- Email: [email protected]
Burning issues down under
392
Forum
TRENDS in Ecology & Evolution Vol.17 No.8 August 2002
Book Review
At the edge Life at the Limits: Organisms in Extreme Environments by David A. Wharton. Cambridge University Press, 2002. £18.95 hbk (307 pages) ISBN 0 521 78212 0
Since I was a child, I have been romanced by life that exists in extreme environments. My first relationship was with the myriad invertebrates that make a living under the salty rigors of estuarine life. As I grew older, I followed the seabed ever deeper, to submarine hot springs, sustaining my passion for life that exists so far outside the bounds of my own tolerance as to seem otherworldly. David Wharton, a New Zealand nematologist and filmmaker, tracked a different path to the extreme, first studying the survival strategies of nematodes living under extreme thermal and chemical insult in the laboratory. In recent years, he has hunted wild nematodes in the Dry Valleys of Antarctica, where a lack of precipitation for at least the past two million years connotes extreme. In Life at the Limits, Wharton presents a zoologist’s natural history of a range of tolerant organisms. It is an easy read, accessible to the nonexpert, and is suitable as reading for a seminar discussion for undergraduates not specializing in biology. The focus of Life at the Limits is mostly on invertebrates, but there is scattered attention to vertebrates (e.g. Antarctic teleosts and Emperor penguins, overwintering frogs and turtles), and even some notice of vegetation, such as mosses and lichens above the treeline, resurrection plants, and the giant lobelias of Mt Kenya. Bacteria and Archaea, which can be most catholic in their extremes, are not particularly featured, although there are a few pages devoted to the subsurface biosphere and to the Archaea and Bacteria of deep-sea hot springs. http://tree.trends.com
As an instructor of invertebrate biology, I take no exception to the invertebratecentric modus operandi. I enjoyed a harvest of exemplars of cryobiosis, anhydrobiosis, thermobiosis, and so on, that I might use to enhance my teaching, although much of what is presented can be found in any good invertebrate zoology text. As for mechanistic underpinnings, Wharton’s work falls short and the lay reader who wishes to be guided in this direction might choose to supplement Life at the Limits with Life on the Edge: Amazing Creatures Thriving in Extreme Environments by Michael Gross [1]. Both Wharton and Gross include the obligatory chapter (ultimate in Life on the Edge; penultimate in Life at the Limits) on the potential for life on other planets, introducing budding scientists to the rapidly developing field of astrobiology. Cindy Lee Van Dover Biology Dept, College of William & Mary, Williamsburg, VA 23187, USA. e-mail: [email protected] Reference 1 Gross, M. (1998) Life on the Edge: Amazing Creatures Thriving in Extreme Environments, Plenum Trade
Published online: 06 June 2002
Burning issues down under Flammable Australia: The Fire Regimes and Biodiversity of a Continent edited by Ross A. Bradstock, Jann E. Williams and , A. Malcolm Gill. Cambridge University Press, 2002. £90.00 hbk (ix + 462 pages) ISBN 0 521 80591 0
You will struggle to find references to fire in general textbooks on ecology, conservation biology or biogeography, in spite of the fact that large parts of the world burn and there is a considerable literature on the ecology of fire and its use
for managing ecosystems. This book on fire in Australia shows both how pervasive fire is in shaping ecosystems but also, perhaps, why fire ecology remains a ‘ghetto’ science. For science to be of general interest, it needs to ask general questions. Flammable Australia offers the reader a mixed menu with a few chapters on general topics and many more on specific vegetation formations of Australia. If you are a fire ecologist with interests in systems with analogues in Australia, this book is indispensable. There are excellent accounts of Australian research on heathlands, ‘temperate’ grasslands (analogous to South African highveld, North American prairies) and savannahs. The writing is parochial and it is generally left to the reader to make comparisons with other parts of the world. If you have no familiarity with fire, it might be harder to extract the central tenets of ‘flammable ecology’. One of these, implicit throughout Flammable Australia, is that species exist in an assemblage because they posses life-history attributes that are compatible with the prevailing fire regime. This, in turn, depends partly on the collective properties of the plant species, because they create the ‘fuel’. This neo-clementsian view of communities has important ramifications. For example, species will not respond individualistically to climate change – they can only migrate to areas with compatible fire regimes. But fire regimes are not simply a property of climate. They vary with physical and biological features of the landscape. For example, alien grasses have invaded West Australian heathlands creating new fire regimes that have eliminated species with incompatible life histories. You will find nothing in this book about competition for resources. Community assembly and response is largely controlled by the timing of life-history events in relation to successive fires. If this is true, changes in fire regimes should trigger extinction cascades of species with incompatible life histories. Managing fire regimes is then of central importance for biodiversity conservation. Excellent chapters by Keith and others show how the life-history traits of species are used to define fire regime properties to meet conservation objectives. Conservation of flammable ecosystems
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.
