Sober and Elgin on laws of biology: a critique

In this short discussion note, I discuss whether any of the generalizations made in biology should be construed as laws. Specifically, I examine a strategy offered by Elliot Sober (1997) and supported by Mehmet Elgin (2006) to reformulate certain biological generalizations so as to eliminate their contingency, thereby allowing them to count as laws. I argue that this strategy entails a conception of laws that is unacceptable on two counts: (1) Sober and Elgin’s approach allows the possibility of formulating laws describing any biological phenomenon whatsoever; and (2) on Sober and Elgin’s view, any interesting contrast between so-called laws and obviously accidental generalizations collapses. I conclude by offering suggestions to refine their view in order to avoid these theoretical problems.     

Chance, explanation, and causation in evolutionary theory

Chance comes into plays at many levels of the explanation of the evolutionary process; but the unity of sense of this category is problematic. The purpose of this talk is to clarify the meaning of chance at various levels in evolutionary theory: mutations, genetic drift, genetic revolutions, ecosystems, macroevolution. Three main concepts of chance are found at these various levels: luck (popular concept), randomness (probabilistic concept), and contingency relative to a given theoretical system (epistemological concept). After identifying which concept(s) of chance fit(s) with these levels, the question is raised whether these concepts can be reduced to a smaller number, and whether chance in evolutionary theory has a subjective or an objective sense.     

Stop competing,start talking!

According to current belief, the molecular networks orchestrating cell death or exit from mitosis upon extended mitotic arrest do not interact, stubbornly executing two parallel biological programs and competing to define a stochastic decision between death and a chance for survival with uncertain destiny. However, recent findings by Diaz‐Martinez et al ( 2014 ) in this issue of The EMBO Journal now call for a reassessment of the “competing network” hypothesis.     

Anthropology and emotion

The centrality of emotion in thought and action is increasingly recognized in the human sciences, though basic questions of definition and scope remain unresolved. Where do emotions begin and end? How should we identify and analyse them? How should we write about them? Ethnographic fieldwork, as pioneered by Malinowski, offers powerful insights into the place of emotion in social life; but emotions are peculiarly difficult to capture in the generalizing format of case study and ethnographic summary. In this article I argue that semantic, structural, and discourse‐based approaches tend to miss what is most important – what counts for the persons concerned and therefore what makes the emotion. I review the conceptual and methodological issues and conclude that only a narrative approach can capture both the particularity and the temporal dimension of emotion, restoring verisimilitude and fidelity to experience.     

Morphological Diversity and the Roles of Contingency,Chance and Determinism in African Cichlid Radiations

Background

Deterministic evolution, phylogenetic contingency and evolutionary chance each can influence patterns of morphological diversification during adaptive radiation. In comparative studies of replicate radiations, convergence in a common morphospace implicates determinism, whereas non-convergence suggests the importance of contingency or chance.

Methodology/Principal Findings

The endemic cichlid fish assemblages of the three African great lakes have evolved similar sets of ecomorphs but show evidence of non-convergence when compared in a common morphospace, suggesting the importance of contingency and/or chance. We then analyzed the morphological diversity of each assemblage independently and compared their axes of diversification in the unconstrained global morphospace. We find that despite differences in phylogenetic composition, invasion history, and ecological setting, the three assemblages are diversifying along parallel axes through morphospace and have nearly identical variance-covariance structures among morphological elements.

Conclusions/Significance

By demonstrating that replicate adaptive radiations are diverging along parallel axes, we have shown that non-convergence in the common morphospace is associated with convergence in the global morphospace. Applying these complimentary analyses to future comparative studies will improve our understanding of the relationship between morphological convergence and non-convergence, and the roles of contingency, chance and determinism in driving morphological diversification.     

Scaling of Size and Dimorphism in Primates I: Microevolution

I used a new quantitative genetics model to predict relationships between sex-specific body size and sex-specific relative variability when populations experience differences in relative intensity of sex-specific selection pressures—stronger selection on males or females—and direction of selection: increase or decrease in size. I combined Lande's (Evolution 34: 292–305) model for the response of sex-specific means to selection with a newly derived generalization of Bulmer's (Am. Nat. 105: 201–211) model for the response of relative variability to selection. I used this combined response model to predict correlations of sex-specific size and relative variability under various starting conditions, which one can compare to correlations between closely related primate populations. One can then compare predicted patterns of sex-specific selection pressures to social and ecological variables pertaining to those populations to identify likely forces producing microevolutionary change in sexual size dimorphism (SSD). I provide examples of this approach for populations representing three taxa: Papio anubis, Saguinus mystax, and Cercopithecus aethiops pygerythrus. Model results suggest that microevolutionary changes in SSD can result from greater selection acting on males or females, and that natural selection or natural and sexual selection combined, rather than sexual selection alone, may sometimes explain sex-specific selection differentials.     

