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Microcosm food webs
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TRENDS in Ecology & Evolution Vol.16 No.6 June 2001
Book Review
Microcosm food webs Food Webs and Container Habitats:The Natural History and Ecology of Phytotelmata by R.L. Kitching. Cambridge University Press, 2000. £65.00 hbk (xiii + 431 pages) ISBN 0 521 77316 4
Roger Kitching’s book could be regarded as the first field guide to the fascinating world of life in ephemeral bodies of water. Phytotelmata, aquatic organisms living in containers of plant origin, which range from flatworms to crustaceans to aquatic larvae of insects and frogs, occur not only in tree holes, bamboo internodes and basins of buttressed trees, but also in bromeliad tanks, palm fronds and other watertight axils of leaves and floral bract, and even in the highly acidic fluid in the pitchers of pitcher plants. How unique are the assemblages of such organisms in phytotelm and do they function as a community, showing the emergent characters, such as stable food webs, that are seen in other communities? This book presents evidence and tantalizing facts about the species diversity, trophic relations and evolution of phytotelmata. Based on his own extensive work, Kitching constructs species-based food webs of the saprophagous and the predatory animals found in tree holes and pitcher plants, and examines global, continental and regional patterns in these and others reported in the literature. Disregarding microbes, rotifers and nematodes, he singles out competition and predation as the key forces that structure the phytotelm community and shows how biogeographical and ecological factors influence the pattern and process in these communities. A drawback to this approach is that it is entirely binary in linking species (having or not having a connection) and suffers from a lack of quantitative information on these links. It is difficult to assess the roles of individual species in these habitats because nutrient input will differ depending on both the host plant and the http://tree.trends.com
nature of its container (pans or rot holes). All species of saprophytes need to be known and their competitive and complementary functions in nutrient and energy consumption worked out to produce comprehensive food webs for these systems. However, the top-down effects of predators are easier to assess and here an experimental approach can be used to manipulate the food-web structure. Not surprisingly, impacts of predators are more dramatic in smaller phytotelm units than in larger ones, but not all predators, even those occurring in high density, have a keystone role in controlling the overall food-web structure. Since 1960 (Ref. 1), ecologists have focused on the analysis of food webs in microcosms, such as small springs, decaying logs and cowpats. This was an attempt to produce an accurate description of the entire community in a semi-closed system so that all species present in that system could be accounted for in terms of energy transfer and trophic relations. This Lindeman-style approach to ecosystem analysis2 was thought to answer questions such as the range of ecological efficiency values (i.e. the ratio of ingestion rates between trophic levels), and ecosystem functioning. However, such an approach failed, because it was difficult to quantify the microbial decomposers so important in detritus-based ecosystems, and because the different types of food sources available complicated energy pathways. This approach is only now beginning to be used successfully to study energy-based food webs3. Sadly, these issues are ignored in the study of phytotelm in the field. An advantage of working on a microcosm is that it is possible to control environmental conditions and manipulate community composition, allowing the mechanisms of microsuccession to be studied experimentally. Although facilitation is alluded to in the book, microsuccession within phytotelmata is less predictable than within many other microcosms, because the supply of nutrients and energy is irregular. Although Kitching acknowledges the great value of an experimental approach in the study of phytotelmata, he does not discuss such approaches in detail. The book is well organized and easy to follow, and includes some delightful accounts of the author’s field experiences.
With an appendix of the phytotelm bestiary and a comprehensive list of some 700 references, the book is a stimulating companion for naturalists and entomologists interested in the study of compact communities in the field, as well as for serious students of phytotelmatology. Jiro Kikkawa Dept of Zoology and Entomology,The University of Queensland, Brisbane, QLD 4072, Australia. References 1 Hairston, N.G. et al. (1960) Community structure, population control, and competition. Am. Nat. 94, 421–425 2 Lindeman, R.L. (1942) The trophic-dynamic aspects of ecology. Ecology 23, 399–418 3 Hall, R.O. et al. (2000) Organic matter flow in stream food webs with reduced detrital resource base. Ecology 81, 3445–3463
So many fish, so little time The Cichlid Fishes: Nature’s Grand Experiment in Evolution by George W. Barlow. Perseus Publishing, 2000. $28.00 hbk (xvi + 335 pages) ISBN 0 7382 0376 9
The cichlids, a family of small- to mediumsized tropical freshwater fish, probably comprise the most species-rich vertebrate family. George Barlow has provided a wonderful, witty and comprehensive account of our current knowledge of cichlid behaviour, accessible to a lay readership, but illuminating to the specialist. At its core lie informative laboratory experiments and field studies on parental care, mate choice and communication. Among the cichlids can be found long-term pair bonds, mouthbrooders, lek-breeders, nest helpers, bower builders, mobile leaf nurseries, brood parasites, sneaker dwarf males, sex changers and even (allegedly) a species that helps protect the young of a predator of their own main competitor. One harem-forming species shows such
