- Email: [email protected]
Population harvesting: Demographic models of fish, forest, and animal resources
TREE vol. 4, no. IO, October
limited to corals; other marine invertebrates, plants, fishes, reptiles and mammals, plus associated terrestrial flora and fauna, are discussed. Particular emphasis is placed on known natural and man-made.disturbances to reefs. The references contain numerous valuable but hardto-find items (e.g. unpublished and governmental reports). The economic importance, legal status, and management plans for reefs are summarized, along with recommendations for future action in some cases. The primary purpose of these volumes is to promote the conservation and management of reefs. The breadth and depth of coverage will be invaluable in planning the protection and rational use of reefs. Moreover, such documents can take on a life of their own by generating interest and momentum; a two-line recommendation in a volume of this distinction can make the difference between governmental neglect and protection. Scientists initiating new projects on reefs (or reviewing old ones) will also come to depend on these volumes for their clearly organized reviews of relevant information. The threats to current or potential research sites are made painfully clear. I was surprised to learn that only four scientific or strict nature reserves exist in the Caribbean (in Belize, Panama, Brazil and Tobago). Their absence on reefs off the continental United States is a disgrace, considering its affluence relative to other countries of the region. Our experience at the Smithsonian Institution (which supervises two of these sites) indicates that such protection is increasingly essential (and difficult). Any reviewer of volumes of such scope will have criticisms that reflect their own biases, and I have a few. First, despite the emphasis on sources of mortality, predators on Caribbean corals have been largely ignored. Although less spectacular than the crown-of-thorns starfish (Acanthasterplanci), these fish, snails cause serious and worms can damage+“; moreover, they may interact with other natural or manmade events to cause catastrophic population collapse12. Second, I would have liked to see a separate listing of the names and mailing addresses of all marine stations located in each country. The recent occurrence of large-scale disturbances (e.g. in the Caribbean, the dieoff of the urchin Diadema anti//at-urn
and coral bleaching) has demonstrated the importance of interregional communication, and the
staff of marine laboratories are often the most appropriate people to contact. This information would also help scientists starting projects in new areas, as would a comparable listing of the procedures and governmental agencies involved in granting permits for research. Although such information exists scattered in a variety of places, these volumes would have been a logical place to bring it together. Similarly, an explicit compilation of all reports presenting quantitative data on abundance of reef organisms would have increased the visibility of these studies and pointed out the general lack of this basic information upon which assessment of responses to disturbance depends13. Finally, some differences in the detail of coverage do not seem justified; for example, the section on Hawaii is 40% longer than that on eastern Australia (even though the latter includes the Great Barrier Reef!). Some unevenness of coverage, however, is due to the editors’ dependence on information received from various countries. Thus, every professional concerned with reefs should review the chapters for which they have experience and send references and suggestions to the address provided, where an updated data base is maintained. Given the continuing explosion of information on reefs, I look forward to a revised edition that will be even more useful
-1
1989
to those who wish to preserve the scientific, economic and aesthetic value of coral reefs. Nancy Knowlton SmithsonianTropicalResearchInstitute, Apattado2072,Balboa,Republicof Panama
References 1 Darwin, C. (1842) The Structure Distribution
and of Coral Reefs, Smith, Elder
&Co. 2 d’Elia, C.F. (1988) in Concepts of Ecosvstem Eco/oav (Pomerov, L.R. and
Albe&, J.J., eds):& 195-23’0, SpringerVerlag 3 Jackson, J.B.C., Buss, L.W. and Cook, R.E., eds (1985) Population Biology and Evolution of Clonal Organisms, Yale University Press 4 Warner, R.R. (1984) Am. Sci. 72, 128-136 5 Connell, J.H. (1978) Science 199, 1302-1310 6 Chesson, P.L. and Warner, R.R. (1981) Am. Nat. 117,923-943 7 Isdale. P. (1984) Nature310.578-579 8 Bloom, A.L., Broecker, WS:, Chappell, J.M.A., Matthews, R.K. and Mesolella, K.J. (1974) Quat. Res. 4,185-205 9 Brawley, S.H. and Adey, W.H. (1982) Bull. Mar. Sci. 32,595-599 IO Kaufman, L.S. (1977) hoc. Third Int. Coral Reef Svmo. I, 559-564 11 Witman, j.D.‘(1988) Bull. Mar. Sci. 42, 446-458 12 Knowlton, N., Lang, J.C. and Keller, B.D. Smithson. Contrib. Mar. Sci. (in press) 13 Loya, Y. (1976) Ecology 57,278-289
._
Resource Management Population Harvesting: DemographicModels of Fish,Forest,and Animal Resources
