Strong Competitive Interactions Research Articles

Macrophyte assemblage associated with an invasive species exhibiting temporal variability in its development pattern

Many invasive species show temporal variations in abundances, such as seasonal cycles and medium to long term variations. The effects of invasive species on native assemblages have, however, mainly been investigated during the maximum abundance of the invasive species and rarely over an entire year. At the north-western limit of its distribution range in the Mediterranean Sea, the invasive marine macrophyte Caulerpa racemosa var. cylindracea shows high temporal variability in its development pattern with complete withdrawal in winter. The present study investigated the variation of the macrophyte assemblage associated with C. racemosa var. cylindracea in the bay of Marseilles (NW Mediterranean, France) over a period of one year. A comparison was made with a non-invaded assemblage at the same site. The results showed a relationship between the development of C. racemosa var. cylindracea and the structure of the macrophyte assemblage. When C. racemosa var. cylindracea was present, the associated assemblage showed significantly lower numbers of species, lower cover of native and introduced macrophytes and lower diversity (Shannon diversity index and Pielou’s evenness) compared to the non-invaded assemblage. During the temporary winter withdrawal of C. racemosa var. cylindracea, an increase in the assemblage descriptors was noted; however, this period was probably not long enough to allow the recovery of a structured macrophyte assemblage comparable to the non-invaded assemblage. Other invasive macrophytes occur in the bay of Marseilles; their cover was, however, greatly reduced in the invaded assemblage, indicating strong competitive interactions between C. racemosa var. cylindracea and the other invasive species.

Genotype‐dependent interactions among sympatric Microcystis strains mediated by Daphnia grazing

Natural populations of the bloom forming cyanobacterium Microcystis are typically composed of several distinct genotypes. Using Microcystis strains that differ in growth rate, microcystin production and colony formation, we conducted a laboratory experiment in the presence and absence of a grazer, the water flea Daphnia, to investigate whether interactions among strains can be predicted from functional traits, and whether the outcome of competition between strains is influenced by a grazer. Two toxic and two non‐toxic Microcystis strains, isolated from a single lake, were grown during four weeks as single strains, in all possible combinations of two strains and all together, in the presence and absence of Daphnia magna. The relative abundance of strains in the populations was assessed using denaturing gradient gel electrophoresis, and the growth rate of each strain in mixed populations was compared to its growth rate in monoculture to determine interactions between strains. The observed interactions were strain‐specific, and the relative abundances of strains in mixed populations could be partially explained by taking toxicity and colony formation into account. Importantly, some of the interactions were strongly altered by the presence of Daphnia. Daphnia induced colony formation in one strain, which then became a better competitor. Daphnia grazing also caused a higher evenness in the populations, both through a weakening of competitive interactions as well as by facilitation effects. Strong facilitation effects were due to non‐toxic strains benefiting from the protection offered by toxic strains in the presence of predation.Overall, our results emphasize the presence of strong competitive interactions between Microcystis strains in the absence of grazing, whereas indirect positive interactions are prevalent in the presence of a generalist grazer. Our results suggest that differences in functional traits and grazer‐mediated facilitation effects may enhance coexistence of Microcystis strains, including toxic and non‐toxic strains.

Stability of regional brachiopod diversity structure across the Mississippian/Pennsylvanian boundary

The middle Carboniferous was an interval of global change when the climate was transitioning from greenhouse to icehouse conditions. Field collections of paleotropical brachiopod assemblages across the Mississippian/Pennsylvanian boundary reveal a taxonomic turnover event in which the overall diversity structure is conserved, despite an apparent regional extinction of 63% of latest Mississippian genera and an apparent regional origination of 50% of earliest Pennsylvanian. An analysis of the global ranges of the brachiopods encountered in the field reveals that turnover was driven primarily by extirpation and immigration rather than true extinctions and originations. Taxonomic richness and evenness are indistinguishable between the latest Mississippian and earliest Pennsylvanian stages. Additive diversity partitioning shows that the within-collection, between-collections (i.e., within-bed), and between-bed diversity components do not change across the Mississippian/Pennsylvanian boundary for richness or evenness. Rank-abundance plots of genera show the same distribution for both stages, but with no correlation between the Mississippian abundances of range-through genera and their abundance in the Pennsylvanian. Detrended correspondence analysis shows a major change in taxonomic composition across that Mississippian/Pennsylvanian boundary and consistency in the general gradient along which genera were distributed. An estimation of spatio-temporal heterogeneity of taxonomic composition within each stage reveals that the earliest Pennsylvanian was significantly more homogeneous. These results suggest that middle Carboniferous brachiopod assemblages from tropical shallow-water carbonate platform settings were organized by some factor that was independent of the specific taxa present. Furthermore, the increased homogeneity in taxonomic composition in the Morrowan did not affect the overall diversity structure. Strong competitive interactions among taxa do not appear to be important in determining the taxonomic compositions and abundances of brachiopod stage-level assemblages.

