Permian–Triassic phylogenetic and morphologic evolution of rhynchonellide brachiopods

The Rhynchonellida is a major group of brachiopods that survived the “big five” mass extinctions and flourished after the Permian/Triassic (P/Tr) crisis. However, phylogenetic and character evolution in the Rhynchonellida across the P/Tr transition is poorly understood. In view of the widespread homoplasy across this order, we employ a tip-dated Bayesian analysis to reconstruct phylogenetic relationships for late Permian–Triassic rhynchonellides. The same data were also analyzed using three other methods: undated Bayesian, equal-weighting, and implied-weighting parsimony. Compared with trees generated by other methods, those constructed by tip-dating best account for the homoplasy in this group and are closer to previous assumptions on the evolution of this order. Based on the analyses of multiple trees, the major increase in lineage richness occurred in the Early and early Middle Triassic. Also, richness in the Anisian almost reached the highest level seen in the Triassic. According to fossil records, a pronounced reduction in shell size and in the development of ornamentation occurred after the P/Tr extinction, which is largely due to the loss of large and highly sculptured genera and the diversification of small-sized and weakly ornamented genera. Ancestral-state estimation of shell size and development of ornamentation, coupled with comparisons of other characters, indicate that the Early–Middle Triassic mature “small-sized taxa” may have characters displayed by juveniles of their ancestors. This suggests that for these genera, paedomorphosis was possibly a strategy to survive and diversify in the harsh environment after the P/Tr extinction.

Continued evolution of the Lower Mississippi: changes to fluvial islands over five decades (1965 to 2015)

<p>The lower Mississippi continues to adjust to upstream human impacts and channel engineering. Fluvial islands (vegetated sandy bars > 1 ha) are a key mode of riverine adjustment along the Lower Mississippi, and have substantially increased in number and size over the past five decades, from 112 in 1965 to 295 by 2015, which can largely be attributed to groyne construction. This study examines the morphologic evolution of fluvial islands from Cairo, IL to the downstream-most island at about Bonnet Carre Spillway (~5 km upstream of New Orleans). The analysis utilizes lidar DEMs, historic air photos, and adjacent hydrologic (stage) data. Additionally, changes to island vegetation were examined by comparison of the Normalized Difference Vegetation Index (NDVI) calculated from analysis of Landsat imagery for 1996 with 2014.</p><p>While each island is somewhat unique and influenced by local scale factors, there are clear geomorphic differences between new islands and older islands. New islands (did not exist in 1965) do not have appreciable natural levees and the island high point is at about flood stage. Older islands that are stable and larger have formed natural levees, which are higher than average flood stage and often higher than the adjacent floodplain surface. The downstream slope of new islands is an order of magnitude higher than old islands, averaging 0.0028 m/m and 0.0009 m/m, respectively. This is likely attributed to the downstream growth of islands, increasing in length and aggradation on the downstream flank. Additionally, between 1996 and 2014 island vegetation matured, with the area of moderate vegetation decreasing at the expense of an increase in denser vegetation. A comparison of the NDVI for the same islands in 1996 and 2014 between Vicksburg and Red River Landing reveals an increase in vegetation health and density. While the area of islands classified as sandy (NDVI 0.1-0.2) and scrubby (NDVI 0.2-0.3) vegetation did not substantially change between 1996 and 2014, the amount of dense vegetation (NDVI > 0.5) considerably increased (from 3.2 km<sup>2</sup> to 9.8 km<sup>2</sup>) as the amount of moderate vegetation (NDVI 0.3-0.5) decreased (15.1 km<sup>2</sup> to 8.4 km<sup>2</sup>). The increase in vegetation density can be attributed to the increased amount of time since island formation was initiated, and a maturation of the island surface with its geomorphic development.</p><p>The change to fluvial islands over the past five decades represents continued geomorphic evolution of the Lower Mississippi. This is of interest because, although it occurs during a period in which sediment supply has dramatically decreased, with the influence of channel engineering there remains sufficient coarse sediment to drive fluvial landform evolution along the Lower Mississippi.</p>