by Wayne M. Getz and Robert G. Haight, Princeton University Press (Monographs in Population Biology 27), 1989. $45.00 hbk, $15.95 pbk (xv+397 pages) ISBN 0 691 08516 I The publication of a Monograph in Population Biology is always an event, and No. 27 is no exception. Getz models fisheries and insect populations, and Haight develops forest management models. In this monograph, they present the methods that they have been using and developing separately as a unified theory to model cohort and stage-structured populations. The originality of their effort resides in this ‘horizontal’ approach. On the 17th anniversary of his death, this book demonstrates how ‘George’ P.H. Leslie’s work ‘On the Use of Matrices in Certain Population Mathematics”,* has been at the basis
of all modelling work on harvested populations. The presentation of the methods is organized in the first two chapters, starting with the Leslie matrix model and its generalization. Birth and death in each age group are either constant, or linear functions of the number of individuals present. This is followed by the more realistic, and complicated, non-linear models (which may or may not boil down to a Leslie matrix model when linearized in the vicinity of their equilibrium solutions), where birth or survival depend on the population density. Each section also discusses how stochasticity has been or can be modelled. With these two chapters alone, this book qualifies to be on the shelf of every postgraduate student of population biology. The presentation is clear and detailed, and the assumptions behind the models are always given. It allows a broad understanding of age- and stage-structured models, and reminds you that you
TREE vol. 4, no. IO, October
7989
need to brush up your algebra, calculus, etc., to embark on modelling population dynamics. Case studies on fisheries and forest stand management occupy the following two chapters, while some modelling of elephant, seal, fruitfly and potato tuberworm populations are examined in the last chapter. Each example emphasizes one or a few aspects of the model development and its use in resource management. This section is not as heavy going as the first part of the book and, as the authors recommend, should be looked through first. Getz’s and Haight’s work will contribute much to the understanding of
Sophie des Clers
the power and limitations of existing models. Comparing the population dynamics of fish and forests will certainly help fisheries scientists separate model development from sampling problems. The agestructured fisheries models have also much to gain from the stagestructured approach of the forest managers. And time will tell if forest managers find equally useful this broadening of their horizons. To build up your mathematical understanding of age- and stagestructured population models, you should definitely have this (not so) little yellow book on your shelf, next to, say, the equally indispensible navy blues and bright green4 ones.
1 Anon. (1972) Nature239,477-478 (Obituary) 2 Leslie, P.H. (1945) Biometrika33, 183-212 3 Nisbet, R.M. and Gurney, W.S.C. (1982) Modelling Fluctuating Populations, John Wiley & Sons 4 Metz, J.A.J. and Diekmann. O., eds (1986) The Dynamics of Physiologically Structured Populations (Lect. Notes Biomath. 68), Springer-Verlag
tine rodents (mainly the montane vole, Microtus montanus) in terms of environmental cues differentiating cohorts in a given breeding season. Essentially, they find that for body size and growth rate there is extreme phenotypic plasticity of cohort life histories, which relates to available food resources and length of growing season. Lastly, Bujalski shows that in bank voles (Clethrionomys glareohs) the maturation rate and density of reproductively active females are restricted by territoriality, with availability of food resources playing a minimal role in life history variation. The next section, on ‘Body Size as a Life History Character’, introduces the one common thread that runs through the volume (and indeed most studies of mammalian life histories): namely, that body size correlates significantly with practically all life history characters. The premise is that body size places limits on physiological investment, which in turn correlates with energy allocation for life history patterns. Chapters in this section develop a number of themes on size effects, such as scaling biological (physiological) time rather than chronological time with species differences (Lindstedt and Swain), and treating body mass as the intermediate variable between selection and life history variation both within populations (Sauer and Slade) and among species (Zeveloff and Boyce). The problem with the allometric approach is that causal mechanisms are unclear. For example, the observation that body mass explains 6491 % of the variation of all life histories in mammalian carnivores3 does not reveal the relative influence of