Synthesis and photophysical properties of a highly fluorescent azo derivative

A highly fluorescent and photochromic azo derivative has been obtained by linking in a covalent manner a red-emitting squaraine unit to an azo dye. The bifunctional molecule exhibits uncoupled chromophores in the ground state allowing for the specific addressing of the azo photoisomerization and squaraine emission. Photosensitization of the squaraine unit by exciting the azo moiety in its UV absorption band has been obtained. Such an unusual energy transfer has been modulated by changing the solvent from chloroform to toluene. This led to a dramatic enhancement of the emission quantum yield Φf (from 0.35 up to 0.71) without affecting the photoisomerization process. Strong competitive π-stacking interactions between toluene and squaraine have been put forward to interpret the emission changes.

Three stage semelparous Leslie models

Nonlinear Leslie matrix models have a long history of use for modeling the dynamics of semelparous species. Semelparous models, as do nonlinear matrix models in general, undergo a transcritical equilibrium bifurcation at inherent net reproductive number R(0) = 1 where the extinction equilibrium loses stability. Semelparous models however do not fall under the purview of the general theory because this bifurcation is of higher co-dimension. This mathematical fact has biological implications that relate to a dichotomy of dynamic possibilities, namely, an equilibration with over lapping age classes as opposed to an oscillation in which age classes are periodically missing. The latter possibility makes these models of particular interest, for example, in application to the well known outbreaks of periodical insects. While the nature of the bifurcation at R(0) = 1 is known for two-dimensional semelparous Leslie models, only limited results are available for higher dimensional models. In this paper I give a thorough accounting of the bifurcation at R(0) = 1 in the three-dimensional case, under some monotonicity assumptions on the nonlinearities. In addition to the bifurcation of positive equilibria, there occurs a bifurcation of invariant loops that lie on the boundary of the positive cone. I describe the geometry of these loops, classify them into three distinct types, and show that they consist of either one or two three-cycles and heteroclinic orbits connecting (the phases of) these cycles. Furthermore, I determine stability and instability properties of these loops, in terms of model parameters, as well as those of the positive equilibria. The analysis also provides the global dynamics on the boundary of the cone. The stability and instability conditions are expressed in terms of certain measures of the strength and the symmetry/asymmetry of the inter-age class competitive interactions. Roughly speaking, strong inter-age class competitive interactions promote oscillations (not necessarily periodic) with separated life-cycle stages, while weak interactions promote stable equilibration with overlapping life-cycle stages. Methods used include the theory of planar monotone maps, average Lyapunov functions, and bifurcation theory techniques.

Diet breadth, coexistence and rarity in bumblebees

Factors that determine the relative abundance of bumblebee species remain poorly understood, rendering management of rare and declining species difficult. Studies of bumblebee communities in the Americas suggest that there are strong competitive interactions between species with similar length tongues, and that this competition determines the relative abundance of species. In contrast, in Europe it is common to observe several short-tongued species coexisting with little or no evidence for competition shaping community structure. In this study we examine patterns of abundance and distribution in one of the most diverse bumblebee communities in Europe, found in the mountains of southern Poland. We quantify forage use when collecting nectar and pollen for 23 bumblebee species, and examine patterns of co-occurrence and niche overlap to determine whether there is evidence for inter-specific competition. We also test whether rarity can be explained by diet breadth. Up to 16 species were found coexisting within single sites, with species richness peaking in mountain pasture at ~1,000 m altitude. Results concur with previous studies indicating that the majority of pollen collected by bumblebees is from Fabaceae, but that some bee species (e.g. B. ruderatus) are much more heavily dependent on Fabaceae than others (e.g. B. lucorum). Those species that forage primarily on Fabaceae tended to have long tongues. In common with studies in the UK, diet breadth was correlated with abundance: rarer species tended to visit fewer flower species, after correcting for differences in sample size. No evidence was found for similarity in tongue length or dietary overlap influencing the likelihood of co-occurrence of species. However, the most abundant species (which co-occurred at most sites) occupied distinct dietary niche space. While species with tongues of similar length tended, overall, to have higher dietary niche overlap, among the group of abundant short-tongued species that commonly co-occurred there was marked dietary differentiation which may explain their coexistence.

