The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Floral diversity and environment during the middle Siwalik sedimentation (Pliocene) in the Arunachal sub-Himalaya

A comprehensive morphotaxonomical evaluation of diverse angiospermic dicotyledonous leaf impressions recovered from the middle part of the Siwalik succession (Subansiri Formation: Pliocene) of Arunachal Pradesh, eastern Himalaya, India, shows that the leaf remains are comparable to modern Glochidion J. R. Forst. and G. Forst. (Phyllanthaceae), Bauhinia L., Callerya Endl. (Fabaceae), Mitragyna Korth. (Rubiaceae), Beilschmiedia Nees (Lauraceae), Uvaria L. (Annonaceae), Neolamarckia Bosser (Rubiaceae), Sorindeia Thouars (Anacardiaceae), Lagerstroemia L. (Lythraceae), and Premna L. (Lamiaceae). Among these taxa, seven species are new to the Neogene floras of the Indian subcontinent. Analyses of the floral assemblage, with respect to the present-day distribution pattern of modern equivalent taxa and the physiognomic characters of the recovered fossil leaves, suggest that a tropical evergreen forest was growing in a warm humid climate in the region at the time of deposition. This qualitative climatic data is also corroborated by our previously published quantitative data obtained from a CLAMP (climate leaf analysis multivariate program) analysis on the middle Siwalik floral assemblage. The presence of some Southeast Asian elements in the fossil assemblage provides clear evidence of free exchange of taxa across southern Asia in the Pliocene

Environmental constraints on terrestrial vertebrate behaviour and reproduction in the high Arctic of the Late Cretaceous

Reconstructions of temperature and moisture regimes based on fossil leaves, combined with tree ring studies, detail the light regime, length of the growing season, and summer and winter temperatures of the Late Cretaceous Arctic. Such constraints have important implications for dinosaur feeding and reproductive behaviour, and the capacity to reside year-round in near-polar environments. At the highest palaeolatitudes where dinosaurs have been found (82-85 degrees N) winter darkness lasted for similar to 120 days and the spring and autumn twilight periods for similar to 15 days. A mostly cloud and mist-shrouded environment witnessed a mean annual temperature (MAT) of 6-7 degrees C, a warm month mean temperature (WMMT) of 14.5 +/- 3.1 degrees C and a cold month mean temperature (CMMT) of -2 +/- 3.9 degrees C. Growth rings in wood suggest summer temperatures frequently fell below + 10 degrees C. Winter temperatures as low as -10 degrees C were likely for short periods. Spring bud break in late February to early March and leaf fall in early October limited the time when fresh food was available in any quantity to not more than 6 months. The diversity of Arctic dinosaur body sizes implies a range of overwintering strategies but year-round residency requires reproduction. Burrowing and enclosed nest building no doubt facilitated overwintering for small animals, but for larger dinosaurs shelter was problematical. No dinosaur egg remains have yet been found as far north as 82 degrees palaeolatitude, but they occur 6 further south in the Early Maastrichtian Kakanaut Formation, Northeastern Russia. Here the winter darkness was shorter (45 days), and the temperature regime warmer (MAT 10 degrees C, WMMT 19 degrees C, CIVIMT +3 degrees C). The growing season (temperatures > 10 degrees C) was similar to 6.3 months and fresh food was available in quantity for slightly longer. These summer temperatures constrain the thermal regime of nest environments and suggest sophisticated nest management and possibly brooding strategies for the necessary rapid incubation and hatching before the onset of winter. (C) 2015 Elsevier B.V. All rights reserved

Environmental adaptations and constraints on latest Cretaceous Arctic dinosaurs

The Arctic hosts an extraordinary wealth of terrestrial fossil biotas of Late Cretaceous age representing a diverse and highly productive near-polar ecosystem that has no modern analogue. Compared to the rest of the Late Cretaceous Maastrichtian plant diversity was at its lowest and the temperature regime the coolest, yet the semi-open forests supported a rich dinosaur fauna made up of a wide range of body sizes and feeding strategies. The combination of mild winter temperatures and continuous darkness lasting several months imposed severe constraints on primary productivity. Plant survival strategies involved almost universal winter loss of foliage, which in turn limited food supply for non-migratory overwintering herbivorous animals. A combination of leaf form and tree ring studies has been used to quantify year round variations in temperature and determine the timing of spring bud-break and autumnal leaf fall. While Maastrichtian winter temperatures were cold enough (down to -10°C for brief intervals) for frequent frosts and snowfall, summer temperatures were cool but highly variable and at ~83°N along the north Alaskan coast frequently fell below +10°C. Theropod egg shell fragments at ~76°N in the Maastrichtian of Northeastern Russia may indicate that dinosaur reproduction took place in the Arctic ecosystem, as distinct from taking place at lower latitude breeding grounds reached by migration. This raises the question of nest management and specifically the maintenance of incubation temperatures, and the duration of incubation. Of critical importance to year-round residency is the timing of hatching and juvenile care before winter darkness set in, temperatures fell to near freezing and food resources became limited

