Body Size Abundance Research Articles

How Do Sampling Methods Affect the Body Size–Abundance Relationships of Benthic Macroinvertebrates in Freshwater Ecosystems? A Comparative Analysis

Body size is a key trait of species, populations, and organisms; it relates to abundance, home range, metabolic rates, and stressors. As reported by Damuth’s law, the relationship between body size and abundance is negative with a slope value of −0.75. In aquatic ecosystems, particularly for benthic macroinvertebrates, the slope value deviates from the expected value of −0.75. This variation may depend on abiotic and biotic factors as well as methods that are used to sample benthic macroinvertebrates. “Leaf-bags” and “Surber-net” are the most used methods and they provide different data about the body size structures and abundance of the sampled benthic macroinvertebrates. Here, we used the slope of the body size–abundance relationships to compare the benthic macroinvertebrate assemblages sampled with two sampling methods (Leaf-bags and Surber-net). We found that Leaf-bags sampled a greater number of smaller taxa than Surber-net, which collected individuals of larger sizes. In our study, differences in the benthic macroinvertebrate body size structures collected with these two sampling methods were evident even if the experiment was performed at a limited spatio–temporal scale. Therefore, Leaf-bags and Surber-net should be used as complementary rather than alternative techniques since they sample integrated information from the benthic macroinvertebrate communities.

Superior predatory ability and abundance predicts potential ecological impact towards early-stage anurans by invasive \u2018Killer Shrimp\u2019 (Dikerogammarus villosus)

Invasive alien species negatively impact upon biodiversity and generate significant economic costs worldwide. Globally, amphibians have suffered considerable losses, with a key driver being predation by large invasive invertebrate and vertebrate predators. However, there is no research regarding the potential ecological impact of small invertebrate invaders. The invasive freshwater amphipod Dikerogammarus villosus can act as a top predator capable of displacing native amphipods and preying heavily upon a range of native species. Listed as one of Europe’s top 100 worst invaders, D. villosus has significantly restructured freshwater communities across western Europe and is expected to invade North America in the near future. Here we explore the ecological impact of invasive D. villosus upon UK native and invasive amphibians (Rana temporaria and Xenopus laevis respectively) using the “Relative Impact Potential” (RIP) metric. By combining estimations of per capita effects (i.e. functional response; FR) and relative field abundances, we apply the RIP metric to quantify the potential ecological impact of invasive D. villosus upon embryonic and larval amphibian prey, compared to the native amphipod Gammarus pulex. Both native and invasive amphipods consumed early-stage amphibians and exhibited potentially destabilising Type II FRs. However, larger body size in invasive D. villosus translated into a superior FR through significantly lower handling times and subsequently higher maximum feeding rates—up to seven times greater than native G. pulex. Higher invader abundance also drove elevated RIP scores for invasive D. villosus, with potential impact scores predicted up to 15.4 times greater than native G. pulex. Overall, D. villosus is predicted to have a greater predatory impact upon amphibian populations than G. pulex, due primarily to its larger body size and superior field abundance, potentially reducing amphibian recruitment within invaded regions.

Importance of metabolic rate to the relationship between the number of genes in a functional category and body size in Peto's paradox for cancer.

Elucidation of tumour suppression mechanisms is a major challenge in cancer biology. Therefore, Peto's paradox, or low cancer incidence in large animals, has attracted focus. According to the gene-abundance hypothesis, which considers the increase/decrease in cancer-related genes with body size, researchers evaluated the associations between gene abundance and body size. However, previous studies only focused on a few specific gene functions and have ignored the alternative hypothesis (metabolic rate hypothesis): in this hypothesis, the cellular metabolic rate and subsequent oxidative stress decreases with increasing body size. In this study, we have elected to explore the gene-abundance hypothesis taking into account the metabolic rate hypothesis. Thus, we comprehensively investigated the correlation between the number of genes in various functional categories and body size while at the same time correcting for the mass-specific metabolic rate (Bc). A number of gene functions that correlated with body size were initially identified, but they were found to be artefactual due to the decrease in Bc with increasing body size. By contrast, immune system-related genes were found to increase with increasing body size when the correlation included this correction for Bc. These findings support the gene-abundance hypothesis and emphasize the importance of also taking into account the metabolic rate when evaluating gene abundance–body size relationships. This finding may be useful for understanding cancer evolution and tumour suppression mechanisms as well as for determining cancer-related genes and functions.

