Philosophical Transactions of the Royal Society B: Biological Sciences

Dispersal is one of the most fundamental components of ecology, and affects processes as diverse as population growth, metapopulation dynamics, gene flow and adaptation. Although the act of moving from one habitat to another entails major costs to the disperser, empirical and theoretical studies suggest that these costs can be reduced by having morphological, physiological or behavioural specializations for dispersal. A few recent studies on different systems showed that individuals exhibit personality-dependent dispersal, meaning that dispersal tendency is associated with boldness, sociability or aggressiveness. Indeed, in several species, dispersers not only develop behavioural differences at the onset of dispersal, but display these behavioural characteristics through their life cycle. While personality-dependent dispersal has been demonstrated in only a few species, we believe that it is a widespread phenomenon with important ecological consequences. Here, we review the evidence for behavioural differences between dispersers and residents, to what extent they constitute personalities. We also examine how a link between personality traits and dispersal behaviours can be produced and how personality-dependent dispersal affects the dynamics of metapopulations and biological invasions. Finally, we suggest future research directions for population biologists, behavioural ecologists and conservation biologists such as how the direction and the strength of the relationship between personality traits and dispersal vary with ecological contexts.

Pollutants, including synthetic organic materials and heavy metals, are known to adversely affect physiological systems in all animal species studied to date. While many individual chemicals can perturb normal functions, the combined actions of multiple pollutants are of particular concern because they can exert effects even when each individual chemical is present at concentrations too low to be individually effective. The biological effects of pollutants differ greatly between species reflecting differences in the pattern of exposure, routes of uptake, metabolism following uptake, rates of accumulation and sensitivity of the target organs. Thus, understanding of the effects of pollutants on wildlife and ecosystems will require detailed study of many different species, representing a wide range of taxa. However, such studies can be informed by knowledge obtained in more controlled conditions which may indicate likely mechanisms of action and suitable endpoint measurements. Responses may be exacerbated by interactions between the effects of pollutants and environmental stressors, such as under-nutrition or osmotic stresses and so changes in such variables associated with climatic changes may exacerbate physiological responses to pollutant burdens.

Most molecular phylogenetic studies place all placental mammals into four superordinal groups, Laurasiatheria (e.g. dogs, bats, whales), Euarchontoglires (e.g. humans, rodents, colugos), Xenarthra (e.g. armadillos, anteaters) and Afrotheria (e.g. elephants, sea cows, tenrecs), and estimate that these clades last shared a common ancestor 90–110 million years ago. This phylogeny has provided a framework for numerous functional and comparative studies. Despite the high level of congruence among most molecular studies, questions still remain regarding the position and divergence time of the root of placental mammals, and certain ‘hard nodes’ such as the Laurasiatheria polytomy and Paenungulata that seem impossible to resolve. Here, we explore recent consensus and conflict among mammalian phylogenetic studies and explore the reasons for the remaining conflicts. The question of whether the mammal tree of life is or can be ever resolved is also addressed.

This article is part of the themed issue ‘Dating species divergences using rocks and clocks’.

The neurotrophins are a family of polypeptide neuronal growth factors related to the prototypical neurotrophic factor, nerve growth factor (NGF). In mammals this gene family encompasses NGF, brain-derived neurotrophic factor (BDNF) and neurotrophins-3 and -4/5, (NT-3, NT-4/5). The neurotrophins initiate signal transduction in responsive cells by ligand induced dimerization and activation of one of theTrkfamily of receptor tyrosine kinases; NGF being specific for Trk A, BDNF and NT-4/5 for TrkB, and TrkC the preferred receptor for NT-3. In accord with differential patterns of distribution of Trk receptors in peripheral ganglia, the neurotrophins show both distinct and overlapping specificity towards subpopulations of sensory neurons of both neural crest and neural placode origin.In vitroandin vivostudies, and transgenic mice baring targeted null mutations of the neurotrophin genes have established that BDNF, NT-3 and NT-4/5, like NGF, play critical roles as classical target-derived survival factors for subclasses of developing sensory neurons. However, much broader effects of neurotrophins on sensory neurons are now evident, including paracrine and autocrine actions on neuroblast proliferation, phenotypic differentiation, and survival and regeneration in the adult. This article provides an overview of the discovery and properties of the neurotrophin family, their receptors and their actions and specificity for both distinct and overlapping subpopulations of spinal and cranial sensory neurons.

Intraspecific variation in diatoms has been shown to play a key role in species' responses to several important environmental factors such as light, salinity, temperature and nutrients. Furthermore, modelling efforts indicate that this variation within species extends bloom periods, and likely provides sufficient variability in competitive interactions between species under hydrographically variable conditions. The intraspecific variation most likely corresponds to optimal fitness in temporary microhabitats and may help to explain the paradox of the plankton. Here, we examine the implications of intraspecific variation for the ecology and success of diatoms in general and emphasize the potential implications for our understanding of carbon metabolism in these important organisms. Additionally, data from palaeoecological studies have the potential for evaluating genetic variation through past climate changes, going thousands of years back in time. We suggest pathways for future research including the adoption of multiple strains of individual species into studies of diatom carbon metabolism, to refine our understanding of the variation within and between species, and the inclusion of experimental evolution as a tool for understanding potential evolutionary responses of diatom carbon metabolism to climate change.

