John H. Lawton’s research while affiliated with The University of Sheffield and other places


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Publications (113)


Patterns in the geographic ranges of the World's Woodpeckers
  • Article

June 2008

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87 Reads

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28 Citations

Ibis

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JOHN H. LAWTON

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We used data on the world's woodpeckers to test for patterns in the geographic distributions of a single group of closely related species. The frequency distribution of woodpecker geographic range sizes is approximately lognormal. Most variation in range sizes is explained by differences between species within genera; that is, range size seems to be an evolutionarily labile trait. The largest woodpecker ranges are found in Eurasia, both when absolute differences are compared and when range size is measured as a proportion of estimated available habitat. Notably, there is a negative relationship between the mean range sizes attained by species in a genus or tribe in South America and the mean ranges attained by species in the same tribe or genus in North America. Large-bodied species tend to be more widely distributed and to live at higher latitudes, but both tendencies disappear if the taxonomic relatedness of species is controlled for. Species living at high latitudes also tend to be more widely distributed. This relationship seems largely due to the effect of North American woodpeckers, which show it even when the taxonomic relatedness of species is controlled. Small continents generally have more woodpecker species than do large ones. Woodpecker geographic range sizes are smaller the more woodpecker species inhabit an area. Species show less overlap in their geographic ranges with species of similar than with species of dissimilar body size. The implications of these results for our understanding of patterns in geographic range sizes are discussed.


Are there latitudinal and altidudinal Rapoport effects in the geographic ranges of Andean passerine birds?

January 2008

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286 Reads

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45 Citations

Biological Journal of the Linnean Society

We analysed the range-sizes of 835 Andean passerine species (including 414 endemics and 421 non-endemics) to test for latitudinal and altitudinal Rapoport effects (LRE and ARE). We tested for positive range-size: latitude/altitude correlations using three different methods: (i) Rohde's mid-point method, (ii) species sorted out by altitude, and (iii) a phylogenetic comparative method (CAIC). Using Rohde's mid-point method, the mean latitudinal extent of species does not follow a Rapoport pattern, but the mean latitudinal occupancy of all passerines and non-endemics do increase with latitude. The latitudinal ranges of endemics sorted out by altitude follow a reverse Rapoport effect, but non-endemics support the pattern. CAIC confirms the latitudinal increase in the occupancy of non-endemics, but regressions have low coefficients of determination. The ARE is supported by the mean altitudinal extent of species, but the trend vanishes when controlling for geometric effects. Low-altitude species occupy about the same proportion of the available altitudinal space as do high-altitude ones. Our analyses suggest that latitude and altitude have low explanatory power for understanding the spatial variation in range-sizes at a continental scale. We show how different patterns can emerge from applying different criteria to the analysis of data.


Aggregation and interspecific abundance–occupancy relationships

February 2003

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93 Reads

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217 Citations

Journal of Animal Ecology
Bryan Shorrocks

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JOHN H. LAWTON

Individualistic species responses invalidate simple physiological models of community dynamics under global environmental change

January 2002

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83 Reads

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306 Citations

1. Most predictions of species distribution and abundance changes in response to global warming relate the individual requirements of a single isolated species to climate variables through some form of climate mapping. This method fails to account for the effects of species dispersal and species interactions, both of which may strongly affect distribution and abundance. 2. We therefore examined the effects of dispersal and species interactions on the distribution and abundance of three Drosophila species in a laboratory system that mimicked a latitudinal cline of 15 °C. We then investigated how species distribution and abundance in this system responded to simulated global warming. 3. Dispersal allowed populations to persist at non-optimum temperatures, overriding physiologically imposed range limits. 4. Temperature determined the outcome of competition. In pairwise interactions, Drosophila subobscura eliminated D. melanogaster or D. simulans at low temperatures but was itself eliminated at high temperatures. 5. Competitive interactions changed abundance and range sizes thus shifting the position of species optima. These changes depended on both the number and the identity of the competing species. 6. Enemy–victim interactions altered range and abundance. Adding the parasitoid Leptopilina boulardi affected the host assemblage directly at high temperatures where the parasitoid was present, and indirectly (mediated by dispersal) at low temperatures where it was scarce or absent. Host species coexisted for longer at low temperatures in clines when parasitoids were present than when they were absent. 7. Simulated global warming produced complex, counter-intuitive effects on distribution and abundance, including the reversal of species’ relative abundance at some temperatures. 8. Because dispersal and species interactions strongly influenced both range and abundance (sometimes in unexpected ways) current species distributions are no guide to what they might be under global climate change. Furthermore, since both these factors are missing from climate envelope models of range and abundance change, their predictions are, at best, incomplete.


Indicator Species

December 2001

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331 Reads

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25 Citations

This article reviews the use of species as indicators of the state of the environment and of human-induced changes to the environment. We focus on five interrelated topics, namely various types of pollution, rising concentrations of atmospheric carbon dioxide, global climate change, patterns in regional and global biodiversity, and the designation of protected areas for nature conservation. Using organisms to indicate the state of, and changes to, the environment has numerous tried and tested applications. Attempts to identify indicator species to predict the diversity of other, unstudied taxa, for scientific or conservation reasons, has proved to be more contentious and much more difficult.


