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1,245 results for “hypothesis”
Data from: Asynchronous hatching in a non-avian species: a test of the hurry-up hypothesis
The hurry-up hypothesis suggests that completing reproduction as soon as possible is favoured when the quantity or quality of resources used for breeding declines over time. However, completing reproduction sooner may incur a cost if it leads to an asynchronous hatching pattern that reduces overall growth and survival of offspring. Here, we present the first test of the hurry-up hypothesis in a non-avian system, the burying beetle Nicrophorus vespilloides, which breeds on small vertebrate carcasses. To this end, we conducted two experiments in which we provided females with an incentive to complete reproduction sooner by giving them carcasses that varied either with respect to decomposition (decomposed or fresh) or size. We recorded the delay until laying, and measures of the laying pattern and fitness consequences for the offspring. As predicted, we found that larvae dispersed from the carcass earlier when females commenced oviposition sooner and that laying spread was greater when females commenced egg laying earlier. However, we found no evidence that females commenced egg laying earlier on either decomposed or larger carcasses. Our results suggest that, although asynchronous hatching might emerge as a by-product of parents attempting to complete reproduction sooner, there is no evidence that females attempt to complete reproduction sooner under conditions where this would be favourable. Our results are therefore inconsistent with the hurry-up hypothesis.
Data from: Testing the Münch hypothesis of long distance phloem transport in plants
Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.
Data from: A test of the hypothesis that correlational selection generates genetic correlations
Theory predicts that correlational selection on two traits will cause the major axis of the bivariate G matrix to orient itself in the same direction as the correlational selection gradient. Two testable predictions follow from this: for a given pair of traits (1) the sign of correlational selection gradient should be the same as that of the genetic correlation, and (2) the correlational selection gradient should be positively correlated with the value of the genetic correlation. We test this hypothesis with a meta-analysis utilizing empirical estimates of correlational selection gradients and measures of the correlation between the two focal traits. Our results are consistent with both predictions and hence support the underlying hypothesis that correlational selection generates a genetic correlation between the two traits and hence orients the bivariate G matrix.
Data from: Personality, immune response and reproductive success: an appraisal of the pace-of-life syndrome hypothesis
The pace-of-life syndrome (POLS) hypothesis is an extended concept of the life-history theory that includes behavioural traits. The studies challenging the POLS hypothesis often focus on the relationships between a single personality trait and a physiological and/or life-history trait. While pathogens represent a major selective pressure, few studies have been interested in testing relationships between behavioural syndrome, and several fitness components including immunity. The aim of this study was to address this question in the mealworm beetle, Tenebrio molitor, a model species in immunity studies. The personality score was estimated from a multidimensional syndrome based of four repeatable behavioural traits. In a first experiment, we investigated its relationship with two measures of fitness (reproduction and survival) and three components of the innate immunity (haemocyte concentration, and levels of activity of the phenoloxidase including the total proenzyme and the naturally activated one) to challenge the POLS hypothesis in T. molitor. Overall, we found a relationship between behavioural syndrome and reproductive success in this species, thus supporting the POLS hypothesis. We also showed a sex-specific relationship between behavioural syndrome and basal immune parameters. In a second experiment, we tested whether this observed relationship with innate immunity could be confirmed in term of differential survival after challenging by entomopathogenic bacteria, Bacillus thuringiensis. In this case, no significant relationship was evidenced. We recommend that future researchers on the POLS should control for differences in evolutionary trajectory between sexes and to pay attention to the choice of the proxy used, especially when looking at immune traits.
Data from: Does bat response to traffic noise support the misleading cue hypothesis?
The world has become a noisier place due to the increase in urbanization. Noise is generally considered an impediment, altering an animal's behavior through masking or distraction. But noise can also provide useful information about the environment. For animals that rely on natural environmental noise as an indicator of favorable foraging conditions, increasing levels of anthropogenic noise might mislead informed decision-making. Bats use rain noise, a natural environmental cue, to delay their emergence from the roost, presumably to avoid sensory and metabolic costs associated with foraging in heavy rain. Here we tested the 'misleading cue hypothesis', asking whether traffic noise is mistaken for rain noise by bats. Given the acoustic similarity between rain noise and traffic noise, we predicted that bats would confuse the two. We conducted a playback experiment using rain, traffic, and ambient noise at natural roosts of common big-eared bats (Micronycteris microtis, Phyllostomidae) and recorded bat emergence behavior. In contrast to their response to rain noise, the bats did not delay roost emergence in response to traffic noise. Thus, we found that bats were able to discriminate between traffic noise and rain noise and were not misled by similarity in acoustic parameters in the two noise types, when emerging from their roost. Emerging bats did show more exploration flights during traffic noise than during rain noise, but not during ambient noise, suggesting that they perceive traffic noise as a novel acoustic cue. Our data provides new insights into perception of traffic noise by bats.
