Ecologists and evolutionary biologists are increasingly using big-data approaches to tackle questions at large spatial, taxonomic, and temporal scales. However, despite recent efforts to gather two centuries of biodiversity inventories into comprehensive databases, many crucial research questions remain unanswered. Here, we update the concept of knowledge shortfalls and review the tradeoffs between generality and uncertainty. We present seven key shortfalls of current biodiversity data. Four previously proposed shortfalls pinpoint knowledge gaps for species taxonomy (Linnean), distribution (Wallacean), abundance (Prestonian), and evolutionary patterns (Darwinian). We also redefine the Hutchinsonian shortfall to apply to the abiotic tolerances of species and propose new shortfalls relating to limited knowledge of species traits (Raunkiaeran) and biotic interactions (Eltonian). We

We present a comprehensive approach to detect pattern in assemblages of plant and animal species linked by interactions such as pollination, frugivory or herbivory. Simple structural models produce gradient, compartmented or nested patterns of interaction; intermediate patterns between a gradient and compartments are possible, and nesting within compartments produces a combined model. Interaction patterns can be visualized and analyzed either as matrices, as bipartite networks or as multivariate sets through correspondence analysis. We argue that differences among patterns represent outcomes of distinct evolutionary and ecological processes in these highly diversified assemblages. Instead of choosing one model a priori, assemblages should be probed for a suite of patterns. A plant Á /pollinator assemblage exemplifies a simple nested pattern, whereas a plant Á / herbivore assemblage illustrates a compound pattern with nested structures within compartments. Compartmentation should reflect coevolutionary histories and constraints, whereas differences in species abundance or dispersal may generate nestedness.

Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in β-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (α)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing β-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in α-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on β-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in β-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local α-diversity in aboveground groups, whereas the α-diversity increased in belowground groups. Correlations between the β-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.

Key Words herbivory, insect-plant interactions, tropical insects, local and regional richness, species diversity ■ Abstract The diversity and composition of herbivore assemblages was a favored theme for community ecology in the 1970s and culminated in 1984 with Insects on Plants by Strong, Lawton and Southwood. We scrutinize findings since then, considering analyses of country-wide insect-host catalogs, field studies of local herbivore communities, and comparative studies at different spatial scales. Studies in tropical forests have advanced significantly and offer new insights into stratification and host specialization of herbivores. Comparative and long-term data sets are still scarce, which limits assessment of general patterns in herbivore richness and assemblage structure. Methods of community phylogenetic analysis, complex networks, spatial and among-host diversity partitioning, and metacommunity models represent promising approaches for future work. INTRODUCTIONSeldom in the history of science is an unmistakable cornerstone laid for a new subject, but Southwood (1961) was undoubtedly the first to consider insect herbivore richness and its variation among host-plant species a phenomenon worthy of explanation. Southwood's inaugural papers remained largely unappreciated until MacArthur & Wilson (1967) presented their theory of island biogeography and Janzen (1968) proposed that its theoretical framework could be applied to the diversity of herbivores on host plants. Within a decade or so, sufficient evidence had been gathered on the diversity of herbivorous insects associated with various host plants to allow inferences on the role of various causative processes, and in 1984 this became the leading theme of the book Insects on Plants (Strong et al. 1984).Insect-plant interactions grew into a research domain in its own right, but its emphasis has shifted toward population-level processes and interactions, and to 598LEWINSOHN NOVOTNY BASSET phylogenetic analyses of herbivore and plant lineages (e.g., Futuyma & Mitter 1996, Herrera & Pellmyr 2002, Schoonhoven et al. 1998. Thus, despite their importance in the 1970s and 1980s, the size of herbivore-host communities and their determinants has seemingly drifted from attention. Twenty years after the publication of Insects on Plants, the time seemed opportune to consider further developments on its leading questions, which remain as relevant as before. We thus set out to evaluate the extent to which subsequent work has produced (a) major data sets that support earlier findings and hypotheses, (b) new empirical results that lead to novel insights, and (c) substantial advances in theory or explanatory models.Our concern here is the size, structure, and composition of herbivore assemblages on particular plant species as well as the processes or factors that determine their variation. We do not consider the effects of herbivores on their hosts or on plant communities.Three fairly distinct approaches can be recognized in studies of host-associated herbivore assemblag...