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23 results for “alternative hypotheses”
Testing alternative hypotheses for the decline of cichlid fish in Lake Victoria using fish fossils time series from sediment cores
<p>Lake Victoria is well known for its high diversity of endemic fish species that provide livelihoods for millions of people. The lake garnered widespread attention during the twentieth century as major environmental and ecological changes modified the fish community with the extinction of ~40% of endemic cichlid species by the 1980s. Suggested causal factors include anthropogenic eutrophication, fishing, and introduced non-native species but their relative importance remains unresolved because monitoring data started in the 1970s when changes were already underway. Here, for the first time, we reconstruct two time series, covering the last ~200 years, of fish assemblage using fish teeth preserved in lake sediments. Two sediment cores Lake Victoria (Mwanza Gulf), were subsampled continuously at intra-decadal resolution, and teeth were identified to major taxa: Cyprinoidea, Haplochromini, Mochokidae, and Oreochromini. None of the fossils could be confidently assigned to non-native Nile Perch. Our data show significant decreases in haplochromine and oreochromine cichlid fish abundances began long before Nile Perch's arrival, while cyprinoids have generally been increasing. Our study is the first to reconstruct a time series of fish assemblage in Lake Victoria extending deeper back in time than the past 50 years, helping shed light on processes underlying Lake Victoria's biodiversity loss.</p>
Fig. 164. Three alternative phylogeographic hypotheses. A in Mammals Of The Rio Juruá And The Evolutionary And Ecological Diversification Of Amazonia
Fig. 164. Three alternative phylogeographic hypotheses. A: Primary Diversification: reciprocally monophyletic and sister clades bounded by a river that imposed itself on an existing species range. B: Secondary Contact: reciprocally monophyletic, but nonsister clades, bounded by a river that served as the secondary meeting point of clades that evolved elsewhere. C: Dispersal: paraphyletic relationship of right bank haplotypes relative to left bank ones due to one episode of crossriver transfer. See text for further explanation.
Testing alternative hypotheses for the decline of cichlid fish in Lake Victoria using fish fossils time series from sediment cores
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Negotiations Over Parental Care: A Test of Alternative Hypotheses in the Clown Anemonefish
<p>In species with biparental care, conflict arises over how much each parent provides to their offspring because both parents benefit from shifting the burden of care to the other. Here, we tested alternative hypotheses for how parents will negotiate offspring care using a wild population of clownfish (Amphiprion percula). We experimentally handicapped parents by fin-clipping the female in 23 groups, the male in 23 groups, and neither parent in 23 groups and measured changes in indicators of female, male, and pair effort in response to handicapping. First, we found that handicapping resulted in a decrease in the number of eggs laid by fin-clipped females and a decrease in the amount of parental care by fin-clipped males. Second, contrary to predictions, female effort did not change in response to the male being handicapped, or vice versa. Finally, the number of embryos that matured to hatching, an indicator of pair effort, was not influenced by the manipulation, suggesting that although the handicap was effective, clownfish do not face the predicted "cost to conflict" when one parent is handicapped. Together, these results test the generality of theoretical predictions and uncover novel questions about whether and how negotiations operate in systems where interests are aligned.</p>
Biological links between personality and plasticity: testing some alternative hypotheses
