Cooperative Behaviors in Group-Living Spider Mites

Cooperative behaviors are evolutionary stable if the direct and/or indirect fitness benefits exceed the costs of helping. Here we discuss cooperation and behaviors akin to cooperation in subsocial group-living species of two genera of herbivorous spider mites (Tetranychidae), i.e., the largely polyphagous Tetranychus spp. and the nest-building Stigmaeopsis spp., which are specialized on grasses, such as bamboo. These spider mites are distributed in patches on various spatial scales, that is, within and among leaves of individual host plants and among individual hosts of single or multiple plant species. Group-living of spider mites is brought about by plant-colonizing foundresses ovipositing at local feeding sites and natal site fidelity, and by multiple individuals aggregating in the same site in response to direct and/or indirect cues, many of which are associated with webbing. In the case of the former, emerging patches are often composed of genetically closely related individuals, while in the case of the latter, local patches may consist of kin of various degrees and/or non-kin and even heterospecific spider mites. We describe and discuss ultimate and proximate aspects of cooperation by spider mites in host plant colonization and exploitation, dispersal, anti-predator behavior, and nesting-associated behaviors and conclude with theoretical and practical considerations of future research on cooperation in these highly rewarding model animals.

The Influence of Ship Rats (Rattus Rattus) on the Habitat Preferences of the House Mouse (Mus Musculus)

<p>As methods and successes of Rattus rattus (ship rat) control progress, particularly in island environments, the importance of managing Mus musculus (house mouse) increases. M. musculus can negatively impact on a variety of native fauna and flora, potentially creating long term cascading effects. M. musculus populations benefit with the reduction in R. rattus abundance and recover sooner from pest control programs. This three-part study investigated the habitat utilisation of M. musculus and how their relationship with R. rattus influences their habitat preferences. Firstly, hypotheses about the habitat preferences of M. musculus were tested over a landscape scale to determine the features of the environment most important to their distribution. Then the direct effect of R. rattus presence on M. musculus habitat-use was investigated in arena trials. Lastly, in the same arenas, canopy cover was tested as an indirect cue for M. musculus to evaluate the presence of R. rattus. Across 32 sites, M. musculus were the most abundant in warm dry habitats. North facing slopes and rank grass cover were the features of the environment that had the strongest relationship with abundance. In arenas M. musculus foraging activity was 52% lower in patches of short grass when R. rattus scent was present but foraging in rank grass and bare ground was not altered, suggesting activity was suppressed not competitive displacement. There were no significant changes in M. musculus foraging behaviour between different canopy treatments. Although a trend of nocturnal foraging activity dropping 26% when high canopy cover was over short grass compared to short grass patches with lower or no canopy treatments may indicate a risky habitat. M. musculus use of dense ground cover was common theme in this study and in the literature. R. rattus do influence the habitat selection of M. musculus though this was with direct presence more than indirect cues.</p>

The Influence of Ship Rats (Rattus Rattus) on the Habitat Preferences of the House Mouse (Mus Musculus)

<p>As methods and successes of Rattus rattus (ship rat) control progress, particularly in island environments, the importance of managing Mus musculus (house mouse) increases. M. musculus can negatively impact on a variety of native fauna and flora, potentially creating long term cascading effects. M. musculus populations benefit with the reduction in R. rattus abundance and recover sooner from pest control programs. This three-part study investigated the habitat utilisation of M. musculus and how their relationship with R. rattus influences their habitat preferences. Firstly, hypotheses about the habitat preferences of M. musculus were tested over a landscape scale to determine the features of the environment most important to their distribution. Then the direct effect of R. rattus presence on M. musculus habitat-use was investigated in arena trials. Lastly, in the same arenas, canopy cover was tested as an indirect cue for M. musculus to evaluate the presence of R. rattus. Across 32 sites, M. musculus were the most abundant in warm dry habitats. North facing slopes and rank grass cover were the features of the environment that had the strongest relationship with abundance. In arenas M. musculus foraging activity was 52% lower in patches of short grass when R. rattus scent was present but foraging in rank grass and bare ground was not altered, suggesting activity was suppressed not competitive displacement. There were no significant changes in M. musculus foraging behaviour between different canopy treatments. Although a trend of nocturnal foraging activity dropping 26% when high canopy cover was over short grass compared to short grass patches with lower or no canopy treatments may indicate a risky habitat. M. musculus use of dense ground cover was common theme in this study and in the literature. R. rattus do influence the habitat selection of M. musculus though this was with direct presence more than indirect cues.</p>