Changes in body size spectra of benthic caridean shrimps (Decapoda: Caridea) and snails (Gastropoda) as response to seasonal variability

Ecologists have been largely interested in the description and understanding of the power scaling relationships between body size and abundance of organisms. Many studies have focused on estimating the exponents of these functions across taxonomic groups and spatial scales, to draw inferences about the processes underlying this pattern. The exponents of these functions usually approximate -3/4 at geographical scales, but they deviate from this value when smaller spatial extensions are considered. This has led to propose that body size-abundance relationships at small spatial scales may reflect the impact of environmental changes. This study tests this hypothesis by examining body size spectra of benthic shrimps (Decapoda: Caridea) and snails (Gastropoda) in the Tamiahua lagoon, a brackish body water located in the Eastern coast of Mexico. We mea- sured water quality parameters (dissolved oxygen, salinity, pH, water temperature, sediment organic matter and chemical oxygen demand) and sampled benthic macrofauna during three different climatic conditions of the year (cold, dry and rainy season). Given the small size of most individuals in the benthic macrofaunal samples, we used body volume, instead of weight, to estimate their body size. Body size-abundance relationships of both taxonomic groups were described by tabulating data from each season into base-2 logarithmic body size bins. In both taxonomic groups, observed frequencies per body size class in each season were standardized to yield densities (i.e., individuals/m(3)). Nonlinear regression analyses were separately performed for each taxonomic group at each season to assess whether body size spectra followed power scaling functions. Additionally, for each taxonomic group, multiple regression analyses were used to determine whether these relationships varied among seasons. Our results indicated that, while body size-abundance relationships in both taxonomic groups followed power functions, the parameters defining the shape of these relationships varied among seasons. These variations in the parameters of the body size-abundance relationships seems to be related to changes in the abundance of individuals within the different body size classes, which seems to follow the seasonal changes that occur in the environmental conditions of the lagoon. Thus, we propose that these body size-abundance relation- ships are influenced by the frequency and intensity of environmental changes affecting this ecosystem.

Parasitism of Ceroglossus buqueti (Coleoptera: Carabidae) by Hexathrombium mites (Acari: Microtrombidiidae): body distribution, prevalence, intensity and attachment preferences in relation to body size and sex

ABSTRACTHost characteristics, including sex, age and size, can influence parasite intensity. Ceroglossus buqueti (Laporte, 1834) and its mites were studied to determine the influence of size and sex on parasite abundance, and check for any preference for a particular region of the body. One hundred and fifty-seven C. buqueti individuals (64 males and 93 females), captured in the summer of 2007 in Villarrica National Park, Chile, were examined. All C. buqueti were parasitized by Hexathrombium c.f marittae (Haitlinger, 1994). Male beetles were significantly smaller than female beetles, but parasite abundance in males and females was the same. Likewise, there was no relationship between host body size and parasite abundance. The body distribution analysis showed that H. c.f. marittae preferred to attach to the head, ventral thorax and ventral abdomen. We speculate that these preferred regions provide more protection and space for the parasite to colonize the host.

Does body size–abundance allometry in soil fauna vary with environment? A field test for nematode communities in response to fertilization

The “energetic equivalence rule” predicts that abundance should always scale as the −3/4 power of body size within a trophic group, but if the body size–abundance allometry (BSA) of soil fauna in fact is labile then the relationship could potentially be used as a standard descriptor for shifts in community functional structure in response to environmental change. To assess the possibility that the BSA could serve as an index of community functional structure, we measured the effect of fertilization on the slope and intercept of the BSA in nematode communities in a rice–wheat crop rotation over three years. Fertilization increased the BSA intercept but did not affect the slope in either rice or wheat phases, which highlights the stable scaling of BSA.

