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The natural history and behavior of North American beewolves
“REE vol. 3, no. 11,. November
_.
1988
Air Pollution
Effects of Atmospheric Pollutants on Forests, Wetlands and Agricultural Ecosystems edited by T.C. Hutchinson and K.M. Meema, Springer-Verlag, 1987. DM 274.00 hbk (xxvii t 652 pages) ISBN :j 540 16084 I The past ten years have seen a major slift in scientific thinking about the effects of air pollutants, a shift that has largely been forced upon us by the dramatic, but scientifically intractable, problems of forest decline il.1 both Western Europe and North America. Previously, it had been possible to demonstrate cause/effect relationships between adverse ecolcgical effects and specific polIi)tants, either around individual point sources’ or on a regional b,jsis2. In contrast, there is a growing consensus that current forest decline problems are much more complex, that air pollutants may only be one of a Jvide range of factors involved, and that the problems observed should be understood as a malfunction of the forest ecosystem, rather than as al adverse impact on individual trees. In the face of this complex problem, many divergent paths have been taken to elucidate the role of at nospheric pollutants in forest decline. The first two contributions to th s volume, which contains papers gil/en at a NATO workshop held in Tcronto in May 1985, illustrate two of the major paths. Prinz, Krause and Jung take a basically reductionist approach, attempting to exclude certain causal factors on the basis of both field observation and laboratory experiment and to demonstrate the: role of ozone and mist, the combined impact of which they believe is of central importance, by means of controlled laboratory expe.imentati0r-r. In contrast, Matzner anlj Ulrich argue that the same pollutsnt may influence many ecosystem components either directly or incirectly, and that demonstration of a ,3articular effect in a controlled laboratory experiment cannot preclude the possibility that other causal mechanisms are actually of greater significance in the field. Their case for the central role of soil acidificat on processes is based around detailed field observation rather than car trolled experiment. Twenty nine of the 43 contributrons, which all originate from either North America or Europe, are concerned either directly or indirectly with forest decline, and include a group of seven papers on acidification of forest soils. This emphasis is ronsistent with a major shift in
balance in international conferences in recent years away from effects on crops to those on forest+. Indeed, it is the section on agricultural ecosystems which is most disappointing. None of the contributions is concerned with the ecosystem as such; instead, they describe experimental studies on individual plants, kept well-watered and pest-free in controlled environment facilities, glasshouses or field chambers. Only the paper by Mansfield and co-workers considers the implications of such experiments for crop growth in adverse conditions. Yet some of the most exciting recent developments in our understanding of crop responses to atmospheric pollutants have been the recognition of the effects of pollutants in modifying crop responses to abiotic stresses, and to fungal diseases and insect pests3, and the successful application of open-air fumigation systems to study these complex interactions at an ecosystem leve14. In contrast to the rapid responses of annual crops, the effects of acid deposition on forest soils may only be detected over periods of decades in the field. The major problems are then of distinguishing the chemical changes induced by increased acid deposition from the natural processes of acidification in regions of high precipitation and the acidifying effects of forest growth and harvesting; these problems are well reviewed by Abrahamsen and Johnson in the first contributions on soil acidification. Similarly, the section on wetland ecosystems, which despite their ecological importance have been little studied, is introduced by two reviews, from Gorham
et al. and Clymo, which consider the need to place the effects of atmospheric pollutants in the context of the natural processes of acidification in such systems. Analogous problems arise in the interpretation of longterm declines in forest growth; the section on dendrochronology contains discussion of the complex statistical problems of analysing the possible impact of increased emissions of atmospheric pollutants in the context of the effects of other climatic variation. The importance of ecosystem response in the interpretation of the impact of atmospheric pollutants is now clear. For many targets, the long-term nature of pollutant impact and the subtle and complex interactions between pollutant input and other ecological processes make the task of understanding the role of pollutants in the changes observed in the field an immense scientific challenge. Many, but by no means all, of the papers in this volume provide useful contributions towards this task.
