The number of species on Earth is one of the most fundamental numbers in science, but one that remains highly uncertain. Clearly, more species exist than the present number of formally described species (approximately 1.5 million), but projected species numbers differ dramatically among studies. Recent estimates range from about 2 million species to approximately 1 trillion, but most project around 11 million species or fewer. Numerous studies have focused on insects as a major component of overall richness, and many have excluded other groups, especially non-eukaryotes. Here, we re-estimate global biodiversity. We also estimate the relative richness of the major clades of living organisms, summarized as a "Pie of Life." Unlike many previous estimates, we incorporate morphologically cryptic arthropod species from molecular-based species delimitation. We also include numerous groups of organisms that have not been simultaneously included in previous estimates, especially those often associated with particular insect host species (including mites, nematodes, apicomplexan protists, microsporidian fungi, and bacteria). Our estimates suggest that there are likely to be at least 1 to 6 billion species on Earth. Furthermore, in contrast to previous estimates, the new Pie of Life is dominated by bacteria (approximately 70-90% of species) and insects are only one of many hyperdiverse groups. 230 Volume 92 THE QUARTERLY REVIEW OF BIOLOGY

The occurrence and extent of multiple paternity is an important component of variation in plant mating dynamics. However, links between pollinator activity and multiple paternity are generally lacking, especially for plant species that attract functionally diverse floral visitors. In this study, we separated the influence of two functionally distinct floral visitors (hawkmoths and solitary bees) and characterized their impacts on multiple paternity in a self-incompatible, annual forb, Oenothera harringtonii (Onagraceae). We also situated pollinator-mediated effects in a spatial context by linking variation in multiple paternity to variation in plant spatial isolation. We documented pronounced differences in the number of paternal sires as function of pollinator identity: on average, the primary pollinator (hawkmoths) facilitated mating with nearly twice as many pollen donors relative to the secondary pollinator (solitary bees). This effect was consistent for both isolated and nonisolated individuals, but spatial isolation imposed pronounced reductions on multiple paternity regardless of pollinator identity. Considering that pollinator abundance and pollen dispersal distance did not vary significantly with pollinator identity, we attribute variation in realized mating dynamics primarily to differences in pollinator morphology and behaviour as opposed to pollinator abundance or mating incompatibility arising from underlying spatial genetic structure. Our findings demonstrate that functionally distinct pollinators can have strongly divergent effects on polyandry in plants and further suggest that both pollinator identity and spatial heterogeneity have important roles in plant mating dynamics.

We conclude that nocturnal pollination of Oenothera harringtonii via hawkmoths is robust to the negative impacts of land-use change.

Pollen-mediated gene flow is a major driver of spatial genetic structure in plant populations. Both individual plant characteristics and site-specific features of the landscape can modify the perceived attractiveness of plants to their pollinators and thus play an important role in shaping spatial genetic variation. Most studies of landscape-level genetic connectivity in plants have focused on the effects of interindividual distance using spatial and increasingly ecological separation, yet have not incorporated individual plant characteristics or other at-site ecological variables. Using spatially explicit simulations, we first tested the extent to which the inclusion of at-site variables influencing local pollination success improved the statistical characterization of genetic connectivity based upon examination of pollen pool genetic structure. The addition of at-site characteristics provided better models than those that only considered interindividual spatial distance (e.g. IBD). Models parameterized using conditional genetic covariance (e.g. population graphs) also outperformed those assuming panmixia. In a natural population of Cornus florida L. (Cornaceae), we showed that the addition of at-site characteristics (clumping of primary canopy opening above each maternal tree and maternal tree floral output) provided significantly better models describing gene flow than models including only between-site spatial (IBD) and ecological (isolation by resistance) variables. Overall, our results show that including interindividual and local ecological variation greatly aids in characterizing landscape-level measures of contemporary gene flow.