ABSTRACT
Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency‐dependent learning. However, widespread ...variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: genetic mechanisms, differences among predators and predator behaviour, and alternative selection pressures upon the signal. The mechanisms producing warning coloration are also important. Detailed studies of the genetic basis of warning signals in some species, most notably Heliconius butterflies, are beginning to shed light on the genetic architecture facilitating or limiting key processes such as the evolution and maintenance of polymorphisms, hybridisation, and speciation. Work on predator behaviour is changing our perception of the predator community as a single homogenous selective agent, emphasising the dynamic nature of predator–prey interactions. Predator variability in a range of factors (e.g. perceptual abilities, tolerance to chemical defences, and individual motivation), suggests that the role of predators is more complicated than previously appreciated. With complex selection regimes at work, polytypisms and polymorphisms may even occur in Müllerian mimicry systems. Meanwhile, phenotypes are often multifunctional, and thus subject to additional biotic and abiotic selection pressures. Some of these selective pressures, primarily sexual selection and thermoregulation, have received considerable attention, while others, such as disease risk and parental effects, offer promising avenues to explore. As well as reviewing the existing evidence from both empirical studies and theoretical modelling, we highlight hypotheses that could benefit from further investigation in aposematic species. Finally by collating known instances of variation in warning signals, we provide a valuable resource for understanding the taxonomic spread of diversity in aposematic signalling and with which to direct future research. A greater appreciation of the extent of variation in aposematic species, and of the selective pressures and constraints which contribute to this once‐paradoxical phenomenon, yields a new perspective for the field of aposematic signalling.
Reproductive interference in insects SHUKER, DAVID M.; BURDFIELD‐STEEL, EMILY R.
Ecological entomology,
August 2017, 2017-08-00, 20170801, Letnik:
42, Številka:
S1
Journal Article
Recenzirano
Odprti dostop
1. Reproductive interference occurs when members of different species engage in reproductive interactions, leading to a fitness cost to one or both actors.
2. These interactions can arise through ...signal interference (‘signal‐jamming’), disrupted mate searching, heterospecific rivalry, mate choice errors, or misplaced courtship, mating attempts or copulation.
3. We present a definition of reproductive interference (RI) and discuss the extent to which a failure of species discrimination is central to a definition of RI.
4. The possible mechanisms of RI are reviewed, using a range of insect examples.
5. Some of the causes and consequences of RI are discussed, focusing in particular on mating systems and mating system evolution.
6. We conclude by considering future ways forward, highlighting the opportunities for new theory and tests of the old theory presented by reproductive interference.
Reproductive interference (RI) can arise through processes such as:
signal jamming;
mis‐directed courtship or copulation;
mis‐directed intrasexualrivalry.
We focus on RI and mating system evolution.
We stress that RI may often involves a failure of species discrimination, but this need not always be the case.
Sequence stratigraphy emphasizes facies relationships and stratal architecture within a chronological framework. Despite its wide use, sequence stratigraphy has yet to be included in any ...stratigraphic code or guide. This lack of standardization reflects the existence of competing approaches (or models) and confusing or even conflicting terminology. Standardization of sequence stratigraphy requires the definition of the fundamental model-independent concepts, units, bounding surfaces and workflow that outline the foundation of the method. A standardized scheme needs to be sufficiently broad to encompass all possible choices of approach, rather than being limited to a single approach or model.
A sequence stratigraphic framework includes genetic units that result from the interplay of accommodation and sedimentation (i.e., forced regressive, lowstand and highstand normal regressive, and transgressive), which are bounded by ‘sequence stratigraphic’ surfaces. Each genetic unit is defined by specific stratal stacking patterns and bounding surfaces, and consists of a tract of correlatable depositional systems (i.e., a ‘systems tract’). The mappability of systems tracts and sequence stratigraphic surfaces depends on depositional setting and the types of data available for analysis. It is this high degree of variability in the precise expression of sequence stratigraphic units and bounding surfaces that requires the adoption of a methodology that is sufficiently flexible that it can accommodate the range of likely expressions. The integration of outcrop, core, well-log and seismic data affords the optimal approach to the application of sequence stratigraphy. Missing insights from one set of data or another may limit the ‘resolution’ of the sequence stratigraphic interpretation.
