Changes In Abiotic Environment Research Articles

Relating environmental change and species stability in Late Ordovician seas

Niche stability of a diverse suite of 21 invertebrate species and genera from the Cincinnatian Series (Katian Stage) of North America was examined using spatial distribution modeling across nine time slices, including abiotic and biotic environmental change. Niche stability varied through time. The focal taxa exhibited niche stability ( = no adaptive response) and tracked their preferred environment laterally to accommodate gradual sea-level fall. Niche evolution increased during the Richmondian Invasion. Species adjusted to the introduction of new competitors by contracting their niche into a subset of their previous niche parameters. In Cincinnatian species and genera, adaptive response (stability vs. evolution) was related to the tempo and mode of environmental change.

Controls on niche stability in geologic time: congruent responses to biotic and abiotic environmental changes among Cincinnatian (Late Ordovician) marine invertebrates

The set of environmental conditions under which a taxon can survive and maintain viable populations, known as the ecological niche, is a fundamental determinant of a taxon's distribution. Because of the central importance of ecological niches, they have been assumed to remain relatively stable during intervals of morphological stasis. However, the assumption of niche stability has rarely been tested directly with fossil data spanning multiple temporal intervals. Thus, the conditions under which this assumption is likely to be accurate are not well understood. In this study, we use ecological niche modeling (ENM) to reconstruct the ecological niche for 11 genera of marine benthos (crinoids, trilobites, molluscs, bryozoans, and corals) from the Type Cincinnatian Series (Late Ordovician, Katian Stage) across nine temporal intervals spanning approximately three million years. This interval includes both abiotic environmental change (gradual sea-level fall) and biotic change (rapid pulses of the Richmondian Invasion), thus allowing the relative effect of different environmental perturbations to be constrained. A previous symmetrical analysis of niche stability of brachiopod species recovered an increase in niche evolution following the Richmondian Invasion. Herein we test the generality of the brachiopod pattern within the community. Niche stability was evaluated in geographic space, ecological space, and niche parameter space. Niche stability varied through time; during the Pre-Invasion interval, taxa exhibited niche stability during gradual shallowing of sea level in the basin, whereas niche evolution became more common during the Richmondian Invasion. Taxa adjusted to the increased competition by altering aspects of their niche. Notably, surviving taxa contracted their niche into a subset of their previous niche parameters. This represents an adaptive response to increased competition for resources with the newly established invader taxa, and it was employed most successfully by generalist taxa. Patterns of niche evolution were congruent between clades, among feeding styles, and across taxonomic levels.

Short- and long-term conditioning of a temperate marine diatom community to acidification and warming.

Ocean acidification and greenhouse warming will interactively influence competitive success of key phytoplankton groups such as diatoms, but how long-term responses to global change will affect community structure is unknown. We incubated a mixed natural diatom community from coastal New Zealand waters in a short-term (two-week) incubation experiment using a factorial matrix of warming and/or elevated pCO2 and measured effects on community structure. We then isolated the dominant diatoms in clonal cultures and conditioned them for 1 year under the same temperature and pCO2 conditions from which they were isolated, in order to allow for extended selection or acclimation by these abiotic environmental change factors in the absence of interspecific interactions. These conditioned isolates were then recombined into 'artificial' communities modelled after the original natural assemblage and allowed to compete under conditions identical to those in the short-term natural community experiment. In general, the resulting structure of both the unconditioned natural community and conditioned 'artificial' community experiments was similar, despite differences such as the loss of two species in the latter. pCO2 and temperature had both individual and interactive effects on community structure, but temperature was more influential, as warming significantly reduced species richness. In this case, our short-term manipulative experiment with a mixed natural assemblage spanning weeks served as a reasonable proxy to predict the effects of global change forcing on diatom community structure after the component species were conditioned in isolation over an extended timescale. Future studies will be required to assess whether or not this is also the case for other types of algal communities from other marine regimes.

