The horse is central to many Indigenous cultures across the American Southwest and the Great Plains. However, when and how horses were first integrated into Indigenous lifeways remain contentious, with extant models derived largely from colonial records. We conducted an interdisciplinary study of an assemblage of historic archaeological horse remains, integrating genomic, isotopic, radiocarbon, and paleopathological evidence. Archaeological and modern North American horses show strong Iberian genetic affinities, with later influx from British sources, but no Viking proximity. Horses rapidly spread from the south into the northern Rockies and central plains by the first half of the 17th century CE, likely through Indigenous exchange networks. They were deeply integrated into Indigenous societies before the arrival of 18th-century European observers, as reflected in herd management, ceremonial practices, and culture.

Abstract Army ants provide nourishment to a large variety of animals. This includes birds that feed on animals flushed out by army ant raids, symbiotic arthropods that consume the ants' prey or their brood, and other arthropods that scavenge on army ant refuse deposits. The latter have not received much attention, and the few published studies lack detailed species identifications. Here we provide a first systematic inventory of the beetle fauna associated with refuse deposits of Eciton army ants, with a focus on Eciton burchellii. We collected 8364 adult beetles, 511 larvae, and 24 eggs from 34 deposits at La Selva Biological Station, Costa Rica. We used a combination of DNA barcoding and morphology to identify a subset of 436 specimens to species level. The samples included several new species, and we here formally describe two water scavenger beetles (Hydrophilidae). Refuse deposits harbored a diverse beetle fauna. The identified subset consisted of 91 beetle species from 12 families, with rove beetles being the most abundant and diverse visitors. Of the 85 species found with E. burchellii, 50 species were collected from only one or two refuse deposits. Conversely, seven species were found in 10 or more refuse deposits, indicating a certain level of habitat specialization. We matched adults and immatures for 22 beetle species via DNA barcodes, demonstrating that army ant middens also serve as a beetle nursery. The present survey highlights the significant ecological function of army ants as promoters of biodiversity and their status as keystone species in tropical rainforests.

Invasive species can impact ecosystem health by introducing parasites during their establishment in new areas. However, the dynamics of parasite loads between invasive and native species remain poorly understood. In the 1940s, Abert’s squirrels ( Sciurus aberti ) were introduced to the Pinaleño Mountains in southeastern Arizona where they now co-occur with endemic endangered Mt. Graham red squirrels ( Tamiasciurus fremonti grahamensis ). The study aimed to identify and quantify parasites in both Abert's and Mt. Graham red squirrels, with a focus on investigating possible parasite spillover between these two species and examining how host-related factors affect parasite presence. PCR amplification and morphological analyses revealed two endoparasite species: Citellinema sp. and Trypanoxyuris ( Rodentoxyuris ) sp. In Abert's squirrels, ectoparasites such as Opisodasys robustus , Anomiopsyllus sp., and Neohaematoinnus sciurinus were encountered, while Mt. Graham red squirrels carried Orchopeas caeden and a mite from the Glycyphagidae family. Our findings suggest new host and geographic record for the Glycphagidae mite in Mt. Graham red squirrels of Arizona and indicate possible spillover of Trypanoxyuris ( Rodentoxyuris ) sp. from Abert’s squirrels to Mt. Graham red squirrels. Additionally, sex influenced presence of ectoparasites in Abert’s squirrels. We can offer a better understanding of factors that place species at risk of extinction with enhanced insights into probable parasite transmission routes and the role that parasites play in biological invasion.

Cochineal is the common name for cactus-feeding scale insects in the Dactylopiidae. These ruby-red insects include the domesticated dye insect Dactylopius coccus. Dactylopius coccus and congeners have been introduced around the world, some accidentally, to become pests of prickly pear cactus species (Opuntia), and some intentionally, for dye production or biological control of pest Opuntia. In the northern Sonoran Desert (Tucson, AZ, USA), we studied the enemy complex of D. opuntiae and D. confusus on Opuntia and characterized two cryptic enemies, a coccinellid beetle predator and a parasitoid wasp. (1) Hyperaspis sp. The coccinellid predator Hyperaspis trifurcata shares a niche with a similar, typically all-black beetle. Morphological data, crossing tests, and phylogenetic results showed the black beetle to be a distinct, undescribed species in the genus Hyperaspis, with a rare spotted phenotype that is similar in appearance to H. trifurcata. Crossing tests among black and spotted forms showed the spotted morph is inherited as a single-locus dominant allele. (2) Formicencyrtus thoreauini. Rearing of this ant-like parasitoid wasp (Encyrtidae) in pure culture of D. opuntiae showed it to be a semi-gregarious primary parasitoid of cochineal. To our knowledge, this is the first confirmed instance of a cochineal parasitoid. Observations of development show early instar larvae keep their posterior end within the egg chorion, attached to an aeroscopic plate with a connection to the cochineal body wall. Late instar larvae are eventually surrounded by a membrane, likely of larval origin. Wasps then pupate in a dry air-filled chamber within the desiccated scale remains before chewing out as an adult. Both Hyperaspis sp. and F. thoreauini may have restricted distributions. Hyperaspis sp. does not appear to be a member of the cochineal community in Mexico or Texas, and scant records suggest F. thoreauini may also be restricted to the Southwestern USA.