Data from: Testing the plant growth-defense hypothesis belowground: do faster-growing herbaceous plant species suffer more negative effects from soil biota than slower-growing ones?
According to the growth-defense hypothesis in ecology, faster-growing plant species should suffer more from herbivores and pathogens than slower-growing species. Tests of this hypothesis have focused on aboveground plant tissues, herbivores, and pathogens; however, it should also apply to root defense. To test whether faster-growing species suffer more negatively from soil biota than slower-growing species, we estimated first-season growth rates of 34 herbaceous plant species and used weighted linear regressions to assess the relationship between growth rates and responses to being grown in sterilized versus unsterilized soil (biotic soil effects) and to growing in soil previously occupied by conspecifics versus a mixture of species (conspecific soil effects). We found a negative relationship between relative growth rate and biotic soil effects, with slower-growing species tending to suffer less or even benefit from the presence of soil biota, while faster-growing species were more negatively affected. Biotic soil effects were also negatively related to size-corrected growth rates. These relationships remained negative after accounting for influential species, but a large amount of variation remained unexplained. Moreover, there was no clear relationship between growth rates and conspecific soil effects. A simple relationship between growth and defense aboveground may not be so clearly reflected belowground because of the many interacting antagonistic and mutualistic organisms likely involved.
Data from: Linking Darwin's naturalisation hypothesis and Elton's diversity‐invasibility hypothesis in experimental grassland communities
1. Darwin's naturalisation hypothesis posing that phylogenetic distance of alien species to native residents predicts invasion success, and Elton's diversity‐invasibility hypothesis posing that diversity of native communities confers resistance to invasion, are both rooted in ideas of species coexistence. Because the two hypotheses are inherently linked, the mechanisms underlying them may interact in driving the invasion success. Even so, these links and interactions have not been explicitly disentangled in one experimental study before. 2. To disentangle the links between the two hypotheses, we used 36 native grassland herbs to create greenhouse mesocosms with 90 grassland communities of different diversities, and introduced each of five herbaceous alien species as seeds and seedlings. We used phylogeny and four functional traits (plant height, specific leaf area, leaf size, seed mass) to calculate different measures of phylogenetic and functional distance and diversity. Specifically, we tested how the alien‐native distance (phylogenetic or functional) and the native diversity (phylogenetic or functional) affected each other in their effects on germination, seedling survival, growth and reproduction of the aliens. 3. Overall, our results supported both hypotheses. Multivariate functional distance based on four traits jointly had stronger positive effects than phylogenetic distance and the univariate ones based on each trait separately. Moreover, the aliens were more successful if they were more competitive by being taller and having larger leaves with a lower SLA than the native residents. Univariate functional diversity based on each trait separately had stronger negative effects than phylogenetic and multivariate functional diversity. Most importantly, we found that the effects of alien‐native phylogenetic and multivariate functional distance became stronger as diversity increased. Our analyses with single traits also showed that the strength of the effects of both alien‐native hierarchical functional distances (indicative of competitive inequalities) and absolute functional distances (indicative of niche differences) increased at higher diversities, where competition is more severe. 4. SynthesisOur study explicitly demonstrates for the first time how the mechanisms underlying the two classical invasion hypotheses interact in driving invasion success in grassland communities. This may help to explain some of the puzzling results of studies testing either of the two hypotheses.
Data from: Testing the phenotype-linked fertility hypothesis in the presence and absence of inbreeding
The phenotype-linked fertility hypothesis suggests that females can judge male fertility by inspecting male phenotypic traits. This is because male sexually selected traits might correlate with sperm quality if both are sensitive to factors that influence male condition. A recent meta-analysis found little support for this hypothesis, suggesting little or no shared condition dependence. However, we recently reported that in captive zebra finches (Taeniopygia guttata) inbreeding had detrimental effects both on phenotypic traits and on measures of sperm quality, implying that variation in inbreeding could induce positive covariance between indicator traits and sperm quality. Therefore, we here assess empirically the average strength of correlations between phenotypic traits (courtship rate, beak colour, tarsus length) and measures of sperm quality (proportion of functional sperm, sperm velocity, sperm length) in populations of only outbred individuals and in mixed populations consisting of inbreds (F = 0.25) and outbreds (F = 0). As expected, phenotype sperm-trait correlations were stronger when the population contained a mix of inbred and outbred individuals. We also found unexpected heterogeneity between our two study populations, with correlations being considerably stronger in a domesticated population than in a recently wild-derived population. Correlations ranged from essentially zero among outbred-only wild-derived birds (mean Fisher's Zr ± SE = 0.03 ± 0.10) to moderately strong among domesticated birds of mixed inbreeding status (Zr ± SE = 0.38 ± 0.08). Our results suggest that, under some conditions, the phenotype-linked fertility hypothesis might apply.
