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1,245 results for “hypothesis”
Data from: Cryptic species diversity reveals biogeographic support for the 'mountain passes are higher in the tropics' hypothesis
The 'mountain passes are higher in the tropics' (MPHT) hypothesis posits that reduced climate variability at low latitudes should select for narrower thermal tolerances, lower dispersal and smaller elevational ranges compared with higher latitudes. These latitudinal differences could increase species richness at low latitudes, but that increase may be largely cryptic, because physiological and dispersal traits isolating populations might not correspond to morphological differences. Yet previous tests of the MPHT hypothesis have not addressed cryptic diversity. We use integrative taxonomy, combining morphology (6136 specimens) and DNA barcoding (1832 specimens) to compare the species richness, cryptic diversity and elevational ranges of mayflies (Ephemeroptera) in the Rocky Mountains (Colorado; approx. 40°N) and the Andes (Ecuador; approx. 0°). We find higher species richness and smaller elevational ranges in Ecuador than Colorado, but only after quantifying and accounting for cryptic diversity. The opposite pattern is found when comparing diversity based on morphology alone, underscoring the importance of uncovering cryptic species to understand global biodiversity patterns.
Data from: History matters more when explaining genetic diversity within the context of the core-periphery hypothesis
The core–periphery hypothesis (CPH) predicts that populations located at the periphery of a species' range should have lower levels of genetic variation than those at the centre of the range. However, most of the research on the CPH focuses on geographic distance and not on ecological distance, or uses categorical definitions of core and periphery to explain the distribution of genetic diversity. We use current climate data and historical climate data from the last glacial maxima to develop quantitative estimates of contemporary and historical ecological suitability using ecological niche models. We analysed genetic diversity using 12 polymorphic microsatellites to estimate changes in heterozygosity, allelic richness and population differentiation in 31 populations of the wood frog (Lithobates sylvaticus) spanning the species' entire eastern clade (33o to 45o latitude) from Alabama, USA, to Nova Scotia, Canada. Our data support predictions based on the CPH. Populations showed significant differences in genetic diversity across the range, with lower levels of genetic variation at the geographic range edge and in areas with lower levels of historical and contemporary ecological suitability. However, history and geography (not current ecological suitability) best explain the patterns. This study highlights the importance of examining more than just geography when assessing the CPH, and the importance of historical ecological suitability in the maintenance of genetic diversity and population differentiation.
Data from: Trophic niche width increases with bill size variation in a generalist passerine: a test of the niche variation hypothesis
1. The niche variation hypothesis (NVH) predicts that populations with wider niches are phenotypically more variable than populations with narrower niches, which is frequently used to explain diversifying processes such as ecological release. However, not all empirical evidence supports the NVH. Furthermore, a relationship between population phenotypic variation and niche width can be caused by sexual selection or environmental gradients, which should be carefully considered along with competition in explaining niche variation. 2. In this study we used eight populations of a generalist passerine species, Paradoxornis webbianus (vinous-throated parrotbill), to test the NVH. We assessed evidence of ecological sexual dimorphism and environmental gradients in bill morphology of P. webbianus. A total of 170 P. webbianus from eight sites ranging 24-2,668 m in altitude were included in this study. We used two principal components to quantify bill morphology, one describes bill size and the other describe bill slenderness. We used stable carbon and nitrogen isotope values of bird feathers to quantify trophic positions, and we estimated population trophic niche width using Bayesian standardized ellipse area. 3. Paradoxornis webbianus with larger and more slender bills fed at higher trophic levels and population trophic niche width tended to increase with bill size variation, supporting the NVH. The males had larger bills and marginally higher nitrogen isotope values than the females, suggesting ecological sexual dimorphism. Despite a positive correlation between bill size and wing length indicating sexual selection for larger male size, only three of the eight populations showed both male-biased bill size and male-biased wing length. Sexual dimorphism explained 13%-64% of bill size variation across sites, suggesting its role in niche variation could vary greatly among populations. The variation in bill slenderness in P. webbianus increased with elevation. However, neither bill size variation nor trophic niche width changed with elevation. Therefore, environmental gradients that could be reflected in the elevation are not likely to drive the observed morphological and niche variation. 4. This study provides an empirical case for the NVH and highlights the importance to investigate sexual dimorphism and environmental gradients in the studies of niche dynamics.