The Natural History and Behavior of North American Beewolves
also the subject of a classic study and doctoral thesis on orientation and recognition w-w bv Tinbergen5-7. This new book falls, then, into a tradition of fine natural history description and experimental field observations. For more than 30 years, Evans and his students have studied groundnesting solitary wasps in the family Sphecidae. Of the 34 species of North American Philanthus, about half have been studied - an unusually high proportion for any insect group. Just as Evans did in an earlier study on another well-studied group, the nyssonine sand waspsW, Evans and O’Neill synthesize published accounts and new observational
by Howard E. Evans and Kevin M. O’Neill, Comstock Publishing Associates of Cornell University Press, 1988, $45.00 hbk, $23.50 pbk (vii + 278 pages) ISBN 0 8014 1839 9 hbk / 080149513Xpbk Beewolves are solitary wasps which, as their name implies, hunt bees. This behavior as well as their large size and aggregated nesting have made them frequent subjects for study. Familiar to most ethologists from graphic natural history accounts by Fabrel, Crompton2, the Peckhams and the Raus4, they were
Mike Ashmore Department of Pure and Applied Biology, lmpertal College of Science and Technology, Srlwood Park, Ascot, Berkshire SL5 7PY, UK.
References 1 Gorham, A.G. and Gorham, E. (1963) Can.J. Bot41,1063-1078 2 Miller,P.R. (1973)Adv. Chem. 101-117 3 Bell, J.N.B. (1987) in Acid&in:
Ser.
122,
Scientific and Technic&Advances (Perry, R., Harrison, R.M., Bell, J.N.B. and Lester, J.N.. eds), pp. 535-545, Seper Ltd 4 Mcleod, A.R., Roberts, T.M., Alexander, K. and Cribb, D.M. (1988) NewPh’vtol. 109,67-78
313
material on North American beewolves. They provide a wealth of comparative material from which the authors piece together patterns of evolution and adaptation. The book begins by reviewing the morphological and behavioral characters common to most members of the genus. Some features are shared with many ground-nesting sphecid wasps, but others are unique to fhilanthus. For example, like other sphecids most male Philanthus defend small territories on leks near nests that females are provisioning or near female emergence sites. Unlike other sphecids, however, most male Philanthus scent mark. With modified brushes they wipe onto the substrate chemicals which are produced in their mandibular glands. These observations suggest that male Philanthus may be applying a sex pheromone that females seek out when ready for mating. Evans and O’Neill make the intriguing suggestion that if this material is expensive to produce, fighting may not be over territories per se, but over areas in which males have applied large quantities of sex pheromone. After giving an account of the natural history of each species of Philanthus, Evans and O’Neill place their observations into a broader context in the summarizing chapters. They find, for example, that within a locality the species of Philanthus differ in their prey choices: the largest tackle bumblebees, the wasps smaller species capture tiny solitary bees. By contrast, the location, structure and placement of nests and the digging behavior is surprisingly uniform throughout the group. Philanthus spp. also have a variety of
behavioral traits that reduce parasitism by flies, cuckoo wasps and velvet ants. Interestingly, similar traits have evolved independently in other groups of ground-nesting bees and sphecid wasps. Beewolf mating systems are an important focus of this book. Intense competition for mates and territories leads to greater reproductive success for larger males. Small males are confined to peripheral territories or alternative strategies where they encounter fewer females, are exposed to higher levels of predation (from predatory flies and in some species from conspecific females) and a more stressful thermal environment. The authors suggest that small males may also produce smaller quantities of sex pheromone, which means that females may be less likely to seek them out. The ability of daughters to provision (and possibly their fecundity) is also affected by their size, although the relative effects of size on the fitness of sons and daughters is not known. Since all selective forces seem to mitigate against small offspring, why do they exist at all? Female Philanthus mass-provision brood cells with entombing each egg indiprey, vidually with a store of food (i.e. paralysed bees) for the developing larva. This is all the food that the individual will receive before emergence as an adult, which means that offspring size is determined largely by maternal behavior. Females must decide both what sex to lay and how much food to allocate to each offspring. They are constrained by the constant risk of parasitism and by the unpredictability of hunting success. Obviously, female wasps
are faced with a surprisingly LOI: plex decision-making process, ;:rc:i no one has yet fully examined etther the proximate or ultimate detetml. nants of these investment decisions At a time when some biologists are dismissing natural history as simple story-telling, it is heartening to see how illuminating comparative field studies of behavior can be for understanding broader issues. Evans and O’Neill not only discuss Philanthus in the context of current theory but they offer numerous suggestions for exciting lines of research on important themes. While this book was obviously written for the serious insect behavioral biologist, it is also for anyone who just enjoys good natural history.