Plant-arthropod associations from the Siwalik forests (middle Miocene) of Darjeeling sub-Himalaya, India

Fossil leaves from the Siwalik sedimentary rocks of Darjeeling sub-Himalaya, evidence a variety of plant-insect interactions that operated during the evolution of monsoon-influenced forests from middle Miocene times. We assessed the diversity and frequency of insect herbivory on 137 specimens representing the Darjeeling lower Siwalik flora (DLSF). We also examined the percent of leaf area removed by herbivory as an independent measure of the effect of insect herbivore removal of host plant photosynthetic tissue. Five functional feeding groups (FFGs) are identified in this study namely leaf mining, hole feeding, skeletonizing, galling and margin feeding. These traces indicate that insects interacted with the plants for various purposes, including feeding, egg laying and sheltering. Furthermore, these morphotraces tend to suggest similarities in insect interactions with leaves of extant plant species such as Persea, Woodfordia, Shorea, Artocarpus, Callicarpa, Albizia, Lagerstroemia etc. On the basis of comparison with extant taxa, possible leaf feeders could have belonged to the insect orders Orthoptera, Coleoptera, Lepidoptera and Diptera. Although the morphology of the phytophagous insects associated with the fossil leaves is unknown, present findings reveal that many modern plant-insect relationships were established by the Miocene time and continue to the present, shaping both the present day flora and fauna. In the present study we compare insect herbivory at DLSF to that of our previously investigated Arunachal lower Siwalik flora and two younger floras from that area. We note a similar range of FFGs and damage types observed among these four fossil floras and conclude that compared to biotic factors climate had little influence in determining the evolution of plant-insect interactions in the eastern Himalayan region. (C) 2015 Elsevier B.V. All rights reserved

Evidence for diversification of Calophyllum L. (Calophyllaceae) in the Neogene Siwalik forests of eastern Himalaya

Here, we report fossil leaves, woods, and pollen grains comparable to Calophyllum L. (mainly to Calophyllum inophyllum L. and Calophyllum polyanthum Wall. ex Choisy) of Calophyllaceae from the upper (Kimin Formation, late Pliocene-early Pleistocene), middle (Subansiri Formation, Pliocene) Siwalik sediments of the Arunachal sub-Himalaya, and lower (Gish Clay Formation of Sevok Group; middle to late Miocene) Siwalik sediments of the Darjeeling foothills, eastern Himalaya. Their presence indicates a warm and humid tropical environment in the region during the period of Siwalik sedimentation. Considering all records of Calophyllum, it is suggested that Calophyllum was a frequent forest element throughout the period of Siwalik sedimentation during the Neogene (Miocene time). At present, C. polyanthum grows in the eastern Himalaya, but C. inophyllum is totally absent from north-eastern regions suggesting differential adaptability of these taxa to changing ecoclimatic conditions. Distinct climate change in the area, possibly related to the Himalayan Orogeny during Miocene-Pleistocene times, might have caused the disappearance of C. inophyllum from the entire eastern Himalaya and north-east Indian plains and a move to littoral/coastal and swampy forests of India and other adjoining south-east Asian regions, Polynesia, and the east coast of Africa. The past global distribution of Calophyllum is also discussed, and it is suggested that India may have been its primary centre of origin. This is the first time Cenozoic fossil leaves Calophyllum siwalikum Khan, R.A.Spicer & Bera, sp. nov. comparable to C. inophyllum are described using the both macro- and micromorphological characters

Woody dicot leaf traits as a palaeoclimate proxy: 100 years of development and application

