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Relationships among spider families that lack support through other lines of evidence (e.g., morphology) have recently been uncovered through molecular phylogenetics. One such group is the “marronoid” clade, which contains about 3,400 described species in 9 families. Marronoids run the gamut of life history strategies, with social species, species producing a variety of silk types, and species occurring in a range of extreme environments. Despite recognition of the ecological variability in the group, there remains uncertainty about family- level relationships, leaving diverse ecologies without an evolutionary context. The phylogenies produced to date have relatively low nodal support, there are few defined morphological synapomorphies, and the internal relationships of many families remain unclear. We use 93 exemplars from all marronoid families and ultraconserved element loci captured in silico from a combination of 48 novel low-coverage whole genomes and genomic data from the Sequence Read Archive (SRA) to produce a 50% occupancy matrix of 1,277 loci from a set of ultraconserved element probes. These loci were used to infer a phylogeny of the marronoid clade and to evaluate the familial relationships within the clade, and were combined with single-locus (Sanger) legacy data to further increase taxonomic sampling. Our results indicate a clearly defined and well-supported marronoid clade and provide evidence for both monophyly and paraphyly within the currently defined families of the clade. We propose taxonomic changes in accordance with the resulting phylogenetic hypothesis, including elevating Cicurinidae (restored status) and Macrobunidae (new rank).

How many species are there on Earth and to what groups do these species belong? These fundamental questions span systematics, ecology, and evolutionary biology. Yet, recent estimates of overall global biodiversity have ranged wildly, from the low millions to the trillions. Insects are a pivotal group for these estimates. Insects make up roughly half of currently described extant species (across all groups), with ~1 million described species. Insect diversity is also crucial because many other taxa have species that may be unique to each insect host species, including bacteria, apicomplexan protists, microsporidian fungi, nematodes, and mites. Several projections of total insect diversity (described and undescribed) have converged on ~6 million species. However, these projections have not incorporated the morphologically cryptic species revealed by molecular data. Here, we estimate the extent of cryptic insect diversity. We perform a systematic review of studies that used explicit species-delimitation methods with multilocus data. We estimate that each morphology-based insect species contains (on average) 3.1 cryptic species. We then use these estimates to project the overall number of species on Earth and their distribution among major groups. Our estimates suggest that overall global biodiversity may range from 563 million to 2.2 billion species. [Biodiversity; cryptic species; insects; species delimitation; species richness.]