Pawar / Woodward Trait-Based Ecology - From Structure to Function

1. Auflage 2015
ISBN: 978-0-12-802635-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 52, 400 Seiten

Reihe: Advances in Ecological Research

The theme of this volume is Trait-Based Ecology - From Structure to Function. - Advances in Ecological Research is one of the most successful series in the highly competitive field of ecology - Each volume publishes topical and important reviews, interpreting ecology as widely as in the past, to include all material that contributes to our understanding of the field - Topics in this invaluable series include the physiology, populations, and communities of plants and animals, as well as landscape and ecosystem ecology

Autoren/Hrsg.

Pawar, Samraat

Woodward, Guy

Leseproben

Chapter One Scaling-up Trait Variation from Individuals to Ecosystems
Jean P. Gibert*,1; Anthony I. Dell†; John P. DeLong*; Samraat Pawar‡    * School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
† National Great Rivers Research and Education Center (NGRREC), East Alton, Illinois, USA
‡ Grand Challenges in Ecosystems and the Environment, Silwood Park, Department of Life Sciences, Imperial College London, Ascot, Berkshire, United Kingdom
1 Corresponding author: email address: [e-mail] Abstract
Ecology has traditionally focused on species diversity as a way of characterizing the health of an ecosystem. In recent years, however, the focus has increasingly shifted towards trait diversity both within and across species. As we increasingly recognize that ecological and evolutionary timescales may not be all that different, understanding the ecological effects of trait variation becomes paramount. Trait variation is thus the keystone to our understanding of how evolutionary processes may affect ecological dynamics as they unfold, and how these may in turn alter evolutionary trajectories. However, a multi-level understanding of how trait variation scales up from individuals to whole communities or ecosystems is still a work in progress. The chapters in this volume explore how functional trait diversity affects ecological processes across levels of biological organization. This chapter aims at binding the messages of the different contributions and considers how they advance our understanding of how trait variation can be scaled up to understand the interplay between ecological and evolutionary dynamics from individuals to ecosystems. Keywords Functional trait Diversity Individual variation Population Community Ecosystem function Dynamics 1 Why Is it Important to Understand Traits and Trait Variation?
Evolutionary theory has long recognized the importance of heritable individual (or intraspecific) variation in phenotypic traits (Fordyce, 2006; Lande, 2013). At the same time, ecology has historically focused on mean traits as both a characterization of populations and a response variable (Araújo et al., 2011; Bolnick et al., 2011; Sherratt and Macdougal, 1995; Violle et al., 2012). This difference in focus, to a large extent, stems from the viewpoint that ecology and evolution operate at vastly different time scales. And the origins of this viewpoint, in turn, are probably to be found in the fact that including Darwin's work, early evolutionary ideas were based on the fossil record and tended to be ‘gradualist’ (Stanley, 1989). In Darwin's (1859) words ‘I do believe that natural selection will generally act very slowly, only at long intervals of time, and only on a few of the inhabitants of the same region. I further believe that these slow, intermittent results accord well with what geology tells us of the rate and manner at which the inhabitants of the world have changed’. This view was reinforced by the fact that examples of evolutionary change mostly came from observations of gradual change over millions of years in the fossil record. We are now becoming increasingly aware that evolutionary and ecological processes do not occur in isolation and that the time scales of ecological (changes in population sizes) and evolutionary (changes in allele frequencies or trait distributions) rates of change often overlap (Hairston et al., 2005; Schoener, 2011; Schoener et al., 2014). Indeed, feedback loops between ecological and evolutionary processes, or ‘eco-evolutionary feedbacks’, may be common in natural systems (Fussmann et al., 2003; Jones et al., 2009; Yoshida et al., 2003). Evolutionary biologists have long recognized that the variation in (heritable) individual traits can change during the course of evolution and can affect the strength of selection (Dobzhansky, 1937)—a process central to the evolutionary component of the eco-evolutionary feedbacks. But the potential effects of this individual variation on ecological processes per se are less well understood (Araújo et al., 2011; Bolnick