Tropical rainforests are among the most diverse biomes on Earth. While species inventories are far from complete for any tropical rainforest, even less is known about the intricate species interactions that form the basis of these ecological communities. One fascinating but poorly studied example are the symbiotic associations between army ants and their rich assemblages of parasitic arthropod guests. Hundreds of these guests, or myrmecophiles, have been taxonomically described. However, because previous work has mainly been based on haphazard collections from disjunct populations, it remains challenging to define species boundaries. We therefore know little about the species richness, abundance and host specificity of most guests in any given population, which is crucial to understand co-evolutionary and ecological dynamics. Here, we report a quantitative community survey of myrmecophiles parasitizing the six sympatric Eciton army ant species in a Costa Rican rainforest. Combining DNA barcoding with morphological identification of over 2,000 specimens, we discovered 62 species, including 49 beetles, 11 flies, one millipede and one silverfish. At least 14 of these species were new to science. Ecological network analysis revealed a clear signal of host partitioning, and each Eciton species was host to both specialists and generalists. These varying degrees in host specificities translated into a moderate level of network specificity, highlighting the system's level of biotic pluralism in terms of biodiversity and interaction diversity. By providing vouchered DNA barcodes for army ant guest species, this study provides a baseline for future work on co-evolutionary and ecological dynamics in these species-rich host-symbiont networks across the Neotropical realm.

The few studies that have addressed past effects of climate change on species distributions have mostly focused on plants due to the rarity of historical faunal baselines. However, hyperdiverse groups like Arthropoda are vital to monitor in order to understand climate change impacts on biodiversity. This is the first investigation of ground-dwelling arthropod (GDA) assemblages along the full elevation gradient of a mountain range in the Madrean Sky Island Region, establishing a baseline for monitoring future changes in GDA biodiversity. To determine how GDA assemblages relate to elevation, season, abiotic variables, and corresponding biomes, GDA were collected for two weeks in both spring (May) and summer (September) 2011 in the Santa Catalina Mountains, Arizona, using pitfall traps at 66 sites in six distinct upland (non-riparian/non-wet canyon) biomes. Four arthropod taxa: (1) beetles (Coleoptera), (2) spiders (Araneae), (3) grasshoppers and crickets (Orthoptera), and (4) millipedes and centipedes (Myriapoda) were assessed together and separately to determine if there are similar patterns across taxonomic groups. We collected 335 species of GDA: 192/3793 (species/specimens) Coleoptera, 102/1329 Araneae, 25/523 Orthoptera, and 16/697 Myriapoda. GDA assemblages differed among all biomes and between seasons. Fifty-three percent (178 species) and 76% (254 species) of all GDA species were found in only one biome and during only one season, respectively. While composition of arthropod assemblages is tied to biome and season, individual groups do not show fully concordant patterns. Seventeen percent of the GDA species occurred only in the two highest-elevation biomes (Pine and Mixed Conifer Forests). Because these high elevation biomes are most threatened by climate change and they harbor a large percentage of unique arthropod species (11-25% depending on taxon), significant loss in arthropod diversity is likely in the Santa Catalina Mountains and other isolated mountain ranges in the Southwestern US.

During the course of recent fieldwork on Venezuelan aquatic insects, a new species of Hydroscaphidae, Hydroscapha perijaensis Hall & Short sp. n., was discovered and is herein described, representing the first known South American species of the genus. The new species was found in association with rock seepages in both the wet and dry seasons. Locality data is provided, plus dorsal and ventral habitus images of both sexes, along with key characters separating the new taxon from other species within the genus.