Forum
TRENDS in Ecology & Evolution Vol.17 No.8 August 2002
has to be interventionist. Keith et al. provide a lucid critique of different options for fire management, including a return to aboriginal burning practises, and advocate a new approach based firmly on scientific understanding. This incorporates new insights into how spatial and temporal variability in fire properties influence biodiversity. An attractive feature of Flammable Australia is that animals have at last been integrated into fire ecology. New models and data are reported that explore the interplay between landscape patchiness produced by different fire regimes and the meta-population dynamics of threatened animals. There is little here on fire as an evolutionary force and a biogeographical agent shaping Australia’s unique biota. Flammable Australia, we learn in a chapter by Kershaw and others, only appeared in the Miocene, when fires began to carve up the ancestral forests, replacing them with the precursors of today’s highly flammable floras. In a book that I strongly recommend as a companion volume, Bowman [1] has explored the biogeography of the tiny islands of ‘rainforest’ remnants surviving in a sea of Eucalyptus- and Acacia-dominated communities. Rainforest is a euphemism – the forests persist in sites with as little as 600 mm of annual rainfall. Rainforest lineages are floristically distinct from adjacent formations of ‘flammable Australia’. Bowman argues that the key difference between rainforest and the rest is relative tolerance to recurrent fires. The implication is that fire has been a major agent shaping the distinctive biogeography of a continent. If fires could be switched off, and the climate remained the same, Australia would look completely different. Did ancient fires create an intracontinental vicariance event after which fire tolerant and fire intolerant biotas evolved side by side? Why did flammable vegetation begin to spread? What limits the domain of fire, in the past and today? What functional attributes allowed access of some lineages to fire-prone ecosystems but denied access to others? Some of the answers are implicit in this book, but are presented for specific vegetation types. We need a general model on synergies between climate and ‘fuel’ to help us understand the ‘big’ questions – why fires began to burn in the Miocene, why human settlement often caused http://tree.trends.com
major changes in fire regimes, or how global vegetation might respond to future climate change. This book is a rich resource on fire in Australian ecosystems, and should be available to all fire ecologists. It contains innovative work on landscape ecology and conservation biology that will be of general interest. However, I do not think that it will do much to increase the citations on fire in our textbooks. Fire ecologists need to ask the general questions to reach the general audience that the topic warrants. William Bond Botany Dept, University of Cape Town, Rondebosch, 7701, South Africa. e-mail:[email protected] Reference 1 Bowman, D.M.J.S. (2000) Australian Rainforests: Islands of Green in a Land of Fire, Cambridge University Press
Published online: 06 June 2002
Life history after ten years Life History Evolution by Derek A. Roff. Sinauer Associates, Inc, 2002. £39.99 (527 pages) ISBN 0 87893 756 0
The new book by Derek Roff, Life History Evolution, differs from his 1992 book The Evolution of Life Histories: Theory and Analysis in emphasis as well as in the inclusion of recent developments in life-history research. In the 1992 book, life-history evolution was detailed by life-history trait: clutch size, age at first reproduction, and so on. Environmental variation was dealt with within each topic, depending on its perceived relevance to that topic. Organizing the book by life-history trait implied that the role of the environment in shaping life histories was secondary. Environmental variation might modify life histories, but it was not seen as deciding the major principles of the evolution of life-history patterns. This has now changed. Life History Evolution is organized not by life-history trait but by the main determinants of life-history evolution. It starts with the principles of the process of the evolution of life-history traits: quantitative genetics,
393