Are the Most Plastic Species the Most Abundant Ones? An Assessment Using a Fish Assemblage

Few studies have evaluated phenotypic plasticity at the community level, considering, for example, plastic responses in an entire species assemblage. In addition, none of these studies have addressed the relationship between phenotypic plasticity and community structure. Within this context, here we assessed the magnitude of seasonal changes in digestive traits (seasonal flexibility), and of changes during short-term fasting (flexibility during fasting), occurring in an entire fish assemblage, comprising ten species, four trophic levels, and a 37-fold range in body mass. In addition, we analyzed the relationship between estimates of digestive flexibility and three basic assemblage structure attributes, i.e., species trophic position, body size, and relative abundance. We found that: (1) Seasonal digestive flexibility was not related with species trophic position or with body size; (2) Digestive flexibility during fasting tended to be inversely correlated with body size, as expected from scaling relationships; (3) Digestive flexibility, both seasonal and during fasting, was positively correlated with species relative abundance. In conclusion, the present study identified two trends in digestive flexibility in relation to assemblage structure, which represents an encouraging departure point in the search of general patterns in phenotypic plasticity at the local community scale.

Characteristic benthic size spectra: potential sampling artefacts

Simple mathematical simulations were carried out to examine the potential influence of sampling protocol on the production of characteristic benthic size spectra (in biomass and species richness). The use of separate samples and sieve meshes for meio- and macro-benthos readily produced a biomass trough at intermediate body sizes, where no trough existed in the sampled population (set by simple body size-abundance allometry). The number of specimens sampled per size class was also bimodal across the meio- to macro-benthos size range, providing a simple mechanism by which bimodal species size spectra may result, i.e. a general positive relationship between estimated species richness and the number of specimens examined. These sampling artefacts have the potential to generate characteristic benthic biomass and species size spectra that reflect the sampling protocol rather than the underlying structure of the benthic community. The results suggest the need for caution in regarding the meio- and macro-benthos as coherent entities with distinct ecological attributes. They also raise the prospect of a useful, single mathematical formulation of standing stock and body size for the metazoan benthos as a whole in biogeochemical modelling.

Topographic complexity and landscape ­temperature patterns create a dynamic habitat structure on a rocky intertidal shore

Habitat complexity is a fundamental dri- ver of ecosystem structure and function. Rocky inter- tidal shores are the classic model system for investi - gating theoretical and mechanistic models of habitat complexity, because the structural topography is largely biologically independent and stable over time. In the present study, we investigate how static (topographic complexity and heterogeneity) and dynamic (tempera- ture landscape) components of habitat structure influ- ence the abundance and body-size distribution of in - vertebrates on a rocky shore. Using a novel approach that included high-resolution 3D fractal surface and temperature measurements, we show that topographic complexity, temperature landscape and habitat hetero- geneity had largely independent effects on species abundance and body size. Invertebrate abundance was associated with temperature landscape in 7 of 11 spe- cies, while variation in body-size was mostly driven by fractal topography in 7 of 10 species. Overall, the body sizeabundance relationship was not influenced by habitat structure, indicating that the effects of habitat structure on body size and abundance were largely independent. The results illustrate the value of combin- ing measures of static and dynamic habitat structure to explain and predict biological patterns on rocky shores.

Food web complexity and allometric scaling relationships in stream mesocosms: implications for experimentation

1. Mesocosms are used extensively by ecologists to gain a mechanistic understanding of ecosystems based on the often untested assumption that these systems can replicate the key attributes of natural assemblages. 2. Previous investigations of stream mesocosm utility have explored community composition, but here for the first time, we extend the approach to consider the replicability and realism of food webs in four outdoor channels (4 m(2)). 3. The four food webs were similarly complex, consisting of diverse assemblages (61-71 taxa) with dense feeding interactions (directed connectance 0.09-0.11). Mesocosm food web structural attributes were within the range reported for 82 well-characterized food webs from natural streams and rivers. When compared with 112 additional food webs from standing freshwater, marine, estuarine and terrestrial environments, stream food webs (including mesocosms) had similar characteristic path lengths, but typically lower mean food chain length and exponents for the species-link relationship. 4. Body size (M) abundance (N) allometric scaling coefficients for trivariate taxonomic mesocosm food webs (-0.53 to -0.49) and individual size distributions (-0.60 to -0.58) were consistent and similar to those from natural systems, suggesting that patterns of energy flux between mesocosm consumers and resources were realistic approximations. 5. These results suggest that stream mesocosms of this scale can support replicate food webs with a degree of biocomplexity that is comparable to 'natural' streams. The findings highlight the potential value of mesocosms as model systems for performing experimental manipulations to test ecological theories, at spatiotemporal scales of relevance to natural ecosystems.