Structural Similarity Enhances Interaction Propensity of Proteins

We study statistical properties of interacting protein-like surfaces and predict two strong, related effects: (i) statistically enhanced self-attraction of proteins; (ii) statistically enhanced attraction of proteins with similar structures. The effects originate in the fact that the probability to find a pattern self-match between two identical, even randomly organized interacting protein surfaces is always higher compared with the probability for a pattern match between two different, promiscuous protein surfaces. This theoretical finding explains statistical prevalence of homodimers in protein–protein interaction networks reported earlier. Further, our findings are confirmed by the analysis of curated database of protein complexes that showed highly statistically significant overrepresentation of dimers formed by structurally similar proteins with highly divergent sequences (“superfamily heterodimers”). We suggest that promiscuous homodimeric interactions pose strong competitive interactions for heterodimers evolved from homodimers. Such evolutionary bottleneck is overcome using the negative design evolutionary pressure applied against promiscuous homodimer formation. This is achieved through the formation of highly specific contacts formed by charged residues as demonstrated both in model and real superfamily heterodimers.

The effect of initial biomass in manipulative experiments on plants

Mass is often used as a measure of plant performance in manipulative experiments (Eviner et al. 2000; Shen & Harte 2000). Experimental manipulations may be very diverse: from addition of nutrients, to changing abiotic growth conditions, to removing or adding biotic components such as neighbours, herbivores, etc. But, in general, researchers try to clarify the effect of one factor by comparing the biomass of naturally growing plants (or transplants, or planted phytometers) under control and manipulated conditions. Experiments usually start with individuals that are young enough to avoid previous environmental effects, but mature enough to ensure survival and correct identification if several species are used. As a consequence, target individuals in both treatment and control have an initial mass prior to experiments. Established individuals are grown in different conditions and then harvested. The performance of target individuals is assessed by their final dry mass, and the initial value is often ignored in these analyses (Goldberg et al. 1999). However, ignoring the initial mass may conceal the treatment effects. Here we explore this problem, and show how ignoring initial biomass can cause systematic bias, particularly when experimental manipulation reduces plant performance compared with the control. Biomass accumulation during the experiment, or net increase in mass per unit time, can be described as:

Centaurea solstitialis Invasion Success Is Influenced by Nassella pulchra Size

Abstract Replacement of perennial grasses with non‐native annual grasses in California's Central Valley grasslands and foothills has increased deep soil water availability. Yellow starthistle (Centaurea solstitialis), a deep‐rooted invasive thistle, can use this water to invade annual grasslands. Native perennial bunchgrasses, such as Purple needlegrass (Nassella pulchra), also use deep soil water, so there is an overlap in resource use between N. pulchra and C. solstitialis. Restoration of N. pulchra to annual grasslands could result in strong competitive interactions between N. pulchra and C. solstitialis, which may reduce survival, growth, and reproduction of the invader. The strength of this competitive interaction can increase as N. pulchra plants mature, increase in size, and develop more extensive root systems. We studied how the size of N. pulchra affected the success of C. solstitialis invasion over 2 years. We allowed C. solstitialis seed to fall naturally into plots containing N. pulchra plants. For each plot, we measured the number of C. solstitialis seedlings and mature plants, as well as C. solstitialis biomass and seedhead production. In both years of the study, C. solstitialis number, biomass, and seedhead production declined significantly as N. pulchra size increased. However, even C. solstitialis grown with the largest N. pulchra plants produced some seed, especially during the higher rainfall year. We conclude that restoration plantings with larger, established N. pulchra plants will be more resistant to invasion by C. solstitialis than young N. pulchra plantings, but site management must continue as long as a C. solstitialis seed source is present.