especially genetic correlations, and tradeoffs among traits. Three chapters follow that deal with the evolved patterns of life-history traits, and are devoted to life-history evolution in a constant environment, in a stochastic environment and in a predictable environment. The emphasis is therefore on the decisive role of the environment in shaping patterns of life-history traits. This is most evident in the chapter on the evolution of life histories in a predictable environment, which contains the most new material. Latitudinal patterns provide much direct evidence for environmental influences on life histories, such as the influence of season length on growth rate and size in univoltine insects, and many experimental examples of such an immediate influence of the environment on life-history patterns are provided. The change in emphasis from the traits themselves to the environment as the principal determinant of life-history patterns is illuminating and one of the strong points of the book. Life History Evolution excels in relating life-history models to experimental evidence. Much care has been taken to document experimental life-history studies, and to relate their data to appropriate theory. Where possible, data are used to evaluate the choice between alternative theories. For instance, both evolution and demography can lead to patterns among life-history traits. Demography, because long-term stable numbers in the population constrain life-history parameters to conform to R0 = 1; and evolution, because a genetic tradeoff might exist in an optimal life history. In some cases, these alternative models lead to different predictions of the sensitivity of, for instance, adult mortality on the age at maturity. The framework for the analysis of life-history theory is found in quantitative genetics. In Life History Evolution, evolutionarily stable strategy (ESS) models are virtually absent; optimization is occasionally referred to and more often implicitly applied. Fitness is based upon the intrinsic rate of increase r, or on R0, as might be convenient in any particular model. There is no sense of any recent debate on fitness measures [1]. Virtually all analyses in the book ignore densitydependent number regulation, although, in the last chapter, the influence of density
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.
Forum
TRENDS in Ecology & Evolution Vol.17 No.8 August 2002
Book Review
At the edge Life at the Limits: Organisms in Extreme Environments by David A. Wharton. Cambridge University Press, 2002. £18.95 hbk (307 pages) ISBN 0 521 78212 0
Since I was a child, I have been romanced by life that exists in extreme environments. My first relationship was with the myriad invertebrates that make a living under the salty rigors of estuarine life. As I grew older, I followed the seabed ever deeper, to submarine hot springs, sustaining my passion for life that exists so far outside the bounds of my own tolerance as to seem otherworldly. David Wharton, a New Zealand nematologist and filmmaker, tracked a different path to the extreme, first studying the survival strategies of nematodes living under extreme thermal and chemical insult in the laboratory. In recent years, he has hunted wild nematodes in the Dry Valleys of Antarctica, where a lack of precipitation for at least the past two million years connotes extreme. In Life at the Limits, Wharton presents a zoologist’s natural history of a range of tolerant organisms. It is an easy read, accessible to the nonexpert, and is suitable as reading for a seminar discussion for undergraduates not specializing in biology. The focus of Life at the Limits is mostly on invertebrates, but there is scattered attention to vertebrates (e.g. Antarctic teleosts and Emperor penguins, overwintering frogs and turtles), and even some notice of vegetation, such as mosses and lichens above the treeline, resurrection plants, and the giant lobelias of Mt Kenya. Bacteria and Archaea, which can be most catholic in their extremes, are not particularly featured, although there are a few pages devoted to the subsurface biosphere and to the Archaea and Bacteria of deep-sea hot springs. http://tree.trends.com
As an instructor of invertebrate biology, I take no exception to the invertebratecentric modus operandi. I enjoyed a harvest of exemplars of cryobiosis, anhydrobiosis, thermobiosis, and so on, that I might use to enhance my teaching, although much of what is presented can be found in any good invertebrate zoology text. As for mechanistic underpinnings, Wharton’s work falls short and the lay reader who wishes to be guided in this direction might choose to supplement Life at the Limits with Life on the Edge: Amazing Creatures Thriving in Extreme Environments by Michael Gross [1]. Both Wharton and Gross include the obligatory chapter (ultimate in Life on the Edge; penultimate in Life at the Limits) on the potential for life on other planets, introducing budding scientists to the rapidly developing field of astrobiology. Cindy Lee Van Dover Biology Dept, College of William & Mary, Williamsburg, VA 23187, USA. e-mail: [email protected] Reference 1 Gross, M. (1998) Life on the Edge: Amazing Creatures Thriving in Extreme Environments, Plenum Trade
