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  • The capacity for auditory-motor coordination (AMC) is shared by several species, among which humans are most flexible in coordinating with tempo changes. We investigated how humans lose this tempo flexibility at their upper rate limit, and the effect of skill level on this phenomenon. Seven skilled street dancers, including a world champion, and ten non-dancers were instructed to bend their knees according to a metronome beat in a standing position at eight constant beat frequencies (3.8-5 Hz). Although maximum frequency of movement during the task was 4.8 Hz in the non-dancers and 5.0 Hz in the dancers, the rate limit for AMC was 4.1 Hz in the non-dancers and 4.9 Hz in the dancers. These results suggest that the loss of AMC was not due to rate limit of movement execution, but rather due to a constraint on the AMC process. In addition, mediation analysis revealed that a kinematic bias (i.e., the extent of knee flexion during the task) causally affected the extent of phase wandering via mediating factors (e.g., the extent to which movement frequency was reduced relative to the beat frequency). These results add evidence that gravity acts as constraint on AMC involving vertical rhythmic movement.
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  • Data relative to subject 5: single trial time-frequency data created by EEGLAB... Data relative to subject 4: single trial time frequency data created by EEGLAB... subject 3 single trial time frequency data... Data relative to subject 1: single trial time frequency data created by EEGLAB... Data relative to subject 2: single trial time frequency data created by EEGLAB... Data relative to subject 3: single trial time frequency data created by EEGLAB... subject 4 single trial time frequency data... subject 2 single trial time frequency data... subject 5 single trial time frequency data... subject 1 single trial time frequency data
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  • With shifts in island area, isolation, and cycles of island fusion-fission, the role of Quaternary sea-level oscillations as drivers of diversification is complex and not well understood. Here we conduct parallel comparisons of population and species divergence between two island areas of equivalent size that have been affected differently by sea-level oscillations, with the aim to understand the micro- and macroevolutionary dynamics associated with sea-level change. Using genome-wide datasets for a clade of seven Amphiacusta ground cricket species endemic to the Puerto Rico Bank (PRB), we found consistently deeper interspecific divergences and higher population differentiation across the unfragmented Western PRB, in comparison to the currently fragmented Eastern PRB that has experienced extreme changes in island area and connectivity during the Quaternary. We evaluate alternative hypotheses related to the microevolutionary processes (population splitting, extinction and merging) that regulate the frequency of completed speciation across the PRB. Our results suggest that under certain combinations of archipelago characteristics and taxon traits the repeated changes in island area and connectivity may create an opposite effect to the hypothesized “species pump” action of oscillating sea levels. Our study highlights how a microevolutionary perspective can complement current macroecological work on the Quaternary dynamics of island biodiversity.
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    • Sequencing Data
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  • Datasets with results from all simulations of trajectories in 40 different conditions of oscillating optimum for d = 70.... Datasets with results from all simulations of trajectories in 40 different conditions of oscillating optimum for d = 40.... Dataset with the frequency of chaos at each simulation time point for different values of dimensionality (number of traits) d.
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    • Software/Code
    • Tabular Data
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  • The high-frequency wing beat of higher-order insects is driven by self-sustained oscillations of constantly activated flight muscles. However, it remains unknown whether its underlying mechanism is based on flight muscle–specific features or on preexisting contractile functions. Here, we recorded x-ray diffraction movies, at a rate of 5000 frames per second, simultaneously from the two antagonistic flight muscles of bumblebees during wing beat. Signals that occurred at the right timing for triggering each wing-beat stroke were resolved in both muscles. The signals likely reflect stretch-induced myosin deformation, which would also enhance force in vertebrate muscles. The results suggest that insects use a refined preexisting force-enhancing mechanism for high-frequency wing beat, rather than developing a novel mechanism.
    Data Types:
    • Tabular Data
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    • Text
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  • Circadian rhythms are common in many cell types but are reported to be lacking in embryonic stem cells. Recent studies have described possible interactions between the molecular mechanism of circadian clocks and the signaling pathways that regulate stem cell differentiation. Circadian rhythms have not been examined well in neural stem cells and progenitor cells that produce new neurons and glial cells during adult neurogenesis. To evaluate circadian timing abilities of cells undergoing neural differentiation, neurospheres were prepared from the mouse subventricular zone (SVZ), a rich source of adult neural stem cells. Circadian rhythms in mPer1 gene expression were recorded in individual spheres, and cell types were characterized by confocal immunofluorescence microscopy at early and late developmental stages in vitro. Circadian rhythms were observed in neurospheres induced to differentiate into neurons or glia, and rhythms emerged within 3–4 days as differentiation proceeded, suggesting that the neural stem cell state suppresses the functioning of the circadian clock. Evidence was also provided that neural stem progenitor cells derived from the SVZ of adult mice are self-sufficient clock cells capable of producing a circadian rhythm without input from known circadian pacemakers of the organism. Expression of mPer1 occurred in high frequency oscillations before circadian rhythms were detected, which may represent a role for this circadian clock gene in the fast cycling of gene expression responsible for early cell differentiation.
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  • The code and data file provided to us by Janz et al. (2016) and used for their response. Note, that one will need to adjust the sampling frequencies to reflect accurate proportions of specialists and herbivores.
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    • Text
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  • Day length (photoperiod) and temperature oscillate daily and seasonally and are important cues for season-dependent behaviour. Larval diapause of the parasitoid Nasonia vitripennis is maternally induced following a certain number of days (switch point) of a given critical photoperiod (CPP). Both the switch point and CPP follow a latitudinal cline in European N. vitripennis populations,. We previously showed that allelic frequencies of the clock gene period correlate with this diapause induction cline. Here, we report that circadian expression of four clock genes, period (per), cryptochrome-2 (cry-2), clock (clk) and cycle (cyc), oscillates as a function of photoperiod and latitude of origin in wasps from populations from the extremes of the cline. Expression amplitudes are lower in northern wasps, indicating a weaker, more plastic, clock. Northern wasps also have a later onset of activity and longer free running rhythms in constant conditions. Per RNAi caused speeding up of the circadian clock, changed the expression of other clock genes and delayed diapause in both southern and northern wasps. These results point towards adaptive latitudinal clock-gene expression differences and to a key role of per in the timing of photoperiodic diapause induction of N. vitripennis.
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  • Time-Frequency data of the ASD group, related to Figure 2... Time-Frequency data of the control group, related to Figure 2
    Data Types:
    • Software/Code
    • Tabular Data
    • Dataset
  • A fundamental question in evolutionary biology is what promotes genetic variation at non-neutral loci, a major precursor to adaptation in changing environments. In particular, balanced polymorphism under realistic evolutionary models of temporally varying environments in finite natural populations remains to be demonstrated. Here, we propose a novel mechanism of balancing selection under temporally varying fitnesses. Using forward-in-time computer simulations and mathematical analysis, we show that cyclic selection that spatially varies in magnitude, such as along an environmental gradient, can lead to elevated levels of non-neutral genetic polymorphism in finite populations. Balanced polymorphism is more likely with an increase in gene flow, magnitude and period of fitness oscillations, and spatial heterogeneity. This polymorphism-promoting effect is robust to small systematic fitness differences between competing alleles or to random environmental perturbation. Furthermore, we demonstrate analytically that protected polymorphism arises as spatially heterogeneous cyclic fitness oscillations generate a type of storage effect that leads to negative frequency-dependent selection. Our findings imply that spatially variable cyclic environments can promote elevated levels of non-neutral genetic variation in natural populations.
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