Discontinuities in ecological data

Historically, ecology has focused on continuous distributions and smooth transitions. Only recently have discontinuities and thresholds become an explicit focus in some areas of ecology, especially in the realm of complex systems. The study of animal body mass distributions has been recognized for its potential to provide insight into the underlying processes shaping animal communities. Hutchinson (1) formalized the understanding of species niches and the potential for competition to shape body mass distributions. However, despite a long history of theoretical and empirical pursuit, the mechanisms driving patterns in body mass distributions remain poorly understood. The work of Scheffer and van Nes (2) in this issue of PNAS demonstrates that community interactions alone can create discontinuous, lumpy distributions of simulated species along a niche axis. Their contribution comes at a time of heightened interest in understanding the mechanisms that may lead to discontinuities in body mass or biomass distributions

Ecosystems and Immune Systems: Hierarchical Response Provides Resilience against Invasions

Janssen (2001) provides the stimulus for thoughtful comparison and consideration of the ranges of responses exhibited by immune systems and ecological systems in the face of perturbations such as biological invasions. It may indeed be informative to consider the similarities of the responses to invasions exhibited by immune systems and ecological systems. Clearly, both types of systems share a general organizational structure with all other complex hierarchical systems. Their organization provides these systems with resilience. However, when describing the response of ecological-economic systems to invasions, Janssen emphasizes the human-economic response. I would like to expand on his comparison by focusing on how resilience is maintained in complex systems under the threat of invasion

The Effects of High-Oil Corn or Typical Corn with or without Supplemental Fat on Diet Digestibility in Finishing Steers

Two 3 x 3 latin squares were utilized in an 84-day digestion trial with ruminally- and duodenallycannulated steers. Diets consisted of 73 to 78% whole corn grain, 12.3% corn silage and 2.0% N, with treatment differences being high-oil corn- (HOC), isogenetic typical-corn- (TC), or isogenetic typical-corn + fat- (TC+F) based diets. The HOC and TC+F diets were formulated to provide the same ether extract (EE) content. All diets were fed at 90% of ad libitum intake. Chromic oxide was used as a digestibility marker. Total tract dry matter (DM) (P=.08), organic matter (OM) (P=.08) and nitrogen (N) (P=.06) digestibilities tended to be greater for TC than HOC diets, whereas starch neutral detergent fiber (NDF), acid detergent fiber (ADF), and ether extract digestibilities were similar (P\u3e.10). There were no differences (P\u3e.10) in total tract dry matter, organic matter, starch, NDF, ADF, ether extract, or nitrogen digestibilities between TC+F and HOC diets or TC and TC+F diets. Ruminal digestion of dry matter, organic matter, starch, NDF, ADF, and feed nitrogen was similar (P\u3e.10) among treatments. Microbial-nitrogen flow and efficiencies were also similar (P\u3e.10) among treatments. Results indicate finishing steer diets composed of primarily HOC are equally or less digestible than similar diets composed of TC, and adding fat to TC diets did not affect the digestibility of the diet when fed to finishing steers

The adaptive cycle: More than a metaphor

The adaptive cycle and its extension to panarchy (nested adaptive cycles) has been a useful metaphor and conceptual model for understanding long-term dynamics of change in ecological and social–ecological systems. We argue that adaptive cycles are ubiquitous in complex adaptive systems because they reflect endogenously generated dynamics as a result of processes of self-organization and evolution. We synthesize work from a wide array of fields to support this claim. If dynamics of growth, conservation, collapse and renewal are endogenous dynamics of complex adaptive systems, then there ought to be signals of system change over time that reflect this. We describe a series of largely thermodynamically based indicators that have been developed for this purpose, and we add a critical and heretofore missing component–namely, that of understanding dynamics of change (adaptive cycles) at objectively identified spatial and temporal scales nested within each system, instead of solely at the system level. The explicit consideration of scales, when coupled with selective indicators, may circumvent the need for multiple indicators to capture system dynamics and will provide a richer picture of system trajectory than that offered by a single-scale analysis. We describe feasible ways in which researchers could systematically and quantitatively look for signatures of adaptive cycle dynamics at scales within ecosystems, rather than relying on metaphor and largely qualitative descriptions

The adaptive cycle: More than a metaphor

The adaptive cycle and its extension to panarchy (nested adaptive cycles) has been a useful metaphor and conceptual model for understanding long-term dynamics of change in ecological and social–ecological systems. We argue that adaptive cycles are ubiquitous in complex adaptive systems because they reflect endogenously generated dynamics as a result of processes of self-organization and evolution. We synthesize work from a wide array of fields to support this claim. If dynamics of growth, conservation, collapse and renewal are endogenous dynamics of complex adaptive systems, then there ought to be signals of system change over time that reflect this. We describe a series of largely thermodynamically based indicators that have been developed for this purpose, and we add a critical and heretofore missing component–namely, that of understanding dynamics of change (adaptive cycles) at objectively identified spatial and temporal scales nested within each system, instead of solely at the system level. The explicit consideration of scales, when coupled with selective indicators, may circumvent the need for multiple indicators to capture system dynamics and will provide a richer picture of system trajectory than that offered by a single-scale analysis. We describe feasible ways in which researchers could systematically and quantitatively look for signatures of adaptive cycle dynamics at scales within ecosystems, rather than relying on metaphor and largely qualitative descriptions

