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CHAPTER THREE

Life histories and body size

DAVID ATKINSON

The University of Liverpool

ANDREW G.HIRST

British Antarctic Survey

Introduction
This chapter demonstrates how investigating patterns of survival, reproduction,
growth and development – life histories – can improve understanding and
prediction in diverse areas of ecology ranging from microevolution and popula-
tion dynamics of individual species, to ecosystem function and biogeochemistry.
To make sense of the huge diversity of life history in nature, a first step is to
derive a common set of traits, such as age and size at first reproduction, number
and size of offspring, inter-clutch interval, and juvenile and adult survival. The
effects of changes in the magnitude of each of these traits on the others
(e.g. increased offspring size may be traded off against a reduction in offspring
number), and their relationship to fitness or population growth under partic-
ular environmental conditions, can then be analyzed.
This chapter initially outlines how this process, life-history analysis, is used
in adaptive evolutionary models that predict adult and offspring size within
species. As there are numerous reviews that introduce life-history analysis
(e.g. Lessells, 1991 ; Roff, 1992 ; Stearns, 1992 ; Daan & Tinbergen, 1997 ; Stearns,
2000 ; Roff, 2002; Begon, Townsend & Harper, 2006 ), this chapter outlines only
the salient features. While some applications of life-history analysis are beyond
the scope of this chapter (e.g. elasticity analysis; Benton & Grant, 1999 ), here
we will evaluate the importance of life-history analysis in understanding and
predicting body-size variation and the scaling of many traits with body size, at
various levels of ecological organization ranging from within-genotype varia-
tion (phenotypic plasticity and changes during ontogeny) to differences among
ecological functional groups that affect ecosystem function and biogeochemistry.
Specifically, the chapter first outlines two main ways of understanding and
predicting the evolution of body size using life-history analysis: optimization
(optimality) and adaptive dynamics. Key elements of these are described, fol-
lowed by a discussion of some methodological issues, and examples of their
ecological application. The second part of the chapter examines scaling relation-
ships between body size and other traits of ecological importance, and follows

Body Size: The Structure and Function of Aquatic Ecosystems, eds. Alan G. Hildrew, David G. Raffaelli and Ronni
Edmonds-Brown. Published by Cambridge University Press.#British Ecological Society 2007.