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1. The early actinopterygian genus Rhadinichthys redefined, the type species ornatissimus redescribed, and the species bearsdeni introduced

   https://doi.org/10.1017/S1755691024000136  

   MO, Yunyan; CARON, Abigail M; COATES, Michael I (October 2024, Earth and Environmental Science Transactions of the Royal Society of Edinburgh)

   ABSTRACT Rhadinichthysis one of the most wide-ranging and speciose genera of Palaeozoic actinopterygians. A classic variety of ‘palaeoniscoid’,Rhadinichthysspecies are generally small (~10–15 cm) and known mostly from dermal skeletal remains that show features commonplace among early ray-finned fishes. For this reason, the genus has long been considered a poorly diagnosed wastebasket taxon in need of revision and rarely included in systematic analyses. In the present work, syntypes ofRhadinichthys ornatissimus, the type species, are re-examined and supplemented with better-preserved material from other localities in the Scottish Midland Valley. A neotype is nominated and a more precise diagnosis presented with a suite of genus-level apomorphies. Unexpectedly, these traits are also evident in the monotypic Lower Carboniferous actinopterygian genusWoodichthys, which the neotype ofR. ornatissimusclosely resembles. As a result, the genusWoodichthysis subsumed within the redefinedRhadinichthys, and the singleWoodichthysspecies is reassigned asR. bearsdeni, comb. nov., bringing with it a set of endoskeletal data. Some of these data are new, derived from μCT scans of the skull of theR. bearsdeniholotype, yielding renderings that update the original description of its skull table, parasphenoid, neurocranium, and otoliths. Further new data concerning the hyoid arch are obtained from a new specimen ofR. bearsdenifrom a site close by the original Bearsden locality. Redefined in this way,Rhadinichthyspresents a data-rich operational taxonomic unit better suited for systematic studies. However, in so doing, it also releases a cluster of fossil species no longer anchored to a genus and now in need of rediagnoses. 

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2. Species delimitation and invasion history of the balsam woolly adelgid, Adelges ( Dreyfusia ) piceae (Hemiptera: Aphidoidea: Adelgidae), species complex

   https://doi.org/10.1111/syen.12456  

   Havill, Nathan_P; Griffin, Brian_P; Andersen, Jeremy_C; Foottit, Robert_G; Justesen, Mathias_J; Caccone, Adalgisa; D'Amico, Vincent; Elkinton, Joseph_S (October 2020, Systematic Entomology)

   Abstract TheAdelges(Dreyfusia)piceae(Ratzeburg) species complex is a taxonomically unstable group of six species. Three of the species are cyclically parthenogenetic [Ad.nordmannianae(Eckstein),Ad.prelli(Grossmann), andAd.merkeri(Eichhorn)] and three are obligately asexual [Ad.piceae,Ad.schneideri(Börner), andAd.nebrodensis(Binazzi & Covassi)]. Some species are high‐impact pests of fir (Abies) trees, so stable species names are needed to communicate effectively about management. Therefore, to refine species delimitation, guided by a reconstruction of their biogeographic history, we genotyped adelgids from Europe, North America, and the Caucasus Mountains region with 19 microsatellite loci, sequenced the COI DNA barcoding region, and compared morphology. Discriminant analysis of principal components of microsatellite genotypes revealed four distinct genetic clusters. Two clusters were morphologically consistent withAd.nordmannianae. One of these clusters consisted of samples from the Caucasus Mountains and northern Turkey, and the other included samples from this region as well as from Europe and North America, whereAd.nordmannianaeis invasive. A third cluster was morphologically consistent withAd.piceae, and included individuals from Europe, where it is native, and North America, where it is invasive. In North America, the majority ofAd.piceaeindividuals were assigned to two geographically widespread clones, suggesting multiple introductions. The fourth cluster included individuals morphologically consistent withAd.prelliorAd.merkeri. However, based on genetic assignments, hybrid simulations, and approximate Bayesian computation, we find it likely that these are contemporary hybrids betweenAd.nordmannianaeandAd.piceaethat arose independently in Europe and North America, so we propose thatAd.prelliandAd.merkeriare invalid. Finally, we synonymiseAd.schneideri(syn.n.)withAd.nordmannianaeand designateAd.nebrodensisas subspeciesAd.piceae nebrodensis(stat.n.). Our revised taxonomy therefore recognises two species:Ad.nordmannianaeandAd.piceae, which we estimate to have diverged recently, during one of the last two interglacial periods. Finally, we comment on this species complex being in the midst of transition between sexual and asexual reproduction, a pattern that is probably common in Adelgidae. 