Scaling up from local competition to regional coexistence across two scales of spatial heterogeneity: insect larvae in the fruits of Apeiba membranacea

Species that live in patchy and ephemeral habitats can compete strongly for resources within patches at a small scale. The ramifications of these interactions for population dynamics and coexistence at regional scales will depend on the intraspecific and interspecific distributions of individuals among patches. Spatial heterogeneity due to independent aggregation of competitors among patchy habitats is an important mechanism maintaining species diversity. I describe regional patterns of aggregation for four species of insect larvae in the fruits of Apeiba membranacea, a Neotropical rainforest tree. This aggregation results from variation in densities at a small scale (among the fruits under a single tree), compounded by significant variation among trees in both mean densities and degrees of aggregation. Both the degrees of aggregation and mean densities are statistically independent within and across species at both spatial scales. I evaluate the regional consequences of these spatial patterns by using maximum likelihood methods to parameterize a model that includes both explicit measures of the strength of competition and spatial variation at both within- and among-tree spatial scales. Despite strong competitive interactions among these species, during 2 years the observed spatial variation at both scales combined was sufficient to explain the coexistence of these species, although other coexistence mechanisms may also operate simultaneously. The observed spatial variation at small spatial scales may not be sufficient for coexistence, indicating the importance of considering multiple sources of spatial heterogeneity when scaling up from experiments that investigate local interactions to regional patterns of coexistence.

On detecting and measuring competition in spatially structured plant communities

Recent models have shown that the development of spatial structure in plant mixtures may make strong competitive interactions between species hard to detect owing to spatial segregation of the competing species. Here we address the issue of measuring interspecific competition using a simulation based on a neighbourhood population model which assumes that both dispersal and competitive interactions are localized. Using known parameter combinations we use the model to test the power and efficiency of two approaches for detecting and measuring competition. The first approach is based on measuring the response of communities to the removal of neighbours. Measures of interspecific competition based on this approach are extremely biased by spatial segregation of species, although this bias may be partially overcome by altering the spatial scale at which the effects of removals are recorded. The second approach is based on multiple regression of per capita population growth rates on local densities of the interacting species. When dispersal is restricted, the regression approach provides accurate estimates of interspecific competition coefficients when the scale of the sampling unit (i.e. the quadrats within which plants are counted) is large compared to the scale at which interactions and dispersal occur. When seeds disperse globally the removal method performs best; the regression method fails because sampling units do not form closed dynamic systems. Our results highlight the importance of tailoring methods for detecting competition to the characteristics of the species in question. They also indicate that rapid nonmanipulative estimates of competition coefficients may be the best approach in communities where dispersal is restricted and competitive interactions localized, which is likely to be the case for the majority of plants.

Resource sharing among cod, haddock, saithe and pollack on a herring spawning ground

Cod Gadus morhua, haddock Melanogrammus aeglefinus, pollack Pollachius pollachius and saithe Pollachius virens were abundant fishes on herring Clupea harengus spawning grounds o. southwestern Norway. Their diets were species specific and ontogenetic changes were similar to patterns observed in other areas, indicating both inter‐ and intraspecific resource sharing. However, strong interspecific diet overlap occurred when cod and pollack preyed upon sandeel Ammodytes marinus, and when all the gadoids fed on herring eggs during the herring spawning season in the spring. These prey items were very abundant and the extensive diet overlap may not reflect strong competitive interaction.

A mechanistic model for the inhibiting effects of aluminium on the uptake of cations

AbstractReported laboratory observations mention inhibiting effects of Al on uptake of cations. However, the diverse conditions of these experiments do not allow conclusions to be drawn about the extent of this inhibiting effect. An uptake model for Ca and Mg was therefore developed to study the interactions of Al and these cations. The model is based on surface complexation of the root surface with both specific adsorption reactions and exchange reactions included. Application of this model to experiments using a nutrient flux growth technique showed that the observed effects are well simulated. The behaviour of the model agreed with reported inhibiting effects of Al. The model showed that Al effects might be reversed by increased nutrient solution concentrations of cations. However, there exists a strong competitive interaction between Ca and Mg. Therefore, high Ca concentrations have a negative effect on the uptake of Mg. Plants with a high growth rate and a high shoot to root ratio appear to be more sensitive to Al effects than more slowly growing plants.