et al., 2011; Lomnicki, 1988; McGill et al., 2006). To fully grasp how individual variation in functional traits can affect ecological dynamics and processes (and thus potentially eco-evolutionary feedbacks), we need to develop a mechanistic understanding of how trait variation ‘scales up’ from individuals, through species interactions, to ecosystem dynamics (Pawar et al., 2014). The goal of this volume is to advance these ideas by proposing ways to assess how variation in functional traits may alter the outcome of ecological interactions. In this introductory chapter, we present a brief description of each of the contributions to the volume, including a discussion about how they fit into a broader perspective of ecological processes, and how they contribute to a better understanding of how trait variation effects scale up from individuals to ecosystems. 2 Traits and Individual-Level Variation
To understand community structure and ecosystem processes, ecologists have long focused on species diversity as an important explanatory mechanism where, for example, decomposition rates, primary production or food web topology results from the number and types of species present (Chapin et al., 1997, 2000; Naeem et al., 2012). This approach has been the basis for some of the most successful ecological theories, such as Tilman's R* competition theory (Tilman, 1982, 1986). Species-centric approaches like these build upon the idea that groups of organisms differing in species composition will differentially impact higher levels of biological organization such as communities or ecosystems. Focusing on groups of species with similar trophic positions or feeding types (functional groups) has also yielded important and powerful insights (Hooper et al., 2005; Loreau et al., 2001), but can mask information regarding the effect of particular species (Naeem and Wright, 2003; Reich et al., 2004), and its predictive capacity has been difficult to assess (McGill et al., 2006; Schmitz, 2010). As a consequence, alternative approaches for understanding the emergence of complex properties of communities and ecosystems have been sought, and many ecologists now consider that it is the specific traits that species have that are largely responsible for determining the properties and dynamics of ecological systems (Eviner and Chapin, 2003; Lavorel and Garnier, 2002; McGill et al., 2006; Mlambo, 2014; Naeem and Wright, 2003; Violle et al., 2007). This perspective suggests that in order to understand and predict community and ecosystem organization, ecologists should also focus on the mechanistic basis of ‘functional traits’ of species in the focal system, instead of simply categorizing their broad functional role (Eviner and Chapin, 2003; Mlambo, 2014). Such a mechanistic trait-based approach should be generalizable across taxa and habitats and may yield general predictions about how ecosystems respond to environmental effects, such as climate change or overharvesting of animals or plants. The definition of exactly what are functional traits remains controversial, and a historical perspective of this issue is provided by Schmitz et al. (2015) in their chapter “Functional Traits and Trait-Mediated Interactions: Connecting Community-Level Interactions with Ecosystem Functioning”. Adopting Schmitz et al.’s definition, a functional trait represents any given trait (whether physiological, behavioural or morphological) that, in the course of maximizing fitness, impacts or regulates higher-level ecological processes and patterns (Mlambo, 2014). At the same time, a functional trait also affects the absolute fitness of individuals, and thus the mean fitness of the population. This is no different from the traditional, evolutionary, quantitative-genetic definition of a trait, but in an ecological framework, heritability of traits is no longer a pre-requisite as purely plastic change can have important ecological implications as well (Gibert and Brassil, 2014). Nor is it necessary to restrict focus of trait variation to phenotypic distributions within populations—as shown by Norberg et al. (Norberg et al., 2001; Savage et al., 2007), it is possible to meaningfully study the effects of across-species trait distributions, especially when it is necessary to tractably link trait variation to ecosystem function. 3 Population-Level Effects of Trait Variation
3.1 Functional response and prey selection
In the chapter “Individual Variability: The Missing Component to our Understanding of Predator -Prey Interactions”, Pettorelli et al. (2015) explore how individual variation in traits controlling ‘predation risk’ in prey and ‘prey selection’ in predators can alter population dynamics. They argue that trait variation can have important yet poorly understood consequences for the shape of predator functional responses, which...