Published online: 06 June 2002
Burning issues down under Flammable Australia: The Fire Regimes and Biodiversity of a Continent edited by Ross A. Bradstock, Jann E. Williams and , A. Malcolm Gill. Cambridge University Press, 2002. £90.00 hbk (ix + 462 pages) ISBN 0 521 80591 0
You will struggle to find references to fire in general textbooks on ecology, conservation biology or biogeography, in spite of the fact that large parts of the world burn and there is a considerable literature on the ecology of fire and its use
for managing ecosystems. This book on fire in Australia shows both how pervasive fire is in shaping ecosystems but also, perhaps, why fire ecology remains a ‘ghetto’ science. For science to be of general interest, it needs to ask general questions. Flammable Australia offers the reader a mixed menu with a few chapters on general topics and many more on specific vegetation formations of Australia. If you are a fire ecologist with interests in systems with analogues in Australia, this book is indispensable. There are excellent accounts of Australian research on heathlands, ‘temperate’ grasslands (analogous to South African highveld, North American prairies) and savannahs. The writing is parochial and it is generally left to the reader to make comparisons with other parts of the world. If you have no familiarity with fire, it might be harder to extract the central tenets of ‘flammable ecology’. One of these, implicit throughout Flammable Australia, is that species exist in an assemblage because they posses life-history attributes that are compatible with the prevailing fire regime. This, in turn, depends partly on the collective properties of the plant species, because they create the ‘fuel’. This neo-clementsian view of communities has important ramifications. For example, species will not respond individualistically to climate change – they can only migrate to areas with compatible fire regimes. But fire regimes are not simply a property of climate. They vary with physical and biological features of the landscape. For example, alien grasses have invaded West Australian heathlands creating new fire regimes that have eliminated species with incompatible life histories. You will find nothing in this book about competition for resources. Community assembly and response is largely controlled by the timing of life-history events in relation to successive fires. If this is true, changes in fire regimes should trigger extinction cascades of species with incompatible life histories. Managing fire regimes is then of central importance for biodiversity conservation. Excellent chapters by Keith and others show how the life-history traits of species are used to define fire regime properties to meet conservation objectives. Conservation of flammable ecosystems
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.
Forum
TRENDS in Ecology & Evolution Vol.17 No.8 August 2002
has to be interventionist. Keith et al. provide a lucid critique of different options for fire management, including a return to aboriginal burning practises, and advocate a new approach based firmly on scientific understanding. This incorporates new insights into how spatial and temporal variability in fire properties influence biodiversity. An attractive feature of Flammable Australia is that animals have at last been integrated into fire ecology. New models and data are reported that explore the interplay between landscape patchiness produced by different fire regimes and the meta-population dynamics of threatened animals. There is little here on fire as an evolutionary force and a biogeographical agent shaping Australia’s unique biota. Flammable Australia, we learn in a chapter by Kershaw and others, only appeared in the Miocene, when fires began to carve up the ancestral forests, replacing them with the precursors of today’s highly flammable floras. In a book that I strongly recommend as a companion volume, Bowman [1] has explored the biogeography of the tiny islands of ‘rainforest’ remnants surviving in a sea of Eucalyptus- and Acacia-dominated communities. Rainforest is a euphemism – the forests persist in sites with as little as 600 mm of annual rainfall. Rainforest lineages are floristically distinct from adjacent formations of ‘flammable Australia’. Bowman argues that the key difference between rainforest and the rest is relative tolerance to recurrent fires. The implication is that fire has been a major agent shaping the distinctive biogeography of a continent. If fires could be switched off, and the climate remained the same, Australia would look completely different. Did ancient fires create an intracontinental vicariance event after which fire tolerant and fire intolerant biotas evolved side by side? Why did flammable vegetation begin to spread? What limits the domain of fire, in the past and today? What functional attributes allowed access of some lineages to fire-prone ecosystems but denied access to others? Some of the answers are implicit in this book, but are presented for specific vegetation types. We need a general model on synergies between climate and ‘fuel’ to help us understand the ‘big’ questions – why fires began to burn in the Miocene, why human settlement often caused http://tree.trends.com