Size–abundance relationships in Florida ant communities reveal how ants break the energetic equivalence rule

1. Ants are among the most abundant terrestrial organisms, yet little is known of how ant communities divide resources because it is difficult to measure the number of individuals in colonies and the density of colonies.2. The body size–abundance relationships of the ants of five upland ecosystems in Florida were examined. The study tested whether abundance, energy use, and total biomass were distributed among species and body sizes as predicted by Damuth's energetic equivalence rule. Estimates of average worker body size, colony size, colony mass, and field metabolic rates were used to examine the relationships among body sizes, energy use, and total biomass.3. Analyses revealed significant variation in energy use and did not support the energetic equivalence hypothesis. Specifically, the energy use and total standing biomass of species with large workers and colonies was much greater than smaller species.4. These results suggest that larger species with larger colonies account for a disproportionate fraction of the total abundance and biomass of ants. A general model of resource allocation in colonies provides a possible explanation for why ants do not conform to the predictions of the energetic equivalence rule and for why ants are so abundant.

Biodiversity conservation in Mediterranean and Black Sea lagoons: a trait-oriented approach to benthic invertebrate guilds

1. The extent to which conservation of biodiversity enforces the protection of ecosystem functioning, goods and services is a key issue in conservation ecology. 2. In order to address this conservation issue, this work focused on community organization, linking community structure, as described both in taxonomic and functional terms, to community functioning and ecosystem processes. 3. Body size is an individual functional trait that is deterministically related to components of ecosystem functioning such as population dynamics and energy flow, and which determines components of community structure. Since body size is an individual trait that reflects numerous factors, it is also exposed to trait selection and the niche filtering underlying the community. 4. An analysis of the relevance of body size to community organization in transitional water ecosystems in the eastern Mediterranean and Black Sea regions is presented, based on field research conducted on a sample of 15 transitional water ecosystems. 5. 250 taxa were identified, clumped in five orders of magnitude of body size. All body size patterns showed triangular distributions with an optimal size range of 0.13 mg to 1.0 mg individual body mass. 6. Deterministic components of size structure were emphasized and a hierarchical organization with dominance of large sizes was demonstrated by the slopes of the body size-abundance distributions, consistently larger than the EER threshold (b=−0.75), and by the direct relationship of energy use to body size for most of the body size range. 7. Consistent variations of body size-related descriptors were observed on three main gradients of environmental stress: eutrophication, confinement and metal pollution. 8. The results support the relevance of constraints imposed by individual body size on community organization in transitional water ecosystems and the adequacy of size patterns as an indicator for ecological conservation of these fragile ecosystems. Copyright © 2008 John Wiley & Sons, Ltd.

Abundance–body size relationships: the roles of metabolism and population dynamics

1. Species' abundance scales approximately as an inverse power of body mass. This property has been explained on the basis of metabolic rates of organisms of different sizes. 2. This paper considers the additional effect of population dynamics on the abundance-body size relationship, on the grounds that mass flow through food webs also depends on interactions between predators and their prey. To do this, an analysis of simple dynamical food-chain models was carried out, using rate parameters which scaled with body mass according to empirically based rules. 3. The analysis shows that a function for the abundance-body size relationship derived from metabolic theory is a good first approximation to a function derived for food chains at dynamic equilibrium, although the mechanistic interpretation of terms in the functions is not the same. 4. The results are sensitive to assumptions about the scaling of the self-limitation of basal species with respect to body size. Depending on the assumption made, the abundance-body size relationship may have a power parameter -1 at all trophic levels, or be described by different functions at different trophic levels.