Data from: Evolution of viviparity: a phylogenetic test of the cold-climate hypothesis in Phrynosomatid lizards
The evolution of viviparity is a key life-history transition in vertebrates, but the selective forces favoring its evolution are not fully understood. With >100 origins of viviparity, squamate reptiles (lizards and snakes) are ideal for addressing this issue. Some evidence from field and laboratory studies supports the "cold-climate" hypothesis, wherein viviparity provides an advantage in cold environments by allowing mothers to maintain higher temperatures for developing embryos. Surprisingly, the cold-climate hypothesis has not been tested using both climatic data and phylogenetic comparative methods. Here, we investigate the evolution of viviparity in the lizard family Phrynosomatidae using GIS-based environmental data, an extensive phylogeny (117 species), and recently developed comparative methods. We find significant relationships between viviparity and lower temperatures during the warmest (egg-laying) season, strongly supporting the cold-climate hypothesis. Remarkably, we also find that viviparity tends to evolve more frequently at tropical latitudes, despite its association with cooler climates. Our results help explain this and two related patterns that seemingly contradict the cold-climate hypothesis: the presence of viviparous species restricted to low-elevation tropical regions and the paucity of viviparous species at high latitudes. Finally, we examine whether viviparous taxa may be at higher risk of extinction from anthropogenic climate change.
Data from: Estimating tempo and mode of Y chromosome turnover: explaining Y chromosome loss with the fragile Y hypothesis
Chromosomal sex determination is phylogenetically widespread, having arisen independently in many lineages. Decades of theoretical work provide predictions about sex chromosome differentiation that are well supported by observations in both XY and ZW systems. However, the phylogenetic scope of previous work gives us a limited understanding of the pace of sex chromosome gain and loss and why Y or W chromosomes are more often lost in some lineages than others, creating XO or ZO systems. To gain phylogenetic breadth we therefore assembled a database of 4724 beetle species' karyotypes and found substantial variation in sex chromosome systems. We used the data to estimate rates of Y chromosome gain and loss across a phylogeny of 1126 taxa estimated from seven genes. Contrary to our initial expectations, we find that highly degenerated Y chromosomes of many members of the suborder Polyphaga are rarely lost, and that cases of Y chromosome loss are strongly associated with chiasmatic segregation during male meiosis. We propose the "fragile Y" hypothesis, that recurrent selection to reduce recombination between the X and Y chromosome leads to the evolution of a small pseudoautosomal region (PAR), which, in taxa that require XY chiasmata for proper segregation during meiosis, increases the probability of aneuploid gamete production, with Y chromosome loss. This hypothesis predicts that taxa that evolve achiasmatic segregation during male meiosis will rarely lose the Y chromosome. We discuss data from mammals, which are consistent with our prediction.
Data from: Primates and their pinworm parasites: the Cameron hypothesis revisited
A morphologically based cladistic analysis of the Enterobiinae, which includes most of the Oxyuridae parasitic in Primates, allows a reevaluation of the Cameron's hypothesis of close coevolution with cospeciation between hosts and parasites. Each of the three genera separated in the Enterobiinae fits with one of the suborders defined in Primates: Lemuricola with the Strepsirhini, Trypanoxyuris with the Platyrrhini, and Enterobius with the Catarrhini. Inside each of the three main groups, the subdivisions observed in the parasite tree also fit with many of the subdivisions generally accepted within the Primate order. These results confirm the subgroups previously described in the subfamily and support Cameron's hypothesis in its aspect of association by descent. Although the classification of the Enterobiinae generally closely underlines the classification of Primates, several discordances also are observed. These are discussed case by case, with use of computed reconstruction scenarios. Given that the occurrences of the same pinworm species as a parasite for several congeneric host species is not the generalized pattern, and given that several occurrences also are observed in which the speciations of the parasites describe a more complex network, Cameron's hypothesis of a slower rhythm of speciation in the parasites can be considered partly refuted. The presence of two genera parasitic on squirrels in a family that contains primarily primate parasites also is discussed. The cladistic analysis does not support close relationships between the squirrel parasites and suggests an early separation from the Enterobiinae for the first (Xeroxyuris), and a tardy host-switching from the Platyrrhini to the squirrels for the second (Rodentoxyuris).
