Evolutionary innovations underlie the rise of diversity and complexity—the 2 long-term trends in the history of life. How does natural selection redesign multiple interacting parts to achieve a new emergent function? We investigated the evolution of a biomechanical innovation, the latch-spring mechanism of trap-jaw ants, to address 2 outstanding evolutionary problems: how form and function change in a system during the evolution of new complex traits, and whether such innovations and the diversity they beget are repeatable in time and space. Using a new phylogenetic reconstruction of 470 species, and X-ray microtomography and high-speed videography of representative taxa, we found the trap-jaw mechanism evolved independently 7 to 10 times in a single ant genus (Strumigenys), resulting in the repeated evolution of diverse forms on different continents. The trap mechanism facilitates a 6 to 7 order of magnitude greater mandible acceleration relative to simpler ancestors, currently the fastest recorded acceleration of a resettable animal movement. We found that most morphological diversification occurred after evolution of latch-spring mechanisms, which evolved via minor realignments of mouthpart structures. This finding, whereby incremental changes in form lead to a change of function, followed by large morphological reorganization around the new function, provides a model for understanding the evolution of complex biomechanical traits, as well as insights into why such innovations often happen repeatedly.

Dated, geo‐referenced museum specimens are a rich data source for reconstructing species' distribution and abundance patterns. However, museum records are potentially biased towards over‐representation of rare species, and it is unclear whether museum records can be used to estimate relative abundance in the field. We assembled 17 coupled field and museum datasets to quantitatively compare relative abundance estimates with the Dirichlet distribution. Collectively, these datasets comprise 73,039 museum records and 1,405,316 field observations of 2,240 species. Although museum records of rare species overestimated relative abundance by 1‐fold to over 100‐fold (median study = 9.0), the relative abundance of species estimated from museum occurrence records was strongly correlated with relative abundance estimated from standardized field surveys (r² range of 0.10–0.91, median study = 0.43). These analyses provide a justification for estimating species relative abundance with carefully curated museum occurrence records, which may allow for the detection of temporal or spatial shifts in the rank ordering of common and rare species.

Strumigenys is a globally distributed genus of mostly cryptic leaf-litter ants. In North America they are common throughout eastern deciduous forests but become increasingly rare to the west. Here I review the Strumigenys fauna of western North America north of the Mexico border including all states west of the eastern border of Texas. Six new native species with ranges entirely within this region are described: S. collinsae sp. nov., S. macgowni sp. nov., S. mendezi sp. nov., S. moreauviae sp. nov., S. lucky sp. nov., and S. subtilis sp. nov. Strumigenys ananeotes Longino & Booher 2019 is given a more thorough description, and S. alberti Forel 1893, a Neotropical species, is reported from the region for the first time. All new species bear clear morphological relationships with a native North American clade of “smithistrumiform” species. I include species accounts and provide an illustrated key for all species of this region.

It is clear from research on pollinator declines that some taxa are more vulnerable than others. The sooner these more sensitive species are detected, and the cause(s) contributing to their decline are identified, the better the chance of developing effective conservation plans. Using data from nine studies conducted in northern Georgia, U.S., we present evidence that Augochlora pura (Say) (Hymenoptera: Halictidae), once one of the most abundant of all forest bee species in our study area, is becoming less common as a proportion of all bees collected and has experienced a 70 % decline in abundance over the past 18 years (2007–2024) at long-term monitoring sites. We hypothesize that Brachyponera chinensis (Emery) (Hymenoptera: Formicidae), the Asian needle ant, is contributing to the decline of A. pura and possibly other bee species within its invaded range.

In this study, we revise two groups of cryptic leaf litter ants, the Strumigenys nitens and Strumigenys simulans species groups. These two groups are restricted to the Greater Antilles and the Bahamas. We redefine the species groups, provide a key for the five species in the S. nitens group, and differentiate the two species in the S. simulans group. Four new species are described: Strumigenys caiman sp. nov., S. economoi sp. nov., S. hubbewatyorum sp. nov., and S. zemi sp. nov. We review and provide a key for the Strumigenys fauna of Hispaniola, which comprises the two endemic species S. economoi and S. zemi, six more broadly distributed Neotropical species, and three pan-tropical “tramp” species.