Abundance–body mass relationships among insects along a latitudinal gradient

Abstract We investigated the relationship between abundance and body size (body mass) of 162 insect herbivore species on the host plant Acacia falcata along its entire coastal latitudinal distribution (eastern Australia), spanning a gradient in mean annual temperature of 4.3°C. We extend previous research by assessing these relationships at different spatial scales (latitudes pooled, among latitudes and within latitudes) and at different taxonomic levels (insect phytophages pooled, phytophagous Coleoptera and Hemiptera, and five component suborders/superfamilies). Insect species were collected from two orders (Hemiptera and Coleoptera) and five component suborders/superfamilies. There were no consistent trends in the relationships (linear or polygonal/hump‐shaped) between abundance and body mass when latitudes were pooled, among latitudes, or when phytophagous insect species were separated into their component suborder/superfamily groups. The reason for the lack of consistent trends might be due to the insect herbivores not fully exploiting their host plant and the relative absence of competition among herbivore species for food resources. This is further assessed in relation to the lack of a consistent pattern in species richness of Coleoptera and Hemiptera herbivores from the same dataset and rates of chewing and sap‐sucking herbivory along the same latitudinal gradient. Future studies of abundance–body size relationships are discussed in relation to sampling across environmental gradients and accounting for the influence of host plant identity and insect phylogeny.

Species richness, abundance, and body size relationships from a neotropical chironomid assemblage: Looking for patterns

Abstract We investigated two of the most studied relationships in the macroecological research program (species richness vs. body size and abundance vs. body size) of a local chironomid assemblage from southeastern Brazil. Although numerous studies have examined these relationships, few have investigated how they vary at different temporal scales. We used data from a forested stream to document and examine these patterns at monthly intervals. Both the species body size distribution and the abundance–body size relationship varied temporally. In some months the body size distribution was skewed to the right, whereas in others it approached normality. We found both linear relationships (with different values of slopes), and a polygonal pattern in the abundance–body size relationship. This temporal variation was not related to environmental variables. Our results suggest that body size relationships are temporally instable properties of this chironomid assemblage.

Diversity surfaces and species wave fronts in a soil microarthropod assemblage: Adding the dimension of time

Summary As a general rule, animal species of intermediate size within a given taxonomic group are most abundant in nature. It is not known if these patterns occur in small-bodied taxa, such as soil microarthropods, or how these patterns change through time. Here I show that Oribatida (Acari), the most abundant and diverse arthropod fauna of coniferous forest soils, exhibit this pattern. However, the pattern is more complex than reported for other arthropods. I analyzed the total species surface comprising 6613 individuals and 54 species by forest stand. The underlying pattern consists of 15-year stands and 30-year stands forming two distinct and separated maxima. These results suggest that assemblage patterns form early in the development of ecological communities, and that these patterns appear within the soil assemblage as waves propagating in species–abundance–body size space during forest development. These results also support the assertion that undescribed species will likely be of intermediate size within a group. This analysis contributes to investigations of biodiversity and body size relationships by adding the temporal dimension. Potential applications are in disturbance and indicator studies or other work where changes in assemblage structure are used as measures of disturbance or as response variables in manipulative studies.

Predicting abundance–body size relationships in functional and taxonomic subsets of food webs

Abundance-body size relationships are widely observed macroecological patterns in complete food webs and in taxonomically or functionally defined subsets of those webs. Observed abundance-body size relationships have frequently been compared with predictions based on the energetic equivalence hypothesis and, more recently, with predictions based on energy availability to different body size classes. Here, we consider the ways in which working with taxonomically or functionally defined subsets of food webs affected the relationship between the predicted and observed scaling of biomass and body mass in sediment dwelling benthic invertebrate communities at three sites in the North Sea. At each site, the energy available to body size classes in the "whole" community (community defined as all animals of 0.03125-32.0 g shell-free wet weight) and in three subsets was predicted from estimates of trophic level based on nitrogen stable isotope analysis. The observed and predicted scalings of biomass and body size were not significantly different for the whole community, and reflected an increase in energy availability with body size. However, the results for subsets showed that energy availability could increase or decrease with body size, and that individuals in the subsets were likely to be competing with individuals outside the subsets for energy. We conclude that the study of abundance-body mass relationships in functionally or taxonomically defined subsets of food webs is unlikely to provide an adequate test of the energetic equivalence hypothesis or other relationships between energy availability and scaling. To consistently and reliably interpret the results of these tests, it is necessary to know about energy availability as a function of body size both within and outside the subset considered.