Species richness and evolutionary speed: the influence of temperature, water and area

AbstractThere are a few patterns in nature that are striking even to casual observers. These include patterns of species richness associated with latitude, elevation, rainfall and area. Current thinking suggests that a number of primary mechanisms determine richness variation and that these differ depending on the type of pattern and the biome to which they apply. Prominent among the many hypotheses that attempt to explain the latitudinal diversity gradient (LDG) are those based either on climate or on historical factors such as past biome area. Climate‐based and historically‐based hypotheses have been regarded as competing alternatives, but there is growing acknowledgement that both are important. The evolutionary speed hypothesis (ESH) is one of several climate‐based hypotheses. According to this hypothesis the LDG is generated by thermally mediated asymmetries in evolutionary speed and diversification. Here we identify five relationships predicted by the ESH and survey the literature for empirical evidence for and against these relationships. We find these five relationships are supported by a number of empirical studies. However, there are gaps in this evidence that require further work and, because the relationship between temperature and species richness is negative when water is limited, a modification to the ESH is necessary. Additionally, we suggest that diversity patterns associated with area, temperature and water availability might all be influenced by a common mechanism associated with biologically available energy and its influence on the tempo of evolution. Rates of genetic evolution might also be influenced by spatial heterogeneity and rates of biotic and abiotic environmental change, potentially introducing positive feedbacks between diversification and genetic evolution.

Dedicated Issue ‐ Adaptations to Changing Environments

How do insects adapt to varying environments? Obviously this is a quite simple question, but at the same time it is tough to answer. The appropriate response has to encompass daily, seasonal and more extended time scales as well as many research fields, from ecology, behaviour, morphometrics, biochemistry and physiology to molecular biology. In temperate zones, insects develop unique morphological or physiological characteristics seasonally to overcome harsh biotic and/or abiotic environmental changes. Some organisms have evolved sophisticated systems that allow them to anticipate forthcoming unfavourable seasons. Insects inhabiting Polar Regions have evolved unique mechanisms to withstand severe environmental challenges. These topics were discussed at two recent symposia - ‘Photoperiodic induction of diapause and seasonal morphs’ and ‘New complexities in the regulation of insect diapause and cold hardiness’ held during the XXIV International Congress of Entomology that convened in Daegu, South Korea, August 19–25, 2012. Many of the symposia participants kindly agreed to contribute papers to this Dedicated Issue of Physiological Entomology. We appreciate their efforts, timely submissions and hope that they enjoy the finished product. Thank you to all of the contributors. In the issue, two reviews focus on photoperiodism and the production of seasonal morphs in aphids and butterflies, and a third on surviving cold temperatures as part of the seasonal diapause syndrome, as well as on more intermittent, much shorter time scales. In addition, this issue includes original papers providing examples of recent advances and approaches to the understanding adaptations to environmental fluctuation in a range of insect species. Although the issue cannot be comprehensive for all aspects related to the topic, it covers a number of research themes, such as diapause, temperature tolerance, circadian rhythms, photoperiodism, polyphenism, seasonal morphs, as well as encompassing techniques from molecular biology to physiology. We believe this issue will introduce and enlighten readers on contemporary aspects of environmental adaptations in insects.

The importance of metacommunity ecology for environmental assessment research in the freshwater realm

Most bioassessment programs rest on the assumption that species have different niches, and that abiotic environmental conditions and changes therein determine community structure. This assumption is thus equivalent to the species sorting perspective (i.e. that species differ in their responses to environmental variation) in metacommunity ecology. The degree to which basing bioassessment on the species sorting perspective is reasonable is likely to be related to the spatial extent of a study and the characteristics of the organism groups (e.g. dispersal ability) with which the effects of anthropogenic changes are assessed. Recent findings in metacommunity research have stressed that community structure is determined not only by local abiotic environmental conditions but also by biotic interactions and dispersal-related effects. For example, dispersal limitation may prevent community structure recovery from the effects of a putative stressor, as organisms may not be able to disperse to all sites in a region. Mass effects (i.e. the presence of species in environmentally suboptimal sites due to high dispersal rates from environmentally suitable sites) may, in turn, obscure the effects of a stressor, as dispersal from source sites (e.g. an unaltered site) allows persistence at sink sites (e.g. an anthropogenically altered site). Better bioassessment should thus take both niche- and dispersal-related processes simultaneously into consideration, which can be accomplished by explicitly modelling spatial location as a proxy for dispersal effects. Such an integrated approach should be included in bioassessment programs using general multivariate approaches, predictive modelling, and multimetric indices.