Size,longevity and cancer: age structure

There is significant recent interest in Peto''s paradox and the related problem of the evolution of large, long-lived organisms in terms of cancer robustness. Peto''s paradox refers to the expectation that large, long-lived organisms have a higher lifetime cancer risk, which is not the case: a paradox. This paradox, however, is circular: large, long-lived organisms are large and long-lived because they are cancer robust. Lifetime risk, meanwhile, depends on the age distributions of both cancer and competing risks: if cancer strikes before competing risks, then lifetime risk is high; if not, not. Because no set of competing risks is generally prevalent, it is instructive to temporarily dispose of competing risks and investigate the pure age dynamics of cancer under the multistage model of carcinogenesis. In addition to augmenting earlier results, I show that in terms of cancer-free lifespan large organisms reap greater benefits from an increase in cellular cancer robustness than smaller organisms. Conversely, a higher cellular cancer robustness renders cancer-free lifespan more resilient to an increase in size. This interaction may be an important driver of the evolution of large, cancer-robust organisms.     

Similarity and local co-existence of species in regional biotas

The notion of community-wide character displacement hypothesizes that locally co-existing sets of competing species should be less similar than expected when compared to random expectations from a broader regional species pool. Here I use a mechanistic approach to the niche concept to show how this expectation is dependent on the types of traits involved. I investigate how two different niche components, those that relate to species' requirements (or responses to environmental factors) versus those that relate to species' impacts (or effects on environmental factors), affect predictions about the similarity of locally co-existing species. In contrast with more conventional approaches that focus on species impacts, I focus on species responses to conclude that locally co-existing species should be more similar in such traits than expected on the basis of random assortment from a larger equilibrium regional biota. In addition, I explore the evolutionary implications of exceptions that might favour the co-existence of species with dissimilar traits (especially those that determine species' impacts on the environment) and conclude that these implications differ when species compete for shared resources, interact via shared predators, or interact via both mechanisms. The analysis developed in this paper shows that the co-existence of species that are more similar than expected by chance is not incompatible with the notion of strongly interacting species in saturated local communities near equilibrium.     

Opening the Black Box of Developmental Experiments: Behavioural Mechanisms Underlying Long‐Term Effects of Early Social Experience

Typically, animals spend a considerable portion of their time with social interactions involving mates, offspring, competitors and group members. The social performance during these interactions can strongly depend on the social environment individuals have experienced early in life. Despite a considerable number of experiments investigating long‐term effects of the early social environment, our understanding of the behavioural mechanisms mediating these effects is still limited, mainly for two reasons. (1) Only in few experimental studies have researchers actually observed and quantified the behaviour of their study animals during the social treatment. (2) Even if differences in social interactions between social rearing treatments are reported, these differences might not be causally linked to any observed long‐term effects later in life. The aim of this review was to investigate whether behavioural records of animals during the experimental manipulation of their social environment can help (1) identifying behavioural mechanisms involved in a long‐term effect and (2) obtaining a better understanding of the long‐term consequences of early manipulations. First, I review studies that manipulated the social environment at an early stage of the ontogeny, observed the social interactions and behaviour during the social experience phase and subsequently tested the performance in social and non‐social behavioural tasks at a later life stage. In all reviewed studies, treatment differences were reported both in social interactions during the social experience phase and in social and/or non‐social behaviours later in life. Second, I discuss four classes of behavioural mechanisms that can cause the reported long‐term effects of social experience, namely learning by experience, social learning, sensory stimulation and social cueing. I conclude that social interactions during the social experience phase should always be recorded for at least two reasons. Knowledge about how the social interactions differ between rearing treatments (1) permits researchers to formulate hypotheses about candidate mechanisms causing long‐term effects on behaviour and (2) can help to interpret unexpected outcomes of developmental experiments. Finally, I propose that as a crucial ultimate step towards understanding effects of the early social environment, we should develop targeted experiments testing for the causality of identified candidate mechanism.     