Forum
TRENDS in Ecology & Evolution Vol.16 No.6 June 2001
Book Review
Microcosm food webs Food Webs and Container Habitats:The Natural History and Ecology of Phytotelmata by R.L. Kitching. Cambridge University Press, 2000. £65.00 hbk (xiii + 431 pages) ISBN 0 521 77316 4
Roger Kitching’s book could be regarded as the first field guide to the fascinating world of life in ephemeral bodies of water. Phytotelmata, aquatic organisms living in containers of plant origin, which range from flatworms to crustaceans to aquatic larvae of insects and frogs, occur not only in tree holes, bamboo internodes and basins of buttressed trees, but also in bromeliad tanks, palm fronds and other watertight axils of leaves and floral bract, and even in the highly acidic fluid in the pitchers of pitcher plants. How unique are the assemblages of such organisms in phytotelm and do they function as a community, showing the emergent characters, such as stable food webs, that are seen in other communities? This book presents evidence and tantalizing facts about the species diversity, trophic relations and evolution of phytotelmata. Based on his own extensive work, Kitching constructs species-based food webs of the saprophagous and the predatory animals found in tree holes and pitcher plants, and examines global, continental and regional patterns in these and others reported in the literature. Disregarding microbes, rotifers and nematodes, he singles out competition and predation as the key forces that structure the phytotelm community and shows how biogeographical and ecological factors influence the pattern and process in these communities. A drawback to this approach is that it is entirely binary in linking species (having or not having a connection) and suffers from a lack of quantitative information on these links. It is difficult to assess the roles of individual species in these habitats because nutrient input will differ depending on both the host plant and the http://tree.trends.com
nature of its container (pans or rot holes). All species of saprophytes need to be known and their competitive and complementary functions in nutrient and energy consumption worked out to produce comprehensive food webs for these systems. However, the top-down effects of predators are easier to assess and here an experimental approach can be used to manipulate the food-web structure. Not surprisingly, impacts of predators are more dramatic in smaller phytotelm units than in larger ones, but not all predators, even those occurring in high density, have a keystone role in controlling the overall food-web structure. Since 1960 (Ref. 1), ecologists have focused on the analysis of food webs in microcosms, such as small springs, decaying logs and cowpats. This was an attempt to produce an accurate description of the entire community in a semi-closed system so that all species present in that system could be accounted for in terms of energy transfer and trophic relations. This Lindeman-style approach to ecosystem analysis2 was thought to answer questions such as the range of ecological efficiency values (i.e. the ratio of ingestion rates between trophic levels), and ecosystem functioning. However, such an approach failed, because it was difficult to quantify the microbial decomposers so important in detritus-based ecosystems, and because the different types of food sources available complicated energy pathways. This approach is only now beginning to be used successfully to study energy-based food webs3. Sadly, these issues are ignored in the study of phytotelm in the field. An advantage of working on a microcosm is that it is possible to control environmental conditions and manipulate community composition, allowing the mechanisms of microsuccession to be studied experimentally. Although facilitation is alluded to in the book, microsuccession within phytotelmata is less predictable than within many other microcosms, because the supply of nutrients and energy is irregular. Although Kitching acknowledges the great value of an experimental approach in the study of phytotelmata, he does not discuss such approaches in detail. The book is well organized and easy to follow, and includes some delightful accounts of the author’s field experiences.
With an appendix of the phytotelm bestiary and a comprehensive list of some 700 references, the book is a stimulating companion for naturalists and entomologists interested in the study of compact communities in the field, as well as for serious students of phytotelmatology. Jiro Kikkawa Dept of Zoology and Entomology,The University of Queensland, Brisbane, QLD 4072, Australia. References 1 Hairston, N.G. et al. (1960) Community structure, population control, and competition. Am. Nat. 94, 421–425 2 Lindeman, R.L. (1942) The trophic-dynamic aspects of ecology. Ecology 23, 399–418 3 Hall, R.O. et al. (2000) Organic matter flow in stream food webs with reduced detrital resource base. Ecology 81, 3445–3463
So many fish, so little time The Cichlid Fishes: Nature’s Grand Experiment in Evolution by George W. Barlow. Perseus Publishing, 2000. $28.00 hbk (xvi + 335 pages) ISBN 0 7382 0376 9
The cichlids, a family of small- to mediumsized tropical freshwater fish, probably comprise the most species-rich vertebrate family. George Barlow has provided a wonderful, witty and comprehensive account of our current knowledge of cichlid behaviour, accessible to a lay readership, but illuminating to the specialist. At its core lie informative laboratory experiments and field studies on parental care, mate choice and communication. Among the cichlids can be found long-term pair bonds, mouthbrooders, lek-breeders, nest helpers, bower builders, mobile leaf nurseries, brood parasites, sneaker dwarf males, sex changers and even (allegedly) a species that helps protect the young of a predator of their own main competitor. One harem-forming species shows such