Ii. Jane Brockmann Department of Zoology, University of Florida, Gainesville, FL 32611 USA
References 1 Fabre, J.H. (1924) The Hunting Wasps, Dodd, Mead &Co. 2 Crompton, J. (1948) The Huntincr Wasp, Collins.
3 Peckham, G.W. and Peckham, E.G. (I 898) On the instincts and Habits of the Solitary Wasps, Wisconsin Geological
and Natural History Survey 4 Rau, P. and Rau, N. (1918) Wasp Afield,
Princeton
5 Tinbergen,
Universitv
N. (1932) Z.
Stud/es Press Vi/. Physiol. 16,
305-334
6 Tinbergen, 699-7
N. (1935)Z. Vgi. Physioi.
7 Tinbergen, Vgl. Physiol.
N. and Kruyt, W. (1938) 2, 25,292-334
8 Evans, H. (19661 The Comparative Ethology Wasps,
and Evolution
of the Sand
Harvard University Press 9 Evans, H. 11957) Studies on the Comparative of the Genus
Ethology Bembix,
of Digger Wasps Cornell Universitv
Press
From October 1988, TREE subscriptions will no longer be handled from Elsevier’s Amsterdam off ice. Henceforth, all new subscriptions, renewals and queries should be addressed to: Trends SubdpticQns Dqmtment, Ebviler S&&MW~ Pwbli Crown House, Lin(t-on Re\gd, BaFking, Esmx 163 1 WU, UK. tel: 01 594 7272 (UK) +44 1 594 7272 (Elsewhere) Note: US and Canadian subscribers may continue to use the New York address on the subscription card. 314
21,
16
_.
1988
Air Pollution
Effects of Atmospheric Pollutants on Forests, Wetlands and Agricultural Ecosystems edited by T.C. Hutchinson and K.M. Meema, Springer-Verlag, 1987. DM 274.00 hbk (xxvii t 652 pages) ISBN :j 540 16084 I The past ten years have seen a major slift in scientific thinking about the effects of air pollutants, a shift that has largely been forced upon us by the dramatic, but scientifically intractable, problems of forest decline il.1 both Western Europe and North America. Previously, it had been possible to demonstrate cause/effect relationships between adverse ecolcgical effects and specific polIi)tants, either around individual point sources’ or on a regional b,jsis2. In contrast, there is a growing consensus that current forest decline problems are much more complex, that air pollutants may only be one of a Jvide range of factors involved, and that the problems observed should be understood as a malfunction of the forest ecosystem, rather than as al adverse impact on individual trees. In the face of this complex problem, many divergent paths have been taken to elucidate the role of at nospheric pollutants in forest decline. The first two contributions to th s volume, which contains papers gil/en at a NATO workshop held in Tcronto in May 1985, illustrate two of the major paths. Prinz, Krause and Jung take a basically reductionist approach, attempting to exclude certain causal factors on the basis of both field observation and laboratory experiment and to demonstrate the: role of ozone and mist, the combined impact of which they believe is of central importance, by means of controlled laboratory expe.imentati0r-r. In contrast, Matzner anlj Ulrich argue that the same pollutsnt may influence many ecosystem components either directly or incirectly, and that demonstration of a ,3articular effect in a controlled laboratory experiment cannot preclude the possibility that other causal mechanisms are actually of greater significance in the field. Their case for the central role of soil acidificat on processes is based around detailed field observation rather than car trolled experiment. Twenty nine of the 43 contributrons, which all originate from either North America or Europe, are concerned either directly or indirectly with forest decline, and include a group of seven papers on acidification of forest soils. This emphasis is ronsistent with a major shift in
