Book Reviews

Heterogeneity: the essence of

ecology

Hutchings, M. J., John, E. A. &Stewart, A. J. A. (2000) The ecologicalconsequences of environmental hetero-geneity. Blackwell Science Ltd, Oxford.iv + 434 pp., figs, tables, index. Hard-back: Price £59.95. ISBN 0-632-05713-0.

As the authors of every chapter in thisvolume are keen to stress, heterogeneity isubiquitous, and almost nothing in ecologycan be understood without taking accountof it. Far from being merely a source ofinconvenient noise in our experimentalresults, heterogeneity is the very essenceof ecology. Therefore, not surprisingly, allthe major ecological topics are coveredhere: competition, herbivory, dispersal,foraging, parasitism and conservation,among others.

Most chapters fall naturally into groups.After a short introductory chapter, Wiensand Pickett et al. consider how heterogen-eity is defined, measured, generated andexperienced by organisms. The question ofscale crops up here, and in nearly everysubsequent chapter. Wilson continues thegeneral theme, but concentrates on therelationship between plant diversity andenvironmental heterogeneity, both bioticand abiotic. The evidence is contradictory,but Wilson concludes that much of theapparent conflict is a result of organisms ofdifferent size both creating and experien-cing heterogeneity at different temporaland spatial scales.

The next four chapters all consider theresponses of plants to environmental het-erogeneity. The first three deal with soils.Fitter et al.’s chapter, in particular, is anexcellent and thoughtful introduction tothe topic. Both Fitter et al. and Casperet al. emphasize the notion that responsesof plants to patchy soils can only beunderstood in the context of competitionbetween plants, and between plants andmicrobes. Both cite examples of how theresponse of individual plants to nutrientpatches fails to predict what happenswhen competitors are present. Therefore,

although one cannot help but admire theingenuity of the experiments on isolatedplants described by Hutchings et al. in themiddle chapter of the three, one alsowonders what they tell us about plants inreal communities. Watling and Press des-cribe how sunflecks can provide most ofthe available energy in the tropical forestunderstorey, yet numerous constraints andtrade-offs prevent plants from exploitingthem fully.

Chapter 9, by Hunter et al., linksplants and animals by looking at theimpact of heterogeneity in plant qualityon insect herbivores. Most, but not all, ofthe accumulating empirical evidenceagrees with theoretical predictions thattop-down control should increase withhost quality. Sticking with animals,Brown examines the all-pervasive conflictbetween food and safety in determiningpopulation densities, preferred habitatsand behaviour. I liked his final squirrelexample, but I am forced to conclude thatAmerican cats and dogs must be better atcatching squirrels than the ones in myneighbourhood. The next chapter, byGodfray et al., is probably my favourite.This is a thoroughly absorbing account ofhow behavioural ecology and populationdynamics may (but not yet) togetheraccount for the existence, compositionand dynamics of complex host–parasitoidcommunities.

It is back to plants for Chapters 12 and13. Seed dispersal is one of many topicsthat only make sense in the context ofheterogeneity, as Rees et al. show, whileBoshier and Billingham examine the gen-etics of tree populations. These chaptersprovide food for thought about how treesmight respond to climate change, andwhat conservationists’ demands for ‘localseed sources’ really mean. Power andRainey then look at how isotopes can beused to define ‘resource sheds’, whichdefine where organisms derive their nutri-ents. There are some counter-intuitiveresults here concerning topics as diverseas where bowhead whales grow and howmarine nitrogen ends up in Alaskan blue-berries.

Four chapters then pursue a conserva-tion theme. Dytham provides a nice dis-cussion of the usefulness (or otherwise) ofmetapopulation models in predictingextinctions, both now and in the future,while Corlett puts some flesh on thetheoretical bones by describing the conse-quences of forest clearance in Singaporeand Hong Kong. Neither chapter is areassuring read. MacDonald et al. in amore cheerful chapter give us an excellentmouse’s-eye view of farmland conserva-tion in the UK. Bakker concludes with areview of the impacts of heterogeneity,particularly of plant propagules in timeand space, on restoration ecology.

Lawton’s concluding remarks are a‘rummage box’ of ecological ideas, somelinked quite closely to the preceding chap-ters, some not at all. One topic thatsurfaces here for the first time is biodiver-sity and ecosystem function. The justifica-tion for including it here is to make thedistinction between within-system studies,where biodiversity seems to be positivelycorrelated with ecosystem function, andacross-system studies, where it is not. Thisseems an odd distinction to make in avolume where every chapter has stressedthe all-pervasive nature of heterogeneity.Convincing within-system effects existonly in a few experiments involving syn-thesized species assemblages, where onlyspecies number is allowed to vary and allother factors are held constant, i.e. allheterogeneity has been expunged. In thereal world, species richness and environ-ment always differ between sites, theformer very much driven by the latter.

Finally, I have to say I approve of the newcolourful covers of recent BES Symposiumvolumes, which now look much less likevolumes of mediaeval poetry. The view ofWasdale, in the English Lake District, mayhave nothing much to do with heterogen-eity, but it is a nice picture all the same. It isjust a pity it is printed back-to-front.Maybe publishers should get out more.

KEN THOMPSON

Department of Animal and Plant Sciences,University of Sheffield,

UK

Journal of Biogeography, 29, 559–560

� 2002 Blackwell Science Ltd