Boldness,Dominance, and Territoriality in the Color Polymorphic Tree Lizard,Urosaurus ornatus

Social dynamics in territorial species often reflect underlying variation in aggression and other aspects of social dominance among individuals. In ornate tree lizards (Urosaurus ornatus), males differing in dewlap color differ in social dominance: while blue males are the dominant, aggressive morph and always territorial, yellow males tend to exhibit a less‐aggressive satellite behavioral tactic. However, in habitats with fewer available territorial resources, yellow males defend territories and increase in relative abundance. These observations suggest that consideration of social dominance alone may be insufficient to explain U. ornatus' territorial dynamics in the wild. Here, we tested how both dominance and another important behavioral trait, boldness, contribute to the outcome of territorial disputes in tree lizards. We recorded the territorial behavior of blue and yellow male tree lizards (entered in pairs) in an experimental arena. At the end of each trial, we then approached each male and recorded whether it fled (shy) or not (bold) in response to our approach. As expected, dominant blue males exploited the higher quality perch more often than yellow males. However, when approached by a simulated predator, blue males were more likely to flee than yellow males. Thus, while blue males are more dominant, yellow is likely the bolder morph. As a result, this morph may be better equipped to defend territories in riskier environments. We conclude that although dominance asymmetries may predictably drive initial territorial interactions among competing males, variation in other behaviors (like boldness) may perturb the long‐term outcome of these interactions across variable environments.     

Partiality,impartiality and the ethics of triage

In this paper, I discuss the question of partiality and impartiality in the application of triage. Triage is a process in medical research which recommends that patients should be sorted for treatment according to the degree or severity of their injury. In employing the triage protocol, however, the question of partiality arises because socially vulnerable groups will be neglected since there is the likelihood that the social determinants of a patient's health may diminish her chance of survival. As a process that is based on the severity of a patient's injury, triage will be unfair, and hence negatively partial, to socially vulnerable people. Thus, I aim in this paper to show that the triage protocol fails as an impartial evaluative process because its only aim is to maximize survivability. I contend that: (i) triage would lead to the neglect of the social condition of patients or victims, and (ii) it will only serve the utilitarian purpose of maximization of outcomes which may not be justified in some cases.     

The social contingency model and olive baboons

A theoretical and illustrative analysis of sequences of actions between pairs of olive baboons (Papio cynocephals anubis) is carried out using the social contingency model originally suggested by Jones and Gerard (1967) in social psychology. The model provides the basis for a step-by-step analysis and a typology. Signals from body postures, facial expressions, and vocalizations are subject to close study by using the model, in a similar fashion to its use in social skills analysis (Argyle, 1988). Sequences are categorized according to individual and joint strategies. Examples are given of three categories of contingency, reactive, mutual, and asymmetrical, which are adapted from their social psychological usage. The model is extended by a new category for competitive relationships between baboons: a conflictive category. The contingencies, as they are shown graphically, have a superficial resemblance to Tinbergen's (1951) zigzag diagrams, but their purpose is distinct in focusing on the detail of both infrequent and repeated interactions. The overall aim of the contingencies is to improve the analysis of social behavior at the proximate level and the model is potentially applicable to observation records at a level of detail that is often not utilized in reporting field studies.     

A randomized trial testing a contingency-based weight loss intervention involving social reinforcement

Even though behavioral weight loss interventions are conducted in groups, a social contingency (SC) paradigm that capitalizes on the social reinforcement potential of the weight loss group has never been tested. We tested a weight loss intervention in which participation in the weight loss group was contingent upon meeting periodic weight goals. We hypothesized that making access to the group dependent upon weight loss would improve weight outcomes. Participants (N = 62; 84% female; 94% white; age = 51.9 ± 9.0; BMI = 34.7 ± 4.5) were randomized to 6‐months of standard behavioral weight loss (SBWL) or to a behavioral program that included a SC paradigm. Both groups engaged in social cohesion activities. Participants in SC who did not meet weight goals did not attend group meetings; instead, they received individual treatment with a new interventionist and returned to group once their weight goals were met. SC did not improve overall weight loss outcomes (SC: ?10.0 ± 4.9 kg, SBWL: ?10.8 ± 6.4 kg, P = 0.63). Similarly, overall weight loss was not significantly different in the subgroup of participants in the SC and SBWL conditions who did not meet periodic weight loss goals (?7.3 ± 4.1 kg vs. ?7.1 ± 3.5 kg, P = 0.90). Surprisingly, “successful” SC participants (who met their weight goals) actually lost less weight than “successful” SBWL participants (?12.4 ± 3.2 kg vs. ?14.5 ± 4.7 kg, P = 0.02). Whereas contingency‐based treatments have been tested for other health behaviors (e.g., substance abuse), this is the first study to test a SC intervention for weight loss. This approach did not improve overall weight loss outcomes. Our attempt to offer appropriate clinical care by providing individual treatment to SC participants when needed may have mitigated the effects of the SC paradigm.     

