Functional traits as predictors of vital rates across the life cycle of tropical trees

Abstract

Summary 1.The 'functional traits' of species have been heralded as promising predictors for species' demographic rates and life history. Multiple studies have linked plant species' demographic rates to commonly measured traits. However, predictive power is usually low -raising questions about the practical usefulness of traits -and analyses have been limited to size-independent univariate approaches restricted to a particular life stage. 2. Here we directly evaluated the predictive power of multiple traits simultaneously across the entire life cycle of 136 tropical tree species from central Panama. Using a model-averaging approach, we related wood density, seed mass, leaf mass per area and adult stature (maximum diameter) to onset of reproduction, seed production, seedling establishment, and growth and survival at seedling, sapling and adult stages. 3. Three of the four traits analysed here (wood density, seed mass and adult stature) typically explained 20-60% of interspecific variation at a given vital rate and life stage. There were strong shifts in the importance of different traits throughout the life cycle of trees, with seed mass and adult stature being most important early in life, and wood density becoming most important after establishment. Every trait had opposing effects on different vital rates or at different life stages; for example, seed mass was associated with higher seedling establishment and lower initial survival, wood density with higher survival and lower growth, and adult stature with decreased juvenile but increased adult growth and survival. 4. Forest dynamics are driven by the combined effects of all demographic processes across the full life cycle. Application of a multitrait and full-life cycle approach revealed the full role of key traits, and illuminated how trait effects on demography change through the life cycle. The effects of traits on one life stage or vital rate were sometimes offset by opposing effects at another stage, revealing the danger of drawing broad conclusions about functional traitdemography relationships from analysis of a single life stage or vital rate. Robust ecological and evolutionary conclusions about the roles of functional traits rely on an understanding of the relationships of traits to vital rates across all life stages.

Survival and growth of tree seedlings as a function of seed size in a gallery forest under restoration

“…The negative relationship between Relative Height Increment and seed mass recorded in our experiment corroborate several other studies using different species and environments (Baraloto et al 2005;Larson et al 2015;Visser et al 2016) including in the Brazilian Cerrado (Pereira et al 2013). Turnbull et al (2012) suggest that this relationship can be related with the strategy of growth rates among species (the fast-slow continuum hypothesis).…”

“…The persistence of the positive effects of seed mass on survival after the stage of seedlings suggests that other correlated functional attributes can be involved in the mechanisms of this relationship (Baraloto et al 2005;Muller-Landau 2010;Laughlin 2014;Visser et al 2016). It is possible that functional traits studies beyond seed mass could explain with more accuracy questions regarding the recruitment and establishment of species on degraded areas, then improving ecological restoration projects (Sandel et al 2011).…”

Surviving in a Cosexual World: A Cost-Benefit Analysis of Dioecy in Tropical Trees

“…j (25) (26) (27) the estimation of effect sizes, especially in cases where multiple variables influence the response variable (Grueber et al 2011). Our normalized traits were only weakly correlated (r 2 SM,WD p 0:026; r 2 SM,Dmax p 0:021; r 2 WD,Dmax p 0:0019), and the statistical approach was also vigorously tested by Visser et al (2016a), who, using the same vital rates and trait data, found no issues with nonlinearity, heteroscedasticity, nature of the random effect structure, and lack of random slopesissues that can potentially impact effect sizes and robustness of conclusions. Parameters were averaged over all models, using the zero method.…”

“…We begin by explaining the structure of the composite IPM and vital rate functions. The vital rate functions incorporate three functional traits (seed mass, wood density, and adult stature; see, e.g., Visser et al 2016a) and breeding system. Second, we explain our statistical approach for fitting the vital rates through model averaging and provide an overview of the study site and data used.…”

“…All free-standing woody plants ≥20 cm tall and !1 cm in DBH were tagged, measured for height, and identified to species in annual censuses of twenty thousand 1-m 2 seedling plots starting in 2001 (details in Comita et al 2007;Visser et al 2016a). Data are deposited in the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad.fm654 (Visser et al 2016b).…”