<p><span class="NormalTextRun SCXW35858018 BCX0">When organisms respond </span><span class="NormalTextRun SCXW35858018 BCX0">behaviorally </span><span class="NormalTextRun SCXW35858018 BCX0">to a stimulus, they </span><span class="NormalTextRun SCXW35858018 BCX0">exhibit</span><span class="NormalTextRun SCXW35858018 BCX0"> plasticity, but s</span><span class="NormalTextRun SCXW35858018 BCX0">ome individuals respond to the same stimulus </span><span class="NormalTextRun SCXW35858018 BCX0">consistently </span><span class="NormalTextRun SCXW35858018 BCX0">di</span><span class="NormalTextRun SCXW35858018 BCX0">fferently than others</span><span class="NormalTextRun SCXW35858018 BCX0">, thereby </span><span class="NormalTextRun SCXW35858018 BCX0">also </span><span class="NormalTextRun SCXW35858018 BCX0">exhibiting</span><span class="NormalTextRun SCXW35858018 BCX0"> personality differences</span><span class="NormalTextRun SCXW35858018 BCX0">. </span><span class="NormalTextRun SCXW35858018 BCX0">Parent house sparrows </span><span class="NormalTextRun SCXW35858018 BCX0">express </span><span class="NormalTextRun SCXW35858018 BCX0">individual differences in how often they feed offspring and how that feeding rate changes with nestling age</span><span class="NormalTextRun SCXW35858018 BCX0">. </span><span class="NormalTextRun SCXW35858018 BCX0">Mean feeding rate and its slope with respect to nestling age were positively correlated at median nestling ages but no</span><span class="NormalTextRun SCXW35858018 BCX0">t at hatching, </span><span class="NormalTextRun SCXW35858018 BCX0">indicating</span><span class="NormalTextRun SCXW35858018 BCX0"> that </span><span class="NormalTextRun SCXW35858018 BCX0">individuality is primarily in plasticity</span><span class="NormalTextRun SCXW35858018 BCX0">.</span> <span class="NormalTextRun SCXW35858018 BCX0">Individual differences </span><span class="NormalTextRun SCXW35858018 BCX0">could </span><span class="NormalTextRun SCXW35858018 BCX0">arise due to</span> <span class="NormalTextRun SCXW35858018 BCX0">1) interacti</span><span class="NormalTextRun SCXW35858018 BCX0">ons</span><span class="NormalTextRun SCXW35858018 BCX0"> between environmental variables, 2) differences in underlying state or 'quality', or 3) differences in the ability to </span><span class="NormalTextRun SCXW35858018 BCX0">update</span><span class="NormalTextRun SCXW35858018 BCX0"> cues</span> <span class="NormalTextRun SCXW35858018 BCX0">of changing nestling demand</span><span class="NormalTextRun SCXW35858018 BCX0">. Individual slopes were modestly repeatable across breeding attempts, </span><span class="NormalTextRun SCXW35858018 BCX0">hinting at the </span><span class="NormalTextRun SCXW35858018 BCX0">likely action</span><span class="NormalTextRun SCXW35858018 BCX0"> of </span><span class="NormalTextRun SCXW35858018 BCX0">additional</span><span class="NormalTextRun SCXW35858018 BCX0"> environmental variables</span><span class="NormalTextRun SCXW35858018 BCX0">, but</span><span class="NormalTextRun SCXW35858018 BCX0"> only brood size </span><span class="NormalTextRun SCXW35858018 BCX0">was important</span><span class="NormalTextRun SCXW35858018 BCX0">.</span><span class="NormalTextRun SCXW35858018 BCX0"> I also found </span><span class="NormalTextRun SCXW35858018 BCX0">few</span><span class="NormalTextRun SCXW35858018 BCX0"> correlates suggesting quality differences. </span><span class="NormalTextRun SCXW35858018 BCX0">I used short-term brood size manipulations at two nestling ages to test divergent predictions between the t</span><span class="NormalTextRun SCXW35858018 BCX0">h</span><span class="NormalTextRun SCXW35858018 BCX0">ree hypotheses. The pattern of correlations between response </span><span class="NormalTextRun SCXW35858018 BCX0">to the manipulation </span><span class="NormalTextRun SCXW35858018 BCX0">and individual slope did not fit any single hypothesis. </span><span class="NormalTextRun SCXW35858018 BCX0">Patterns of s</span><span class="NormalTextRun SCXW35858018 BCX0">parrow parental care </span><span class="NormalTextRun SCXW35858018 BCX0">reveal </span><span class="NormalTextRun SCXW35858018 BCX0">that personality and plasticity are not cleanly </span><span class="NormalTextRun SCXW35858018 BCX0">separable, </span><span class="NormalTextRun SCXW35858018 BCX0">and their biology is </span><span class="NormalTextRun SCXW35858018 BCX0">likely intertwined</span><span class="NormalTextRun SCXW35858018 BCX0">. </span><span class="NormalTextRun SCXW35858018 BCX0">N</span><span class="NormalTextRun SCXW35858018 BCX0">ew thinking may be needed about the factors parents use in decisions about care and the</span><span class="NormalTextRun SCXW35858018 BCX0"> relevant</span><span class="NormalTextRun SCXW35858018 BCX0"> fitness consequences</span><span class="NormalTextRun SCXW35858018 BCX0">.</span></p>
Negotiations Over Parental Care: A Test of Alternative Hypotheses in the Clown Anemonefish
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Biological links between personality and plasticity: testing some alternative hypotheses
Open the record for dataset details and reuse information.
