Explore the vast range of titles available.

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.

A critical and poorly understood aspect of food-web theory concerns the possibility that variable observation effort, such as widely different sampling intensities among investigators, confounds structural food-web patterns. We evaluated this possibility by simulating the effects of variable observation effort on the structure of a food web including 77 insect species found inside the stems of 10 species of grasses. A highly detailed description of the trophic structure of this community was provided by an exhaustive sampling program involving dissection of 164 215 grass stems over 12 yr. Most significantly, the data describe the frequency at which each of the consumers and their 126 different trophic links were observed. During the simulated increase in sampling, consistent trends were observed among trophic-species webs as the species richness of these webs increased to a maximum of 73 trophic species. Connectance remained surprisingly constant, while the fractions of top and basal species decreased, and the fraction of intermediate species increased. These trends were much less consistent among taxonomic-species webs. This suggests that comparative analyses of connectance among trophic-species webs constructed with varying degrees of moderate observation effort are generally robust. In contrast, the fractions of species appear to require corrections for variable sample sizes for such analyses. These corrections may be easier to develop for trophic-species webs because of their relatively simple changes with sampling effort.

Despite the species richness of the blow fly (Calliphoridae: Diptera) fauna (1600 species), the relevant environmental, medical, agricultural, and forensic knowledge of these species found in Saudi Arabia is limited. As part of a study on the biodiversity of Diptera of south-western Saudi Arabia a survey of the Diptera fauna of Jazan, Asir and Najran was performed between 2010-2016 at 17 sites, mainly using Malaise traps, sweep nets and baited traps. Eighteen species of Calliphoridae were identified and recorded in this study, seven of which were recorded for the first time. This makes the total number of Calliphoridae species in Saudi Arabia (including 26 species previously recorded and excluding two species which were synonymized namely: Rhyncomya zumptii Peris 1952; Chrysoma regalis Robineau-Desvoidy 1830) to be 44. A list of all species of Calliphoridae recorded from Saudi Arabia is provided. Images of five species are presented. Biological information on each species (where known) and geographical distribution are included. In addition to the results of the identifications all available literature about Calliphoridae of Saudi Arabia is summarized and analysed. The species recorded in this study are more Afrotropical in origin than they are to other regions. The need for further field and laboratory work and surveillance is highlighted.

1. The parasitoid assemblages associated with 18 species of chalcid wasps feeding on 10 grass species were sampled quantitatively between 1980 and 1992 at 24 sites in Wales and England to examine food web structure, the size and composition of the parasitoid complexes, and structures of the local communities. 2. The complete food web included 87 species organized into five trophic levels. The lower two consumer trophic levels (the herbivores and primary parasitoids) were characterized by extreme host specificity, whereas the top two trophic levels (hyperparasitoids and tertiary parasitoids) comprised more generalized omnivores. The high levels of specialization resulted in a compartmentalized web. 3. The regional species richness of the parasitoid complexes associated with Tetramesa species (Eurytomidae) depends primarily on measures of host abundance. Total species richness was significantly positively correlated with mean log host density (number per m2) and the number of larvae per grass stem, explaining 70.5% of the variance in richness. Similarly, the number of specialist parasitoids was correlated with host density, whereas generalist species richness was most strongly correlated with host density and more weakly with host gall-formation and voltinism. 4. The only determinant of local parasitoid species richness is regional richness (the latter explained 97.3% of the variance in the former). Further, there was no beta -diversity in this food web, and every species found on a host species in Britain is found in virtually every local host population. The relatively few cases where fewer parasitoid species were found represent undersampling at particular sites. Limited evidence indicates that similar results apply to host populations on continental Europe. Thus, there is no evidence that the richness of local communities is constrained by species interactions. 5. Variation in parasitism rates both between and within host species cannot be explained by the available variables, so the forces affecting host utilization rates remain unknown. We found that the formation of a gall had no influence on host mortality rates, offering no support for the hypothesis that galling provides protection from parasitoids. 6. The parasitoids of most host species have consistent relative abundances over time and space. We could not identify any ecological correlates of the degree of consistency, but it may be due to the extremely widespread occurrence of all of the parasitoids coupled with their innate host-finding abilities.

Trophic information-who eats whom-and species' body sizes are two of the most basic descriptions necessary to understand community structure as well as ecological and evolutionary dynamics. Consumer-resource body size ratios between predators and their prey, and parasitoids and their hosts, have recently gained increasing attention due to their important implications for species' interaction strengths and dynamical population stability. This data set documents body sizes of consumers and their resources. We gathered body size data for the food webs of Skipwith Pond, a parasitoid community of grass-feeding chalcid wasps in British grasslands; the pelagic community of the Benguela system, a source web based on broom in the United Kingdom; Broadstone Stream, UK; the Grand Cariçaie marsh at Lake Neuchâtel, Switzerland; Tuesday Lake, USA; alpine lakes in the Sierra Nevada of California; Mill Stream, UK; and the eastern Weddell Sea Shelf, Antarctica. Further consumer-resource body size data are included for planktonic predators, predatory nematodes, parasitoids, marine fish predators, freshwater invertebrates, Australian terrestrial consumers, and aphid parasitoids. Containing 16 807 records, this is the largest data set ever compiled for body sizes of consumers and their resources. In addition to body sizes, the data set includes information on consumer and resource taxonomy, the geographic location of the study, the habitat studied, the type of the feeding interaction (e.g., predacious, parasitic) and the metabolic categories of the species (e.g., invertebrate, ectotherm vertebrate). The present data set was gathered with the intent to stimulate research on effects of consumer-resource body size patterns on food-web structure, interaction-strength distributions, population dynamics, and community stability. The use of a common data set may facilitate cross-study comparisons and understanding of the relationships between different scientific approaches and models.

Trophic information—who eats whom—and species' body sizes are two of the most basic descriptions necessary to understand community structure as well as ecological and evolutionary dynamics. Consumer–resource body size ratios between predators and their prey, and parasitoids and their hosts, have recently gained increasing attention due to their important implications for species' interaction strengths and dynamical population stability. This data set documents body sizes of consumers and their resources. We gathered body size data for the food webs of Skipwith Pond, a parasitoid community of grass‐feeding chalcid wasps in British grasslands; the pelagic community of the Benguela system, a source web based on broom in the United Kingdom; Broadstone Stream, UK; the Grand Cariçaie marsh at Lake Neuchtel, Switzerland; Tuesday Lake, USA; alpine lakes in the Sierra Nevada of California; Mill Stream, UK; and the eastern Weddell Sea Shelf, Antarctica. Further consumer–resource body size data are included for planktonic predators, predatory nematodes, parasitoids, marine fish predators, freshwater invertebrates, Australian terrestrial consumers, and aphid parasitoids. Containing 16 807 records, this is the largest data set ever compiled for body sizes of consumers and their resources. In addition to body sizes, the data set includes information on consumer and resource taxonomy, the geographic location of the study, the habitat studied, the type of the feeding interaction (e.g., predacious, parasitic) and the metabolic categories of the species (e.g., invertebrate, ectotherm vertebrate). The present data set was gathered with the intent to stimulate research on effects of consumer–resource body size patterns on food‐web structure, interaction‐strength distributions, population dynamics, and community stability. The use of a common data set may facilitate cross‐study comparisons and understanding of the relationships between different scientific approaches and models.