On the Ordered Development of Plants 2. Self-thinning in Plant Communities

It is shown that the hypothesis that a growing point on a vegetativeplant requires a minimum rate of supply of assimilate to continuegrowth can quantitatively describe self-thinning in communitiesof Trifolium subterraneum. The hypothesis can also be used toexplain the different relationships observed between mean plantweight and plant density when plants are grown in full daylight,70 per cent shade, and transferred between the two light environments.The implications of the hypothesis to self-thinning in naturalplant communities are discussed. Self-thinning, assimilate, plant development     

Efficacy and honesty in communication between relatives

Abstract The evolution of honest communication has recently become the focus of intense theoretical attention. However, strategic models dealing with honesty have largely ignored the implications of noise and perceptual error for signal evolution (just as models dealing with signal detection in the presence of noise ignore strategic issues). Here, I analyze an extended version of Maynard Smith's strategic model of signaling of need between relatives, the Philip Sidney game, that incorporates the possibility of perceptual error. I show that even in the presence of noise, there exists over a wide range of parameter values a unique, continuously stable signaling equilibrium, at which the signaler employs a costly display when needy but refrains from doing so when healthy. For a subset of this range, there also exists a second, lower cost signaling equilibrium that is not continuously stable. At the former equilibrium, predicted signal cost is inversely related to the coefficient of relatedness (r) between signaler and receiver. Cost is not, however, predicted to drop to zero even when r = 1 and there is no conflict of interest between the two (as is the case in errofree models), because it serves to enhance the efficacy of communication as well as to discourage deceit. Equilibrium signal cost is inversely related to the probability that the signaler is needy, and tends to increase with the level of noise. If noise becomes too great (i.e., if a detectable signal is too costly to produce), signaling is no longer stable; surprisingly, it is also unstable if the level of noise is too low (i.e., if a detectable signal is too cheap to produce).     

Acoustic communication and sexual selection in Orthoptera (Insecta)

Comparison of calling and courtship songs and mating strategies in different groups of Orthoptera shows that acoustic signals in bush crickets (Tettigonioidea) are used for searching conspecific mates at a distance, and song evolution is primarily driven by the acoustic surroundings and simultaneously singing other species. The role of sexual selection in the evolution of acoustic signals in bush crickets is much less important than in the evolution of other nonacoustic signals employed during direct contact. Acoustic signals of crickets (Grylloidea) are involved in both distant and short-range communication. Acoustic courtship signals, along with other courtship components, may offer the material for sexual selection, although, essentially, evolution of acoustic signals in crickets is determined by the acoustic surroundings. Acoustic communication in the grasshoppers of the subfamily Gomphocerinae is mainly a short-distance communication. Acoustic signals of Gomphocerinae are highly variable and elaborate in temporal parameters, and therefore can serve for evaluation of the mate "quality". Song evolution in this group is to a greater extent driven by sexual selection than by the acoustic surroundings and, therefore, could proceed faster than in other groups of Orthoptera and play a major role in speciation.     

Physician perspectives on resuscitation status and DNR order in elderly cancer patients

Aim

To evaluate the process of placing DNR order in elderly cancer patients in practice and analysis of physician perspectives on the issue.

Background

Decision not to resuscitate (DNR/DNAR) is part of practice in elderly cancer care. Physicians issue such orders when a patient is suffering from irreversible disease and the patient''s life is coming to an end. Modern practice emphasises the need of communication with the patients and their relatives while issuing a DNR. The decision making process of placing DNR can be quite daunting. The moral and ethical dimensions surrounding such a decision make it a contentious topic.

Materials and methods

We searched the literature to find relevant works that would help physicians and especially the junior health care staff in dealing with the complexities. In this article, we discuss the issues that physicians encounter whilst dealing with a DNR order in elderly cancer patients.

Results

There are no objective adjuncts or guidelines directed towards the approach of placing a DNR in elderly cancer patients. Better communication with the patients and relatives when making such decision remains a very important aspect of a DNR decision. Most health care staff find themselves ill equipped to deal with such situation. Active training and briefing of junior staff would help them deal better with the stresses involved in this process.

Conclusion

There are complex psychosocial, medical, ethical and emotive aspects associated with placing a DNR order. Patients and their loved ones and the junior staff involved in the care of patient need early communication and briefing for better acceptance of DNR. Studies that could devise or identify tools or recommendations would be welcome.     

The evolutionary sequence: origin and emergences

The evolutionary sequence is being reexamined experimentally from a "Big Bang"origin to the protocell and from the emergence of protocell and variety of species to Darwin's mental power (mind) and society (The Descent of Man). A most fundamentally revisionary consequence of experiments is an emphasis on endogenous ordering. This principle, seen vividly in ordered copolymerization of amino acids, has had new impact on the theory of Darwinian evolution and has been found to apply to the entire sequence. Herein, I will discuss some problems of dealing with teaching controversial subjects.     

