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What controls species diversity and diversification is one of the major questions in evolutionary biology and paleontology. Previous studies have addressed this issue based on various plant and animal groups, geographic regions, and time intervals. However, as most previous research focused on terrestrial or marine ecosystems, our understanding of the controls on diversification of biota (and particularly invertebrates) in freshwater environments in deep time is still limited. Here, we infer diversification rates of North American freshwater gastropods from the Late Triassic to the Pleistocene and explore potential links between shifts in speciation and extinction and major changes in paleogeography, climate, and biotic interactions. We found that variation in the speciation rate is best explained by changes in continental fragmentation, with rate shifts coinciding with major paleogeographic reorganizations in the Mesozoic, in particular the retreat of the Sundance Sea and subsequent development of the Bighorn wetland and the advance of the Western Interior Seaway. Climatic events in the Cenozoic (Middle Eocene Climate Optimum, Miocene Climate Optimum) variably coincide with shifts in speciation and extinction as well, but no significant long-term association could be detected. Similarly, no influence of diversity dependence was found across the entire time frame of ~ 214 Myr. Our results indicate that short-term climatic events and paleogeographic changes are relevant to the diversification of continental freshwater biota, while long-term trends have limited effect.

The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.

Popliteal artery entrapment syndrome remains difficult to diagnose. Meanwhile, our limited knowledge and understanding make treatment decisions complex. The list of differential diagnoses for exertional leg pain is broad. Oftentimes, patients exhibit confounding and coexisting diagnoses. However, accurate and rapid diagnosis of popliteal artery entrapment syndrome is essential to reduce potential lasting damage to the popliteal artery. A combination of clinical history, physical examination, ankle-brachial index, along with dynamic and static imaging such as duplex ultrasound, computed tomography angiogram, and magnetic resonance angiography, aids diagnosis. Surgical treatment may be definitive depending on the type of popliteal artery entrapment syndrome, but there have been recent advances in diagnostics with intravascular ultrasound and nonsurgical treatment with botulinum toxin type A. Further research is needed to standardize diagnostic criteria, uncover innovative diagnostic methods, and validate promising nonoperative treatment options. [ABSTRACT FROM AUTHOR]

We examined the spread and distribution in the Danube River of a new alien gastropod species, Clathrocaspia knipowitschii (Makarov, 1938) (Gastropoda: Hydrobiidae: Caspiinae). First findings of this species for Hungary, Slovakia, Romania, Bulgaria and Serbia are presented. Clathrocaspia knipowitschii was initially found in 2013 in the Iron Gate stretch of the Danube River at the border between Romania and Serbia. In 2019 and 2020, the species was found at several sites in the lower Danube in Romania, Serbia and Bulgaria, and also upstream in the middle Hungarian Danube in high population densities. The species appears to have spread along more than 800 km in six years. This finding together with the available abundance data indicates that C. knipowitschii is potentially an invasive species, but further observations are needed.

Ab initio chemical shielding calculations greatly facilitate the interpretation of nuclear magnetic resonance (NMR) chemical shifts in biological systems, but the large sizes of these systems requires approximations in the chemical models used to represent them. Achieving good convergence in the predicted chemical shieldings is necessary before one can unravel how other complex structural and dynamical factors affect the NMR measurements. Here, we investigate how to balance trade-offs between using a better basis set or a larger cluster model for predicting the chemical shieldings of the substrates in two representative examples of protein-substrate systems involving different domains in tryptophan synthase: the N-(4'-trifluoromethoxybenzoyl)-2-aminoethyl phosphate (F9) ligand which binds in the α active site, and the 2-aminophenol quinonoid intermediate formed in the β active site. We first demonstrate that a chemically intuitive three-layer, locally dense basis model that uses a large basis on the substrate, a medium triple-zeta basis to describe its hydrogen-bonding partners and/or surrounding van der Waals cavity, and a crude basis set for more distant atoms provides chemical shieldings in good agreement with much more expensive large basis calculations. Second, long-range quantum mechanical interactions are important, and one can accurately estimate them as a small-basis correction to larger-basis calculations on a smaller cluster. The combination of these approaches enables one to perform density functional theory NMR chemical shift calculations in protein systems that are well-converged with respect to both basis set and cluster size.