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3. Morphometrics in the Recurved Corolla Clade of Burmeistera (Campanulaceae) Clarifies Species Limits and Identifies a New Species

   https://doi.org/10.1600/036364424X17110456120730  

   Mashburn, Brock; Trigueros, Andrea; Ulloa, Carmen Ulloa; Muchhala, Nathan (May 2024, Systematic Botany)

   Abstract—The genus Burmeistera consists mostly of cloud forest species occurring from Guatemala to Peru. Molecular work on this group has revealed previously established subgeneric groupings to be non-monophyletic, while also identifying several monophyletic groups with recognizable synapomorphies. One such monophyletic group is a clade of species with recurved corolla lobes which contains three species: B. crispiloba, B. sodiroana, and B. succulenta. As many as nine names have been recognized previously for these species, though the most recent taxonomic treatments recognize only these three. Additional collections of these species made in the last forty years have uncovered phenotypic variation showing that characters traditionally used to differentiate them no longer do so clearly and suggest the possibility of introgression between them. Here, we report morphometric analyses of herbarium specimens of the recurved corolla clade, using both hierarchical and normal mixture model-based clustering methods to test the current species hypotheses. Our results support the recognition of the three known species plus the newly described Burmeistera kitrinaima sp. nov. We provide complete descriptions of all four species, and include photographs, distributions maps, taxonomic discussion, and an identification key. Keywords—Andes, biodiversity, cluster analysis, hybridization, taxonomy. 

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4. The Sphagnum cuspidatum complex: phylogeny, species delimitation, and morphology

   https://doi.org/10.1093/biolinnean/blad111  

   Robinson, Sean C; Nieto-Lugilde, Marta; Duffy, Aaron M; Martinez_Muñoz, Katherine; Aguero, Blanka; Merced, Amelia; Hassel, Kristian; Flatberg, Kjell Ivar; Shaw, A Jonathan (September 2023, Biological Journal of the Linnean Society)

   Abstract The use of species as a concept is an important metric for assessing biological diversity and ecosystem function. However, delimiting species based on morphological characters can be difficult, especially in aquatic plants that exhibit high levels of variation and overlap. The Sphagnum cuspidatum complex, which includes plants that dominate peatland hollows, provides an example of challenges in species delimitation. Microscopic characters that have been used to define taxa and the possibility that these characters may simply be phenoplastic responses to variation in water availability make species delimitation in this group especially difficult. In particular, the use of leaf shape and serration, which have been used to separate species in the complex, have resulted in divergent taxonomic treatments. Using a combination of high-resolution population genomic data (RADseq) and a robust morphological assessment of plants representing the focal species, we provide evidence to evaluate putative species in this complex. Our data support the recognition of S. cuspidatum, S. fitzgeraldii, S. mississippiense, and S. trinitense as genetically distinct species that can be separated morphologically. These results indicate that S. viride does not differ genetically from S. cuspidatum. Our results are broadly relevant to other aquatic groups where leaf shape and marginal teeth are used to distinguish species. 

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5. Mitochondrial DNA and other lines of evidence clarify species diversity in the Peromyscus truei species group (Cricetidae: Neotominae)

   https://doi.org/10.1515/mammalia-2021-0146  

   Hernández-Canchola, Giovani; León-Paniagua, Livia; Esselstyn, Jacob A. (January 2022, Mammalia)

   Abstract Deer mice (genus Peromyscus ) are among the commonest small mammals in the Nearctic zoogeographic region. Nevertheless, systematic relationships are only partially settled and numerous taxonomic questions await resolution. For instance, researchers have found that some members of the Peromyscus truei species group contain high levels of genetic divergence that could indicate the presence of cryptic species. We analyzed the systematics and phylogenetic relationships of the P. truei group using new and previously published mitochondrial cytochrome b sequences. Our analyses verify several earlier conclusions, but we also detected new clades that deserve recognition. Considering their mitochondrial distinctiveness, allopatric ranges, and previously reported molecular, biochemical, chromosomal, morphological, and ecological differences, we elevate three previously described taxa to species. We support the recognition of two subgroupings. The first comprises P. gratus , P. truei , and possibly P. cf. martirensis and P. cf.  zapotecae . The second contains to P. amplus , P. attwateri , P. collinus , P. difficilis , P. felipensis , P. laceianus , P. nasutus , P. ochraventer , and P. pectoralis. Placement of P. bullatus will likely remain unknown until genetic data are available. Further research could improve our understanding of the evolutionary history of Peromyscus , but in some cases taxonomic issues must be resolved first. 

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