Being John Harper: Using evolutionary ideas to improve understanding of global patterns in plant traits

Abstract

Abstract1. This review summarizes current understanding of five key plant traits: seed mass, plant height, wood density, leaf mass per unit area and leaf size, emphasizing ways in which our understanding of large-scale patterns in plant traits have improved over the last two decades.2. Notable advances include: (1) large-seeded species have greater seed dispersal distances than do small-seeded species, (2) leaf mass per unit area is not strongly or consistently related to plant traits outside the leaf economics spectrum, or to broad gradients in environmental conditions, and (3) fleshy fruit could not have first evolved for seed dispersal, as the first fleshy fruit appeared millions of years before the first potential seed dispersers.3. While quantifying large-scale patterns in plant traits has yielded many important discoveries, it is clear that the next major leap in understanding will not come from simply including ever more variables in our analyses. I suggest that we build upon Harper's "Darwinian approach to plant ecology" and apply evolutionary ideas to large-scale trait ecology. For example, quantifying trait impacts on lifetime fitness rather than on particular stages of plant regeneration can allow us to understand the coordination between seemingly disparate traits. I use this approach to bring seed mass and plant height together as integrated parts of a species' life-history spectrum. I then point out problems associated with the implicit assumption that selection acts on species' mean trait values and show how considering the way selection acts can improve our understanding of the effects of climate on plant traits. A goal for the future is to quantify the full suite of biotic and abiotic factors that shape plant strategy in complex, real-world situations.4. Synthesis. Enormous data availability and ever more powerful computational and statistical tools have given ecologists unprecedented power to quantify large-scale patterns in plant ecology. However, there is a limit to how far big data alone can take us. The time is ripe for a new generation of hypotheses and ecological theory built on strong evolutionary foundations. Let the creativity begin! K E Y W O R D Sglobal-scale ecology, leaf mass per unit area (LMA), leaf size, plant ecological strategy, plant height, seed size, specific leaf area (SLA), stem density

A research agenda for seed‐trait functional ecology

“…A coordinated effort by many plant ecologists studying how plants optimize productivity, light capture and water use, enabled an understanding of the leaf economic spectrum (Wright et al ., ; Sack & Scoffoni, ). Along with plant height and seed mass, these traits are used to describe the global spectrum of plant form and function (Díaz et al ., ; Moles, ). Likewise, studies of variation in water and nutrient uptake by plants, soil anchorage and the effects of plants on soil moisture, erosion and nitrogen fixation provide a better understanding of the functions of root traits (Mommer & Weemstra, ).…”

Delivering the promises of trait‐based approaches to the needs of demographic approaches, and vice versa

“…However, these connections are poorly understood in most taxa (Violle et al., ). Further, such correlative exercises remain a weak demonstration of the adaptive nature of functional traits and their role in adaptation (Moles, ). The reasons for this weakness include the static nature of the approach, which impedes tracking organismal responses over time, and trait covariation, which can blur causal trait~environment relationships (Wüest, Münkemüller, Lavergne, Pollock, & Thuiller, ).…”

Natural selection acting on integrated phenotypes: covariance among functional leaf traits increases plant fitness

“…The covariation of plant functional traits has been studied through descriptions of functional strategies in different species and ecosystems (Wright et al ., ; Díaz et al ., ). However, the microevolutionary processes shaping these strategies have not been fully described (Donovan et al ., ; Moles, ). Interspecific patterns of covariation among functional traits constitute a first line of evidence of the restrictions in the expression of particular combinations of traits (Díaz et al ., ).…”