Negotiations over offspring care: a test of alternative hypotheses in the clown anemonefish
<p>In species with biparental care, conflict arises over how much each parent provides to their offspring because both benefit from shifting the burden of care to the other. Here, we tested alternative models for how parents negotiate offspring care using a wild population of clownfish (<i>Amphiprion percula</i>). Using 60 breeding groups, we experimentally handicapped parents by fin-clipping the female in 20 groups, the male in 20 groups, and neither parent in 20 groups and measured changes in female, male, and pair combined effort in response to handicapping. First, we found that handicapping resulted in a decrease in the number of eggs laid by fin-clipped females and a decrease in the amount of parental care by fin-clipped males. Second, contrary to predictions, female effort did not change in response to the male being handicapped, or vice versa. Finally, the number of embryos that matured to hatching, an indicator of pair effort, was not influenced by the manipulation, suggesting that although the handicap was effective, clownfish do not face the predicted "cost to conflict" when one parent is handicapped. Together, these results question the generality of current theoretical predictions and expand our understanding of the diverse possible outcomes of parental conflict.</p>
Data from: Testing alternative hypotheses for evolutionary diversification in an African songbird: rainforest refugia versus ecological gradients
Geographic isolation in rainforest refugia and local adaptation to ecological gradients may both be important drivers of evolutionary diversification. However, their relative importance and the underlying mechanisms of these processes remain poorly understood because few empirical studies address both putative processes in a single system. A key question is to what extent is divergence in signals that are important in mate and species recognition driven by isolation in rainforest refugia or by divergent selection across ecological gradients? We studied the little greenbul, Andropadus virens, an African songbird, in Cameroon and Uganda, to determine whether refugial isolation or ecological gradients better explain existing song variation. We then tested whether song variation attributable to refugial or ecological divergence was biologically meaningful using reciprocal playback experiments to territorial males. We found that much of the existing song variation can be explained by both geographic isolation and ecological gradients, but that divergence across the gradient, and not geographic isolation, affects male response levels. These data suggest that ecologically divergent traits, independent of historical isolation during glacial cycles, can promote reproductive isolation. Our study provides further support for the importance of ecology in explaining patterns of evolutionary diversification in ecologically diverse regions of the planet.
Comparing the strength of modular signal, and evaluating alternative modular hypotheses, using covariance ratio effect sizes with morphometric data
<p>The study of modularity is paramount for understanding trends of phenotypic evolution, and for determining the extent to which covariation patterns are conserved across taxa and levels of biological organization. However, biologists currently lack quantitative methods for statistically comparing the strength of modular signal across datasets, and a robust approach for evaluating alternative modular hypotheses for the same dataset. As a solution to these challenges, we propose an effect size measure (Z_CR) derived from the covariance ratio, and develop hypothesis-testing procedures for their comparison. Computer simulations demonstrate that Z_CR displays appropriate statistical properties and low levels of misspecification, implying that it correctly identifies modular signal, when present. By contrast, alternative methods based on likelihood (EMMLi) and goodness of fit (MINT) suffer from high false positive rates and high model misspecification rates. An empirical example in sigmodontine rodent mandibles is provided to illustrate the utility of Z_CR for comparing modular hypotheses. Overall, we find that covariance ratio effect sizes are useful for comparing patterns of modular signal across datasets or for evaluating alternative modular hypotheses for the same dataset. Finally, the statistical philosophy for pairwise model comparisons using effect sizes should accommodate any future analytical developments for characterizing modular signal.</p>
Data from: Evolution of leap-frog migration: A test of alternative hypotheses
<p>Leap-frog migration is a common migration pattern in birds where the breeding and wintering latitudes between populations are in reversed latitudinal sequence. Competition for wintering and breeding sites has been suggested to be an ultimate factor and several competitor-based hypotheses have been proposed to explain this pattern. If wintering sites close to the breeding sites are favored, competitive exclusion could force subdominant individuals to winter further away. Competitive exclusion could be mediated either through body size or by prior occupancy. The alternative "spring predictability" hypothesis assumes competition for sufficiently close wintering areas, allowing the birds to use autocorrelated weather cues to optimally time spring migration departure. To test predictions and assumptions of these hypotheses, we combined morphometrics, migration and weather data from four populations of common ringed plover breeding along a latitudinal (56-68°N) and climatic gradient (temperate to Arctic). Critical for our evaluation was that two populations were breeding on the same latitude in subarctic Sweden and had the same distance to the closest potential wintering site, but differ in breeding phenology, and wintered in West Africa and Europe, respectively. Thus, while breeding on the same latitude, their winter distribution overlapped with that of an Arctic and temperate population, respectively. Body size was largest within the temperate population, but there was no size difference between the two subarctic. Populations wintering in Europe arrived there before populations wintering in Africa. The largest variation in arrival of meteorological spring occurred at the temperate breeding site, while there was almost no difference among the other sites. In general, temperatures at the northernmost wintering area correlated well with each breeding site prior to breeding site-specific spring arrival. Based on these observations, we conclude that competitive exclusion through body-size related dominance cannot explain leap-frog migration. Furthermore, the assumptions on which the 'spring predictability' hypothesis is based did not match the observed wintering ranges either. However, we could not reject the hypothesis that competitive exclusion mediated by prior occupancy in the wintering area could lead to leap-frog migration, and therefore this hypothesis should be retained as working hypothesis for further work.</p>
