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1. Six New Species of Burmeistera (Campanulaceae) from Ecuador

   https://doi.org/10.3417/2021589  

   Mashburn, Brock; Ulloa Ulloa, Carmen; Muchhala, Nathan (February 2021, Novon, A Journal for Botanical Nomenclature)

   null (Ed.)

   Six species of Burmeistera H. Karst. & Triana are described as new from Ecuador: B. chrysothrix Mashburn & Muchhala, B. crocodila Mashburn & Muchhala, B. erosa Mashburn, B. lingulata Mashburn & Muchhala, B. sierrazulensis Mashburn & Muchhala, and B. valdiviana Mashburn. These discoveries bring the total number of Burmeistera species in Ecuador to ca. 47. Descriptions are given for each species, as well as diagnoses to differentiate them from other Burmeistera. Also provided is a discussion of each species’ etymology, phenology, and ecology, a list of all specimens examined, and distribution maps and photos, when available. 

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2. Pervasive mitochondrial tRNA gene loss in the clade B of haplosclerid sponges (Porifera, Demospongiae)

   https://doi.org/10.1101/2024.03.04.583380  

   Lavrov, Dennis V; Turner, Thomas L; Vicente, Jan (March 2024, bioRxiv)

   <bold>Abstract</bold> Mitochondrial tRNA gene loss and cytosolic tRNA import to mitochondria are two common phenomena in mitochondrial biology, but their importance is often under-appreciated in animals. This is because most bilaterally symmetrical animals (Bilateria) encode a complete set of tRNAs needed for mitochondrial translation. By contrast, studies of mitochondrial genomes in non-bilaterian animals have shown a reduced tRNA gene content in several lineages, necessitating tRNA import. Interestingly, in most of these lineages tRNA gene content appears to be set early in the evolution of the group and conserved thereafter. Here we demonstrate that Clade B of Haplosclerid Sponges (CBHS) represent an exception to this pattern. We determined mt-genome sequences for eight species from this group and analyzed them with six that had been previously available. In addition, we determined mt-genome sequences for two species of haploslerid sponges outside the CBHS and used them with eight previously available sequences as outgroups. We found that tRNA gene content varied widely among CBHS species: from three in an undescribedHaliclonaspecies (Haliclona sp. TLT785) to 25 inXestospongia mutaandX. testudinaria. Furthermore, we found that all CBHS species outside the genusXestospongialackedatp9, while some also lackedatp8. Analysis of nuclear sequences fromNiphates digitalisrevealed that bothatp8andatp9had transferred to the nuclear genome, while the absence of mt-tRNA genes represented their genuine loss. Overall, CBHS can be a useful animal system to study mt-tRNA genes loss, mitochondrial import of cytosolic tRNA, and the impact of both of these processes on mitochondrial evolution. Significance statementIt is generally believed that the gene content is stable in animal mitochondrial (mt) DNA. Indeed, mtDNA in most bilaterally symmetrical animals encompasses a conserved set of 37 genes coding for 13 proteins, two rRNAs and 22 tRNAs. By contrast, mtDNA in non-bilaterian animals shows more variation in mt gene content, in particular in the number of tRNA genes. However, most of this variation occurs between major non-bilaterian lineages. Here we demonstrate that a group of demosponges called Clade B of Haplosclerid Sponges (CBHS) represents a fascinating exception to this pattern, with species experiencing recurrent losses of up to 22 mt-tRNA genes. We argue that this group constitutes a promising system to investigate the effects of tRNA gene loss on evolution of mt-genomes as well as mitochondrial tRNA import machinery. 

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3. 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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4. Comparative analysis of corolla tube development across three closely related Mimulus species with different pollination syndromes

   https://doi.org/10.1111/ede.12368  

   Gurung, Vandana; Yuan, Yao‐Wu; Diggle, Pamela K. (January 2021, Evolution & Development)

   Abstract Fusion of petals to form a corolla tube is considered a key innovation contributing to the diversification of many flowering plant lineages. Corolla tube length often varies dramatically among species and is a major determinant of pollinator preference. However, our understanding of the developmental dynamics underlying corolla tube length variation is very limited. Here we examined corolla tube growth in theMimulus lewisiispecies complex, an emerging model system for studying the developmental genetics and evo‐devo of pollinator‐associated floral traits. We compared developmental and cellular processes associated with corolla tube length variation among the bee‐pollinatedM. lewisii, the hummingbird‐pollinatedMimulus verbenaceus, and the self‐pollinatedMimulus parishii. We found that in all three species, cell size is non‐uniformly distributed along the mature tube, with the longest cells just distal to the stamen insertion site. Differences in corolla tube length among the three species are not associated with processes of organogenesis or early development but are associated with variation in multiple processes occurring later in development, including the location and duration of cell division and cell elongation. The tube growth curves of the small‐floweredM. parishiiand large‐floweredM. lewisiiare essentially indistinguishable, except thatM. parishiitubes stop growing earlier at a smaller size, suggesting a critical role of heterochrony in the shift from outcrossing to selfing. These results not only highlight the developmental process associated with corolla tube variation among species but also provide a baseline reference for future developmental genetic analyses of mutants or transgenic plants with altered corolla tube morphology in this emerging model system. 

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5. Notes from the taxonomic disaster zone: Evolutionary drivers of intractable species boundaries in an Australian lizard clade (Scincidae: Ctenotus )

   https://doi.org/10.1111/mec.17074  

   Prates, Ivan; Hutchinson, Mark N.; Singhal, Sonal; Moritz, Craig; Rabosky, Daniel L. (July 2023, Molecular Ecology)

   Abstract Genomic‐scale datasets, sophisticated analytical techniques, and conceptual advances have disproportionately failed to resolve species boundaries in some groups relative to others. To understand the processes that underlie taxonomic intractability, we dissect the speciation history of an Australian lizard clade that arguably represents a “worst‐case” scenario for species delimitation within vertebrates: theCtenotus inornatusspecies group, a clade beset with decoupled genetic and phenotypic breaks, uncertain geographic ranges, and parallelism in purportedly diagnostic morphological characters. We sampled hundreds of localities to generate a genomic perspective on population divergence, structure, and admixture. Our results revealed rampant paraphyly of nominate taxa in the group, with lineages that are either morphologically cryptic or polytypic. Isolation‐by‐distance patterns reflect spatially continuous differentiation among certain pairs of putative species, yet genetic and geographic distances are decoupled in other pairs. Comparisons of mitochondrial and nuclear gene trees, tests of nuclear introgression, and historical demographic modelling identified gene flow between divergent candidate species. Levels of admixture are decoupled from phylogenetic relatedness; gene flow is often higher between sympatric species than between parapatric populations of the same species. Such idiosyncratic patterns of introgression contribute to species boundaries that are fuzzy while also varying in fuzziness. Our results suggest that “taxonomic disaster zones” like theC. inornatusspecies group result from spatial variation in the porosity of species boundaries and the resulting patterns of genetic and phenotypic variation. This study raises questions about the origin and persistence of hybridizing species and highlights the unique insights provided by taxa that have long eluded straightforward taxonomic categorization. 

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