) cotyledons hairy vs. glabrous; (5) hypocotyl hairy vs glabrous, and (6) embryo green vs non-green at maturity. Seed volume was calculated from measurements of seed dimensions. Three approaches were used in analysing the data: (1) the taxonomic distribution of binary character states was described; (2) the strength of bivariate character associations was quantified at species level ('cross-species' correlations and regressions); (3) the data were arrayed on a phylogenetic tree in order to analyse by 'phylogenetic regression' for correlated evolutionary shifts in trait pairs. All the traits appeared evolutionarily malleable. For example, while cryptocotyly was the minority condition (22% of species), it occurred in many different taxa (124 genera, 40 families, 24 orders) with high levels of polymorphy (ISYO, 25% and 42% for genera, families and orders). Similarly, the less common attribute states for first leaf type, hypocotyl texture, cotyledon texture and embryo colour occurred in species from right across the dicotyledon phylogeny, as did independent evolutionary divergences in each of these characters. These patterns indicate that debate over which conditions are primitive and which are advanced will not have any general answer, only an answer for a specific branch-step in the phylogenetic tree. In nearly all cases, correlated-divergence analyses showed the same patterns as cross-species analyses. The strongest associations were between seed volume and cryptocotyIy, seed volume and scale-like first leaf, and seed volume and presence of green embryo. In addition, cryptocotyly and scale-like first leaf, and cotyledon and hypocotyl type, were strongly associated in both correlated-divergence and cross-species analyses. Interpretation of results was mostly presented with respect to seed size, a trait which we consider to be pivotal inaspecies' seedling establishment strategy. All possible pairwisecombinationsofbinary seedling traits were found in our study species. Taken together, the various lines of evidence presented here suggest that the traits have assorted more or less independently of each other and provide no evidence of functional groups based an these attributes. Thus, the several existing seedling typologies should be regarded as classifications of convenience rather than as reflecting fundamental types.

The evolution of the worldwide leaf economics spectrum

“…Similar to Shipley et al [15], we focus our review on four of the traits that make up the WLES: (i) photosynthesis per unit leaf mass (A mass ); (ii) leaf nitrogen per unit leaf mass (N mass ); (iii) leaf mass per unit area (LMA); and leaf lifespan (LL). However, the same framework can be used to examine the evolution of two additional traits often included in the WLES (leaf respiration rate and phosphorus content; Box 1), as well as proposed economics spectra for other plant functional traits [3,[16][17][18][19][20]. We conclude that the population-level data on variation in leaf functional traits suggest that genetic constraints have had a smaller role than selection in shaping WLES evolution.…”

Corrigendum to: New handbook for standardised measurement of plant functional traits worldwide

“…References on theory, significance and large datasets: Ng (1978);De Vogel (1980); Hladik and Miquel (1990);Garwood (1996); Kitajima (1996); Wright et al (2000); Ibarra-Manriquez et al (2001); Zanne et al (2005); Leck et al (2008).…”

Local climate adaptations in two ubiquitous Mojave Desert shrub species, Ambrosia dumosa and Larrea tridentata

“…Much of plant trait variation can be attributed to adaptations to the physical environment, including soil properties and climate (Caruso et al, 2020;Li et al, 2018;Oliveira et al, 2019;Shipley et al, 2012;Wright et al, 2000). The direction of quantitative trait change along ubiquitous environmental gradients such as elevation (Halbritter et al, 2018), aridity (Ivanova et al, 2019) or seasonality (Pearse & Hipp, 2012) is often repeated within and across species, providing fertile ground for the development of general principles of environmental adaptation to inform theories of species coexistence (Chesson et al, 2004), the role of 'environmental filtering' in community assembly (Ackerly & Cornwell, 2007;Adler et al, 2010;Kraft et al, 2015) and climate niche evolution (Martinez-Cabrera & Peres-Neto, 2013).…”