A standardized workflow of sequence stratigraphic analysis requires the identification of all genetic units and bounding surfaces that can be delineated objectively, at the selected scale of observation, within a stratigraphic section. Construction of this model-independent framework of genetic units and bounding surfaces ensures the success of the sequence stratigraphic method. Beyond this, the interpreter may make model-dependent choices with respect to which set of sequence stratigraphic surfaces should be elevated in importance and be selected as sequence boundaries. In practice, the succession often dictates which set of surfaces are best expressed and hold the greatest utility at defining sequence boundaries and quasi-chronostratigraphic units. The nomenclature of systems tracts and sequence stratigraphic surfaces is also model-dependent to some extent, but a standard set of terms is recommended to facilitate communication between all practitioners.
The microstructure and mechanical properties of friction stir (FS) welded SAF 2507 super duplex stainless steel were examined. High-quality, full-penetration welds were successfully produced in the ...super duplex stainless steel by friction stir welding (FSW) using polycrystalline cubic boron nitride (PCBN) tool. The base material had a microstructure consisting of the ferrite matrix with austenite islands, but FSW refined grains of the ferrite and austenite phases in the stir zone through dynamic recrystallisation. Ferrite content was held between 50 and 60% throughout the weld. The smaller grain sizes of the ferrite and austenite phases caused increase in hardness and strength within the stir zone. Welded transverse tensile specimen failed near the border between the stir zone and TMAZ at the retreating side as the weld had roughly the same strengths as the base material.
Since their inception, the Perspectives in Logic and Lecture Notes in Logic series have published seminal works by leading logicians. Many of the original books in the series have been unavailable ...for years, but they are now in print once again. In this volume, the third publication in the Lecture Notes in Logic series, Mitchell and Steel construct an inner model with a Woodin cardinal and develop its fine structure theory. This work builds upon the existing theory of a model of the form LE, where E is a coherent sequence of extenders, and relies upon the fine structure theory of LE models with strong cardinals, and the theory of iteration trees and 'backgrounded' LE models with Woodin cardinals. This work is what results when fine structure meets iteration trees.
Since their inception, the Perspectives in Logic and Lecture Notes in Logic series have published seminal works by leading logicians. Many of the original books in the series have been unavailable ...for years, but they are now in print once again. Large cardinal hypotheses play a central role in modern set theory. One important way to understand such hypotheses is to construct concrete, minimal universes, or 'core models', satisfying them. Since Gödel's pioneering work on the universe of constructible sets, several larger core models satisfying stronger hypotheses have been constructed, and these have proved quite useful. In this volume, the eighth publication in the Lecture Notes in Logic series, Steel extends this theory so that it can produce core models having Woodin cardinals, a large cardinal hypothesis that is the focus of much current research. The book is intended for advanced graduate students and researchers in set theory.
Display omitted
•Metal-based drugs are widely used in the treatment of cancer.•Synergistic activity between ruthenium centers and bioactive ligands.•Multimodal anticancer agents formed from bioactive ...ligands and ruthenium.•Bioactivity of Ru complexes is often determined by monodentate ligands.•Donor atoms of ligands determine the stability of the Ru complexes.
Metallodrugs have a central role in the treatment and diagnosis of diseases. To overcome potential toxicity and equip metal-based anticancer agents with biological activity, the choice of the ligands coordinated to the metal center is essential. A recent strategy to address the shortcomings of current drugs and improve their targeted properties, is to introduce bioactive ligands, which may result in synergistic activity between the metal center and the ligand system. In this review, we discuss such efforts in the development of Ru half-sandwich compounds, a class of promising anticancer agents which have been widely studied. We explore here strategies to introduce monodentately-coordinated bioactive moieties into such metal complexes by a variety of design concepts and review their potential as multimodal anticancer agents.
Objectives
To identify CT features of canine hepatic masses that could be used to determine their divisional or lobar origin.
Materials and Methods
Preoperative, postcontrast CT images of 57 ...surgically resected hepatic masses were reviewed with respect to their size, position relative to the midline, gallbladder and portal vein, nearest recognisable hepatic lobar vein or portal vein and point of contact with the diaphragm and displacement of adjacent organs.
