Do predators prefer toxic animals? A case of chemical discrimination by an asian snake that sequesters firefly toxins

Several Asian natricine snakes of the genus Rhabdophis feed on toads and sequester steroidal cardiac toxins known as bufadienolides (BDs) from them. A recent study revealed that species of the R. nuchalis Group ingest lampyrine fireflies to sequester BDs. Although several species of fireflies are distributed in the habitat of the R. nuchalis Group, only lampyrine fireflies, which have BDs, included in the diet of these snakes. Thus, we hypothesized that the R. nuchalis Group chemically distinguishes fireflies that have BDs from those that do not have BDs. We also predicted that the R. nuchalis Group detects BDs as the chemical cue of toxin source. To test these predictions, we conducted three behavioral experiments using R. chiwen, which belongs to the R. nuchalis Group. In the first experiment, R. chiwen showed a moderate tongue flicking response to cinobufagin, a compound of BDs. On the other hand, the snake showed a higher response to the chemical stimuli of lampyrine fireflies (BD fireflies) than those of lucioline fireflies (non-BD fireflies). In the second experiment, in which we provided live BD and non-BD fireflies, the snake voluntarily consumed only the former. In the third, a Y-maze experiment, the snake tended to select the chemical trail of BD fireflies more frequently than that of non-BD fireflies. These results demonstrated that R. chiwen discriminates BD fireflies from non-BD fireflies, but the prediction that BDs are involved in this discrimination was not fully supported. To identify the proximate mechanisms of the recognition of novel toxic prey in the R. nuchalis Group, further investigation is necessary.

The evolution of quantitative sensitivity

The ability to represent approximate quantities appears to be phylogenetically widespread, but the selective pressures and proximate mechanisms favouring this ability remain unknown. We analysed quantity discrimination data from 672 subjects across 33 bird and mammal species, using a novel Bayesian model that combined phylogenetic regression with a model of number psychophysics and random effect components. This allowed us to combine data from 49 studies and calculate the Weber fraction (a measure of quantity representation precision) for each species. We then examined which cognitive, socioecological and biological factors were related to variance in Weber fraction. We found contributions of phylogeny to quantity discrimination performance across taxa. Of the neural, socioecological and general cognitive factors we tested, cortical neuron density and domain-general cognition were the strongest predictors of Weber fraction, controlling for phylogeny. Our study is a new demonstration of evolutionary constraints on cognition, as well as of a relation between species-specific neuron density and a particular cognitive ability. This article is part of the theme issue ‘Systems neuroscience through the lens of evolutionary theory’.

Dead infant carrying by chimpanzee mothers in the Budongo Forest

It has been suggested that non-human primates (hereafter primates) can respond to deceased conspecifics in ways that suggest they experience psychological states not unlike humans, which would indicate they exhibit some notion of death. Here, we report long-term demographic data from two East African chimpanzee groups. During a combined 40-year observation period we recorded 191 births of which around a third died in infancy, mostly within the first year. We documented the post-mortem behaviour of the mothers and found that Budongo chimpanzee mothers routinely carried deceased infants after their death, usually until the body started to decompose after a few days. However, we also observed three cases of extended carrying lasting for more than 2-weeks, one of which was followed by the unusual extended carrying of a substitute object and another which lasted three months. In each case, the corpses mummified. We discuss these data in view of functional hypotheses of dead infant carrying in primates and regarding the potential proximate mechanisms involved in this behaviour. We suggest that chimpanzees may exhibit psychological processes related to death of conspecifics similar to human grieving.

Sexual Development Dysgenesis in Interspecific Hybrids of Rice Fish

Fish are amongst vertebrates the group with the highest diversity of known sex-determining genes. Particularly, the genus Oryzias is a suitable taxon to understand how different sex determination genetic networks evolved in closely related species. Two closely related species, O. latipes and O. curvinotus, do not only share the same XX/XY sex chromosome system, but also the same male sex-determining gene, dmrt1bY. We performed whole mRNA transcriptomes and morphology analyses of the gonads of hybrids resulting from reciprocal crosses between O. latipes and O. curvinotus. XY male hybrids, presenting meiotic arrest and no production of sperm were sterile, and about 30% of the XY hybrids underwent male-to-female sex reversal. Both XX and XY hybrid females exhibited reduced fertility and developed ovotestis while aging. Transcriptome data showed that male-related genes are upregulated in the XX and XY female hybrids. The transcriptomes of both types of female and of the male gonads are characterized by upregulation of meiosis and germ cell differentiation genes. Differences in the parental species in the downstream pathways of sexual development could explain sex reversal, sterility, and the development of intersex gonads in the hybrids. Our results provide molecular clues for the proximate mechanisms of hybrid incompatibility and Haldane’s rule.