The effect of termite biomass and anthropogenic disturbance on the CH4 budgets of tropical forests in Cameroon and Borneo

December 2001

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57 Reads

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32 Citations

Global Change Biology

The exchange of CH4 between tropical forests and the atmosphere was determined by simultaneously measuring the net CH4 flux at the soil surface and assessing the flux contribution from soil-feeding termite biomass, both within the soil profile and in mounds. In Cameroon the flux of CH4 ranged from a net emission of 40.7 ng m–2 s–1 to a net CH4 oxidation of –53.0 ng m–2 s–1. Soil-inhabiting termite biomass was significantly correlated with CH4 flux. Termite mounds emitted up to 2000 ng s–1 mound–1. Termite-derived CH4 emission reduced the soil sink strength by up to 28%. Disturbance also had a strong effect on the soil sink strength, with the average rate of CH4 oxidation, at – 17.5 ng m–2 s–1, being significantly smaller (≈ 36%) at the secondary forest site than the –27.2 ng m–2 s–1, observed at the primary forest site. CH4 budgets calculated for each site indicated that both forests were net sinks for CH4 at – 6.1 kg ha–1 y–1 in the near-primary forest and – 3.1 kg ha–1 y–1 in the secondary forest.


Mechanisms of positive biodiversity-production relationships: Insights provided by δ13C analysis in experimental Mediterranean grassland plots

August 2001

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96 Reads

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141 Citations

Ecology Letters

We investigated the role of water use in a Mediterranean grassland, in which diversity was experimentally manipulated, and a positive relationship was observed between plant species richness and productivity. Soil moisture patterns and stable carbon isotope ratios (δ13C) in leaves indicated greater water use by plants growing in species-rich mixtures compared to monocultures. These results suggest that complementarity or facilitation may be the mechanism responsible for the positive relationship between plant diversity and ecosystem processes.


Fig. 1. The effect of the initial size of the regional pool and changing the fecundity parameter (F mn ) on the resulting species richness of the assemblages for the four different coexistence mechanisms. Each point represents the average value of 50 simulations. Error bars of one standard error are smaller than the symbols and so have not been included (all standard errors B 0.25).
Fig. 2. The effect of the initial size of the regional pool and changing the fecundity parameter ( F mn ) on invasion resistance of the invader for 
Coexistence, saturation and invasion resistance in simulated plant assemblages
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  • Full-text available

August 2001

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104 Reads

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88 Citations

Oikos

A popular hypothesis is that species-rich systems are less susceptible to invasion. This hypothesis is based on the idea that species richness correlates with community saturation so that establishment by a new species is more difficult in saturated communities. Little attention has been focussed on how changing assumptions about the processes regulating species richness will alter community properties such as invasion resistance. Here, we simulate plant community assembly using four models that have different underlying coexistence mechanisms (and so differ in the amount of available niche space) and subject them to invasion. We created species richness gradients by comparing between models or by considering the output of a single model with different parameter values. We found that the relation between species richness and invasion resistance depends critically on the model considered and the cause of the species richness gradient. Overall, our results suggest that species richness does not necessarily correlate with saturation and is likely to be a poor predictor of invasion resistance. These results provide a possible explanation for the variety of outcomes reported in recent experimental and observational studies that examine the relationship between species richness and invasion resistance. We con-clude that consideration of the processes regulating species richness is crucial for a successful understanding of invasion resistance along species richness gradients.

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Scale and species number

August 2001

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53 Reads

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127 Citations

Trends in Ecology & Evolution

One of the main tasks confronting community ecologists is to explain why a particular site harbours a certain number of species. The site might range from a drop of water to the whole Earth, and the species might be drawn from a very restricted taxon or include all living organisms. The common problem, however, is to understand the relative importance of speciation and extinction and, more locally, of immigration and loss. Speciation is the ultimate motor driving biodiversity and ecologists need to know the factors influencing rates of speciation, and whether there is a feedback, positive or negative, between species numbers and the generation of new taxa. However, the relative importance of speciation and other factors determining species numbers varies crucially across different scales of enquiry. Here, we explore some of these issues as we move from a macro- to microscale perspective, focusing on a limited number of studies that we believe make important advances in the field.


Abundance–occupancy relationship

September 2000

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506 Reads

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804 Citations

1. The abundance and distribution of species tend to be linked, such that species declining in abundance often tend also to show declines in the number of sites they occupy, while species increasing in abundance tend also to be increasing in occupancy. Therefore, intraspecific abundance–occupancy relationships are commonly positive. 2. The intraspecific pattern is mirrored by more general positive interspecific abundance–occupancy relationships: widespread species tend to be abundant, and narrowly distributed species rare. 3. Here, we review recent research on these patterns based on the flora and fauna of the British Isles. We assess their generality, describe what is currently known about their structure, and summarize the results of tests of the several hypotheses proposed to explain their existence. 4. The positive form generally exhibited by abundance–occupancy relationships, intraspecific or interspecific, has consequences for several areas of applied ecology, including conservation, harvesting, biological invasions and biodiversity inventorying. These implications are discussed briefly.