Host marking behavior in phytophagous insects and parasitoids

Oviposition behavior in phytophagous insects and entomophagous parasitoids is often modified by the presence of conspecific brood (eggs and larvae). Often, females avoid laying eggs on or in hosts bearing brood, a behavior that acts to reduce the level of competition suffered by their offspring. Avoidance of occupied hosts is typically mediated by cues and/or signals associated with brood. In this article, we review the role of Marking Pheromones (MPs) as signals of brood presence in both phytophagous and entomophagous insects. We place information about the function and evolution of MPs in the context of recent theory in the field of animal communication. We highlight the dynamics of host-marking systems and discuss how effects of MPs vary according to factors such as female experience and egg load. We also examine variation in the form and function of MP communication across a variety of insect taxa. While studies of MP communication in phytophagous insects have focused on the underlying behavioral mechanisms and chemistry of MP communication, studies in entomophagous insects have focused on the functional aspects of MPs and their role in decision-making in insects. We argue that an approach that incorporates the important contributions of both of these somewhat independent, but complementary areas of research will lead to a more complete understanding of MPs in insects. Finally, we suggest that MP systems are model systems for the study of animal signaling and its evolution.     

Explaining Religion without Explaining It Away: Trust, Truth, and the Evolution of Cooperation in Roy A. Rappaport's "The Obvious Aspects of Ritual"

Moving beyond the ecological functionalism of Pigs for the Ancestors, Roy Rappaport's subsequent work on ritual explored how the "obvious aspects" of ritual's formalism and the need to perform it literally embody in its performers expressions of sanctity and truth that counter the threats of lying and alternative inherent in symbolic communication. He recognized that symbolic meaning and truth presuppose social cooperation and trust between individuals, and ritual serves uniquely to reaffirm this mutuality at the level of both individual behavior and conventional meaning. Through a study of male greetings among olive baboons (Papio cynocephalus anubis), this paper illustrates how ritual in Rappaport's sense may indeed intensify cooperation in socially complex but nonlinguistic contexts by establishing a behaviorally transparent means of certifying otherwise opaque individual intentions. Thus, not only may ritual sanctify symbolic communication, but it also may have played a crucial role in its evolution, [ritual, sociocultural evolution, religion and society, symbolic communication, olive baboons, primate social behavior]     

Functionally referential communication in a chimpanzee

The evolutionary origins of the use of speech signals to refer to events or objects in the world have remained obscure. Although functionally referential calls have been described in some monkey species, studies with our closest living relatives, the great apes, have not generated comparable findings. These negative results have been taken to suggest that ape vocalizations are not the product of their otherwise sophisticated mentality and that ape gestural communication is more informative for theories of language evolution. We tested whether chimpanzee rough grunts, which are produced during feeding contexts, functioned as referential signals. Individuals produced acoustically distinct types of "rough grunts" when encountering different foods. In a naturalistic playback experiment, a focal subject was able to use the information conveyed by these calls produced by several group mates to guide his search for food, demonstrating that the different grunt types were meaningful to him. This study provides experimental evidence that our closest living relatives can produce and understand functionally referential calls as part of their natural communication. We suggest that these findings give support to the vocal rather than gestural theories of language evolution.     

Addressing teachers' concerns about teaching evolution

Evolution was introduced into the senior secondary school Life Sciences curriculum in South Africa for the first time in 2008. Research in other countries shows that evolution is an extremely controversial topic to teach, raising serious concerns for teachers. Curriculum change theory dealing with ‘stages of concern’ suggests that teachers implementing a new curriculum move through a predictable series of types of concerns, and that if their initial concerns are not addressed then teachers are slow to move on to more important task-related matters. This has serious implications for both professional development programmes and the development of support materials for teachers: information about teachers' concerns is needed so that those having to support teachers can do so on an informed basis. This article identifies the concerns of 125 secondary school teachers having to teach evolution for the first time. Data was gathered using an activity-based questionnaire administered in a workshop setting to four different groups of biology teachers attending inservice workshops on the teaching of evolution, at stages progressively closer to the implementation date. The majority of concerns identified were early-stage ‘self-concerns’, dealing with personal worries and a need for information. Implications of the findings for providing support for teachers with concerns about teaching evolution are discussed.     

Developmental gene regulation by an ancient intercellular communication system in social amoebae

The social amoebae (Dictyostelia) use quorum sensing-like communication systems to coordinate the periodic transition from uni- to multicellularity. The monophyletic descent of the Dictyostelia provides a unique opportunity to study the origin and adaptive evolution of such intercellular communication systems. We determined that the ability of aggregation-competent cells to respond to the intercellular messenger glorin occurred in the most ancient taxa of the Dictyostelia. We show using Illumina sequencing technology that glorin mediates rapid changes in gene expression at the transition from vegetative growth to aggregation. We conclude that peptide-based communication is the most ancient form of intercellular signaling in the evolution of multicellularity in the social amoebae, but has been repeatedly replaced by other communication systems during the monophyletic evolution of the social amoebae. Glorin communication has parallels with quorum sensing in that the molecule diffuses into the field, stimulates gene expression in receptive cells and coordinates a population-wide response.     

