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A COMING OF AGE FOR THE
TRAIT-BASED APPROACH
IN PLANT ECOLOGY
Plant Functional Diversity: Organism
Traits, Community Structure, and
Ecosystem Properties. Eric Garnier,
Marie-Laure Navas, Karl Grigulis.
Oxford University Press, 2016. 231 pp.,
illus. $125.00 (ISBN: 9780198757368
cloth).
E
ric Garnier, at the Centre d’Ecologie
Fonctionnelle
et
Evolutive
(the premier French research institute
in plant ecology), and Marie-Laure
Navas, at Montpellier SupAgro (the
French National Institute of Higher
Education in Agricultural Sciences),
have a long-standing and productive collaboration. They published a
French-language monograph in 2013
on plant functional diversity. The
present book, coauthored with Karl
Grigulis, from the Université Joseph
Fourier in Grenoble, is a ­significantly
revised and updated translation of their
original monograph. The book marks
a coming of age for the trait-based
approach in plant ecology, providing a
concise summary of developments in
the field as it has rapidly taken hold in
the past decade.
The trait-based approach follows
from the premise that a focus on variation in the traits of plants can yield
deeper insights into the scaling of
function from individual plants to
communities and ecosystems than can
a simple tally of species diversity. In
a sense, this book is a revision of the
history of all plant ecology viewed
through the prism of the trait-based
perspective that breaks species into
their functional parts. Themes come
into discussion that can be traced
back to nineteenth-century studies of
plant form and function in Andreas
Schimper’s 1898 Pflanzengeographie
auf Physiologischer Grundlage, but
the traditional focus on comparisons
among species is set aside in favor
of an emphasis on the response of
selected “functional traits” to environmental conditions and the consequent
effects at the level of communities and
ecosystems.
An emphasis on traits over species
certainly is not alien to biologists; it
figures centrally in studies of evolutionary adaptation, quantitative genetics, and somewhat ironically in the
context of the trait-based perspective,
taxonomy. In these disciplines, any
discussion of species is filtered through
the study of variation in the characteristics of individuals. Taxonomists seek
traits that are stable under individual
and environmental variation, hence
providing reliable markers of species identity. Conversely, evolutionary
biologists identify the values of a trait
that are differentially favored in an
environment and the degree to which
favored variation in traits is heritable
and therefore subject to natural selection. In the context of evolutionary
biology, the trait-based approach in
functional ecology opens a path to a
novel synthesis, with recent developments in both community ecology
(Vellend 2016) and ecoevolutionary
dynamics (Hendry 2016).
For the moment, that potential is
somewhat limited by a lack of data,
because trait-based analyses draw
largely on only mean trait values even
though functional responses along
environmental gradients are expressed
through not only interspecific but also
intraspecific trait variation. Trait data
are compiled as species means from
an eclectic mix of past studies using
reasonably well-standardized methods but with considerable disparity
1082 BioScience • December 2016 / Vol. 66 No. 12
in associated metadata on growing
conditions, plant age, and other f­ actors
that can influence trait values. Most of
the collated studies also report only
one or a few traits, making it difficult to assess the coordinated interactions among a suite of traits affecting
a particular function, such as establishment, growth, or fecundity. The
authors recognize these limitations of
available trait data and provide both
a review of the existing compilations
and an authoritative summary of ways
to strengthen the database on which
the trait-based approach depends.
Despite the constraints imposed
by the presently available data, the
trait-based approach has established
the existence of broadly consistent
tradeoff relationships among traits
­
that serve as markers of key plant
functions. The most definitive of these
is a trade-off between the construction cost of leaves and their rates of
carbon gain (Wright et al. 2004), the
trigger for a burgeoning literature on
the intrinsic architecture of plant function (Reich 2014, Diaz et al. 2016).
This book effectively summarizes the
functional ecology that inspired the
trait-based approach and then turns
to the question of whether an understanding of how traits affect plant
function can in turn reveal aspects
of community assembly and ecosystem function. Patterns of abundanceweighted trait values of the species
constituting a community are shown
to provide insights into the degree
to which abiotic versus biotic factors
affect community assembly, as well as
the degree to which dominance versus complementarity effects influence
ecosystem properties and the provision of ecosystem services. A chapter on the management of rangeland
and crop ecosystems nicely illustrates
the reciprocal utilitarian and scientific
value of the trait-based approach to
plant functional diversity. Finally, a
closing chapter on future prospects
for plant functional diversity touches
on perhaps one of the more exciting paths forward in the trait-based
approach: trait driver theory (Enquist
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et al. 2015), which uses the frequency
distribution of traits to predict shifts in
community composition and ecosystem function in response to environmental change.
In conclusion, this book lays out
with impressive clarity, depth, and
breadth the conceptual framework of
plant functional diversity as it stands
today. The central ideas of the traitbased approach are firmly in place,
rooted in the comparative ecology of
species but consistently focused on
trait variation and its effects on community assembly and ecosystem function. The review of relevant ­literature
is selective but broadly representative, informatively blending European
and Anglo-American perspectives on
plant function. It is clear that the
trait-based approach is not yet fully
formed—the available trait database
is a work in progress, and there are
unresolved issues even in the nature
of traits and their relationship to function—but the authors do a good job
laying out the ambiguities and uncertainties of the approach, providing a
well-referenced summary of the key
issues. The book provides a definitive
reading for a graduate-level seminar
on plant functional diversity and an
excellent desk reference for any biologist interested in the evolutionary and
ecological implications of trait variation. Garnier, Navas, and Grigulis have
laid an admirably solid foundation for
the lines of inquiry that will lead to the
maturation of the trait-based approach
and its integration into a larger synthesis of ecological and evolutionary
theory.
References cited
Díaz S, et al. 2016. The global spectrum of plant
form and function. Nature 529: 167–171.
Enquist BJ, Norberg J, Bonser SP, Violle C,
Webb CT, Henderson A, Sloat LL, Savage
VM. 2015. Scaling from traits to ecosystems:
Developing a general trait driver theory via
integrating trait-based and metabolic scaling
theories. Advances in Ecological Research
52: 249–318.
Hendry AP. 2016. Eco-Evolutionary Dynamics.
Princeton University Press.
Reich P. 2014. The world-wide “fast–slow” plant
economics spectrum: A traits manifesto.
Journal of Ecology 102: 275–301.
Vellend M. 2016. The Theory of Ecological
Communities. Princeton University Press.
Wright IJ, et al. 2004. The worldwide leaf economics spectrum. Nature 428: 821–827.
MARTIN J. LECHOWICZ
Martin J. Lechowicz (http://biology.
mcgill.ca/faculty/lechowicz) is a
professor emeritus and Liber Ero Chair
in Conservation Biology at McGill
University, in Montréal, Québec.
doi:10.1093/biosci/biw134
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December 2016 / Vol. 66 No. 12 • BioScience 1083