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Citations (97)


... This phenomenon is known as 'conditionality' and has been documented in many studies of competitive (Siemann & Rogers 2003, Pollock et al. 2009, Chamberlain et al. 2014) and mutualistic interactions (e.g., Cushman & Whitham 1989, Bronstein 1994, Chamberlain & Holland 2009, Chamberlain et al. 2014. Conditionality can occur in mutualistic interactions because different species can differ in the quality of services provided to their partners, which in turn may show spatial or temporal variation on their level of dependence to these services (e.g., Bristow 1984, Rashbrook et al. 1991, Zamora 1999, Lee et al. 2009). Therefore, predicting the outcomes of a mutualistic interaction and the ecological variables governing them is often a difficult task (Bronstein 1998, Chamberlain et al. 2014. ...

Reference:

Plant Ontogeny as a Conditionality Factor in the Protective Effect of Ants on a Neotropical Tree
Bracken And Ants: Why Is There No Mutualism?
  • Citing Article
  • August 1991

... Despite knowing the importance of biodiversity and the need for conservation, biodiversity is still under threat due to multiple anthropogenic factors such as habitat loss and degradation, fragmentation, overgrazing, pollution, poaching, encroachment and land use changes, climate change, and the introduction of invasive alien species (Rawat & Agarwal,2015;Bhat et al,2020). The severity of this threat is increasing day by day which has upsurged the rate of extinction of species 1000 to 10,000 times faster than the estimated natural rate of extinction (May et al. 1995;Hilton-Taylor,2000). ...

Assessing extinction rates
  • Citing Chapter
  • January 1995

... This classic theory can be extended to take into account trophic interactions, which implies that the properties of the regional food web influence the species-area rela- tionships [3]. As the trophic rank increases (higher up in the foodweb), the stronger should be the species-area and species-distance effects [4]. Though there are some cases when there are no such expected effects. ...

TROPHIC RANK AND THE SPECIES–AREA RELATIONSHIP
  • Citing Article
  • July 1999

... What is clear is that the creation and enhancement of hard-bottom habitat distinguishes E. morio and possibly L. campechanus as ecosystem engineers (Coleman & Williams 2002, Ellis 2019. Therefore, it is important to quantify the effects of this habitat-engineering function so that they may be incorporated into an ecosystem-based management strategy for the WFS (Jones et al. 1994, 1997, Hastings et al. 2007. The objectives of this study were to (1) measure and compare physical characteristics of excavations (e.g. ...

POSITIVE AND NEGATIVE EFFECTS OF ORGANISMS AS PHYSICAL ECOSYSTEM ENGINEERS
  • Citing Article
  • October 1997

... The environment of the mother plant affects the germination traits of the produced seeds. Different levels of defoliation in vetch (Vicia sativa) produce seeds with the same germination percentage and germination time (Koptur et al., 1996). Artificial defoliation of wheat (Triticum aestivum L.) has little effect on the germination traits of produced seeds . ...

Effects of artificial defoliation on reproductive allocation in the common vetch, Vicia sativa (Fabaceae: Papilionoideae)

American Journal of Botany

... A central goal of community ecology is to identify factors that contribute to the abundance of individuals of different species within groups of interacting organisms (i.e., a community's "structure") (Wisz et al. 2013;D'Amen et al. 2017). Traditional models of community assembly contend that community structure is controlled by historical contingency and stochastic processes based on the pool of species available in an area, plus perhaps abiotic or biotic "environmental-filtering" factors (Strong et al. 1984;Lawton et al. 1993;Lewinsohn et al. 2005;HilleRisLambers et al. 2012). In contrast, a growing body of theory suggests a more evolutionarily dynamic picture of community structure (Lankau 2011;Koch et al. 2014;Mittelbach and Schemske 2015;Andreazzi et al. 2018;terHorst et al. 2018). ...

Patterns of diversity for the insect herbivores on bracken

... The nematode abundance and diversity in managed forests are correlated with the successional stage of the forest vegetation [24,[68][69][70]. Older stands usually had more nematode species than younger stands due to the late appearance of rare and localised species [71], but a management strategy that increased the growth of the understory and the herbal layer could also stimulate nematode populations in the soil [54]. ...

The effects of clearing and subsequent land-use on abundance and biomass of soil nematodes in tropical forest
  • Citing Article
  • July 1997

Pedobiologia

... Species diversity and productivity of biological communities are important indicators of environmental health (Rapport et al., 1998;Gerlach et al., 2013) that can be used to assess the state of pasture (Lawton and Gaston, 2001). For example, epiphytic lichens have been successfully used as indicators of overgrazing in Mongolian forest steppes . ...

Indicator Species
  • Citing Article
  • December 2001