Data from: The phenology-substrate-match hypothesis explains decomposition rates of evergreen and deciduous oak leaves.
1. There is substantial evidence that the rate of litter decomposition is affected by the match between the litter substrate and the soil matrix (decomposer community). We introduce and test the phenology-substrate-match hypothesis, which predicts that both litter composition and soil matrix will change over the course of the year, and that a lagged match between litter type and soil matrix will result in an optimal decomposition environment. 2. We conducted a decomposition experiment in a Mediterranean mixed deciduous-evergreen oak savanna in California. We initiated litter decomposition of both a deciduous oak (whose leaves fall in autumn) and an evergreen oak (whose leaves fall in spring) in both autumn and spring. 3. Consistent with the phenology-substrate-match hypothesis, we found that decomposition of deciduous oak litter was accelerated compared to evergreen oak litter when decomposition was initiated in spring, while evergreen litter was accelerated compared to deciduous litter when decomposition was initiated in autumn. 4. We also found a small effect of microsite on leaf decomposition, where both evergreen and deciduous oak leaves decomposed faster under the canopy of a conspecific. 5. Synthesis: Our study extends theory of litter quality and the decomposer community into a temporal context which may be an important source of variation in decomposition rates when species with different litterfall phenologies co-occur.
Data from: Extended haplodiploidy hypothesis
Evolution of altruistic behaviour was a hurdle for the logic of Darwinian evolution. Soon after Hamilton formalised the concept of inclusive fitness, which explains how altruism can evolve, he suggested that the high sororal relatedness brought by haplodiploidy could be why Hymenopterans have a high prevalence in eusocial species, and why helpers in Hymenoptera are always female. Later it was noted that in order to capitalize on the high sororal relatedness, helpers would need to direct help towards sisters, and this would bias the population sex ratio. Under a 1:3 males:females sex ratio, the inclusive fitness valuation a female places on her sister, brother and an own offspring are equal – apparently removing the benefit of helping over independent reproduction. Based on this argumentation, haplodiploidy hypothesis has been considered a red herring. However, here we show that when population sex ratio, cost of altruism, and population growth rate are considered together, haplodiploidy does promote female helping even with female-biased sex ratio, due the lowered cost of altruism in such populations. Our analysis highlights the need to re-evaluate the role of haplodiploidy in the evolution of helping, and the importance of fully exploring the model assumptions when comparing interactions of population sex ratios and social behaviours.
Data from: The nest defence by the red-backed shrike (Lanius collurio) - support for the vulnerability hypothesis
The majority of altricial bird species defend their brood against predators more intensively in nestlings rather than eggs stage. Several hypotheses have been proposed to explain this difference. The majority of existing experimental studies have recorded a gradually increasing intensity of nest defence supporting the reproductive value hypothesis. We have compared nest defence in two nesting stages of the red-backed shrike against two predators of adult birds and against two predators of nests. While the nests with nestlings were defended by parents against three out of four predators, nests with eggs were almost not defended at all. This rapid change in parent nest defence supports rather the vulnerability hypothesis, predicting that the threat to nests with nestlings increases rapidly after hatching, as they became more conspicuous due to their begging and parental provisioning. Unlike most of the species tested previously, the red-backed shrike uses very vigorous mobbing towards predators. We suggest that the occurrence of this active mobbing (strikes, including physical contact) is a good proxy of the current threat to the nest.
Data from: Behavioral, energetic, and color trait integration in guppies: testing the melanocortin hypothesis
Individuals of the same population differ consistently from each other in the average expression of behavioral and physiological traits. Often, such traits are integrated and thus correlated with each other. However, the underlying proximate mechanisms generating and maintaining this among-individual covariation are still poorly understood. The melanocortin hypothesis suggests that the melanocortin pathway can have pleiotropic effects linking the expression of melanin-based coloration with physiological and behavioral traits. In the present study, we test this hypothesis in adult male guppies (Poecilia reticulata), by estimating among individual correlations between behaviors (activity, feeding, boldness, display and chase during courtship), stress response (peak metabolic rate), and coloration (black spot, fuzzy black, orange). The lack of correlation of any behavior or metabolism with black coloration indicates that the melanocortin hypothesis is not supported in this species. However, we observed covariation among coloration traits, as well as among behavioral traits. Our findings suggest that, although there appear to be constraints within sets of related traits, coloration, physiology, and behaviors can potentially evolve as independent modules in response to selection in this species.