Data from: Genetic evidence for prevalence of alloparental care in a socially monogamous biparental cichlid fish, Perissodus microlepis, from Lake Tanganyika supports the "selfish shepherd effect" hypothesis
Alloparental care – care for unrelated young – is rare in animals, and its ecological or evolutionary advantages or, alternative maladaptive nature, remain unclear. We investigate alloparental care in the socially monogamous cichlid fish Perissodus microlepis from Lake Tanganyika that exhibits bi-parental care. In a genetic parentage analysis, we discovered a surprisingly high percentage of alloparental care represented by brood mixing, extra-pair paternity and extra-pair maternity in all broods that we investigated. The percentage of nondescendant juveniles of other parents, i.e., brood mixing, ranged from 5% to 57% (mean = 28%). The distribution of genetic parentage also suggests that this socially monogamous species has, in fact, polygamous mating system. The prevalence of genetically mixed broods can be best explained by two, not mutually exclusive hypotheses on farming-out and fostering behaviors. In the majority of broods, the sizes of the parents' own (descendant) offspring were significantly larger than those of the adopted (nondescendant) juveniles, supporting the 'selfish shepherd effect' hypothesis, i.e., that foster parents preferentially accept unrelated "smaller or not larger" young since this would tend to lower the predation risks for their own larger offspring. There was also a tendency for larger parents particularly mothers, more so than smaller parents, to care predominantly for their own offspring. Larger parents might be better at defending against cuckoldry and having foreign young dumped into their broods through farming-out behavior. This result might argue for maladaptive effects of allopatric care for the foster parents that only larger and possibly more experienced pairs can guard against. It needs to be determined why, apparently, the ability to recognize one's own young has not evolved in this species.
Data from: Is sex advantageous in adverse environments? A test of the abandon-ship hypothesis
Understanding the evolution and maintenance of sexual reproduction remains a long-standing challenge in evolutionary biology. Stress often induces sexual reproduction in facultatively sexual species (those species capable of both sexual and asexual reproduction). The abandon-ship hypothesis predicts higher allocation to sex under stress to allow low-fitness individuals to recombine their genotype, potentially increasing offspring fitness. However, effective tests of the abandon-ship hypothesis, particularly in multicellular organisms, are lacking. Here we test the abandon-ship hypothesis, using cyanogenic and acyanogenic defense phenotypes of the short-lived perennial herb Trifolium repens. Cyanogenesis provides an effective defense against herbivores and is under relatively simple genetic control (plants dominant for cyanogenesis at two alleles express the defended phenotype). Thus, maladapted individuals can acquire adaptive defense alleles for their offspring in a single episode of sexual reproduction. Plants were grown under high- and low-herbivory treatments (plants were exposed to herbivorous snails) and a control treatment (no herbivory). Herbivores reduced growth and fitness in all treated plants, but herbivory induced higher sexual allocation only in maladapted (acyanogenic) individuals. Overall, our results support the abandon-ship hypothesis.
Data from: Testing the depth-differentiation hypothesis in a deepwater octocoral
The depth-differentiation hypothesis proposes that the bathyal region is a source of genetic diversity and an area where there is a high rate of species formation. Genetic differentiation should thus occur over relatively small vertical distances, particularly along the upper continental slope (200–1000 m) where oceanography varies greatly over small differences in depth. To test whether genetic differentiation within deepwater octocorals is greater over vertical rather than geographical distances, Callogorgia delta was targeted. This species commonly occurs throughout the northern Gulf of Mexico at depths ranging from 400 to 900 m. We found significant genetic differentiation (FST = 0.042) across seven sites spanning 400 km of distance and 400 m of depth. A pattern of isolation by depth emerged, but geographical distance between sites may further limit gene flow. Water mass boundaries may serve to isolate populations across depth; however, adaptive divergence with depth is also a possible scenario. Microsatellite markers also revealed significant genetic differentiation (FST = 0.434) between C. delta and a closely related species, Callogorgia americana, demonstrating the utility of microsatellites in species delimitation of octocorals. Results provided support for the depth-differentiation hypothesis, strengthening the notion that factors covarying with depth serve as isolation mechanisms in deep-sea populations.