Predictors of Lesion Cavitation After Recent Small Subcortical Stroke

Morphologic evolution of recent small subcortical infarcts (RSSI) ranges from lesion disappearance to lacune formation and the reasons for this variability are still poorly understood. We hypothesized that diffusion tensor imaging (DTI) and blood-brain-barrier (BBB) abnormalities early on can predict tissue damage 1 year after an RSSI. We studied prospectively recruited patients with a symptomatic MRI-defined RSSI who underwent baseline and two pre-specified MRI examinations at 1–3-month and 1-year post-stroke. We defined the extent of long-term tissue destruction, termed cavitation index, as the ratio of the 1-year T1-weighted cavity volume to the baseline RSSI volume on FLAIR. We calculated fractional anisotropy and mean diffusivity (MD) of the RSSI and normal-appearing white matter, and BBB leakage in different tissues on dynamic contrast-enhanced MRI. Amongst 60 patients, at 1-year post-stroke, 44 patients showed some degree of RSSI cavitation on FLAIR, increasing to 50 on T2- and 56 on T1-weighted high-resolution scans, with a median cavitation index of 7% (range, 1–36%). Demographic, clinical, and cerebral small vessel disease features were not associated with the cavitation index. While lower baseline MD of the RSSI (rs = − 0.371; p = 0.004) and more contrast leakage into CSF (rs = 0.347; p = 0.007) were associated with the cavitation index in univariable analysis, only BBB leakage in CSF remained independently associated with cavitation (beta = 0.315, p = 0.046). Increased BBB leakage into CSF may indicate worse endothelial dysfunction and increased risk of tissue destruction post RSSI. Although cavitation was common, it only affected a small proportion of the original RSSI.

Impact of Anthropogenic Facilities on the Morphodynamic Evolution of an Estuarine System: The Case of Oum Er-Rbia Estuary (Azemmour, Morocco)

The Oum Er-Rbia estuary is located on the Atlantic littoral of Morocco. It undergoes severe clogging due to the sand deposition in its outlet. The current study examined the indicators of the morphodynamic evolution in the littoral system including the Oum Er-Rbia estuary and the neighboring beaches over 1970–2017. The methodology adopted was based on the analysis and the interpretation of aerial photographs and Google Earth images under a GIS environment and field work. The morphodynamic evolution was discussed by taking into account the evolution of hydraulic facilities installed in the watershed area, especially the construction of dams, as well as the dredging works in the Oum Er-Rbia estuary. The results highlight the morphologic evolution estimated in terms of surface units observed in the estuary and the neighboring beaches. The evolution of the littoral system was mainly influenced by the closest dam location and by the dredging works, in addition to the regulation of the river flow by the installation of hydraulic facilities upstream.

Mosaic evolution in the middle Miocene planktonic foraminifera Fohsella lineage

Recent studies have shown that modes of evolution, namely directional trend, random walk, and stasis, vary across morphologic traits and over the geographic range of a taxon. If so, is it possible that our interpretation of evolutionary modes is actually driven by our selection of traits in a study? In an attempt to answer this question, we have restudied the middle Miocene planktonic foraminifera Fohsella lineage, an iconic example of gradual morphologic evolution. In contrast to previous studies that have focused on the gross morphology as embodied by the edge view of tests, we analyze here multiple phenotypic traits chosen because their biologic and ecologic significance is well understood in living populations. We find that traits in the lineage did not evolve in concert. The timing and geographic pattern of changes in shape, coiling direction, size, and ecology were different. The evolution of this lineage is a mosaic combination of different evolutionary modes for different traits. We suggest that overemphasis on the evolution of some single trait, such as the edge-view outline, from narrow geographic ranges has significantly underestimated the dynamic evolutionary history of this group.