The significance of optical properties in competition among visual and tactile planktivores: a theoretical study

A mathematical model describing competition for a common food resource among visual and tactile planktivores is developed. Sensitivity of the competitive regime to environmental changes are studied by analysing their effects on foraging rates and niche availability of both planktivore types. Depth, spatial, daily and seasonal variations in factors of biotic and abiotic origin may result in great changes in the competitive regime. Optical properties of the water column is of greatest importance for competition. In addition the abundance and size of prey, small scale turbulence, and the seasonal and daily variations in sun irradiance are of importance. Inherent contrast of prey organisms is likely to modify the effect from the above factors under certain circumstances only, but may together with prey size, also enhance niche differentiation among the competitors. By studying the zero growth rate isoclines for populations of tactile and visual planktivores at different depths, we show that the water column is a habitat divided into different competitive regimes. These can be thought of as relatively stable niches separated by an ecotone of rather unpredictable and ever changing competitive regime, due to changes in environmental factors. In most cases it is optimal for visual planktivores to stay at shallow depths, while tactile planktivores compete better at greater depths. However, by simulations we show that high predation pressure can make near surface waters hostile to many visual planktivores such as fish, thereby making this highly productive niche available to tactile planktivores such as jellyfish. Results are discussed in relation to naturally occurring environmental variations and the impact of anthropogenic factors. Changes in optical properties due to eutrophication might have drastic effects on the outcome of competition, and thus on the structure of marine food chains. While too little is known about the physiology, life history and behaviour of most pelagic organisms to make specific predictions, this work indicates a potential for strong competitive interactions among different functional types of planktivores.

Implications of increased UV-B induced photoreduction: iron(II) enrichment stimulates picocyanobacterial growth and the microbial food web in clear-water acidic Canadian Shield lakes

Ozone depletion and associated increases in UV-B radiation could increase the photoreduction of iron in Canadian Shield lakes of the boreal forest zone. Since photoreduced iron(II) is more soluble than iron(III), and the reoxidation rate slower in acidic (pH = 5–6) lakes, phytoplanktonic growth and (or) species composition may be altered where iron is growth limiting. This hypothesis was tested by amending herbivore-free lake-water enclosures with phosphorus, phosphorus and iron(II), or phosphorus, ammonium, and iron(II) in lac Tantaré, a clear-water acidic lake in Quebec. In herbivore-free unenriched control enclosures, phytoplanktonic abundance doubled within 48 h, demonstrating unequivocally that herbivore grazing (top-down control) intensity controls phytoplanktonic abundance in early spring in this lake. However, at chlorophyll a concentrations 2–3 times the ambient lake levels, picocyanobacterial production and abundance were greater in the phosphorus and iron enclosures, relative to the phosphorus-only enclosures. This resulted in enhanced growth of the indigenous chrysophytes presumably through increased mixotrophy. In spite of a 10-fold increase in nanoflagellate abundance, we were unable to discern any strong competitive interactions among the mixotrophic chrysophytes. This strongly suggests that most if not all of their iron quotas are obtained from their picoplanktonic prey.

Rainforest fragmentation and the structure of small mammal communities in tropical Queensland

There is a dire need to assess the impacts of habitat fragmentation on tropical forest biotas. In 1986–1987 three live-trapping methods were used to census small mammals at 52 sites in fragmented and unfragmented rainforest in NE Queensland, Australia. Forest structural, floristic, edaphic and landscape data from each site were used to assess patterns of microhabitat use in common species. Trapping censuses yielded 5,784 captures of 15 species of rodents or marsupials. Species encountered in modified habitats surrounding fragments usually remained stable or increased in fragments ( Melomys cervinipes, Rattus leucopus, R. fuscipes, Uromys caudimaculatus, Antechinus flavipes, Hydromys chrysogaster), whereas those that avoided these habitats declined or disappeared ( A. stuartii, A. godmani, Hypsiprimnodon moschatus). Fragments were more heavily disturbed within 200–500 m of forest edges, and mammals that favored disturbed forest or edges ( Melomys, R. leucopus, A. flavipes) increased in many fragments. Assemblages of abundant native rodents appeared more intensively structured in fragments than in unfragmented forest, with strong competitive interactions occurring between ecologically similar species in fragments.