Direct and indirect cues can enable dual-adaptation, but through different learning processes

Switching between motor tasks requires accurate adjustments for changes in dynamics (grasping a cup) or sensorimotor transformations (moving a computer mouse). Dual-adaptation studies have investigated how learning of context-dependent dynamics or transformations is enabled by sensory cues. However, certain cues, such as color, have shown mixed results. We propose that these mixed results may arise from two major classes of cues: "direct" cues, which are part of the dynamic state and "indirect" cues, which are not. We hypothesized that explicit strategies would primarily account for adaptation for an indirect color cue but would be limited to simple tasks while a direct visual separation cue would allow implicit adaptation regardless of task complexity. To test this idea, we investigated the relative contribution of implicit and explicit learning in relation to contextual cue type (colored or visually shifted workspace) and task complexity (one or eight targets) in a dual-adaptation task. We found that the visual workspace location cue enabled adaptation across conditions primarily through implicit adaptation. In contrast, we found that the color cue was largely ineffective for dual adaptation, except in a small subset of participants who appeared to use explicit strategies. Our study suggests that the previously inconclusive role of color cues in dual-adaptation may be explained by differential contribution of explicit strategies across conditions.

Effects of conspecific density on tadpole risk assessment and defensive behaviour

Prey species assess predation risk by using either direct and indirect cues and both may contribute to a proper evaluation of the actual risk. As postulated by the risk assessment hypothesis, conspecific density may also provide useful information for tuning defensive responses. We tested this hypothesis using a combination of five density levels (1, 2, 4, 8 and 16 individuals) of Italian agile frog Rana latastei tadpoles and three treatments (control, predatory cues of common backswimmer Notonecta glauca and a waterjet of tap water as mechanical disturbance). Tadpole activity decreased in response to all stimuli but, as expected, backswimmer cues induced a stronger and lasting response. However, tadpole activity level did not vary with group size, thus providing no support for the risk assessment hypothesis and confirming that conspecific density might have less consistent effects on short-term behavioural responses than morphological and life history traits.

Kin recognition and step-paternal investment: the effect of childhood co-residence duration

Evolutionarily relevant nepotistic kin investment requires reliable kin detection. Evolutionary scholars have argued that childhood co-residence is one of the most important indirect cues for kinship. While childhood co-residence duration has been found to correlate with kin investment in intragenerational studies (i.e., among siblings), intergenerational investigations considering the association between childhood co-residence duration and kin investment have been scarce. Here, we investigate whether the investment of biological and stepfathers is correlated with childhood co-residence duration. We used data from adolescents and adults (aged 17–19, 27–29, and 37–39 years) from the German Panel Analysis of Intimate Relationships and Family Dynamics (Pairfam), wave 2, collected in 2010–2011. Paternal investment was measured as financial and practical help, emotional support, intimacy, and emotional closeness. We found that while stepfathers invested less than biological fathers, both biological and stepfathers’ investments increased with increased childhood co-residence duration in most measures. Financial help correlated with childhood co-residence in stepfathers but not in biological fathers who helped financially more than stepfathers regardless of childhood co-residence duration. Emotional support, intimacy, and emotional closeness were correlated with childhood co-residence in both biological fathers and stepfathers. Practical help did not correlate with co-residence in either father. Thus, our results partially support the hypothesis that childhood co-residence duration serves as a kin detection cue and directs intergenerational altruism.

Direct and indirect cues can enable dual-adaptation, but through different learning processes

Switching between motor tasks requires accurate adjustments for changes in dynamics (grasping a cup) or sensorimotor transformations (moving a computer mouse). Dual-adaptation studies have investigated how learning of context-dependent dynamics or transformations is enabled by sensory cues. However, certain cues, such as color, have shown mixed results. We propose that these mixed results may arise from two major classes of cues: "direct" cues, which are part of the dynamic state and "indirect" cues, which are not. We hypothesized that explicit strategies would primarily account for adaptation for an indirect color cue but would be limited to simple tasks while a direct visual separation cue would allow implicit adaptation regardless of task complexity. To test this idea, we investigated the relative contribution of implicit and explicit learning in relation to contextual cue type (colored or visually shifted workspace) and task complexity (one or eight targets) in a dual-adaptation task. We found that the visual workspace location cue enabled adaptation across conditions primarily through implicit adaptation. In contrast, we found that the color cue was largely ineffective for dual adaptation, except in a small subset of participants who appeared to use explicit strategies. Our study suggests that the previously inconclusive role of color cues in dual-adaptation may be explained by differential contribution of explicit strategies across conditions.