The interspecific relationship between abundance and body size in central European land snail assemblages

Summary The distributions of abundance and body size and the interspecific relationship between abundance and body size in Central European assemblages of terrestrial snails were analysed to investigate whether the characteristics of land snails, especially their limited active dispersal abilities, result in differences from the macroecological patterns mainly found in analyses of vertebrates. The distributions of crude density (number of specimens divided by the sum of the sampled areas) and ecological density (number of specimens divided by the sum of the areas sampled in the habitat types where a given species had been recorded) and of body size are approximately log-normal. Controlling for phylogenetic relationships there was a significant positive correlation between the number of habitat types occupied by a species and its crude and ecological density. The negative relationship between the two measures of abundance and body size found in the across-species analyses could not be confirmed in the phylogenetic contrasts analyses. The slopes of the body size–abundance relations are shallower than predicted by the energetic equivalence rule, even if only the upper bound slopes are considered and irrespective of the regression method used. This indicates that large snail species control a greater proportion of available resources than smaller species. Most of the macroecological patterns found in land snails are similar to those of other animal groups. An exception is the approximately log-normal distribution of log-transformed body sizes which may be a consequence of the better passive dispersal ability of smaller snails.

Think Globally, Conserve Locally

ECOLOGY/EVOLUTION Insects are undoubtedly the most diverse multicellular organisms on Earth, yet our understanding of the extent of this diversity is still patchy, and to be able to predict patterns of community structure and local diversity would be important in the context of conservation. Finlay et al. analyzed data for more than 600,000 insect species from a wide variety of localities, and report self-similar patterns of body size distribution, species-area relationships, and abundance distributions at spatial scales ranging from a few hectares (Hilbre Island) to the land surface of the entire planet. The similarity of the observed patterns presents a useful tool for monitoring the status of insect communities in the face of human disturbance (including climate change); deviations from the general patterns, such as an unusual distribution of body sizes in an insect community, could provide useful indicators of local extinctions. — AMS Proc. R. Soc. London Ser. B 273 , 10.1098/rspb.2006.3525 (2006).

Body size–abundance distributions of nano- and micro-phytoplankton guilds in coastal marine ecosystems

This study focuses on body size–abundance distributions of nano- and micro-phytoplankton guilds in coastal marine areas of the Southern Adriatic–Ionian region. The aim of the study was to evaluate the occurrence of common patterns of body size–abundance distributions in relation to physical, chemical and biological environmental forcing factors and to taxonomic composition of phytoplankton guilds. This paper is based on data collected during four oceanographic cruises carried out seasonally along the Southern Apulian coast (Adriatic and Ionian Seas, SE Italy) as a part of the INTERREG II Italy–Greece Program. The study was performed at 21 stations located on 7 transects perpendicular to the coastline, with 3 stations per transect at a distance of 3, 9 and 15 NM from the coastline. At each station, profiles of the major physical features of the water were determined and water samples were collected for phytoplankton and nutrient analysis. Overall, 320 nano- and micro-phytoplankton taxa were identified, 76% of which at species level, with phytoplankton cells ranging in size from 0.008 to 4697.54 ng. Body size–abundance distributions showed some common features: they were relatively invariant (average similarity 65%) with respect to taxonomic composition (average similarity 32%), right skewed (90%), leptokurtic (77%) and log normal (76%). Moreover, abiotic, biotic and spatial ecosystem components accounted for up to 75% of body size–abundance distribution variation. The results of this study suggest that body size–abundance distributions are an intrinsic property of marine phytoplankton communities, emphasising functional dependence on ecological constraints related to trophic factors and intra-guild coexistence relationships.