Plant‐herbivore coevolution in a changing world

AbstractCurrent anthropogenic environmental change causes rapid loss of biodiversity. Although the effects of the main causes of this loss (habitat fragmentation, climate change, and invasive species) on single species have been widely studied, the effects on species interactions are poorly understood. In particular, we do not yet understand how these phenomena affect the evolutionary processes that impact species interactions. Coevolution is a dominant process that organizes the web of life: most species are involved in at least one coevolved interaction. Due to rapid human modification of landscapes it is important to understand how subsequent changes in biotic and abiotic environment and in the level and distribution of genetic variation, as well as changes in population structures, influence the elements of the coevolutionary process. In this review, we synthesize recent development of theoretical work on the coevolution of interacting species with conservation genetics and the impact of anthropogenic environmental changes on single species to address the potential effects of habitat fragmentation, climate change, and invasive species on plant‐herbivore coevolution.

Tangled in a sparse spider web: single origin of orb weavers and their spinning work unravelled by denser taxonomic sampling.

In order to study the tempo and the mode of spider orb web evolution and diversification, we conducted a phylogenetic analysis using six genetic markers along with a comprehensive taxon sample. The present analyses are the first to recover the monophyly of orb-weaving spiders based solely on DNA sequence data and an extensive taxon sample. We present the first dated orb weaver phylogeny. Our results suggest that orb weavers appeared by the Middle Triassic and underwent a rapid diversification during the end of the Triassic and Early Jurassic. By the second half of the Jurassic, most of the extant orb-weaving families and web designs were already present. The processes that may have given origin to this diversification of lineages and web architectures are discussed. A combination of biotic factors, such as key innovations in web design and silk composition, as well as abiotic environmental changes, may have played important roles in the diversification of orb weavers. Our analyses also show that increased taxon sampling density in both ingroups and outgroups greatly improves phylogenetic accuracy even when extensive data are missing. This effect is particularly important when addition of character data improves gene overlap.

Ecological metabolomics: overview of current developments and future challenges

Ecometabolomics, which aims to analyze the metabolome, the total number of metabolites and its shifts in response to environmental changes, is gaining importance in ecological studies because of the increasing use of new technical advances, such as modern HNMR spectrometers and GC-MS coupled to bioinformatic advances. We review here the state of the art and the perspectives of ecometabolomics. The studies available demonstrate ecometabolomic techniques have great sensitivity in detecting the phenotypic mechanisms and key molecules underlying organism responses to abiotic environmental changes to biotic interactions. But such studies are still scarce, and in most cases they are limited to the direct effects of a single abiotic factor or of biotic interactions between two trophic levels under controlled conditions. Several exciting challenges remain to be achieved through the use of ecometabolomics in field conditions, involving more than two trophic levels, or combining the effects of abiotic gradients with intra- and inter-specific relationships. The coupling of ecometabolomic studies with genomics, transcriptomics, ecosystem stoichiometry, community biology and biogeochemistry may provide a further step forward in many areas of ecological sciences, including stress responses, species lifestyle, life history variation, population structure, trophic interaction, nutrient cycling, ecological niche and global change.

