Phylogenomic analyses are instrumental in enhancing our comprehension of evolutionary relationships across the tree of life. Among eukaryotes, ciliates are one of the most diverse groups of single-cell eukaryotes that play important roles in microbial food webs and have been used as important model organisms in a wide range of studies. However, evolutionary relationships within ciliates remain contentious due to low resolution of limited molecular markers and/or limited taxa. To provide a more comprehensive understanding of the evolutionary relationships within the clade Ciliophora, we sequenced the genomes and/or transcriptomes of 52 ciliate species from 10 classes. Combining analyses of these with publicly available data, we generated a dataset that comprises 190 ciliate species spanning 49 orders, encompassing 16 of the 17 recognized classes within the phylum Ciliophora, thereby achieving nearly complete class-level representation of this diverse group. Among these species, 74 were analyzed for the first time from a phylogenomic perspective. We provided an updated classification of Ciliophora, comprising the class Mesodiniea and two major clades, i.e., Postciliodesmatophora and Intramacronucleata, with Intramacronucleata comprising two main clades (CONthreeP and SLAOMP) and Protocruziea. We also evaluated the effect of missing data and provided datasets-a 200 core-gene family list and multiple sequence alignments-to facilitate future phylogenomic analyses. Furthermore, based on the highly reliable phylogenomic tree, we estimated that the phylum Ciliophora originated approximately 1,052 million years ago (Mya) at the beginning of the Meso-proterozoic period. The robust phylogenomic framework presented here not only facilitates a deeper exploration of ciliate evolution but also provides a reference for future phylogenetic and taxonomic studies.
Whether early Earth had a mobile lithosphere and plate tectonics is debated. We present paleomagnetic data quantifying differential motion between lithospheric blocks at ~3.48 billion years ago (Ga). This manifested as [Formula: see text]centimeters per year latitudinal motion of the East Pilbara Craton (Western Australia) across high latitudes, whereas the Barberton Greenstone Belt (South Africa) was stationary at low latitudes. Comparison of this plate motion with candidate analogs suggests either rapid collisional plate tectonics (i.e., an "active-lid") or an episodically mobile lithosphere. We also document the oldest known geomagnetic reversal at ~3.46 Ga, consistent with an axial dipolar dynamo that reversed less frequently than today's. The existence and rates of these surface and core geophysical phenomena provide geodynamic context to Earth's early geophysical and biological evolution.
We report on a study of 36 pairs of "twin" M dwarfs in wide binaries and assess how similarly the stars behave. Stars in each twin pair have BP, RP, J, H, and K-s differing by <0.10 mag, mass estimates matching within <3%, and presumably the same age and composition. We utilize short- and long-term photometry, multiepoch spectroscopy, and archival data to measure rotation periods, photometric activity levels, and H alpha equivalent widths for many systems. Speckle imaging, radial velocities, and long-term astrometry are used to identify unresolved companions, yielding three systems with unseen components. Among the 33 remaining twin systems, numerous remarkable pairs show nearly identical rotation rates and activity levels between their twin components, including cases throughout the lower main sequence and across a broad range of rotation-activity parameter space. In contrast, mismatches with >25% differences exist in rotation period for 21%(+14%)(-7%) of twin pairs, in rotation amplitude for 67%(+10%)(-15%) of pairs, in multiyear photometric variability for 33%(+12%)(-9%) of pairs, and in H alpha activity for 21%(+9%)(-6%) of pairs, with fully convective systems generally mismatched more often. Thus, roughly one out of five M dwarf twin sets does not match in rotation and/or activity despite otherwise identical fundamental parameters. Furthermore, we compile three key systems showing larger relative active/inactive H alpha mismatches. We propose the various mismatches likely stem from factors such as dynamo stochasticity, activity cycles, formative disk aspects, and/or star-planet interactions, depending on the system. These well-vetted twins offer ripe targets for many future investigations.