Data from: Testing an hypothesis of hybrid zone movement for toads in France
Hybrid zone movement may result in substantial unidirectional introgression of selectively neutral material from the local to the advancing species, leaving a genetic footprint. This genetic footprint is represented by a trail of asymmetric tails and displaced cline centres in the wake of the moving hybrid zone. A peak of admixture linkage disequilibrium is predicted to exist ahead of the centre of the moving hybrid zone. We test these predictions of the movement hypothesis in a hybrid zone between common (Bufo bufo) and spined toads (B. spinosus), using 31 nuclear and one mtDNA SNPs along a transect in the northwest of France. Average effective selection in Bufo hybrids is low and clines vary in shape and centre. A weak pattern of asymmetric introgression is inferred from cline discordance of seven nuclear markers. The dominant direction of gene flow is from B. spinosus to B. bufo and is in support of southward movement of the hybrid zone. Conversely, a peak of admixture linkage disequilibrium north of the hybrid zone suggests northward movement. These contrasting results can be explained by reproductive isolation of the B. spinosus and B. bufo gene pools at the southern (B. spinosus) side of the hybrid zone. The joint occurrence of asymmetric introgression and admixture linkage disequilibrium can also be explained by the combination of low dispersal and random genetic drift due to low effective population sizes.
FIGURE 116. Phylogenetic hypothesis for the New World Craspedochaeta, using a in Revision of the New World species of Craspedochaeta (Diptera: Clusiidae)
FIGURE 116. Phylogenetic hypothesis for the New World Craspedochaeta, using a hypothetical ancestor as an outgroup (removed from final figure). Selected from one of the 48 equally parsimonious trees calculated by PAUP (Phylogenetic Analysis Using Parsimony (Swofford, 2003)) from the matrix in table 2, using a simple heuristic search with all characters unweighted (length=74 steps, CI=0.48, RI=0.83), and using the command "condense collapse=minbrlen". Solid circles indicate unique characters and open circles are homoplasies or character reversals.
FIGURES 60–63. 60, K in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 60–63. 60, K. nr lanceolatus, dorsal head; 61, K. nr lanceolatus, male antenna; 62, K. nr lanceolatus, male antenna, clava; 63, K. nr lanceolatus, male antenna, pedicel to F3; 64, K. nr lanceolatus, propodeum; 65, K. gothmogi, lateral head; 66, K. gothmogi, lateral scutellum; 67, K. gothmogi, propodeum. Note: all females unless otherwise noted.
FIGURES 60–63. 60, K in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 60–63. 60, K. nr lanceolatus, dorsal head; 61, K. nr lanceolatus, male antenna; 62, K. nr lanceolatus, male antenna, clava; 63, K. nr lanceolatus, male antenna, pedicel to F3; 64, K. nr lanceolatus, propodeum; 65, K. gothmogi, lateral head; 66, K. gothmogi, lateral scutellum; 67, K. gothmogi, propodeum. Note: all females unless otherwise noted.
FIGURES 52–59. 52, K in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 52–59. 52, K. erwini, lateral gaster; 53, K. erwini, lateral petiole; 54, K. tolkeini, lateral head; 55, K. tolkeini, lateral habitus; 56, K. tolkeini, propodeum; 57, K. tolkeini, fore wing venation; 58, K. erwini, lateroventral mesosoma; 59, K. lanceolatus, lateral petiole. Note: all females.