Modelling the effects of recent changes in climate, host density and acaricide treatments on population dynamics of Ixodes ricinus in the UK

Summary 1. A population model for the tick Ixodes ricinus, the most significant vector of pathogens in Europe, is used to explore the relative impact of changes in climate, host density and acaricide-treated hosts on tick abundance and seasonality. 2. A rise in temperature of the sort witnessed since 1989 speeds up the inter-stadial development of ticks, thereby reducing the cumulative effect of constant daily mortality rates and potentially raising population levels. The predicted earlier onset of tick-questing activity in the spring, due to stage-specific temperature thresholds, could increase contact between ticks and humans during recreational visits to the countryside in spring holidays. These tick population effects vary geographically with background climate. 3. The significant increase in deer abundance across Europe, including the UK, in recent decades is predicted to drive tick population increases, the effect varying with the initial density of hosts. In areas only recently colonized by deer, tick numbers are predicted to rise dramatically (given suitable climatic conditions). Where host densities are already high, however, further increases may reduce numbers of questing ticks; unfed ticks leave the questing population more rapidly, even though the overall tick population (and therefore pathogen transmission potential) increases. 4. Culling high-density deer populations as a control measure could, therefore, initially cause an apparent increase in questing ticks, with the predicted long-term population trajectory depending on the severity of the cull. 5. Conversely, the further addition of large hosts (e.g. sheep) would effectively reduce the number of questing ticks and therefore the risk to humans. If such sheep were treated with acaricide, tick populations are predicted to decrease rapidly, to an extent that depends on the relative abundance of wild (untreated) and treated hosts. Tick control in designated areas may be achieved by using sheep in this way as ‘lethal mops’, as used to occur in the past when sheep were regularly dipped. 6. Synthesis and applications. Both abiotic and biotic environmental changes witnessed recently could have contributed to apparent increases in tick populations, especially where these environmental factors were limiting in the past. The release of additional hosts treated with long-lasting acaricide is potentially an effective control strategy.

In Medicago truncatula, water deficit modulates the transcript accumulation of components of small RNA pathways.

BackgroundSmall RNAs (sRNAs) are 20-24 nucleotide (nt) RNAs and are involved in plant development and response to abiotic stresses. Plants have several sRNA pathways implicated in the transcriptional and post-transcriptional silencing of gene expression. Two key enzyme families common to all pathways are the Dicer-like (DCL) proteins involved in sRNAs maturation and the Argonautes (AGOs) involved in the targeting and functional action of sRNAs. Post-transcriptional silencing mediated by AGOs may occur by cleavage or translational repression of target mRNA's, while transcriptional silencing may be controlled by DNA methylation and chromatin remodeling. Thus far, these gene families have not been characterized in legumes, nor has their involvement in adaptation to water deficit been studied.ResultsA bioinformatic search in Medicago truncatula genome databases, using Arabidopsis thaliana AGO and DCL cDNA and protein sequences, identified three sequences encoding for putative Dicer-like genes and twelve sequences encoding for putative Argonaute genes. Under water deficit conditions and mainly in roots, MtDCL1 and MtAGO1, two enzymes probably involved in the processing and activation of microRNAs (miRNAs), increased their transcript levels. mir162 which target DCL1 mRNA and mir168 which target AGO1 mRNA reduced their expression in the roots of plants subjected to water deficit. Three putative genes, MtDCL3, MtAGO4b and MtAGO4c probably involved in DNA methylation mechanisms, increased their mRNA levels. However, the mRNA levels of MtAGO6 reduced, which probably encodes a protein with functions similar to MtAGO4. MtAGO7 mRNA levels increased and possibly encodes a protein involved in the production of trans-acting small interfering RNAs. The transcript abundance of MtAGO12a, MtAGO12b and MtAGO12c reduced under water deprivation. Plants recovered from water deprivation reacquire the mRNA levels of the controls.ConclusionsOur work demonstrates that in M. truncatula the transcript accumulation of the components of small RNA pathways is being modulated under water deficit. This shows that the transcriptional and post-transcriptional control of gene expression mediated by sRNAs is probably involved in plant adaptation to abiotic environmental changes. In the future this will allow the manipulation of these pathways providing a more efficient response of legumes towards water shortage.