This article is part of the themed issue ‘The peculiar carbon metabolism in diatoms’.

How and when did hominins move from the numerical cognition that we share with the rest of the animal world to number symbols? Objects with sequential markings have been used to store and retrieve numerical information since the beginning of the European Upper Palaeolithic (42 ka). An increase in the number of markings and complexity of coding is observed towards the end of this period. The application of new analytical techniques to a 44–42 ka old notched baboon fibula from Border Cave, South Africa, shows that notches were added to this bone at different times, suggesting that devices to store numerical information were in use before the Upper Palaeolithic. Analysis of a set of incisions on a 72–60 ka old hyena femur from the Les Pradelles Mousterian site, France, indicates, by comparison with markings produced by modern subjects under similar constraints, that the incisions on the Les Pradelles bone may have been produced to record, in a single session, homologous units of numerical information. This finding supports the view that numerical notations were in use among archaic hominins. Based on these findings, a testable five-stage scenario is proposed to establish how prehistoric cultures have moved from number sense to the use of number symbols.

This article is part of a discussion meeting issue ‘The origins of numerical abilities’.

Emotion is a cultural and psychobiological adaptation mechanism which allows each individual to react flexibly and dynamically to environmental contingencies. From this claim flows a description of the elements theoretically needed to construct a virtual agent with the ability to display human-like emotions and to respond appropriately to human emotional expression. This article offers a brief survey of the desirable features of emotion theories that make them ideal blueprints for agent models. In particular, the component process model of emotion is described, a theory which postulates emotion-antecedent appraisal on different levels of processing that drive response system patterning predictions. In conclusion, investing seriously in emergent computational modelling of emotion using a nonlinear dynamic systems approach is suggested.

Older people are more susceptible to infection, less responsive to vaccination and have a more inflammatory immune environment. Using spectratype analysis, we have previously shown that the B-cell repertoire of older people shows evidence of inappropriate clonal expansions in the absence of challenge, and that this loss of B-cell diversity correlates with poor health. Studies on response to vaccination, using both spectratyping and high-throughput sequencing of the repertoire, indicate that older responses to challenge are lacking in magnitude and/or delayed significantly. Also that some of the biologically significant differences may be in different classes of antibody. We have also previously shown that normal young B-cell repertoires can vary between different phenotypic subsets of B cells. In this paper, we present an analysis of immunoglobulin repertoire in different subclasses of antibody in five different populations of B cell, and show how the repertoire in these different groups changes with age. Although some age-related repertoire differences occur in naive cells, before exogenous antigen exposure, we see indications that there is a general dysregulation of the selective forces that shape memory B-cell populations in older people.

Finch trichomonosis, caused by the protozoal parasiteTrichomonas gallinae, was first recognized as an emerging infectious disease of British passerines in 2005. The first year of seasonal epidemic mortality occurred in 2006 with significant declines of greenfinchCarduelis chlorisand chaffinchFringilla coelebspopulations. Here, we demonstrate that large-scale mortality, principally of greenfinch, continued in subsequent years, 2007–2009, with a shifting geographical distribution across the British Isles over time. Consequent to the emergence of finch trichomonosis, the breeding greenfinch population in Great Britain has declined fromca4.3 million toca2.8 million birds and the maximum mean number of greenfinches (a proxy for flock size) visiting gardens has declined by 50 per cent. The annual rate of decline of the breeding greenfinch population within England has exceeded 7 per cent since the initial epidemic. Although initially chaffinch populations were regionally diminished by the disease, this has not continued. Retrospective analyses of disease surveillance data showed a rapid, widespread emergence of finch trichomonosis across Great Britain in 2005 and we hypothesize that the disease emerged byT. gallinaejumping from columbiforms to passeriforms. Further investigation is required to determine the continuing impact of finch trichomonosis and to develop our understanding of how protozoal diseases jump host species.

In this paper we review recent models that provide adaptive explanations for animal personalities: individual differences in behaviour (or suites of correlated behaviours) that are consistent over time or contexts. We start by briefly discussing patterns of variation in behaviour that have been documented in natural populations. In the main part of the paper we discuss models for personality differences that (i) explain animal personalities as adaptive behavioural responses to differences in state, (ii) investigate how feedbacks between state and behaviour can stabilize initial differences among individuals and (iii) provide adaptive explanations for animal personalities that are not based on state differences. Throughout, we focus on two basic questions. First, what is the basic conceptual idea underlying the model? Second, what are the key assumptions and predictions of the model? We conclude by discussing empirical features of personalities that have not yet been addressed by formal modelling. While this paper is primarily intended to guide empiricists through current adaptive theory, thereby stimulating empirical tests of these models, we hope it also inspires theoreticians to address aspects of personalities that have received little attention up to now.