FIGURES 36–43. 36, K in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 36–43. 36, K. erwini, lateral prepectus; 37, K. erwini, lateral mesosoma; 38, K. erwini, anterior head; 39, K. erwini, posterior head; 40, K. erwini, anterior fore leg; 41, K. erwini, scrobal depression; 42, K. erwini, lateral gaster; 43, K. erwini, malar space. Note: all females.
FIGURES 68–75. 68, P in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 68–75. 68, P. javensis, lateral mesosoma; 69, K. erwini, male antenna, dorsal flagellomeres; 70, M. oecanthi, posterior head, postgenal bridge; 71, M. oecanthi, anterior head; 72, Chryseida sp. Bolivia, anterior head; 73, P. latrodecti, posterior head; 74, Bephratelloides cubensis, posterior head; 75, B. cubensis, posterior head, postgenal bridge. Note: all females unless otherwise noted.
FIGURES 26–33. 26, K in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 26–33. 26, K. erwini (variant), lateral mesosoma; 27, Isosomodes n. sp., lateral mesosoma; 28, Philolema sp., lateral mesosoma; 29, Tenuipetiolus mentha, dorsal mesosoma; 30, K. lanceolatus, ventral costal cell; 31, K. gothmogi, fore wing venation; 32, Axima zabriskiei, ventral costal cell; 33, K. erwini, fore wing. Note: all females.
FIGURES 10–17. 10 in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 10–17. 10, Conura sp., antenna; 11, Aximopsis vogti, pedicel; 12, Heimbra opaca, antenna; 13, K. erwini, pedicel; 14, Axima diabolus, lateral head and basal antenna; 15, K. erwini, clypeus; 16, K. lanceolatus, clypeus; 17, Eurytoma solenozopheriae, apex clava. Note: all females.
FIGURES 76–81. 76 in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 76–81. 76, Plutarchia sp. Kenya, posterior head, postgenal bridge 77, Heimbra opaca, posterior head, postgenal bridge; 78, Axima n. sp. Ecuador, posterior head, postgenal bridge; 79, Systole albipennis, lateral mesosoma; 80, P. latrodecti, lateral mesosoma; 81, Chryseida sp. Bolivia, anterior procoxa. Note: all females.
FIGURES 2–9. 2 in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 2–9. 2, Macrorileya oecanthi, propodeum; 3, K. erwini, propodeum; 4, K. lanceolatus, posterolateral propodeum; 5, Eurytoma bugbeei, antenna; 6, K. erwini, antenna; 7, K. erwini, flagellomere close up; 8, Systole albipennis, antenna; 9, Dirhinus n. sp., antenna. Note: all females.
FIGURES 68–75. 68, P in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 68–75. 68, P. javensis, lateral mesosoma; 69, K. erwini, male antenna, dorsal flagellomeres; 70, M. oecanthi, posterior head, postgenal bridge; 71, M. oecanthi, anterior head; 72, Chryseida sp. Bolivia, anterior head; 73, P. latrodecti, posterior head; 74, Bephratelloides cubensis, posterior head; 75, B. cubensis, posterior head, postgenal bridge. Note: all females unless otherwise noted.
FIGURES 18–25. 18, K in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 18–25. 18, K. lanceolatus, apex clava; 19, K. erwini (variant), mandibles; 20, K. lanceolatus, mandible; 21, M. oecanthi, dorsal mesosoma; 22, K. erwini (variant), dorsal mesosoma; 23, K. erwini, ventrolateral mesosoma; 24, Bruchodape sp., ventral mesosoma; 25, A. vogti, dorsal mesosoma. Note: all females.
FIGURES 34 in Description of Khamul, gen. n. (Hymenoptera: Chalcidoidea: Eurytomidae), with a hypothesis of its phylogenetic placement
FIGURES 34. Strict consensus tree of 286 MPTs from unweighted analysis (step = 156; CI=0.53; RI=0.80).
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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.