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Most models of animal foraging and consumer choice assume that individuals make choices based on the absolute value of items and are therefore ‘economically rational’. However, frequent violations of rationality by animals, including humans, suggest that animals use comparative valuation rules. Are comparative valuation strategies a consequence of the way brains process information, or are they an intrinsic feature of biological decision-making? Here, we examine the principles of rationality in an organism with radically different information-processing mechanisms: the brainless, unicellular, slime mould Physarum polycephalum. We offered P. polycephalum amoebas a choice between food options that varied in food quality and light exposure (P. polycephalum is photophobic). The use of an absolute valuation rule will lead to two properties: transitivity and independence of irrelevant alternatives (IIA). Transitivity is satisfied if preferences have a consistent, linear ordering, while IIA states that a decision maker's preference for an item should not change if the choice set is expanded. A violation of either of these principles suggests the use of comparative rather than absolute valuation rules. Physarum polycephalum satisfied transitivity by having linear preference rankings. However, P. polycephalum's preference for a focal alternative increased when a third, inferior quality option was added to the choice set, thus violating IIA and suggesting the use of a comparative valuation process. The discovery of comparative valuation rules in a unicellular organism suggests that comparative valuation rules are ubiquitous, if not universal, among biological decision makers.

Spatial memory enhances an organism’s navigational ability. Memory typically resides within the brain, but what if an organism has no brain? We show that the brainless slime mold Physarum polycephalum constructs a form of spatial memory by avoiding areas it has previously explored. This mechanism allows the slime mold to solve the U-shaped trap problem—a classic test of autonomous navigational ability commonly used in robotics—requiring the slime mold to reach a chemoattractive goal behind a U-shaped barrier. Drawn into the trap, the organism must rely on other methods than gradient-following to escape and reach the goal. Our data show that spatial memory enhances the organism’s ability to navigate in complex environments. We provide a unique demonstration of a spatial memory system in a nonneuronal organism, supporting the theory that an externalized spatial memory may be the functional precursor to the internal memory of higher organisms.

The introduction of non-native bee species is a major driver of ecosystem change resulting in the spread of non-native weeds, alterations to plant-pollinator interactions and competition with native species for food and nesting resources. Our lack of ecological information for many non-native organisms hinders our ability to understand the impacts of species introductions. This is often compounded by the Wallacean Shortfall—a lack of adequate knowledge of a species’ distribution in geographic space. In Australia, the African carder bee (Pseudoanthidium (Immanthidium) repetitum) was first observed in 2000 and has since become one of the most common bees in some regions. Despite its rapid population increase and range expansion, little is known about the ecology or distribution of P. repetitum. In this study, we determine the flower preferences, current distribution and predicted areas at risk of future invasion of P. repetitum using opportunistic data collected from citizen science websites, social media and museum records. We found that the current distribution of P. repetitum in Australia encompasses approximately 332,000 km2 concentrated along the eastern coast. We found considerable suitable habitat outside the current distribution including biodiversity hotspots and world heritage listed natural areas. Pseudoanthidium repetitum foraged on a wide range of plants from many families and can thus be classified as a generalist forager (polylectic). Our results suggest that P. repetitum is well suited for continued expansion in coastal Australia. Our results demonstrate the effective application of opportunistic data in overcoming knowledge gaps in species ecology and modelling of introduced species distribution.

As growing urban populations have fewer chances to experience nature, i.e., ‘the extinction of experience’, the subsequent loss of emotional affinities for biodiversity (biophilia) pose major challenges to environmental conservation. Gardening, as an everyday nature interaction and window into invertebrate ecological functioning may offer opportunities to develop biophilia. However, the associations between gardening and biophilia/biophobia towards invertebrates remains untested. We conducted an online survey (n = 443) with adults in Japan about their nature and gardening experiences, demographics, and species identification knowledge in relation to their biophilia (like) and biophobia (dislike, fear, and disgust) towards invertebrates. We also asked participants about their perceptions of invertebrates as ‘beneficials’ or ‘pests’. From responses, we ranked invertebrates according to the attitudes held towards them. We found that frequent gardeners were more likely to express biophilia and perceive invertebrates as beneficial, and generally less likely to express biophobia towards invertebrates. Frequency of visits to recreational parks, but not national/state parks was associated with increased biophilia and reduced dislike and fear of invertebrates. Our results suggest that gardening, in addition to localised nature experiences, acts as a possible pathway towards appreciation of invertebrate biodiversity. We recommend that policymakers and conservation organisations view urban gardening as a potential tool to minimise the negative impacts of the extinction of experience.Implications for insect conservationAs people are more likely to conserve what they love, finding ways to nurture positive attitudes towards insects is critical for the public support needed for successful insect conservation. Considering gardening is a relatively accessible form of nature connection even in cities, our findings of the association between gardening and biophilia towards invertebrates holds promise for potential pathways towards fostering support for insect conservation now and into the future.