metabolism, pelvic structure, teat number or any number of other morphological variables that directly impinge on the allometry of life histories. More importantly, these factors may not reflect one-to-one correlations with body mass, so that size alone as an explanatory factor may be misleading. As with other areas of ‘allometricks’4, experimental studies are long overdue for determining why size-dependent relations exist. The section on ‘Genetics of Life History Characteristics’ fills a critical void in life history analyses as well as producing some rather surprising results. Boag and Boonstra, following a useful review of available quantitative genetic techniques, show that in meadow voles (Microtus pennsylvanicus) traits such as body weight, growth rate, and age or weight at sexual maturity are unlikely to be heritable in nature; moreover, maternal effects exert a major influence on sibling resemblance. The other chapters, by Leamy and Bradley on growth rates in laboratory populations of rats and by Dobson on plasticity in litter size and body weight in Columbian ground squirrels (Spermophilus columbianus), reaffirm the idea that mammalian life histories are likely to be low in heritability. The main message from these chapters is that, contrary to previous thinking, there is substantial phenotypic plasticity of life history characteristics in mammals, which will make evolutionary analyses difficult. The largest section is on ‘The Comparative Method in Life History Studies’. A burgeoning of statistical analyses of interspecific variation in life histories has occurred in the last five years. I suspect this is due
Renewable Resources Assessment Group, Centre for Environmental Technology, Imperial College of Science, Technology and Medicine, 8 Prince’s Gardens, London SW7 lNA, UK
References
Life History Patterns Evolutionof LifeHistoriesof Mammals: Theory and Pattern
edited by Mark S. Boyce, Yale University Press, 1988. $45.00 (xvi + 373 paged ISBN 0 300 04084 9 Life history patterns represent various reproductive characters and the probabilities of survival at each age during a life span. Life history traits such as gestation period, growth rate, age between successive births and age at first reproduction are generally thought to have evolved in response to demographic and other environmental demands, although genetic variance and evolutionary history impose some constraints. Mammals possess a number of features that give interesting twists to these issues; for example, all mammals provide parental care and rear young during a phase of lactation. Despite considerable theoretical advances and empirical data bases, a coherent theory of mammalian life history evolution has remained elusive’,*. The aim of this book, derived from papers given in 1985 at the International Theriological Conference, is critically to summarize major approaches to the study of mammalian life history evolution. Following a brief introduction by the editor, on various theoretical models, the first section comprises three chapters on ‘Pattern and Process in Mammal Life History Variation’. Cameron and McClure analyse geographic variation in life history traits of the hispid cotton rat (Sigmodon hispidus) and show that litter size is correlated with latitude, longitude and body size. Negus and Berger assess life histories of micro-
307
limited to corals; other marine invertebrates, plants, fishes, reptiles and mammals, plus associated terrestrial flora and fauna, are discussed. Particular emphasis is placed on known natural and man-made.disturbances to reefs. The references contain numerous valuable but hardto-find items (e.g. unpublished and governmental reports). The economic importance, legal status, and management plans for reefs are summarized, along with recommendations for future action in some cases. The primary purpose of these volumes is to promote the conservation and management of reefs. The breadth and depth of coverage will be invaluable in planning the protection and rational use of reefs. Moreover, such documents can take on a life of their own by generating interest and momentum; a two-line recommendation in a volume of this distinction can make the difference between governmental neglect and protection. Scientists initiating new projects on reefs (or reviewing old ones) will also come to depend on these volumes for their clearly organized reviews of relevant information. The threats to current or potential research sites are made painfully clear. I was surprised to learn that only four scientific or strict nature reserves exist in the Caribbean (in Belize, Panama, Brazil and Tobago). Their absence on reefs off the continental United States is a disgrace, considering its affluence relative to other countries of the region. Our experience at the Smithsonian Institution (which supervises two of these sites) indicates that such protection is increasingly essential (and difficult). Any reviewer of volumes of such scope will have criticisms that reflect their own biases, and I have a few. First, despite the emphasis on sources of mortality, predators on Caribbean corals have been largely ignored. Although less spectacular than the crown-of-thorns starfish (Acanthasterplanci), these fish, snails cause serious and worms can damage+“; moreover, they may interact with other natural or manmade events to cause catastrophic population collapse12. Second, I would have liked to see a separate listing of the names and mailing addresses of all marine stations located in each country. The recent occurrence of large-scale disturbances (e.g. in the Caribbean, the dieoff of the urchin Diadema anti//at-urn
and coral bleaching) has demonstrated the importance of interregional communication, and the