Evolution Under Environmental Stress at Macro- and Microscales

Environmental stress has played a major role in the evolution of living organisms (Hoffman AA, Parsons PA. 1991. Evolutionary genetics and environmental stress. Oxford: Oxford University Press; Parsons PA. 2005. Environments and evolution: interactions between stress, resource inadequacy, and energetic efficiency. Biol Rev Camb Philos Soc. 80:589–610). This is reflected by the massive and background extinctions in evolutionary time (Nevo E. 1995a. Evolution and extinction. Encyclopedia of Environmental Biology. New York: Academic Press, Inc. 1:717–745). The interaction between organism and environment is central in evolution. Extinction ensues when organisms fail to change and adapt to the constantly altering abiotic and biotic stressful environmental changes as documented in the fossil record. Extreme environmental stress causes extinction but also leads to evolutionary change and the origination of new species adapted to new environments. I will discuss a few of these global, regional, and local stresses based primarily on my own research programs. These examples will include the 1) global regional and local experiment of subterranean mammals; 2) regional experiment of fungal life in the Dead Sea; 3) evolution of wild cereals; 4) “Evolution Canyon”; 5) human brain evolution, and 6) global warming.

Plasticity in the timing of a major life-history transition and resulting changes in the age structure of populations of the salamander Hynobius retardatus

Variation in age and size at life-history transitions is a reflection of the diversifying influence of biotic or abiotic environmental change. Examples abound, but it is not well understood how such environmental changes influence the age structure of a population. I experimentally investigated the effects of water temperature and food type on age and body size at metamorphosis in larvae of the salamander Hynobius retardatus. In individuals grown at a cold temperature (15 °C) or given Chironomidae as prey, the time to metamorphosis was significantly prolonged, and body size at metamorphosis was significantly enlarged, compared with individuals grown at a warmer temperature (20 °C) or fed larvae. I also examined whether larval density (a possible indicator of cannibalism in natural habitats) generated variation in the age structure of natural populations in Hokkaido, Japan, where the climate is subarctic. Natural ponds in Hokkaido may contain larvae that have overwintered for 1 or 2 years, as well as larvae of the current year, and I found that the number of age classes was related to larval density. Although cool water temperatures prolong the larval period and induce later metamorphosis, in natural ponds diet-based enhancement of development translated into a shorter larval duration and earlier metamorphosis. Geographic variation in the frequency of cannibalism resulted in population differences in metamorphic timing in H. retardatus larvae. It is important to understand how environmental effects are ultimately transduced through individual organisms into population-level phenomena, with the population response arising as the summation of individual responses. Without a thorough comprehension of the mechanisms through which population and individual responses to environmental conditions are mediated, we cannot interpret the relationship between population-level and individual-level phenomena. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102, 100–114.

GENETICS AND MANAGEMENT TOOLS FOR EFFICIENT ORCHARD PRODUCTION: PROSPECTS FOR A SUSTAINABLE ORGANIC FRUIT INDUSTRY

The notable potentialities of new breeding tools underpinned by molecular biology to develop new genotypes of high quality fruit for the organic orchard industry are explored. In effect, the prospect of bringing online new cultivars has so far proved fruitless, at least where apple is concerned. Today research centres throughout the world are using molecular screening techniques to identify and transfer useful genes that will enable crops, including OFP - organically-managed products - not only to upgrade resistance/tolerance to diseases and pests, abiotic environmental stresses and climate changes but also to incorporate other tree and fruit traits that will enable growers to lower overhead and increase their competitive market edge. Researchers are also working on improving organic orchard management practices in efforts to overcome or reduce the two main handicaps that have so far hobbled organics: reduced per-unit yields and crop losses because of quality defects or insufficient protection. Reasons why appear to include poor timing of energy inputs with respect to peak crop demand periods and the fact that allowable crop protection compounds are too few in number or not effective enough to deal with critical mass levels of pathogen populations. One approach discussed in addressing these issues is the use of alternative biotech tools like cisgenesis, an approach that rules out the insertion of genes from foreign species. A method already tested successfully in the Netherlands, Germany, Switzerland and Italy, cisgenesis introgresses only genes already present in the same genus or species as that of the cultivar in question that carry useful new traits that cannot otherwise be acquired.