balance in international conferences in recent years away from effects on crops to those on forest+. Indeed, it is the section on agricultural ecosystems which is most disappointing. None of the contributions is concerned with the ecosystem as such; instead, they describe experimental studies on individual plants, kept well-watered and pest-free in controlled environment facilities, glasshouses or field chambers. Only the paper by Mansfield and co-workers considers the implications of such experiments for crop growth in adverse conditions. Yet some of the most exciting recent developments in our understanding of crop responses to atmospheric pollutants have been the recognition of the effects of pollutants in modifying crop responses to abiotic stresses, and to fungal diseases and insect pests3, and the successful application of open-air fumigation systems to study these complex interactions at an ecosystem leve14. In contrast to the rapid responses of annual crops, the effects of acid deposition on forest soils may only be detected over periods of decades in the field. The major problems are then of distinguishing the chemical changes induced by increased acid deposition from the natural processes of acidification in regions of high precipitation and the acidifying effects of forest growth and harvesting; these problems are well reviewed by Abrahamsen and Johnson in the first contributions on soil acidification. Similarly, the section on wetland ecosystems, which despite their ecological importance have been little studied, is introduced by two reviews, from Gorham
et al. and Clymo, which consider the need to place the effects of atmospheric pollutants in the context of the natural processes of acidification in such systems. Analogous problems arise in the interpretation of longterm declines in forest growth; the section on dendrochronology contains discussion of the complex statistical problems of analysing the possible impact of increased emissions of atmospheric pollutants in the context of the effects of other climatic variation. The importance of ecosystem response in the interpretation of the impact of atmospheric pollutants is now clear. For many targets, the long-term nature of pollutant impact and the subtle and complex interactions between pollutant input and other ecological processes make the task of understanding the role of pollutants in the changes observed in the field an immense scientific challenge. Many, but by no means all, of the papers in this volume provide useful contributions towards this task.
The Natural History and Behavior of North American Beewolves
also the subject of a classic study and doctoral thesis on orientation and recognition w-w bv Tinbergen5-7. This new book falls, then, into a tradition of fine natural history description and experimental field observations. For more than 30 years, Evans and his students have studied groundnesting solitary wasps in the family Sphecidae. Of the 34 species of North American Philanthus, about half have been studied - an unusually high proportion for any insect group. Just as Evans did in an earlier study on another well-studied group, the nyssonine sand waspsW, Evans and O’Neill synthesize published accounts and new observational
by Howard E. Evans and Kevin M. O’Neill, Comstock Publishing Associates of Cornell University Press, 1988, $45.00 hbk, $23.50 pbk (vii + 278 pages) ISBN 0 8014 1839 9 hbk / 080149513Xpbk Beewolves are solitary wasps which, as their name implies, hunt bees. This behavior as well as their large size and aggregated nesting have made them frequent subjects for study. Familiar to most ethologists from graphic natural history accounts by Fabrel, Crompton2, the Peckhams and the Raus4, they were
Mike Ashmore Department of Pure and Applied Biology, lmpertal College of Science and Technology, Srlwood Park, Ascot, Berkshire SL5 7PY, UK.
References 1 Gorham, A.G. and Gorham, E. (1963) Can.J. Bot41,1063-1078 2 Miller,P.R. (1973)Adv. Chem. 101-117 3 Bell, J.N.B. (1987) in Acid&in:
Ser.