Random patch dynamics of larval Chironomidae (Diptera) in the bed sediments of a gravel stream

SUMMARY The larval chironomid community of the sediment surface and the hyporheic inters titial was investigated in two longitudinal transects of an alpine gravel stream between September 1984 and August 1985. Eighty larval species and species groups were identified, most of which belonged to the subfamily Orthocladiinae. Of all larval individuals 51.1% inhabited the first 10cm of the bed sediments, and 93.2% occurred between the surface and 40cm depth. The spatial species turnover showed marked variations between horizontally adjacent sampling sites in each of the four sediment depth layers. In both transects the species composition showed a significantly lower turnover in the upper 10cm of the bed sediments than in the deeper layers. Spatial community stability showed an oscillating pattern between all sampling sites due to density shifts of larvae between depth layers. Temporal differences in resilience (local stability) were significantly and positively related to changes in the cumulative discharge pattern in the gravel brook, thus indicating the apparent ability of the community to recover quickly following disturbances. The five abundant species, Corynoneura lobata, Synorthocladius semivirens, Tvetenia calvescens, Micropsectra atrofasciata and Rheotanytarsus nigricauda, exhibited significant differences in their sediment depth distribution, with density maxima shifting between depth layers. Spatial autocorrelations suggest that these larvae form patches between neighbouring sampling sites with varying sizes and inter‐patch distances in each of four sediment layers. A simulation test, in which individuals of each species were randomly permuted between microhabitats of each depth layer separately, indicated that the patches might have arisen by chance. To evaluate the significance of observed spatial resource overlap values amongst these five chironomid species, neutral models were developed based on 300 randomizations of each possible species pair‐wise association of individuals and patches of species. The spatial organization of a larval chironomid assemblage in the stream Oberer Seebach seemed to be governed by coexistence due to random patch formation and dispersal patterns within the interstitial habitats, which reduce the probability of strong competitive interactions.

The structure and function of the Namib Dune grasslands: species interactions

This paper describes interactions between species of perennial grasses occupying the sides of sand dunes on the eastern edge of the south-central Namib Desert. Nearest-neighbour analysis indicate that strong competitive interactions are occurring between these grasses, both intraspecifically within a vegetation zone and interspecifically where one species replaces another over the dune slope. Ratios of the diameter of the smaller individual to the distance from its neighbour showed that, for individuals of the same size, interspecific nearest-neighbours are located closer to each other on the upper dune slope than are intraspecific nearest-neighbours. Generally, species lower on the dune slope show no significant differences in these ratios unless the species are different in growth form. Irrigation resulted in changes of xylem water potentials which indicate differences in rates of water uptake, particularly between species on the upper dune slope. It is suggested that Stipagrostis subulicola stabilizes the shifting sand of the upper dune slope through a process of mound-building and is replaced over time by S. (cf.) namaquensis. The process is a cyclical succession as strong winds bury the mid-dune species, causing its eventual death. On the more stable sands of the lower dune slope, morphologically similar species coexist by habitat partitioning resulting in strong zonation patterns while morphologically dissimilar species coexist as a result of root zonation and differences in seasonal patterns of soil water utilization.

Competitive interactions between the perennial shrub Leipoldtia constricta and an annual forb, Gorteria diffusa

Competitive interactions were studied between individuals of the perennial shrub, Leipoldtia constricta L. Bol., and an annual forb, Gorteria diffusa Thunb. in the winter rainfall region of the Karoo using nearest-neighbour analysis. Strong competitive interactions were measured between intraspecific and interspecific nearest-neighbour pairs. In particular, the size and reproductive potential of the annual forb was reduced whenever it established next to the perennial shrub. This reduction was greater than that occurring intraspecifically among individuals of the annual forb. Despite this effect, more annuals established close to the perennial shrub, presumably as the result of the latter’s multiple-stemmed growth habit which traps soil at its base providing a ‘safe site’ for germination and establishment.

Competitive effects of long-chain-triglyceride emulsion on the metabolism of medium-chain-triglyceride emulsions

This study was conducted to assess the potential metabolic competitive interactions of intravenous medium-chain-triglyceride (MCT) and long-chain-triglyceride (LCT) lipid emulsions. To assess this competition increasing concentrations of LCT emulsion were added to an intravenous dose of MCT emulsion of 3.0 g/kg body wt up to a maximum dose of 3.0 g LCTs/kg body wt. Blood samples were assessed for competitive interactions by analyzing the following metabolites: glucose, insulin, lactate, pyruvate, ketones (acetoacetate, beta-hydroxybutyrate), elimination of triglycerides, and free fatty acids. Evaluation of the data showed a strong competitive interaction between the MCT and LCT emulsions. This competition was evident as soon as LCTs were added to the MCT infusions and appeared to favor LCTs for removal and metabolism over MCTs. This appears to indicate that there is a peripheral, strong affinity site for LCT removal and metabolism and a shared peripheral site and specific visceral site for MCT removal and metabolism.