staff of marine laboratories are often the most appropriate people to contact. This information would also help scientists starting projects in new areas, as would a comparable listing of the procedures and governmental agencies involved in granting permits for research. Although such information exists scattered in a variety of places, these volumes would have been a logical place to bring it together. Similarly, an explicit compilation of all reports presenting quantitative data on abundance of reef organisms would have increased the visibility of these studies and pointed out the general lack of this basic information upon which assessment of responses to disturbance depends13. Finally, some differences in the detail of coverage do not seem justified; for example, the section on Hawaii is 40% longer than that on eastern Australia (even though the latter includes the Great Barrier Reef!). Some unevenness of coverage, however, is due to the editors’ dependence on information received from various countries. Thus, every professional concerned with reefs should review the chapters for which they have experience and send references and suggestions to the address provided, where an updated data base is maintained. Given the continuing explosion of information on reefs, I look forward to a revised edition that will be even more useful
-1
1989
to those who wish to preserve the scientific, economic and aesthetic value of coral reefs. Nancy Knowlton SmithsonianTropicalResearchInstitute, Apattado2072,Balboa,Republicof Panama
References 1 Darwin, C. (1842) The Structure Distribution
and of Coral Reefs, Smith, Elder
&Co. 2 d’Elia, C.F. (1988) in Concepts of Ecosvstem Eco/oav (Pomerov, L.R. and
Albe&, J.J., eds):& 195-23’0, SpringerVerlag 3 Jackson, J.B.C., Buss, L.W. and Cook, R.E., eds (1985) Population Biology and Evolution of Clonal Organisms, Yale University Press 4 Warner, R.R. (1984) Am. Sci. 72, 128-136 5 Connell, J.H. (1978) Science 199, 1302-1310 6 Chesson, P.L. and Warner, R.R. (1981) Am. Nat. 117,923-943 7 Isdale. P. (1984) Nature310.578-579 8 Bloom, A.L., Broecker, WS:, Chappell, J.M.A., Matthews, R.K. and Mesolella, K.J. (1974) Quat. Res. 4,185-205 9 Brawley, S.H. and Adey, W.H. (1982) Bull. Mar. Sci. 32,595-599 IO Kaufman, L.S. (1977) hoc. Third Int. Coral Reef Svmo. I, 559-564 11 Witman, j.D.‘(1988) Bull. Mar. Sci. 42, 446-458 12 Knowlton, N., Lang, J.C. and Keller, B.D. Smithson. Contrib. Mar. Sci. (in press) 13 Loya, Y. (1976) Ecology 57,278-289
._
Resource Management Population Harvesting: DemographicModels of Fish,Forest,and Animal Resources
by Wayne M. Getz and Robert G. Haight, Princeton University Press (Monographs in Population Biology 27), 1989. $45.00 hbk, $15.95 pbk (xv+397 pages) ISBN 0 691 08516 I The publication of a Monograph in Population Biology is always an event, and No. 27 is no exception. Getz models fisheries and insect populations, and Haight develops forest management models. In this monograph, they present the methods that they have been using and developing separately as a unified theory to model cohort and stage-structured populations. The originality of their effort resides in this ‘horizontal’ approach. On the 17th anniversary of his death, this book demonstrates how ‘George’ P.H. Leslie’s work ‘On the Use of Matrices in Certain Population Mathematics”,* has been at the basis
of all modelling work on harvested populations. The presentation of the methods is organized in the first two chapters, starting with the Leslie matrix model and its generalization. Birth and death in each age group are either constant, or linear functions of the number of individuals present. This is followed by the more realistic, and complicated, non-linear models (which may or may not boil down to a Leslie matrix model when linearized in the vicinity of their equilibrium solutions), where birth or survival depend on the population density. Each section also discusses how stochasticity has been or can be modelled. With these two chapters alone, this book qualifies to be on the shelf of every postgraduate student of population biology. The presentation is clear and detailed, and the assumptions behind the models are always given. It allows a broad understanding of age- and stage-structured models, and reminds you that you
TREE vol. 4, no. IO, October
7989
need to brush up your algebra, calculus, etc., to embark on modelling population dynamics. Case studies on fisheries and forest stand management occupy the following two chapters, while some modelling of elephant, seal, fruitfly and potato tuberworm populations are examined in the last chapter. Each example emphasizes one or a few aspects of the model development and its use in resource management. This section is not as heavy going as the first part of the book and, as the authors recommend, should be looked through first. Getz’s and Haight’s work will contribute much to the understanding of
Sophie des Clers
the power and limitations of existing models. Comparing the population dynamics of fish and forests will certainly help fisheries scientists separate model development from sampling problems. The agestructured fisheries models have also much to gain from the stagestructured approach of the forest managers. And time will tell if forest managers find equally useful this broadening of their horizons. To build up your mathematical understanding of age- and stagestructured population models, you should definitely have this (not so) little yellow book on your shelf, next to, say, the equally indispensible navy blues and bright green4 ones.