Results
The most prevalent histological diagnoses were hepatocellular carcinoma (n=26; 46%) and adenoma (n=10; 18%). Based on surgical assessment, it was observed that masses originated in the left hepatic division in 30 (53%) instances, central division in seven (12%) and right division in 20 (35%). All masses to the left of midline were left divisional, but only 18/30 (60%) masses to the right of midline were right divisional. Most (26/31; 84%) masses to the left of the gallbladder were left divisional and 84% (16/19) masses to the right of the gallbladder were right divisional. Half (10/20; 50%) of the right‐divisional masses were medial, lateral or dorsal to the portal vein, but all other hepatic masses were ventral to the portal vein. A hepatic lobar vein or portal vein branch adjacent to the mass was observed in 53 (93%) instances; this feature correlated with surgical assessment of the affected division in 53 (93%) hepatic masses and the affected lobe in 32 (56%).
Clinical Significance
Combining CT features of hepatic masses appears to be an accurate method for determining their divisional or lobar origin.
The most widely used, although not as widely documented, explanation for initiation of turbidites is the conversion of catastrophic sediment failures into turbidites. Such instantaneous sediment ...failures generate short-lived surge-type flows that deposit turbidite beds described as Bouma sequences. In this communication, we present data from the Eocene Central Basin of Spitsbergen that shows turbidite systems that are volumetrically dominated by thick ungraded and laminated sandy turbidite beds, deposited by gradual aggradation from sustained flows. Sustained flows are long-lived and more or less continuous. They can be generated by a variety of mechanisms, e.g.: (1) instability during volcanic eruptions and the consequent remobilisation of unconsolidated material; (2) seismically triggered subaerial sliding within the drainage; (3) storm surges; (4) retrogressive slope failure; (5) breaching; and (6) hyperpycnal flows. Our database shows that in the Eocene Central Basin, the sustained flows were generated by hyperpycnal flows, i.e., by direct river effluent.
The hyperpycnal flow turbidites have been recognized on the basis of (1) physical connection between fluvial and turbidite channels at the shelf edge, (2) abundance of thick turbidite sandstone beds, (3) sand-prone nature of the turbidite systems, (4) downslope changes of individual thick, sandy turbidite beds, and their collapsed pinch-out segments, (5) great abundance of continental material (leaves, coal fragments) in turbidite beds, (6) low abundance of associated slumped or debris-flow beds, and (7) the occurrence of turbidites in systematically accreted shelf-margins. These features strongly suggest that hyperpycnal flow, generated by direct river effluent, deposited significant number of turbidite beds in the documented slope and basin-floor turbidite successions. We also argue that the hyperpycnal flows are preferentially fed into the deepwater slopes beyond the shelf edge during the falling stage and lowstand of relative sea level.
The turbidite beds were studied in the context of seismic-scale (1×15 km), dip-oriented outcrops by measuring detailed vertical sections, following individual beds and packages of beds downslope for distances over 5 km, lateral mapping, and helicopter-taken photomosaics.
The concept of frailty, a relative state of weakness reflecting multiple functional and health domains, continues to receive attention within the geriatrics field. It offers a summary of key personal ...characteristics, providing perspective on an individual's life course. There have been multiple attempts to measure frailty, some focusing on physiologic losses, others on specific diseases, disabilities or health deficits. Recently, multidimensional approaches to measuring frailty have included cognition, mood and social components. The purpose of this project was to develop and evaluate a Home Care Frailty Scale and provide a grounded basis for assessing a person's risk for decline that included functional and cognitive health, social deficits and troubling diagnostic and clinical conditions.
A secondary analysis design was used to develop the Home Care Frailty Scale. The data set consisted of client level home care data from service agencies around the world. The baseline sample included 967,865 assessments while the 6-month follow-up sample of persons still being served by the home care agencies consisted of 464,788 assessments. A pool of 70 candidate independent variables were screened for possible inclusion and 16 problem outcomes referencing accumulating declines and clinical complications served as the dependent variables. Multiple regression techniques were used to analyze the data.
The resulting Home Care Frailty Scale consisted of a final set of 29 items. The items fall across 6 categories of function, movement, cognition and communication, social life, nutrition, and clinical symptoms. The prevalence of the items ranged from a high of 87% for persons requiring help with meal preparation to 3.7% for persons who have experienced a recent decline in the amount of food eaten.
The interRAI Home Care Frailty Scale is based on a strong conceptual foundation and in our analysis, performed as expected. Given the use of the interRAI Home Care Assessment System in multiple, diverse countries, the Home Care Frailty Scale will have wide applicability to support program planning and policy decision-making impacting home care clients and their formal and informal caregivers throughout the world.
PDF