Durability of Simuliid Silk Pads (Simuliidae,Diptera)

A central aspect of simuliid adaption to life in moving water is a silky secretion which they produce in their salivary glands. This secretion is spread on the substrate surface thereby enabling adhesion of the posterior abdominal hooks of the larvae to the substrate surface. Therefore, silk pads are a prerequisit for simuliid filter‐feeding as well as any kind of locomotive activity. If silk pad adhesion is weak, larvae risk drifting off, either directly or during locomotion. Properties of the adhesive (=silk) as well as the substrate surface may cause weak adhesion. A specialist such as S. noelleri which has little chance of surviving after drifting off its lake outlet habitat, should have adaptations to reduce this risk. Such an adaptation could be very durable silk pads, giving larvae the chance to be safely attached for a relatively long time. In this study larval silk pads of S. ornatum and S. noelleri were stained using Giemsa's staining procedures. Changes in silk pad structure and traces of rot after 2–33 days of exposure to stream water were recorded and compared. Silk pads of S. ornatum and S. noelleri showed differences which indicate differences in ageing processes and biochemistry of this secretion.     

Local and Regional vs. Global Contingency Testing

Contingency analysis of r × c-tables is systematized as follows: Global contingency testing based on the total chisquare under H₀ of independent row and column variables is least favorable to exhaustive interpretation. Local contingency testing based on chi-square components of the individual cells of an r × c-table and realized in Configural frequency analysis (KRAUTH and LIENERT, 1973) is more favourable to substantive interpretation. Compromising between global and local contingency testing leads to so-called generalized local and regional contingency testing. Every contingency testing (local, regional and naturally global) is including all N individuals of a sample supposed to have been drawn randomly from a defined population. Extension to 3-and t-dimensional contingency analysis is outlined, and biomedical applications are discussed.     

Hit‐and‐run trophallaxis of small hive beetles

Some parasites of social insects are able to exploit the exchange of food between nestmates via trophallaxis, because they are chemically disguised as nestmates. However, a few parasites succeed in trophallactic solicitation although they are attacked by workers. The underlying mechanisms are not well understood. The small hive beetle (=SHB), Aethina tumida, is such a parasite of honey bee, Apis mellifera, colonies and is able to induce trophallaxis. Here, we investigate whether SHB trophallactic solicitation is innate and affected by sex and experience. We quantified characteristics of the trophallactic solicitation in SHBs from laboratory‐reared individuals that were either bee‐naïve or had 5 days experience. The data clearly show that SHB trophallactic solicitation is innate and further suggest that it can be influenced by both experience and sex. Inexperienced SHB males begged more often than any of the other groups had longer breaks than their experienced counterparts and a longer soliciting duration than both experienced SHB males and females, suggesting that they start rather slowly and gain more from experience. Successful experienced females and males were not significantly different from each other in relation to successful trophallactic interactions, but had a significantly shorter soliciting duration compared to all other groups, except successful inexperienced females. Trophallactic solicitation success, feeding duration and begging duration were not significantly affected by either SHB sex or experience, supporting the notion that these behaviors are important for survival in host colonies. Overall, success seems to be governed by quality rather than quantity of interactions, thereby probably limiting both SHB energy investment and chance of injury (<1%). Trophallactic solicitation by SHBs is a singular example for an alternative strategy to exploit insect societies without requiring chemical disguise. Hit‐and‐run trophallaxis is an attractive test system to get an insight into trophallaxis in the social insects.     