By‐product information can stabilize the reliability of communication

Although communication underpins many biological processes, its function and basic definition remain contentious. In particular, researchers have debated whether information should be an integral part of a definition of communication and how it remains reliable. So far the handicap principle, assuming signal costs to stabilize reliable communication, has been the predominant paradigm in the study of animal communication. The role of by‐product information produced by mechanisms other than the communicative interaction has been neglected in the debate on signal reliability. We argue that by‐product information is common and that it provides the starting point for ritualization as the process of the evolution of communication. Second, by‐product information remains unchanged during ritualization and enforces reliable communication by restricting the options for manipulation and cheating. Third, this perspective changes the focus of research on communication from studying signal costs to studying the costs of cheating. It can thus explain the reliability of signalling in many communication systems that do not rely on handicaps. We emphasize that communication can often be informative but that the evolution of communication does not cause the evolution of information because by‐product information often predates and stimulates the evolution of communication. Communication is thus a consequence but not a cause of reliability. Communication is the interplay of inadvertent, informative traits and evolved traits that increase the stimulation and perception of perceivers. Viewing communication as a complex of inadvertent and derived traits facilitates understanding of the selective pressures shaping communication and those shaping information and its reliability. This viewpoint further contributes to resolving the current controversy on the role of information in communication.     

Linking signal fidelity and the efficiency costs of communication

The handicap principle has been the overarching framework to explain the evolution and maintenance of communication. Yet, it is becoming apparent that strategic costs of signalling are not the only mechanism maintaining signal honesty. Rather, the fidelity of detecting signals can itself be strongly selected. Specifically, we argue that the fidelity of many signals will be constrained by the investment in signal generation and reception by the signaller and perceiver, respectively. Here, we model how investments in signal fidelity influence the emergence and stability of communication using a simple theoretical framework. The predictions of the model indicate that high‐cost communication can be stable whereas low‐cost intermediates are generally selected against. This dichotomy suggests that the most parsimonious route to the evolution of communication is for initial investment in communicative traits to be driven by noncommunicative functions. Such cues can appeal to pre‐existing perceptual biases and thereby stimulate signal evolution. We predict that signal evolution will vary between systems in ways that can be linked to the economics of communication to the two parties involved.     

The sequenced genomes of nonflowering land plants reveal the innovative evolutionary history of peptide signaling

An understanding of land plant evolution is a prerequisite for in-depth knowledge of plant biology. Here we extract and explore information hidden in the increasing number of sequenced plant genomes, from bryophytes to angiosperms, to elucidate a specific biological question—how peptide signaling evolved. To conquer land and cope with changing environmental conditions, plants have gone through transformations that must have required innovations in cell-to-cell communication. We discuss peptides mediating endogenous and exogenous changes by interaction with receptors activating intracellular molecular signaling. Signaling peptides were discovered in angiosperms and operate in tissues and organs such as flowers, seeds, vasculature, and 3D meristems that are not universally conserved across land plants. Nevertheless, orthologs of angiosperm peptides and receptors have been identified in nonangiosperms. These discoveries provoke questions regarding coevolution of ligands and their receptors, and whether de novo interactions in peptide signaling pathways may have contributed to generate novel traits in land plants. The answers to such questions will have profound implications for the understanding of the evolution of cell-to-cell communication and the wealth of diversified terrestrial plants. Under this perspective, we have generated, analyzed, and reviewed phylogenetic, genomic, structural, and functional data to elucidate the evolution of peptide signaling.

The identification of orthologs of Arabidopsis signaling peptides and their receptors in nonflowering plants suggest their importance in cell-to-cell communication in all land plants.     

The facial expression musculature in primates and its evolutionary significance

Facial expression is a mode of close-proximity non-vocal communication used by primates and is produced by mimetic/facial musculature. Arguably, primates make the most-intricate facial displays and have some of the most-complex facial musculature of all mammals. Most of the earlier ideas of primate mimetic musculature, involving its function in facial displays and its evolution, were essentially linear "scala natural" models of increasing complexity. More-recent work has challenged these ideas, suggesting that ecological factors and social systems have played a much larger role in explaining the diversity of structures than previously believed. The present review synthesizes the evidence from gross muscular, microanatomical, behavioral and neurobiological studies in order to provide a preliminary analysis of the factors responsible for the evolution of primate facial musculature with comparisons to general mammals. In addition, the unique structure, function and evolution of human mimetic musculature are discussed, along with the potential influential roles of human speech and eye gaze.     