Data from: Testing the reproductive groundplan hypothesis in ants (Hymenoptera: Formicidae)
The evolution of complex societies with obligate reproductive division of labour represents one of the major transitions in evolution. In such societies, functionally sterile individuals (workers) perform many of fitness-relevant behaviours including allomaternal ones, without getting any direct fitness benefits. The question of how such worker division of labour has evolved remains controversial. The reproductive groundplan hypothesis (RGPH) offers a powerful proximate explanation for this evolutionary leap. The RGPH argues that the conserved genetic and endocrinological networks regulating fitness relevant behaviour (e g. foraging and brood care) in their solitary ancestors have become decoupled from actual reproduction in the worker caste and now generate worker behavioural phenotypes. However, the empirical support for this hypothesis remains limited to a handful of species making its general validity uncertain. In this study we combine data from the literature with targeted sampling of key species and apply phylogenetically controlled comparative analysis to investigate if the key prediction of the RGPH, namely an association between allomaternal behaviour and a allomaternal physiological state holds in the largest and most species-rich clade of social insects, the ants. Our findings clearly support the RPGH as a general framework to understand the evolution of the worker caste and shed light on one of the major transition in evolutionary history.
Data from: An experimental test of the transmission−virulence trade-off hypothesis in a plant virus
The transmission–virulence trade-off hypothesis is one of the few adaptive explanations of virulence evolution, and assumes that there is an overall positive correlation between parasite transmission and virulence. The shape of the transmission–virulence relationship predicts whether virulence should evolve toward either a maximum or to an intermediate optimum. A positive correlation between each of these traits and within-host growth is often suggested to underlie the relationship between virulence and transmission. There are few experimental tests of this hypothesis; this study reports on the first empirical test on a plant pathogen. We infected Brassica rapa plants with nine natural isolates of Cauliflower mosaic virus and then estimated three traits: transmission, virulence, and within-host viral accumulation. As predicted by the trade-off hypothesis, we observed a positive correlation between transmission and virulence, suggestive of the existence of an intermediate optimum. We discovered the unexpected existence of two groups of within-host accumulation, differing by at least an order of magnitude. When accumulation groups were not accounted for, within-host accumulation was correlated neither to virulence nor transmission, although our results suggest that within each group these correlations exist.
Figure 3 from: Cumming RT, Tirant SL (2021) Drawing the Excalibur bug from the stone: adding credibility to the double-edged sword hypothesis of coreid evolution (Hemiptera, Coreidae). ZooKeys 1043: 117-131. https://doi.org/10.3897/zookeys.1043.67730
Figure 3 Ferriantenna excalibur gen. et sp. nov. holotype A dorsolateral habitus B left antennae lateral and head dorsal C amber specimen #BHM10200800678 showing the inclusion.
Figure 1 from: Cumming RT, Tirant SL (2021) Drawing the Excalibur bug from the stone: adding credibility to the double-edged sword hypothesis of coreid evolution (Hemiptera, Coreidae). ZooKeys 1043: 117-131. https://doi.org/10.3897/zookeys.1043.67730
Figure 1 Examples of ornamentation in live extant coreids. Images A–C, G with expansions on the hind tibiae. Images D–H with hind leg spination D with expansions to the third antennal segment. Images B, C, E–H photographed by Andreas Kay (Ecuador), other images with appropriate citations given individually AAnisocelis flavolineata from Veraguas Province, Panama, photographed by Dirk van der Made (Netherlands) B Unidentified Coreidae from Ecuador CAnisoscelis foliacea from Ecuador DThasus sp. from Santa Cruz County, Arizona, USA, photographed by Alan Schmierer (USA) E Unidentified Coreidae from Ecuador F Unidentified Coreidae from Ecuador GMelucha quinquelineata from Ecuador HPiezogaster cf. humeralis from Ecuador.
Figure 2 from: Cumming RT, Tirant SL (2021) Drawing the Excalibur bug from the stone: adding credibility to the double-edged sword hypothesis of coreid evolution (Hemiptera, Coreidae). ZooKeys 1043: 117-131. https://doi.org/10.3897/zookeys.1043.67730
Figure 2 Artist recreation of the presently known three Cretaceous coreids with elaborate antennae. Illustrations by Liz Sisk (USA). Dorsal habitus scaled to same uniform length to highlight the antennae to body ratios. Colorations are artistic recreations based upon extant coreids rather than the actual specimen, whose color was not preserved in the amber AFerriantenna excalibur gen. et sp. nov. BFerriantenna "club-like antennae" CMagnusantenna wuae.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.