Mechanically Activated Extracellular Vesicle Functionalised Melt Electrowritten Materials for Bone Regeneration: A Mechano-Biomimetic Scaffold

Mechanobiological cues arising directly via tissue/scaffold mechanics or indirectly via mechanically activated cell secretomes represent potent stimuli that mediate cell behaviour and tissue adaptation. Exploiting these cues in regeneration strategies holds great promise for tissue repair. In this study, we harness indirect biophysical cues originating from osteocytes in a combination with direct biophysical cues from Melt ElectroWritten (MEW) scaffolds to form a single engineered construct with the aim of synergistically enhancing osteogenesis. The secretome of mechanically activated osteocytes was collected within conditioned media (CM) and extracellular vesicles (EV) were subsequently isolated. Building on MEW micro-fibrous scaffolds with controlled microarchitecture and mineral nanotopography optimised for bone repair, a protocol was developed to functionalise these materials with CM or EVs. Human MSC proliferation was enhanced in both CM and EV functionalised scaffolds. EV functionalised scaffolds were further found to significantly enhance MSC osteogenesis, with enhanced alkaline phosphatase expression, collagen production, and mineralisation compared to control scaffolds. Furthermore, enhanced formation of mineralised nodules was identified in EV functionalised materials. Combining direct biophysical cues provided by the fibrous architecture/mineral nanotopography with the indirect cues provided by EVs, these constructs hold great promise to enhance the repair of damaged bone in a physiologically relevant manner.

The influence of pupil responses on subjective brightness perception

When pupil size changes, the amount of light that falls onto the retina changes as well. However, in daily life, this does not make us perceive the world as brighter or darker. There are many indirect cues in our environment (e.g., ambient light intensity, world knowledge about object brightness) that support brightness constancy. Here we asked whether pupil-size changes influence subjective brightnessin the absence of such indirect cues. To investigate this, we measured the subjective brightness of a tester stimulus relative to a referent stimulus as a function of pupil size during presentation of the tester. In Experiment 1, we manipulated pupil size by varying memory load in a working-memory task (i.e., larger pupils with higher load as well as after incorrect responses). We found some evidence that the tester stimulus was perceived as darker when pupils were larger. In Experiment 2, we presented a red or blue display (i.e., larger pupils with red light). Here, we again found that the tester stimulus was perceived as darker when pupils were larger. We speculate that the visual system takes pupil size into account when making brightness judgements, possibly even relying on a large-pupils- indicate-darkness heuristic; this could explain why large pupils lead to an underestimation of brightness, despite an increase in light influx. (And also why a recent study using a pharmacological manipulation of pupil size, which the visual system can likely not take into account, found the opposite pattern.) This is an intriguing step towards understanding the role of pupil size in brightness perception.

Designing Personas for Expressive Robots

Imbuing robots with personality has been shown to be an effective design approach in HRI, promoting user trust and acceptance. We explore personality design in a non-anthropomorphic voice-assisted home robot. Our design approach developed three distinct robot personas: Butler, Buddy, and Sidekick, intended to differ in proactivity and emotional impact. Persona differences were signaled to users by a combination of humanoid (speech, intonation), and indirect cues (colors and movement). We use Big Five personality theory to evaluate perceived differences between personas in an exploratory Wizard of Oz study. Participants were largely able to recognize underlying personality traits expressed through these cue combinations in ways that were consistent with our design goals. The proactive Buddy persona was judged as more Extravert than the more passive Sidekick persona, and the Butler persona was perceived as more Conscientious and less Neurotic than either Buddy or Butler personas. Users also had clear preferences between different personas; they wanted robots that mimicked but accentuated their own personality. Results suggest that future designs might exploit abstract cues to signal personality traits.