major changes in fire regimes, or how global vegetation might respond to future climate change. This book is a rich resource on fire in Australian ecosystems, and should be available to all fire ecologists. It contains innovative work on landscape ecology and conservation biology that will be of general interest. However, I do not think that it will do much to increase the citations on fire in our textbooks. Fire ecologists need to ask the general questions to reach the general audience that the topic warrants. William Bond Botany Dept, University of Cape Town, Rondebosch, 7701, South Africa. e-mail:[email protected] Reference 1 Bowman, D.M.J.S. (2000) Australian Rainforests: Islands of Green in a Land of Fire, Cambridge University Press
Published online: 06 June 2002
Life history after ten years Life History Evolution by Derek A. Roff. Sinauer Associates, Inc, 2002. £39.99 (527 pages) ISBN 0 87893 756 0
The new book by Derek Roff, Life History Evolution, differs from his 1992 book The Evolution of Life Histories: Theory and Analysis in emphasis as well as in the inclusion of recent developments in life-history research. In the 1992 book, life-history evolution was detailed by life-history trait: clutch size, age at first reproduction, and so on. Environmental variation was dealt with within each topic, depending on its perceived relevance to that topic. Organizing the book by life-history trait implied that the role of the environment in shaping life histories was secondary. Environmental variation might modify life histories, but it was not seen as deciding the major principles of the evolution of life-history patterns. This has now changed. Life History Evolution is organized not by life-history trait but by the main determinants of life-history evolution. It starts with the principles of the process of the evolution of life-history traits: quantitative genetics,
393
especially genetic correlations, and tradeoffs among traits. Three chapters follow that deal with the evolved patterns of life-history traits, and are devoted to life-history evolution in a constant environment, in a stochastic environment and in a predictable environment. The emphasis is therefore on the decisive role of the environment in shaping patterns of life-history traits. This is most evident in the chapter on the evolution of life histories in a predictable environment, which contains the most new material. Latitudinal patterns provide much direct evidence for environmental influences on life histories, such as the influence of season length on growth rate and size in univoltine insects, and many experimental examples of such an immediate influence of the environment on life-history patterns are provided. The change in emphasis from the traits themselves to the environment as the principal determinant of life-history patterns is illuminating and one of the strong points of the book. Life History Evolution excels in relating life-history models to experimental evidence. Much care has been taken to document experimental life-history studies, and to relate their data to appropriate theory. Where possible, data are used to evaluate the choice between alternative theories. For instance, both evolution and demography can lead to patterns among life-history traits. Demography, because long-term stable numbers in the population constrain life-history parameters to conform to R0 = 1; and evolution, because a genetic tradeoff might exist in an optimal life history. In some cases, these alternative models lead to different predictions of the sensitivity of, for instance, adult mortality on the age at maturity. The framework for the analysis of life-history theory is found in quantitative genetics. In Life History Evolution, evolutionarily stable strategy (ESS) models are virtually absent; optimization is occasionally referred to and more often implicitly applied. Fitness is based upon the intrinsic rate of increase r, or on R0, as might be convenient in any particular model. There is no sense of any recent debate on fitness measures [1]. Virtually all analyses in the book ignore densitydependent number regulation, although, in the last chapter, the influence of density
0169-5347/02/$ – see front matter © 2002 Elsevier Science Ltd. All rights reserved.