Area and the latitudinal diversity gradient for terrestrial birds

Hawkins, Bradford A.; Porter, Eric E.

doi:10.1046/j.1461-0248.2001.00271.x

Cited by 34 publications

(38 citation statements)

References 19 publications

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“…It has been argued that species richness increases with increasing area sampled (Hawkins and Porter 2001; but see Rohde 1997). Therefore, we included total surface area per country (in square kilometers) in our analyses, in order to control for its effect in the multivariate analysis.…”

Section: Methodsmentioning

confidence: 99%

“…Generally, the number of plant and animal species declines as one moves away from the equator (Pianka 1966; Stevens 1989, 1992; Rohde 1992; Brown 1995; Kaufman 1995; Rosenzweig 1995; Roy et al 1998; Huston 1999; Chown and Gaston 2000; Hawkins and Porter 2001). This pattern, known as the latitudinal species diversity gradient, has been documented for many contemporary taxonomic groups (see Brown 1995; Rosenzweig 1995; Gaston and Blackburn 2000; Allen et al 2002; Stevens et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Ecology Drives the Worldwide Distribution of Human Diseases

2004

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Identifying the factors underlying the origin and maintenance of the latitudinal diversity gradient is a central problem in ecology, but no consensus has emerged on which processes might generate this broad pattern. Interestingly, the vast majority of studies exploring the gradient have focused on free-living organisms, ignoring parasitic and infectious disease (PID) species. Here, we address the influence of environmental factors on the biological diversity of human pathogens and their global spatial organization. Using generalized linear multivariate models and Monte Carlo simulations, we conducted a series of comparative analyses to test the hypothesis that human PIDs exhibit the same global patterns of distribution as other taxonomic groups. We found a significant negative relationship between latitude and PID species richness, and a nested spatial organization, i.e., the accumulation of PID species with latitude, over large spatial scales. Additionally, our results show that climatic factors are of primary importance in explaining the link between latitude and the spatial pattern of human pathogens. Based on our findings, we propose that the global latitudinal species diversity gradient might be generated in large part by biotic interactions, providing strong support for the idea that current estimates of species diversity are substantially underestimated. When parasites and pathogens are included, estimates of total species diversity may increase by more than an order of magnitude.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ecology Drives the Worldwide Distribution of Human Diseases

2004

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“…Consequently, if high-energy areas are more extensive than low-energy ones, positive species-energy relationships may arise through the effects of area, rather than energy, on species richness. Area effects on species richness have been debated with reference to latitudinal species richness gradients, but without consensus (Rosenzweig & Sandlin, 1997 ;Rohde, 1997Rohde, , 1998Ruggiero, 1999;Hawkins & Porter, 2001 ;Astorga et al, 2003 ;Rosenzweig, 2003).…”

Section: Confounding Variablesmentioning

confidence: 99%

Species–energy relationships at the macroecological scale: a review of the mechanisms

2005

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Correlations between the amount of energy received by an assemblage and the number of species that it contains are very general, and at the macro-scale such species-energy relationships typically follow a monotonically increasing curve. Whilst the ecological literature contains frequent reports of such relationships, debate on their causal mechanisms is limited and typically focuses on the role of energy availability in controlling the number of individuals in an assemblage. Assemblages from high-energy areas may contain more individuals enabling species to maintain larger, more viable populations, whose lower extinction risk elevates species richness. Other mechanisms have, however, also been suggested. Here we identify and clarify nine principal mechanisms that may generate positive species-energy relationships at the macro-scale. We critically assess their assumptions and applicability over a range of spatial scales, derive predictions for each and assess the evidence that supports or refutes them. Our synthesis demonstrates that all mechanisms share at least one of their predictions with an alternative mechanism. Some previous studies of species-energy relationships appear not to have recognised the extent of shared predictions, and this may detract from their contribution to the debate on causal mechanisms. The combination of predictions and assumptions made by each mechanism is, however, unique, suggesting that, in principle, conclusive tests are possible. Sufficient testing of all mechanisms has yet to be conducted, and no single mechanism currently has unequivocal support. Each may contribute to species-energy relationships in some circumstances, but some mechanisms are unlikely to act simultaneously. Moreover, a limited number appear particularly likely to contribute frequently to species-energy relationships at the macro-scale. The increased population size, niche position and diversification rate mechanisms are particularly noteworthy in this context.

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“…Some studies revealed positive correlations between regional area and species richness (Blackburn & Gaston 1997, Ruggiero 1999. However, other studies falsified this pattern, stating that neither were tropical biomes larger nor was richness related to area at biome scales (Hawkins & Porter 2001). A common notion in several contributions on the area hypothesis, however, is that productivity may influence the importance of area as a factor determining latitudinal gradients (Rohde 1997, Rosenzweig & Sandlin 1997, Chown & Gaston 2000.…”

Section: Underlying Causes Of the Latitudinal Gradientmentioning

confidence: 99%

Strength, slope and variability of marine latitudinal gradients

Hillebrand¹

2004

Mar. Ecol. Prog. Ser.

183

165

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Latitudinal declines of species richness from the tropics to the poles represent a general spatial pattern of diversity on land. For the marine realm, the generality of this pattern has frequently been questioned. Here, I use a database with nearly 600 published gradients (198 of which were marine) to assess whether there is a marine latitudinal diversity gradient of similar average strength and slope as that for terrestrial organisms. Using meta-analysis techniques, I also tested which characteristics of organisms or habitats affected gradient strength and slope. The overall strength and slope of the gradient for marine organisms was significantly negative and of similar magnitude compared to gradients for terrestrial organisms. Marine gradients were on average stronger as well as steeper than freshwater gradients. Latitudinal gradients were clearly a regional phenomenon, with stronger gradients and steeper slopes for diversity assessed on regional than on local scales. The gradient parameters differed also between oceans and between different habitats, with steeper gradients related to the pelagial rather than the benthos. There were on the other hand no significant differences between hemispheres and between different gradient ranges, although such differences have often been presumed. The most important organismal characteristic related to gradient structure was body mass, with significant gradients related to large organisms. A significant increase in gradient strength with increasing trophic level was observed. The meta-analysis also revealed strongest gradients for nekton and mobile epifauna, whereas the gradients were weak for sessile epifauna and for infauna. In conclusion, marine biota reveal a similar overall decline in diversity with latitude to that observed in terrestrial realms, but the strength and slope of the gradient are clearly subject to regional, habitat and organismal features.

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Area and the latitudinal diversity gradient for terrestrial birds

Cited by 34 publications

References 19 publications

Ecology Drives the Worldwide Distribution of Human Diseases

Ecology Drives the Worldwide Distribution of Human Diseases

Species–energy relationships at the macroecological scale: a review of the mechanisms

Strength, slope and variability of marine latitudinal gradients

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