1 Anon. (1972) Nature239,477-478 (Obituary) 2 Leslie, P.H. (1945) Biometrika33, 183-212 3 Nisbet, R.M. and Gurney, W.S.C. (1982) Modelling Fluctuating Populations, John Wiley & Sons 4 Metz, J.A.J. and Diekmann. O., eds (1986) The Dynamics of Physiologically Structured Populations (Lect. Notes Biomath. 68), Springer-Verlag
tine rodents (mainly the montane vole, Microtus montanus) in terms of environmental cues differentiating cohorts in a given breeding season. Essentially, they find that for body size and growth rate there is extreme phenotypic plasticity of cohort life histories, which relates to available food resources and length of growing season. Lastly, Bujalski shows that in bank voles (Clethrionomys glareohs) the maturation rate and density of reproductively active females are restricted by territoriality, with availability of food resources playing a minimal role in life history variation. The next section, on ‘Body Size as a Life History Character’, introduces the one common thread that runs through the volume (and indeed most studies of mammalian life histories): namely, that body size correlates significantly with practically all life history characters. The premise is that body size places limits on physiological investment, which in turn correlates with energy allocation for life history patterns. Chapters in this section develop a number of themes on size effects, such as scaling biological (physiological) time rather than chronological time with species differences (Lindstedt and Swain), and treating body mass as the intermediate variable between selection and life history variation both within populations (Sauer and Slade) and among species (Zeveloff and Boyce). The problem with the allometric approach is that causal mechanisms are unclear. For example, the observation that body mass explains 6491 % of the variation of all life histories in mammalian carnivores3 does not reveal the relative influence of
metabolism, pelvic structure, teat number or any number of other morphological variables that directly impinge on the allometry of life histories. More importantly, these factors may not reflect one-to-one correlations with body mass, so that size alone as an explanatory factor may be misleading. As with other areas of ‘allometricks’4, experimental studies are long overdue for determining why size-dependent relations exist. The section on ‘Genetics of Life History Characteristics’ fills a critical void in life history analyses as well as producing some rather surprising results. Boag and Boonstra, following a useful review of available quantitative genetic techniques, show that in meadow voles (Microtus pennsylvanicus) traits such as body weight, growth rate, and age or weight at sexual maturity are unlikely to be heritable in nature; moreover, maternal effects exert a major influence on sibling resemblance. The other chapters, by Leamy and Bradley on growth rates in laboratory populations of rats and by Dobson on plasticity in litter size and body weight in Columbian ground squirrels (Spermophilus columbianus), reaffirm the idea that mammalian life histories are likely to be low in heritability. The main message from these chapters is that, contrary to previous thinking, there is substantial phenotypic plasticity of life history characteristics in mammals, which will make evolutionary analyses difficult. The largest section is on ‘The Comparative Method in Life History Studies’. A burgeoning of statistical analyses of interspecific variation in life histories has occurred in the last five years. I suspect this is due
Renewable Resources Assessment Group, Centre for Environmental Technology, Imperial College of Science, Technology and Medicine, 8 Prince’s Gardens, London SW7 lNA, UK
References
Life History Patterns Evolutionof LifeHistoriesof Mammals: Theory and Pattern
edited by Mark S. Boyce, Yale University Press, 1988. $45.00 (xvi + 373 paged ISBN 0 300 04084 9 Life history patterns represent various reproductive characters and the probabilities of survival at each age during a life span. Life history traits such as gestation period, growth rate, age between successive births and age at first reproduction are generally thought to have evolved in response to demographic and other environmental demands, although genetic variance and evolutionary history impose some constraints. Mammals possess a number of features that give interesting twists to these issues; for example, all mammals provide parental care and rear young during a phase of lactation. Despite considerable theoretical advances and empirical data bases, a coherent theory of mammalian life history evolution has remained elusive’,*. The aim of this book, derived from papers given in 1985 at the International Theriological Conference, is critically to summarize major approaches to the study of mammalian life history evolution. Following a brief introduction by the editor, on various theoretical models, the first section comprises three chapters on ‘Pattern and Process in Mammal Life History Variation’. Cameron and McClure analyse geographic variation in life history traits of the hispid cotton rat (Sigmodon hispidus) and show that litter size is correlated with latitude, longitude and body size. Negus and Berger assess life histories of micro-
307