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Two new species of root mealybugs (Hemiptera: Rhizoecidae) from South America are described and illustrated based on the morphology of the adult females: Coccidella advena Schneider & LaPolla, sp. nov. from Peru and Rhizoecus peripotaro Schneider & LaPolla, sp. nov. from Guyana and Peru. Both species were collected with colonies of Acropyga ants (Hymenoptera: Formicidae) but only R. peripotaro was found to be trophobiotic; C. advena was ignored by the ants and is considered to be free-living. A guide to aid in identification is provided for each species.  

  Widespread concern about the “decline of taxonomy” has motivated calls to action to re-invigorate the field by enhancing taxonomic training, along with increasing taxonomy funding and positions, improving citation rates, and describing species more rapidly. Taxonomic training has historically been apprentice style, with individuals training for years under expert guidance. This approach offers a rich learning experience but inherently limits trainee number and relies on students’ earlier exposure to taxonomy. We describe a scaled-up taxonomic training model using a Course-based Undergraduate Research Experience (CURE) to provide early taxonomy research experience and broadly applicable scientific research skills. Results from a 45-student taxonomy-focused course conducted concurrently at 2 universities resulted in increased interest in taxonomic revisions and ability to explain taxonomic concepts, with one-third of students developing more interest in taxonomic careers. General science skill development was high when compared to a large sample of other CURE courses. The research focus of the course was taxonomic revision of the ant genus Nylanderia in Meso-America; students worked with instructors to delimit and describe new species. Here, we present 4 newly described species: Nylanderia ambulator, sp. nov. Nylanderia aurantia, sp. nov., Nylanderia collaborans, sp. nov., and Nylanderia maximon, sp. nov., with an additional 13 putative species noted for further revisionary work. This expanded taxonomic training model combines hands-on research experience with peer-learning and caters to students with minimal exposure to taxonomy. As a result, this approach broadens recruitment to more diverse audiences and results in enhanced awareness of and appreciation for taxonomy. 

Globally, potentially hundreds of Nylanderia species remain undescribed, hidden within several broadly distributed complexes of morphologically cryptic species. By integrating phylogenomics, geography, and morphology, we describe eight new Nylanderia species from southern Mexico and Mesoamerica, increasing the total number of known species in the genus to 131. In the Americas, Nylanderia is divided into two distantly related clades: American Clade I (AC1) and American Clade II (AC2). Within AC1, Nylanderia austroccidua (Trager) was originally described as a widespread and morphologically variable species distributed from Utah to Costa Rica. This species was diagnosed by a slight concavity in the anterior face of the pronotum and varying degrees of fine cuticular microsculpturing across the body that causes blue cuticular iridescence under microscopic examination. Using Ultraconserved Elements (UCEs) for molecular phylogenetic analysis, we found that taxa matching the original description of N. austroccidua are paraphyletic with respect to Nearctic Nylanderia species. We also found that AC1 includes a Neotropical subclade extending into Mesoamerica, the distribution of which overlaps with AC2, which is exclusively Neotropical. Along with an updated description of N. austroccidua, we also describe the following new species belonging to clade AC1: N. breviscapa, sp. nov., N. contraria, sp. nov., N. lazulina, sp. nov., N. luceata, sp. nov., N. mendax sp. nov., N. mosaica sp. nov., N. polita sp. nov., and N. usul, sp. nov. A dichotomous key and images of the worker caste of these species are included and, where available, images of queens and males are provided.  

Abstract Ants (Hymenoptera: Formicidae) have great potential to exert influence over the morphological evolution of their obligate mutualist partners. Obligately myrmecophilic mealybugs are noted for their unusual morphology, and while this is often attributed to their relationship with ants, a quantitative assessment of this link is lacking. We address this need by evaluating morphological change among mealybugs as a function of ant association. This study considers the associates of 2 independent ant clades—Acropyga Roger, 1862 ants associated with root mealybugs from the families Xenococcidae and Rhizoecidae and herdsmen ants from the Dolichoderus cuspidatus (Smith, F., 1857) species-group associated with mealybugs from the tribe Allomyrmococcini (Pseudococcidae)—and compares them to free-living or potentially myrmecophilic species sampled from among the mealybugs and root mealybugs. We use a combination of geometric morphometric and linear datasets to evaluate characteristics of body shape, body size, leg metrics, and ostiole development. Obligate myrmecophily significantly influences both body shape and size. Myrmecophilous mealybugs are smaller than their free-living counterparts and are either pyriform or rotund in shape rather than oval. Ant-associates from Rhizoecidae also have significantly reduced anterior pairs of ostioles compared to free-living species. Ostioles are involved in defense against natural enemies and mutualist ants typically protect their partners, presumably supplanting the need for structures like ostioles among myrmecophilous species. We discuss the influence ants have on the evolution of their associates in the context of domestication and offer avenues for future exploration. 

We describe a new pair of trophobiotic partners from the ant genus Acropyga and the root mealybug genus Neochavesia . A recent field study on Acropyga ants and associated root mealybugs, conducted in the Peruvian Amazon, led to the discovery of Acropyga manuense LaPolla & Schneider, sp. nov. and its root mealybug symbiont Neochavesia podexuta Schneider & LaPolla, sp. nov. The new root mealybug belongs to the family Xenococcidae, whose members are all obligate associates of Acropyga ants. Providing joint descriptions of new mutualist partners in the same article is a novel approach for this system, and it offers benefits to the ongoing study of mutualism and patterns of association among these symbiotic ants and scales. Here, we also begin to revise the species-group composition of Acropyga by establishing the smithii species-group, and we provide updated information to aid in identifying the new ant species and root mealybug species. 