Spatial and temporal variations in aboveground and belowground biomass of Spartina maritima (small cordgrass) in created and natural marshes

Spartina species are commonly used for salt marsh manipulative projects, where aboveground and belowground biomasses are functional traits that play important roles, showing high spatial and temporal variations. This work analyses variations in AGB and BGB of Spartina maritima and abiotic environmental parameters along a chronosequence of six marshes created from 1997 to 2003 with disparate sediment dynamics, and adjacent natural marshes and unvegetated tidal flats. S. maritima behaved as an autogenic engineer, as its colonization of bare sediments yielded abiotic environmental changes: specifically, bed level rise accompanied by higher oxygenation and salinity. These modifications of the environment were site-specific, depending mainly on sedimentary dynamics. At the same time, abiotic environmental changes determined biomass production rates of S. maritima that were higher in more-accreting marshes; however, AGB was kept constant from early in its development (2 years). The increase in BGB with elevation seemed to be related to the inhibition of subsurface tissue development in anoxic sediments. Biomass accumulation and production varied markedly, depending on the spatial scale, indicating the relevance of the plot size chosen for the analysis of biomass of cordgrasses. Our results show that managers of salt marshes should consider sedimentary dynamics carefully when setting realistic expectations for success criteria of created and restored wetlands.

Tick-borne encephalitis incidence in Central and Eastern Europe: consequences of political transition

The variable, often dramatic, upsurge in tick-borne encephalitis in Central and Eastern Europe can best be understood as the result of a multi-factorial system of causes, including abiotic and biotic environmental changes, and human behaviour determined by socio-economic conditions. Many of these stem from the political transition with the end of Soviet rule.

Structural and functional diversity of a culturable bacterial community during the early stages of revegetation near a Pb/Zn smelter in Guangdong, PR China

The land near a Pb/Zn smelter in the vicinity of Shaoguan city of Southern China, contaminated with heavy metals by smelting activities, was revegetated using an indigenous plant ( Paulownia fortunei). The structure and function of the soil bacterial community were investigated to examine whether such microbial indexes could be used as indicators of changes in abiotic environment and vegetative parameters. Soil samples were analyzed for bacterial community level physiological profiles (CLPP) and molecular fingerprinting of 16S rRNA genes. The average well color development (AWCD), functional diversity ( H F), and carbon substrate richness ( R S) were high in the two young revegetated sites (revegetated for 2 and 3 years, respectively), and low in the old revegetated site (revegetated for 5 years). The structural diversity ( H S) and ribotype ( R T) showed an identical trend. Changes in the culturable bacterial community structure and function were not correlated with the revegetation age or heavy metal content, but were closely correlated with a number of soil physico-chemical and vegetative parameters. Therefore, the results suggest that the structural and functional parameters of soil culturable bacterial community may be used as sensitive indicators of changes in soil physico-chemical and vegetative parameters during the early stage of revegetation in this area that has been chronically contaminated by heavy metals.

Structure and function of microbial communities during the early stages of revegetation of barren soils in the vicinity of a Pb/Zn Smelter

Microbial community structure (expressed as phospholipid fatty acids) and function (expressed as enzyme activities) were studied in an industrial barren resulting from smelting activities, and three revegetated sites dominated by native plant Paulownia fortunei under the subtropical conditions of Southern China in order to determine whether microbial community structure and function can be used as indicators of changes in abiotic environment during the revegetation process. An adjacent area under natural vegetative cover was used as a control. The revegetation did not lead to consistent shifts of individual phospholipid fatty acids (PLFAs) and enzyme profiles with time. However, the levels of some signature PLFAs, such as Gram negative bacteria (16:1ω9c), arbuscular mycorrhizal (AM) fungi (16:1ω5c), fungi (18:2ω6c), actinomycetes (10Me16:0 + 10Me17:0 + 10Me18:0), saturated fatty acid (18:0), monounsaturated fatty acids (16:19c + 16:1ω7c + 16:1ω5c + 17:1ω8c + 18:1ω7c + 18:1ω9c), algae (20:5ω3c), protozoa (20:2ω6c + 20:3ω6c), PLFA ratios including fung/bact and monounsat/sat fatty acids, and enzyme activities including protease, CM-cellulase and β-glucosidase consistently increased with time after revegetation, corresponding to the increase in total N, pH and porosity in the revegetated soils. Moreover, cyclopropyl fatty acids/monoenoic precursors (cy17:0/16:1ω7c and cy19:0/18:1ω7c) significantly decreased during time after revegetation and was inversely correlated with the above soil physico-chemical parameters. Principal component analysis (PCA) indicated that the three revegetated sites were separated from the control sites with time after revegetation based on either the PLFA or enzyme activity data. Canonical correlation analysis (CCA) confirmed that the microbial community structure was closely linked to its function during the revegetation. Our data showed that the revegetative cover dominated by P. fortunei had considerably improved the structure and function of the soil microbial community, and was thus effective for remediation of industrial barrens contaminated with heavy metals. Of the biotic and abiotic factors determined in the present study, soil physico-chemical parameters (except for available P and WHC) may be more important factors in determining the structure and function of soil microbial community than heavy metal contents during the revegetation.