The Impacts of Sprawl on Biodiversity: the Ant Fauna of the Lower Florida Keys

Sprawling development can affect species composition by increasing the rate of invasion by non-native species, and decreasing the persistence of native species. This paper briefly reviews the scientific literature on the impacts of sprawl on biological diversity, with specific emphasis on the influence of sprawl on non-native species richness. We then explore the relationship between sprawl and biodiversity using a data set of ant species collected from 46 habitat patches located in the increasingly suburbanized Florida Keys, USA. We quantified sprawl as the proximity of roads and amount of development surrounding a habitat patch. Using bait transects, we identified 24 native and 18 non-native species of ants. Neither the overall number of native species nor the number of rare native species were significantly affected by the amount of development or proximity to roads, however, the number of non-native species was significantly correlated with the amount of development. Surprisingly, the number of native species and rare native species was significantly positively correlated with the number of non-native species. Areas that supported many species of native ants also supported a diverse non-native ant fauna, and the species distribution was highly nested. Currently, the native ant fauna of the Florida Keys does not appear to be dramatically influenced by sprawl, however, if development increases, the number of non-native ants may increase, and many of these species have been documented as decreasing native ant diversity. If development plateaus, there is evidence that the native ant fauna could persist and could decrease non-native species richness through competition or predation

The adaptive cycle: More than a metaphor

The adaptive cycle and its extension to panarchy (nested adaptive cycles) has been a useful metaphor and conceptual model for understanding long-term dynamics of change in ecological and social–ecological systems. We argue that adaptive cycles are ubiquitous in complex adaptive systems because they reflect endogenously generated dynamics as a result of processes of self-organization and evolution. We synthesize work from a wide array of fields to support this claim. If dynamics of growth, conservation, collapse and renewal are endogenous dynamics of complex adaptive systems, then there ought to be signals of system change over time that reflect this. We describe a series of largely thermodynamically based indicators that have been developed for this purpose, and we add a critical and heretofore missing component–namely, that of understanding dynamics of change (adaptive cycles) at objectively identified spatial and temporal scales nested within each system, instead of solely at the system level. The explicit consideration of scales, when coupled with selective indicators, may circumvent the need for multiple indicators to capture system dynamics and will provide a richer picture of system trajectory than that offered by a single-scale analysis. We describe feasible ways in which researchers could systematically and quantitatively look for signatures of adaptive cycle dynamics at scales within ecosystems, rather than relying on metaphor and largely qualitative descriptions

Complexity versus certainty in understanding species’ declines

Aim Our understanding of and ability to predict species declines is limited, despite decades of study. We sought to expand our understanding of species declines within a regional landscape by testing models using both traditional hypotheses and those derived from a complex adaptive systems approach. Location Our study area was the dry mixed grassland of south-eastern Alberta, Canada, one of the largest remnants of native grassland in North America, and the adjacent grassland in Saskatchewan. Methods We used the breeding birds of the grassland to test the relationship between species declines and a suite of traits associated with decline (such as size, specialization and rarity, as well as distance to edge of a discontinuity, and edge of geographic range) in a stepwise regression with AICc values and bootstrapping via model averaging, followed by a refit procedure to obtain model-averaged parameter estimates. We used both provincial government and Breeding Bird Survey (BBS) classifications of decline. We also modelled degree of decline in the Alberta and Saskatchewan grasslands, which differ in amount of habitat remaining, to test whether severity of decline was explained by the same traits as species decline/not- decline. Results We found that the model for government-defined decline fulfilled government expectations that species’ extinction risk is a function of being large, specialized, rare and carnivorous, whereas the model for BBS-defined decline suggested that the biological reality of decline is more complex, requiring the need to explicitly model scale-specific patterns. Furthermore, species decline/ not- decline was explained by different traits than those that fit degree of decline, though complex systems- derived traits featured in both sets of models. Main conclusions Traditional approaches to predict species declines (e.g. government processes or IUCN Red Lists), may be too simplistic and may therefore misguide management and conservation. Using complex systems approaches that account for scale-specific patterns and processes have the potential to overcome these limitations

The adaptive cycle: More than a metaphor

The adaptive cycle and its extension to panarchy (nested adaptive cycles) has been a useful metaphor and conceptual model for understanding long-term dynamics of change in ecological and social–ecological systems. We argue that adaptive cycles are ubiquitous in complex adaptive systems because they reflect endogenously generated dynamics as a result of processes of self-organization and evolution. We synthesize work from a wide array of fields to support this claim. If dynamics of growth, conservation, collapse and renewal are endogenous dynamics of complex adaptive systems, then there ought to be signals of system change over time that reflect this. We describe a series of largely thermodynamically based indicators that have been developed for this purpose, and we add a critical and heretofore missing component–namely, that of understanding dynamics of change (adaptive cycles) at objectively identified spatial and temporal scales nested within each system, instead of solely at the system level. The explicit consideration of scales, when coupled with selective indicators, may circumvent the need for multiple indicators to capture system dynamics and will provide a richer picture of system trajectory than that offered by a single-scale analysis. We describe feasible ways in which researchers could systematically and quantitatively look for signatures of adaptive cycle dynamics at scales within ecosystems, rather than relying on metaphor and largely qualitative descriptions