The function and evolution of child-directed communication

Humans communicate with small children in unusual and highly conspicuous ways (child-directed communication (CDC)), which enhance social bonding and facilitate language acquisition. CDC-like inputs are also reported for some vocally learning animals, suggesting similar functions in facilitating communicative competence. However, adult great apes, our closest living relatives, rarely signal to their infants, implicating communication surrounding the infant as the main input for infant great apes and early humans. Given cross-cultural variation in the amount and structure of CDC, we suggest that child-surrounding communication (CSC) provides essential compensatory input when CDC is less prevalent—a paramount topic for future studies.

Child-directed communication is considered essential for language acquisition, yet appears to be near-absent in some human cultures and in our closest-living relatives, the great apes. This Essay sheds light on the evolution of child-directed and child-surrounding communication.     

Formation of evolutionary approach as an explanatory principle for ecology

Although the connection of ecology with evolutionary idea and specifically with Darwinism was proclaimed for a long time it seems that Herbert Spencer's approach with its emphasize on natural equilibrium was much more often used as its real theoretical base. Elements of Darwinian approach appeared only in 1920-30s in works of those few researchers who studying the distribution and population dynamics of different species tried to understand general mechanisms providing their continuing existence. Later, in the middle of 1950s the first attempts were undertaken to consider the population life history (primarily the age specific schedule of death and reproduction) as a result of natural selection aimed to maintain the necessary level of fitness. A special attention in these studies that burgeoned in 1980-90s was paid to looking for various trade-offs between particular parameters of life history, e.g., between the survival of juveniles and fecundity of adults. The problem of life history optimization became central for the whole branch of science named "evolutionary ecology". Though traditionally this branch is connected with Darwinism, it is rooted rather in Spencer's ideas on moving equilibrium and deals more with static than dynamic. Disproportionately less attention was paid to the evolution of communities since these formations could be hardly interpreted as units of Darwinian selection. Moreover, the ecologists dealing with biosphere as a unified biogeochemical system began insist on "nondarwinian" nature of its evolution. The author considers this opinion as not sufficiently grounded. Darwin's ideas about unavoidable exponential growth, intrinsic for any population, consequent deficiency of resources, and differential survival and reproduction of individuals are still useful while studying the evolution of living organisms (phylogenetics) or the development of biosphere as a global ecosystem.     

Cultural evolution: implications for understanding the human language faculty and its evolution

Human language is unique among the communication systems of the natural world: it is socially learned and, as a consequence of its recursively compositional structure, offers open-ended communicative potential. The structure of this communication system can be explained as a consequence of the evolution of the human biological capacity for language or the cultural evolution of language itself. We argue, supported by a formal model, that an explanatory account that involves some role for cultural evolution has profound implications for our understanding of the biological evolution of the language faculty: under a number of reasonable scenarios, cultural evolution can shield the language faculty from selection, such that strongly constraining language-specific learning biases are unlikely to evolve. We therefore argue that language is best seen as a consequence of cultural evolution in populations with a weak and/or domain-general language faculty.     

The origin and dynamic evolution of chemical information transfer

Although chemical communication is the most widespread form of communication, its evolution and diversity are not well understood. By integrating studies of a wide range of terrestrial plants and animals, we show that many chemicals are emitted, which can unintentionally provide information (cues) and, therefore, act as direct precursors for the evolution of intentional communication (signals). Depending on the content, design and the original function of the cue, there are predictable ways that selection can enhance the communicative function of chemicals. We review recent progress on how efficacy-based selection by receivers leads to distinct evolutionary trajectories of chemical communication. Because the original function of a cue may channel but also constrain the evolution of functional communication, we show that a broad perspective on multiple selective pressures acting upon chemicals provides important insights into the origin and dynamic evolution of chemical information transfer. Finally, we argue that integrating chemical ecology into communication theory may significantly enhance our understanding of the evolution, the design and the content of signals in general.     

Social cognition,Stag Hunts,and the evolution of language

According to the socio-cognitive revolution (SCR) hypothesis, humans but not other great apes acquire language because only we possess the socio-cognitive abilities required for Gricean communication, which is a pre-requisite of language development. On this view, language emerged only following a socio-cognitive revolution in the hominin lineage that took place after the split of the Pan-Homo clade. In this paper, I argue that the SCR hypothesis is wrong. The driving forces in language evolution were not sweeping biologically driven changes to hominin social cognition. Our LCA with non-human great apes was likely already a Gricean communicator, and what came with evolution was not a raft of new socio-cognitive abilities, but subtle tweaks to existing ones. It was these tweaks, operating in conjunction with more dramatic ecological changes and a significant increase in general processing power, that set our ancestors on the road to language.