The active grandparent hypothesis: Physical activity and the evolution of extended human healthspans and lifespans

The proximate mechanisms by which physical activity (PA) slows senescence and decreases morbidity and mortality have been extensively documented. However, we lack an ultimate, evolutionary explanation for why lifelong PA, particularly during middle and older age, promotes health. As the growing worldwide epidemic of physical inactivity accelerates the prevalence of noncommunicable diseases among aging populations, integrating evolutionary and biomedical perspectives can foster new insights into how and why lifelong PA helps preserve health and extend lifespans. Building on previous life-history research, we assess the evidence that humans were selected not just to live several decades after they cease reproducing but also to be moderately physically active during those postreproductive years. We next review the longstanding hypothesis that PA promotes health by allocating energy away from potentially harmful overinvestments in fat storage and reproductive tissues and propose the novel hypothesis that PA also stimulates energy allocation toward repair and maintenance processes. We hypothesize that selection in humans for lifelong PA, including during postreproductive years to provision offspring, promoted selection for both energy allocation pathways which synergistically slow senescence and reduce vulnerability to many forms of chronic diseases. As a result, extended human healthspans and lifespans are both a cause and an effect of habitual PA, helping explain why lack of lifelong PA in humans can increase disease risk and reduce longevity.

Atypical functioning of female genitalia explains monandry in a butterfly

Monandrous species are rare in nature, especially in animals where males transfer nutrients to females in the ejaculate. The proximate mechanisms responsible for monandry are poorly studied. In butterflies and moths, the male transfers a nutritious spermatophore into the corpus bursae (CB) of the female. The CB is a multifunctional organ that digests the spermatophore and has partial control of the post-mating sexual receptivity of the female. The spermatophore distends the CB and the post-mating sexual receptivity of the female is inversely proportional to the degree of distension. The CB of many butterfly species has a muscular sheath whose contractions mechanically contribute to digest the spermatophore. As the contents of the CB are absorbed, the degree of distension decreases and the female recovers receptivity. We studied the monandrous butterfly Leptophobia aripa (Boisduval, 1836) (Pieridae) and found that females do not digest the spermatophores. We investigated the structure of the CB and found that a muscular sheath is absent, indicating that in this butterfly females lack the necessary “apparatus” for the mechanical digestion of the spermatophore. We propose that female monandry in this species is result of its incapability to mechanically digest the spermatophore, which results in a constant degree of CB distension after mating and, thus, in the maintenance of the sexually unreceptive state of females. Hypotheses on the evolution of this mechanism are discussed.

Why Sing and Dance: an Examination of the Cooperative Effects of Group Synchrony

<p>The universality and antiquity of music and dance suggest that they may serve some important adaptive function. Why are music and dance cultural universals? One popular theory is that music and dance function to enhance mutually benefiting cooperation. While the cooperation hypothesis finds support from anthropological observations and recent experiments, the proximate mechanisms remain unclear. In this thesis, I examine if being in synchrony is a critical factor underlying music and dance’s cooperative effects. I define synchrony as rhythmically moving or vocalising in time with others. In support of synchrony’s role in fostering cooperation, a number of studies exploring two person interactions have found positive social effects from synchrony. However, it is not clear whether synchrony enhances cooperation in groups larger than two as typical with music and dance. This thesis describes five laboratory experiments that were conducted to investigate: (1) whether group synchrony increases cooperation; and (2) which psychological mechanisms are involved in producing synchrony’s cooperative effects. In the first three experiments, small groups of participants were asked to perform body movements or to vocalise words in time with the same (synchrony condition) or different (asynchrony condition) metronome beats. Cooperative behaviour was measured with a helping scenario and an economic game. A small increase in cooperation was found with synchronous movement compared to asynchronous movement (experiment 1 and 3). However, this difference was only significant with the economic game measure (experiment 3). When vocalisation was isolated (experiment 2), contrary to expectations, the highest level of helping occurred after the asynchrony vocal condition. A plausible explanation for such small and inconsistent effects comes from the method in which synchrony was manipulated. Following previous methodologies, the goal for participants was to entrain to their own beat. Yet in natural human ecologies, synchrony is a product of shared intentionality – the sharing of psychological states to produce collaborative behaviour. To better understand the contribution of shared intentionality, experiments 4 and 5 varied synchrony with shared intentionality, and then measured cooperation. These experiments revealed that when participants worked together to create synchrony, substantial increases in cooperation were found, for both synchronous vocalisations (experiment 4) and for synchronous movements (experiment 5). Synchrony was also found to significantly amplify two key hypothesised mediating variables: perceived similarity and entitativity (the degree to which a collection of people are perceived as a group). Path analysis supported a proposed mechanism by which synchrony combines with shared intentionality to produce greater cooperation through: (1) increased attention to the behaviours of other participants; and (2) reinforcement of successful cooperation. This thesis, therefore, extends previous research on group music and dance in three ways. First, the combined effect of synchrony and shared intentionality is identified as critical to the cooperation enhancing effects of music and dance. Second, it describes plausible mechanisms for how synchrony may lead to increased cooperation. Third, it provides empirical evidence in support of these mechanisms.</p>