We describe five new Neotropical species ofRipersiellaliving in association withAcropygaants:R. campensissp. nov.,R. illicianssp. nov.,R. montanaesp. nov.,R. pediandensissp. nov., andR. telaliasp. nov.We also redescribeR. andensisandR. colombiensisbased on type specimens and other collections. Together, these seven species form a morphologically similar group that we informally refer to as theandensis-complex ofRipersiella. All members of theandensis-complex are confirmed or are speculated to be mutualists ofAcropygaants. We discuss the implications of these associations and provide an identification key to the Neotropical species ofRipersiellathat are lacking bitubular cerores, including the new species. 

Abstract The ant genus Nylanderia Emery has a cosmopolitan distribution and includes 150 extant described species and subspecies, with potentially hundreds more undescribed. Global taxonomic revision has long been stalled by strong intra- and interspecific morphological variation, limited numbers of diagnostic characters, and dependence on infrequently collected male specimens for species description and identification. Taxonomy is further complicated by Nylanderia being one of the most frequently intercepted ant genera at ports of entry worldwide, and at least 15 globetrotting species have widespread and expanding ranges, making species-level diagnoses difficult. Three species complexes (‘bourbonica complex’, ‘fulva complex’, and ‘guatemalensis complex’) include globetrotting species. To elucidate the phylogenetic positions of these three complexes and delimit species boundaries within each, we used target enrichment of ultraconserved elements (UCEs) from 165 specimens representing 98 Nylanderia morphospecies worldwide. We also phased the UCEs, effectively doubling sample size and increasing population-level sampling. After recovering strong support for the monophyly of each complex, we extracted COI barcodes and SNPs from the UCE data and tested within-complex morphospecies hypotheses using three molecular delimitation methods (SODA, bPTP, and STACEY). This comparison revealed that most methods tended to over-split taxa, but results from STACEY were most consistent with our morphospecies hypotheses. Using these results, we recommend species boundaries that are conservative and most congruent across all methods. This work emphasizes the importance of integrative taxonomy for invasive species management, as globetrotting occurs independently across at least nine different lineages across Nylanderia. 

A new myrmecophilous species of root mealybug, Williamsrhizoecus udzungwensis sp. n., is described from individuals found living within a nest of Acropyga silvestrii in the Udzungwa Mountains of Tanzania. Acropyga ants are highly specialized, obligate associates of scale insects, typically members of the scale family Xenococcidae. Acropyga are best known for vertically transmitting trophobiotic partners during their nuptial flights and for housing them within brood chambers. This article presents the first record of trophobiosis between a species of Williamsrhizoecus and Acropyga, and only the second record of an association between Acropyga and rhizoecids in the Old World. This discovery contributes important information about the few species of Rhizoecidae confirmed to engage in these unique symbioses, each putatively the result of a past horizontal transmission event from a xenococcid to a rhizoecid lineage. Included is a discussion on the diagnosis of Williamsrhizoecus and an updated key to the species.  

Abstract Nylanderia(Emery) is one of the world's most diverse ant genera, with 123 described species worldwide and hundreds more undescribed. Fifteen globetrotting or invasive species have widespread distributions and are often encountered outside their native ranges. A molecular approach to understanding the evolutionary history and to revision ofNylanderiataxonomy is needed because historical efforts based on morphology have proven insufficient to define major lineages and delimit species boundaries, especially where adventive species are concerned. To address these problems, we generated the first genus‐wide genomic dataset ofNylanderiausing ultraconserved elements (UCEs) to resolve the phylogeny of major lineages, determine the age and origin of the genus, and describe global biogeographical patterns. Sampling from seven biogeographical regions revealed a Southeast Asian origin ofNylanderiain the mid‐Eocene and four distinct biogeographical clades in the Nearctic, the Neotropics, the Afrotropics/Malagasy region, and Australasia. The Nearctic and Neotropical clades are distantly related, indicating two separate dispersal events to the Americas between the late Oligocene and early Miocene. We also addressed the problem of misidentification that has characterized species‐level taxonomy inNylanderiaas a result of limited morphological variation in the worker caste by evaluating the integrity of species boundaries in six of the most widespreadNylanderiaspecies. We sampled across ranges of species in theN. bourbonicacomplex (N. bourbonica(Forel) + N. vaga(Forel)), theN. fulvacomplex (N. fulva(Mayr) + N. pubens(Forel)), and theN. guatemalensiscomplex (N. guatemalensis(Forel) + N. steinheili(Forel)) to clarify their phylogenetic placement. Deep splits within these complexes suggest that some species names – specificallyN. bourbonicaandN. guatemalensis– each are applied to multiple cryptic species. In exhaustively samplingNylanderiadiversity in the West Indies, a ‘hot spot’ for invasive taxa, we found five adventive species among 22 in the region; many remain morphologically indistinguishable from one another, despite being distantly related. We stress that overcoming the taxonomic impediment through the use of molecular phylogeny and revisionary study is essential for conservation and invasive species management.