Data from: Does functional trait diversity predict aboveground biomass and productivity of tropical forests? Testing three alternative hypotheses
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Negotiations over offspring care: a test of alternative hypotheses in the clown anemonefish
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Stamen dimorphism in bird-pollinated flowers – investigating alternative hypotheses on the evolution of heteranthery
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Comparing the strength of modular signal, and evaluating alternative modular hypotheses, using covariance ratio effect sizes with morphometric data
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Data from: Testing alternative hypotheses for evolutionary diversification in an African songbird: rainforest refugia versus ecological gradients
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Data from: Evolution of leap-frog migration: A test of alternative hypotheses
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Data from: Is sociality required for the evolution of communicative complexity? Evidence weighed against alternative hypotheses in diverse taxonomic groups
Complex social communication is expected to evolve whenever animals engage in many and varied social interactions; that is, sociality should promote communicative complexity. Yet informal comparisons among phylogenetically independent taxonomic groups seem to cast doubt on the putative role of social factors in the evolution of complex communication. Here, we provide a formal test of the sociality hypothesis along side alternative explanations for the evolution of communicative complexity. We compiled data documenting variation in signal complexity among closely related species for several case study groups – ants, frogs, lizards and birds – and used new phylogenetic methods to investigate the factors underlying communication evolution. Social factors were only implicated in the evolution of complex visual signals in lizards. Ecology, and to some degree allometry, were most likely explanations for complexity in the vocal signals of frogs (ecology) and birds (ecology and allometry). There was some evidence for adaptive evolution in the pheromone complexity of ants, although no compelling selection pressure was identified. For most taxa, phylogenetic null models were consistently ranked above adaptive models and, for some taxa, signal complexity seems to have accumulated in species via incremental or random changes over long periods of evolutionary time. Becoming social presumably lead to the origin of social communication in animals, but its subsequent influence on the trajectory of signal evolution has been neither clear-cut nor general among taxonomic groups.
Data from: Patterns and processes in complex landscapes: testing alternative biogeographic hypotheses through integrated analysis of phylogeography and community ecology in Hawai'i
The Island of Hawai'i is a dynamic assemblage of five volcanoes with wet forest habitat currently existing in four distinct natural regions that vary in area, age, and geographic isolation. In this complex landscape, alternative assumptions of the relative importance of specific habitat characteristics on evolutionary and ecological processes predict strikingly different general patterns of local diversity and regional similarity. In this study we compare alternative a priori hypotheses against observed patterns within two distinct biological systems and scales: community composition of wet forest vascular plant species and mitochondrial and nuclear genes of Drosophila sproati, a wet forest restricted endemic. All observed patterns display strong and similar regional structuring, with the greatest local diversity found in Kohala and the windward side of Mauna Loa, the least in Ka'ū and Kona, and a distinctive pattern of regional similarity that likely reflects the historical development of this habitat on the island. These observations largely corroborate a biogeographic model that integrates multiple lines of evidence, including climatic reconstruction, over those relying on single measures, such as current habitat configuration or substrate age. This method of testing alternative hypotheses across biological systems and scales is an innovative approach for understanding complex landscapes and should prove valuable in diverse biogeographic systems.
Data from: Integrating genomic and phenotypic data to evaluate alternative phylogenetic and species delimitation hypotheses in a recent evolutionary radiation of grasshoppers
Although resolving phylogenetic relationships and establishing species limits is a primary goal of systematics, these tasks remain challenging at both conceptual and analytical levels. Here, we integrated genomic and phenotypic data and employed a comprehensive suite of coalescent-based analyses to develop and evaluate competing phylogenetic and species delimitation hypotheses in a recent evolutionary radiation of grasshoppers (Chorthippus binotatus group) composed of two species and eight putative subspecies. To resolve the evolutionary relationships within this complex, we first evaluated alternative phylogenetic hypotheses arising from multiple schemes of genomic data processing and contrasted genetic-based inferences with different sources of phenotypic information. Second, we examined the importance of number of loci, demographic priors, number and kind of phenotypic characters, and sex-based trait variation for developing alternative species delimitation hypotheses. The best-supported topology was largely compatible with phenotypic data and showed the presence of two clades corresponding to the nominative species groups, one including three well-resolved lineages and the other comprising a four-lineage polytomy and a well-differentiated sister taxon. Integrative species delimitation analyses indicated that the number of employed loci had little impact on the obtained inferences but revealed the higher power provided by an increasing number of phenotypic characters and the usefulness of assessing their phylogenetic information-content and differences between sexes in among-taxa trait variation. Overall, our study highlights the importance of integrating multiple sources of information to test competing phylogenetic hypotheses and elucidate the evolutionary history of species complexes representing early-stages of divergence where conflicting inferences are more prone to appear.
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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.