Social recognition and approach in the chick: lateralization and effect of visual experience

Chicks, Gallus gallus domesticus, tested monocularly on day 3 after hatching recognize familiar versus unfamiliar conspecifics and choose to approach one or other when they use the left eye, whereas they approach familiar and unfamiliar chicks at random when they use the right eye. In experiment 1 we investigated the effects of light exposure of embryos prior to hatching on this particular form of lateralization. Irrespective of whether they hatched from eggs incubated in the dark or from eggs exposed to light during the final days of incubation, chicks using the left eye had higher choice scores (meaning they chose to approach either a familiar or an unfamiliar chick) than chicks using the right eye or both eyes. Therefore, light experience prior to hatching did not influence the lateralization of individual recognition or choice behaviour, although it did affect latency to move out of, and time spent in, the centre of the runway. Experiment 2 showed that visual/social experience posthatching influences choice behaviour: chicks housed in a group in the light for 12 h on day 1 posthatching made a clear choice between familiar and unfamiliar chicks when tested on day 3, but chicks kept in a group in the dark on day 1 did not make a choice, instead alternating between the two stimuli. In experiment 3 we found that posthatching visual/social experience increased the choice scores of chicks using the right eye and thereby removed any lateralization of choice behaviour. The results suggest that visual experience of a social group is required before chicks using their right eye (and left hemisphere) will pay attention to the cues that distinguish one chick from another. Chicks using their left eye (and right hemisphere) recognize the difference between individuals without requiring visual experience with other chicks. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Shifting continents, not behaviours: independent colonization of solitary and subsocial Anelosimus spider lineages on Madagascar (Araneae, Theridiidae)

Agnarsson, I., Kuntner, M., Coddington, J. A. & Blackledge, T. A. (2009). Shifting continents, not behaviours: independent colonization of solitary and subsocial Anelosimus spider lineages on Madagascar (Araneae, Theridiidae). —Zoologica Scripta, 39, 75–87. Madagascar is a biodiversity hotspot, thought to be colonized mostly via Cenozoic dispersal from Africa, followed by endemic radiation of multiple lineages. Anelosimus spiders are diverse in Madagascar, and, like their congeners in the Americas, are most diverse in wet montane forests. Most Anelosimus species are social in that they cooperate in web building and prey capture either during a part of their life cycles (subsocial), including hitherto studied Malagasy species, or permanently (quasisocial). One Central American coastal species, Anelosimus pacificus, has secondarily switched to solitary living, and available evidence suggests that its closest relatives from S. America and Europe are likely also solitary. Here, we show that the only known coastal Anelosimus species in Madagascar and Comoros –Anelosimus decaryi and Anelosimus amelie sp. n. – are also solitary. Using a phylogenetic approach, we test two competing hypotheses: (i) that Malagasy Anelosimus are monophyletic and thus represent a second example of reversal to solitary living in a littoral habitat or (ii) that solitary and subsocial lineages independently colonized Madagascar. We find that solitary Malagasy Anelosimus are closely related to their solitary counterparts from Europe and the Americas, while subsocial Malagasy species nest sister to Anelosimus nelsoni from S. Africa. This finding suggests that (i) the two Anelosimus lineages colonized Madagascar independently and (ii) a reversal to solitary behaviour has occurred only once in Anelosimus. Thus, solitary littoral Malagasy species did not descend from Malagasy mountains, but arrived from much further afar. African and possibly American origin of the two lineages is implied by our findings. To restore natural classification of Anelosimus, Seycellocesa Koçak & Kemal is synonymized with it.     

Social immunity in honeybees—Density dependence,diet, and body mass trade‐offs

Group living is favorable to pathogen spread due to the increased risk of disease transmission among individuals. Similar to individual immune defenses, social immunity, that is antiparasite defenses mounted for the benefit of individuals other than the actor, is predicted to be altered in social groups. The eusocial honey bee (Apis mellifera) secretes glucose oxidase (GOX), an antiseptic enzyme, throughout its colony, thereby providing immune protection to other individuals in the hive. We conducted a laboratory experiment to investigate the effects of group density on social immunity, specifically GOX activity, body mass and feeding behavior in caged honey bees. Individual honeybees caged in a low group density displayed increased GOX activity relative to those kept at a high group density. In addition, we provided evidence for a trade‐off between GOX activity and body mass: Individuals caged in the low group density had a lower body mass, despite consuming more food overall. Our results provide the first experimental evidence that group density affects a social immune response in a eusocial insect. Moreover, we showed that the previously reported trade‐off between immunity and body mass extends to social immunity. GOX production appears to be costly for individuals, and potentially the colony, given that low body mass is correlated with small foraging ranges in bees. At high group densities, individuals can invest less in social immunity than at low densities, while presumably gaining shared protection from infection. Thus, there is evidence that trade‐offs at the individual level (GOX vs. body mass) can affect colony‐level fitness.