A fundamental question in nutritional biology is how distributed systems maintain an optimal supply of multiple nutrients essential for life and reproduction. In the case of animals, the nutritional requirements of the cells within the body are coordinated by the brain in neural and chemical dialogue with sensory systems and peripheral organs. At the level of an insect society, the requirements for the entire colony are met by the foraging efforts of a minority of workers responding to cues emanating from the brood. Both examples involve components specialized to deal with nutrient supply and demand (brains and peripheral organs, foragers and brood). However, some of the most species-rich, largest, and ecologically significant heterotrophic organisms on earth, such as the vast mycelial networks of fungi, comprise distributed networks without specialized centers: How do these organisms coordinate the search for multiple nutrients? We address this question in the acellular slime mold Physarum polycephalum and show that this extraordinary organism can make complex nutritional decisions, despite lacking a coordination center and comprising only a single vast multinucleate cell. We show that a single slime mold is able to grow to contact patches of different nutrient quality in the precise proportions necessary to compose an optimal diet. That such organisms have the capacity to maintain the balance of carbon- and nitrogen-based nutrients by selective foraging has considerable implications not only for our understanding of nutrient balancing in distributed systems but for the functional ecology of soils, nutrient cycling, and carbon sequestration.

A quantitative understanding of the dynamics of bee colonies is important to support global efforts to improve bee health and enhance pollination services. Traditional approaches focus either on theoretical models or data-centred statistical analyses. Here we argue that the combination of these two approaches is essential to obtain interpretable information on the state of bee colonies and show how this can be achieved in the case of time series of intra-day weight variation. We model how the foraging and food processing activities of bees affect global hive weight through a set of ordinary differential equations and show how to estimate the parameters of this model from measurements on a single day. Our analysis of 10 hives at different times shows that the estimation of crucial indicators of the health of honey bee colonies are statistically reliable and fall in ranges compatible with previously reported results. The crucial indicators, which include the amount of food collected (foraging success) and the number of active foragers, may be used to develop early warning indicators of colony failure. Author summary Honey bees are under threat and dying at an alarming rate due to pesticides, parasites, and other stressors. Obtaining information about the health of bee colonies is essential to understand how this happens and to identify measures that can prevent this from happening. Herein, we built a mathematical model of the daily dynamics of hives that allows such information to be extracted without detailed and expensive measurements. Based only on measurements of how the weight of the hive changes during the day, our model can be used to estimate how many bees are collecting food, how successful they are, and how much time they spend outside the hive. Due to its simplicity, the model presented here can be applied to a wide range of hive scale systems and help beekeepers track how healthy and productive their bees are.

A quantitative understanding of the dynamics of bee colonies is important to support global efforts to improve bee health and enhance pollination services. Traditional approaches focus either on theoretical models or data-centred statistical analyses. Here we argue that the combination of these two approaches is essential to obtain interpretable information on the state of bee colonies and show how this can be achieved in the case of time series of intra-day weight variation. We model how the foraging and food processing activities of bees affect global hive weight through a set of ordinary differential equations and show how to estimate the parameters of this model from measurements on a single day. Our analysis of 10 hives at different times shows that the estimation of crucial indicators of the health of honey bee colonies are statistically reliable and fall in ranges compatible with previously reported results. The crucial indicators, which include the amount of food collected (foraging success) and the number of active foragers, may be used to develop early warning indicators of colony failure.

Urban community gardens are potentially important sites for urban pollinator conservation because of their high density, diversity of flowering plants, and low pesticide use (relative to agricultural spaces). Selective planting of attractive crop plants is a simple and cost-effective strategy for attracting flower visitors to urban green spaces, however, there is limited empirical data about which plants are most attractive. Here, we identified key plant species that were important for supporting flower visitors using a network-based approach that combined metrics of flower visitor abundance and diversity on different crop species. We included a metric of ‘popularity’ which assessed how frequently a particular plant appeared within community gardens. We also determined the impact of garden characteristics such as size, flower species richness, and flower species density on the abundance and diversity of flower visitors. Two plant species, Brassica rapa and Ocimum basilicum were identified as being particularly important species for supporting flower visitor populations. Flower species richness had a strong positive effect on both the abundance and diversity of flower visitors. We suggest that gardeners can maximise the conservation value of their gardens by planting a wide variety of flowering plants including attractive plants such as B. rapa and O. basilicum.

How individuals deal with multiple conflicting demands is an important aspect of foraging ecology, yet work on foraging behavior has typically neglected neurologically simple organisms. Here we examine the impact of an abiotic risk (light) and energetic status on the foraging decisions of a protist, the slime mold Physarum polycephalum. We examined patch choice in a “non‐risky” environment by presenting starved and non‐starved P. polycephalum amoebas with a choice between two shaded food patches (one high quality, one low quality). We next examined patch choice in the presence of a conflict between foraging risk (light exposure) and food quality by presenting amoebas with a choice between a shaded, low‐quality patch, and a light‐exposed, high‐quality patch. When both patches were shaded, 100% of amoebas selected the higher quality food patch, irrespective of food‐quality differences or the individual's energetic status. When light exposure and food quality conflicted, amoebas selected the patch with the higher food quality when the quality difference between the patches was high. When the quality difference between patches was small, amoebas selected the shaded, lower quality patch.