Why Sing and Dance: an Examination of the Cooperative Effects of Group Synchrony

<p>The universality and antiquity of music and dance suggest that they may serve some important adaptive function. Why are music and dance cultural universals? One popular theory is that music and dance function to enhance mutually benefiting cooperation. While the cooperation hypothesis finds support from anthropological observations and recent experiments, the proximate mechanisms remain unclear. In this thesis, I examine if being in synchrony is a critical factor underlying music and dance’s cooperative effects. I define synchrony as rhythmically moving or vocalising in time with others. In support of synchrony’s role in fostering cooperation, a number of studies exploring two person interactions have found positive social effects from synchrony. However, it is not clear whether synchrony enhances cooperation in groups larger than two as typical with music and dance. This thesis describes five laboratory experiments that were conducted to investigate: (1) whether group synchrony increases cooperation; and (2) which psychological mechanisms are involved in producing synchrony’s cooperative effects. In the first three experiments, small groups of participants were asked to perform body movements or to vocalise words in time with the same (synchrony condition) or different (asynchrony condition) metronome beats. Cooperative behaviour was measured with a helping scenario and an economic game. A small increase in cooperation was found with synchronous movement compared to asynchronous movement (experiment 1 and 3). However, this difference was only significant with the economic game measure (experiment 3). When vocalisation was isolated (experiment 2), contrary to expectations, the highest level of helping occurred after the asynchrony vocal condition. A plausible explanation for such small and inconsistent effects comes from the method in which synchrony was manipulated. Following previous methodologies, the goal for participants was to entrain to their own beat. Yet in natural human ecologies, synchrony is a product of shared intentionality – the sharing of psychological states to produce collaborative behaviour. To better understand the contribution of shared intentionality, experiments 4 and 5 varied synchrony with shared intentionality, and then measured cooperation. These experiments revealed that when participants worked together to create synchrony, substantial increases in cooperation were found, for both synchronous vocalisations (experiment 4) and for synchronous movements (experiment 5). Synchrony was also found to significantly amplify two key hypothesised mediating variables: perceived similarity and entitativity (the degree to which a collection of people are perceived as a group). Path analysis supported a proposed mechanism by which synchrony combines with shared intentionality to produce greater cooperation through: (1) increased attention to the behaviours of other participants; and (2) reinforcement of successful cooperation. This thesis, therefore, extends previous research on group music and dance in three ways. First, the combined effect of synchrony and shared intentionality is identified as critical to the cooperation enhancing effects of music and dance. Second, it describes plausible mechanisms for how synchrony may lead to increased cooperation. Third, it provides empirical evidence in support of these mechanisms.</p>

Climate change and plant reproduction: trends and drivers of mast seeding change

Climate change is reshaping global vegetation through its impacts on plant mortality, but recruitment creates the next generation of plants and will determine the structure and composition of future communities. Recruitment depends on mean seed production, but also on the interannual variability and among-plant synchrony in seed production, the phenomenon known as mast seeding. Thus, predicting the long-term response of global vegetation dynamics to climate change requires understanding the response of masting to changing climate. Recently, data and methods have become available allowing the first assessments of long-term changes in masting. Reviewing the literature, we evaluate evidence for a fingerprint of climate change on mast seeding and discuss the drivers and impacts of these changes. We divide our discussion into the main characteristics of mast seeding: interannual variation, synchrony, temporal autocorrelation and mast frequency. Data indicate that masting patterns are changing but the direction of that change varies, likely reflecting the diversity of proximate factors underlying masting across taxa. Experiments to understand the proximate mechanisms underlying masting, in combination with the analysis of long-term datasets, will enable us to understand this observed variability in the response of masting. This will allow us to predict future shifts in masting patterns, and consequently ecosystem impacts of climate change via its impacts on masting. This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.

The ecology and evolution of synchronized reproduction in long-lived plants

Populations of many long-lived plants exhibit spatially synchronized seed production that varies extensively over time, so that seed production in some years is much higher than on average, while in others, it is much lower or absent. This phenomenon termed masting or mast seeding has important consequences for plant reproductive success, ecosystem dynamics and plant–human interactions. Inspired by recent advances in the field, this special issue presents a series of articles that advance the current understanding of the ecology and evolution of masting. To provide a broad overview, we reflect on the state-of-the-art of masting research in terms of underlying proximate mechanisms, ontogeny, adaptations, phylogeny and applications to conservation. While the mechanistic drivers and fitness consequences of masting have received most attention, the evolutionary history, ontogenetic trajectory and applications to plant–human interactions are poorly understood. With increased availability of long-term datasets across broader geographical and taxonomic scales, as well as advances in molecular approaches, we expect that many mysteries of masting will be solved soon. The increased understanding of this global phenomenon will provide the foundation for predictive modelling of seed crops, which will improve our ability to manage forests and agricultural fruit and nut crops in the Anthropocene. This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.