The relationship between plant form and climate has been recognised for more than two millennia, and the idea that fossils can indicate climate change was first recorded almost a thousand years ago. Here we review ways of using plant form to reconstruct, quantitatively, past climates, focussing on techniques that have been developed over the past century. We begin with the relationship between woody dicot leaf margins and temperature, and trace the development of the approach through to the modern multivariate tool known as Climate-Leaf Analysis Multivariate Program (CLAMP), which can derive 24 different climate parameters from 31 macroscopic leaf traits commonly preserved in leaf fossils. We review the complex inter-dependant correlations between leaf traits and climate, recognising that leaves develop and function as integrated systems, and that there is a selective premium on them being well adapted to their immediate climatic environment. We discuss different ways of understanding and decoding climate from leaf form in multidimensional trait space, and provide an over-view of CLAMP applications for tracking climate change, monsoon evolution, and in palaeoaltimetry, from the middle Cretaceous to the Pleistocene

Sun and shade leaf variability in <i>Liquidambar chinensis</i> and <i>Liquidambar formosana</i> (Altingiaceae): implications for palaeobotany

Many factors influence leaf anatomy and morphology in the crown of a tree, particularly those resulting from microclimatic differences between the periphery and the interior of the crown. These influences can be so strong that single species can produce different leaf forms in which shade and sun leaves exhibit consistently distinctive morphological and epidermal character sets. Here we show, using Liquidambar as a model system, that the principal morphological characters for distinguishing shade and sun leaves in two modern Liquidambar spp. with different lamina types (entire in L. chinensis and lobate in L. formosana) are the leaf lamina length to width ratio, the degree of development of venation networks, tooth size and tooth shape. The main epidermal characters are ordinary cell size and anticlinal wall outlines. Many fossils, however, are only preserved as impressions and morphological characters alone have been used to distinguish shade and sun leaf morphotypes. To evaluate the utility of our approach, populations of fossil Liquidambar leaves from the Eocene of southern China, preserved only as impressions, were categorized into sun and shade morphotypes. Recognition that sun and shade leaf morphological diversity exists in fossil populations will enable palaeobotanists to identify more reliably foliar polymorphisms that would otherwise be used to describe, incorrectly, different species

Why do foliar physiognomic climate estimates sometimes differ from those observed? Insights from taphonomic information loss and a CLAMP case study from the Ganges Delta

Palaeoclimate estimates derived from plant-based proxies are potentially subject to uncertainties arising from taphonomic filtering. In any given fossil assemblage it is possible to identify the kinds of likely taphonomic in␣uences, but virtually impossible to quantify the uncertainties they introduce because ␣ltering removes information. Because that information is missing it cannot be measured. An alternative approach is to measure the maximum uncertainty possible due to specific information loss within recognised analytical protocols. In respect of the multivariate foliar physiognomic technique known as CLAMP (Climate Leaf Analysis Multivariate Program) we have attempted to do this by experimentally degrading both the character state scores and the number and composition of taxa as subsets of the full range of character states and taxonomic diversity in the source vegetation. In this study a stand of protected vegetation on Green Island (23° 08' 58" N, 88° 26' 59.19" E) within the Ganges Delta was sampled following standard CLAMP protocols. The island is subject to annual ␣ooding during the monsoon season and is typical of the kinds of naturally disturbed vegetation likely to be represented in ancient delta ␣oodplain assemblages. A total of 56 woody dicot taxa were scored in the living vegetation. From this ‘complete’ sample leaf character states for lobing, margin, size, apex, base, length-to- width ratio and shape were removed in turn from all 56 taxa to give 7 analyses simulating worst case taphonomic loss of physiognomic data. Ten subsets of 20 randomly selected taxa were also analysed to simulate taphonomic diversity loss of almost two thirds of the potentially available taxa in the source vegetation. In all cases the completeness statistic remained above the CLAMP recommended minimum of 0.66. The results show that in all cases the uncertainties arising from taphonomic processes, either through taphonomic diversity or character state filtering, were not significantly different from the statistical CLAMP uncertainties associated with the most commonly used calibration dataset (Physg3brc), and gave similar climatic estimates as the source vegetation in its entirety. This suggests that stratigraphically well constrained museum collections lacking detailed sedimentary or taphonomic context can still be used with confidence for CLAMP analyses. Leaf margin analysis displayed a greater sensitivity to diversity loss. The Green Island estimates suggested a cooler, moister climate than that indicated by the observed regional climate as derived from a 0.5 × 0.5° gridded data set used in climate modelling evaluation. The likely cause for this disparity is the prevalence of a sub-canopy microclimate signal developed by the vegetation itself, and this is strongly dependant on the temperature and humidity characteristics of the regional climate as well as the proximity to water bodies. Within the sample size limitations of this study this disparity is larger than that introduced by taphonomic processes, but potentially can be corrected for