Functional Traits

Abstract

Functional traits are morphological, biochemical, physiological, structural, phenological or behavioural characteristics of organisms that influence performance or fitness. Grouping species by functional characteristics is a long‐standing idea, but there has more recently been rapid development in the application of trait‐based approaches to diverse topics in ecology. Two common applications of functional traits are to characterise community responses to changes in the environment, including community assembly processes, and to quantify the influence of community shifts on ecosystem processes. Practical decisions include: What types of traits should be considered? How can traits be measured or inferred? Are traits correlated or traded‐off? Which, and how many, traits should be assessed? How should trait data be analysed? Functional trait approaches enhance ecological understanding by focusing on the mechanisms that govern interactions between organisms and their environments. Measuring and understanding traits increases our understanding of ecological processes, thus also informing conservation and restoration.

Key Concepts

  • Functional traits are morphological, biochemical, physiological, structural, phenological or behavioural characteristics that influence organism performance or fitness.
  • Traits can be broadly classified either as having an effect on ecosystem properties and the services that human societies derive from them, or as characterising a response to environmental change or with respect to processes affecting community assembly.
  • Common data types for traits include continuous, categorical, ordinal and binary variable formats. The data type has repercussions for subsequent data analyses.
  • Methods for measuring traits vary from time‐consuming (hard traits) to rapid (soft traits), and in turn the information content of the resulting data also varies.
  • Trait syndromes describe patterns of inter‐trait correlation that define differences and trade‐offs in ecological strategies.
  • When choosing traits for calculating functional diversity it is important to consider which, and how many, traits are included, as well as what insights they will provide into the ecosystem processes, community structure or assembly processes under consideration.
  • Functional traits are at the forefront of efforts to develop a mechanistic understanding of how species diversity influences ecosystem functioning, and the current ecological literature presents many indices by which functional diversity can be computed.

Keywords: biodiversity; ecosystem function; response traits; effect traits; trait syndromes; functional diversity

Figure 1. Overview of organismal functional traits showing how certain traits determine species' responses to the environment, and/or their effects on ecosystem processes, and in turn ecosystem services and people (redrawn from Diaz et al., ). Shapes indicate the particular trait variables (e.g. leaf mass per unit area, body size) and the size of the shapes indicate the magnitude of the trait state.
Figure 2. Relationships among key functional traits are central to functional ecology. (a) Photosynthetic rate (a performance currency) is related to SLA (specific leaf area) and nitrogen content. (Reproduced with permission from McGill et al., (2006) © Elsevier.) (b) The affinity‐storage‐velocity trade‐off in phytoplankton traits. (Reproduced with permission from Edwards et al., (2013) © The University of Chicago Press.)
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Further Reading

Phylogenetic considerations and traits

Cavender‐Bares J, Ackerly DD and Kozak KH (2012) Integrating ecology and phylogenetics: the footprint of history in modern‐day communities. Ecology 93 (sp8): S1–S3. Special issue: http://www.esajournals.org/doi/abs/10.1890/12‐0092.1.

Díaz S, Purvis A, Cornelissen JHC, et al. (2013) Functional traits, the phylogeny of function, and ecosystem service vulnerability. Ecology and Evolution 3 (9): 2958–2975.

Inferring unknown trait values

Guénard G, Legendre P and Peres‐Neto P (2013b) Phylogenetic eigenvector maps: a framework to model and predict species traits. Methods in Ecology and Evolution 4 (12): 1120–1131.

Intraspecific trait variation

Albert CH, Thuiller W, Yoccoz NG, et al. (2010) Intraspecific functional variability: extent, structure and sources of variation. Journal of Ecology 98 (3): 604–613.

Violle C, Enquist BJ, McGill BJ, et al. (2012b) The return of the variance: intraspecific variability in community ecology. Trends in Ecology and Evolution 27 (4): 244–252.

Functional traits, conservation and restoration

Cadotte MW, Carscadden K and Mirotchnick N (2011b) Beyond species: functional diversity and the maintenance of ecological processes and services. Journal of Applied Ecology 48 (5): 1079–1087.

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Nock, Charles A, Vogt, Richard J, and Beisner, Beatrix E(Feb 2016) Functional Traits. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0026282]