122,
Scientific and Technic&Advances (Perry, R., Harrison, R.M., Bell, J.N.B. and Lester, J.N.. eds), pp. 535-545, Seper Ltd 4 Mcleod, A.R., Roberts, T.M., Alexander, K. and Cribb, D.M. (1988) NewPh’vtol. 109,67-78
313
material on North American beewolves. They provide a wealth of comparative material from which the authors piece together patterns of evolution and adaptation. The book begins by reviewing the morphological and behavioral characters common to most members of the genus. Some features are shared with many ground-nesting sphecid wasps, but others are unique to fhilanthus. For example, like other sphecids most male Philanthus defend small territories on leks near nests that females are provisioning or near female emergence sites. Unlike other sphecids, however, most male Philanthus scent mark. With modified brushes they wipe onto the substrate chemicals which are produced in their mandibular glands. These observations suggest that male Philanthus may be applying a sex pheromone that females seek out when ready for mating. Evans and O’Neill make the intriguing suggestion that if this material is expensive to produce, fighting may not be over territories per se, but over areas in which males have applied large quantities of sex pheromone. After giving an account of the natural history of each species of Philanthus, Evans and O’Neill place their observations into a broader context in the summarizing chapters. They find, for example, that within a locality the species of Philanthus differ in their prey choices: the largest tackle bumblebees, the wasps smaller species capture tiny solitary bees. By contrast, the location, structure and placement of nests and the digging behavior is surprisingly uniform throughout the group. Philanthus spp. also have a variety of
behavioral traits that reduce parasitism by flies, cuckoo wasps and velvet ants. Interestingly, similar traits have evolved independently in other groups of ground-nesting bees and sphecid wasps. Beewolf mating systems are an important focus of this book. Intense competition for mates and territories leads to greater reproductive success for larger males. Small males are confined to peripheral territories or alternative strategies where they encounter fewer females, are exposed to higher levels of predation (from predatory flies and in some species from conspecific females) and a more stressful thermal environment. The authors suggest that small males may also produce smaller quantities of sex pheromone, which means that females may be less likely to seek them out. The ability of daughters to provision (and possibly their fecundity) is also affected by their size, although the relative effects of size on the fitness of sons and daughters is not known. Since all selective forces seem to mitigate against small offspring, why do they exist at all? Female Philanthus mass-provision brood cells with entombing each egg indiprey, vidually with a store of food (i.e. paralysed bees) for the developing larva. This is all the food that the individual will receive before emergence as an adult, which means that offspring size is determined largely by maternal behavior. Females must decide both what sex to lay and how much food to allocate to each offspring. They are constrained by the constant risk of parasitism and by the unpredictability of hunting success. Obviously, female wasps
are faced with a surprisingly LOI: plex decision-making process, ;:rc:i no one has yet fully examined etther the proximate or ultimate detetml. nants of these investment decisions At a time when some biologists are dismissing natural history as simple story-telling, it is heartening to see how illuminating comparative field studies of behavior can be for understanding broader issues. Evans and O’Neill not only discuss Philanthus in the context of current theory but they offer numerous suggestions for exciting lines of research on important themes. While this book was obviously written for the serious insect behavioral biologist, it is also for anyone who just enjoys good natural history.
Ii. Jane Brockmann Department of Zoology, University of Florida, Gainesville, FL 32611 USA
References 1 Fabre, J.H. (1924) The Hunting Wasps, Dodd, Mead &Co. 2 Crompton, J. (1948) The Huntincr Wasp, Collins.
3 Peckham, G.W. and Peckham, E.G. (I 898) On the instincts and Habits of the Solitary Wasps, Wisconsin Geological
and Natural History Survey 4 Rau, P. and Rau, N. (1918) Wasp Afield,
Princeton
5 Tinbergen,
Universitv
N. (1932) Z.
Stud/es Press Vi/. Physiol. 16,
305-334
6 Tinbergen, 699-7
N. (1935)Z. Vgi. Physioi.
7 Tinbergen, Vgl. Physiol.
N. and Kruyt, W. (1938) 2, 25,292-334
8 Evans, H. (19661 The Comparative Ethology Wasps,
and Evolution
of the Sand
Harvard University Press 9 Evans, H. 11957) Studies on the Comparative of the Genus
Ethology Bembix,
of Digger Wasps Cornell Universitv
Press
From October 1988, TREE subscriptions will no longer be handled from Elsevier’s Amsterdam off ice. Henceforth, all new subscriptions, renewals and queries should be addressed to: Trends SubdpticQns Dqmtment, Ebviler S&&MW~ Pwbli Crown House, Lin(t-on Re\gd, BaFking, Esmx 163 1 WU, UK. tel: 01 594 7272 (UK) +44 1 594 7272 (Elsewhere) Note: US and Canadian subscribers may continue to use the New York address on the subscription card. 314
21,
16