Linking a cougar decline, trophic cascade, and catastrophic regime shift in Zion National Park

The strength of top-down forces in terrestrial food webs is highly debated as there are few examples illustrating the role of large mammalian carnivores in structuring biotic and abiotic systems. Based on the results of this study we hypothesize that an increase in human visitation within Zion Canyon of Zion National Park ultimately resulted in a catastrophic regime shift through pathways involving trophic cascades and abiotic environmental changes. Increases in human visitors in Zion Canyon apparently reduced cougar ( Puma concolor) densities, which subsequently led to higher mule deer ( Odocoileus hemionus) densities, higher browsing intensities and reduced recruitment of riparian cottonwood trees ( Populus fremontii), increased bank erosion, and reductions in both terrestrial and aquatic species abundance. These results may have broad implications with regard to our understanding of alternative ecosystem states where large carnivores have been removed or are being recovered.

Rapid evolution and the convergence of ecological and evolutionary time

AbstractRecent studies have documented rates of evolution of ecologically important phenotypes sufficiently fast that they have the potential to impact the outcome of ecological interactions while they are underway. Observations of this type go against accepted wisdom that ecological and evolutionary dynamics occur at very different time scales. While some authors have evaluated the rapidity of a measured evolutionary rate by comparing it to the overall distribution of measured evolutionary rates, we believe that ecologists are mainly interested in rapid evolution because of its potential to impinge on ecological processes. We therefore propose that rapid evolution be defined as a genetic change occurring rapidly enough to have a measurable impact on simultaneous ecological change. Using this definition we propose a framework for decomposing rates of ecological change into components driven by simultaneous evolutionary change and by change in a non‐evolutionary factor (e.g. density dependent population dynamics, abiotic environmental change). Evolution is judged to be rapid in this ecological context if its contribution to ecological change is large relative to the contribution of other factors. We provide a worked example of this approach based on a theoretical predator–prey interaction [Abrams, P. & Matsuda, H. (1997). Evolution, 51, 1740], and find that in this system the impact of prey evolution on predator per capita growth rate is 63% that of internal ecological dynamics. We then propose analytical methods for measuring these contributions in field situations, and apply them to two long‐term data sets for which suitable ecological and evolutionary data exist. For both data sets relatively high rates of evolutionary change have been found when measured as character change in standard deviations per generation (haldanes). For Darwin's finches evolving in response to fluctuating rainfall [Grant, P.R. & Grant, B.R. (2002). Science, 296, 707], we estimate that evolutionary change has been more rapid than ecological change by a factor of 2.2. For a population of freshwater copepods whose life history evolves in response to fluctuating fish predation [Hairston, N.G. Jr & Dillon, T.A. (1990). Evolution, 44, 1796], we find that evolutionary change has been about one quarter the rate of ecological change – less than in the finch example, but nevertheless substantial. These analyses support the view that in order to understand temporal dynamics in ecological processes it is critical to consider the extent to which the attributes of the system under investigation are simultaneously changing as a result of rapid evolution.