Institution
University of British Columbia
Education•Vancouver, British Columbia, Canada•
About: University of British Columbia is a education organization based out in Vancouver, British Columbia, Canada. It is known for research contribution in the topics: Population & Poison control. The organization has 89939 authors who have published 209679 publications receiving 9226862 citations. The organization is also known as: UBC & The University of British Columbia.
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TL;DR: It is established that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase, and frequency estimates are higher by a factor of four than earlier estimates and lead to a standing incidence of polyploid species within genera of 35% (n = 1,506).
Abstract: Since its discovery in 1907, polyploidy has been recognized as an important phenomenon in vascular plants, and several lines of evidence indicate that most, if not all, plant species ultimately have a polyploid ancestry. However, previous estimates of the frequency of polyploid speciation suggest that the formation and establishment of neopolyploid species is rare. By combining information from the botanical community's vast cytogenetic and phylogenetic databases, we establish that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase. These frequency estimates are higher by a factor of four than earlier estimates and lead to a standing incidence of polyploid species within genera of 35% (n = 1,506). Despite this high incidence, we find no direct evidence that polyploid lines, once established, enjoy greater net species diversification. Thus, the widespread occurrence of polyploid taxa appears to result from the substantial contribution of polyploidy to cladogenesis, but not from subsequent increases in diversification rates of polyploid lines.
1,119 citations
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TL;DR: A gradient from near-primary, through old-growth secondary and plantation forests to complete clearance, for eight animal groups in the Mbalmayo Forest Reserve, south-central Cameroon is examined, indicating the huge scale of the biological effort required to provide inventories of tropical diversity, and to measure the impacts of tropical forest modification and clearance.
Abstract: Despite concern about the effects of tropical forest disturbance and clearance on biodiversity1,2, data on impacts, particularly on invertebrates, remain scarce3,4,5,6,7,8. Here we report a taxonomically diverse inventory on the impacts of tropical forest modification at one locality. We examined a gradient from near-primary, through old-growth secondary and plantation forests to complete clearance, for eight animal groups (birds, butterflies, flying beetles, canopy beetles, canopy ants, leaf-litter ants, termites and soil nematodes) in the Mbalmayo Forest Reserve, south-central Cameroon. Although species richness generally declined with increasing disturbance, no one group serves as a good indicator taxon9,10,11,12 for changes in the species richness of other groups. Species replacement from site to site (turnover) along the gradient also differs between taxonomic groups. The proportion of ‘morphospecies’ that cannot be assigned to named species and the number of ‘scientist-hours’ required to process samples both increase dramatically for smaller-bodied taxa. Data from these eight groups indicate the huge scale of the biological effort required to provide inventories of tropical diversity, and to measure the impacts of tropical forest modification and clearance.
1,119 citations
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TL;DR: A novel approach to modelling life expectancy, all-cause mortality and cause of death forecasts —and alternative future scenarios—for 250 causes of death from 2016 to 2040 in 195 countries and territories is provided.
1,118 citations
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TL;DR: In this paper, the authors argue that the emergence of classically connected spacetimes is intimately related to the quantum entanglement of degrees of freedom in a nonperturbative description of quantum gravity.
Abstract: In this essay, we argue that the emergence of classically connected spacetimes is intimately related to the quantum entanglement of degrees of freedom in a non-perturbative description of quantum gravity. Disentangling the degrees of freedom associated with two regions of spacetime results in these regions pulling apart and pinching off from each other in a way that can be quantified by standard measures of entanglement.
1,117 citations
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TL;DR: Using hippocampal slice preparations, it is shown that selectively blocking NMDARs that contain the NR2B subunit abolishes the induction of LTD but not LTP, demonstrating that distinct N MDAR subunits are critical factors that determine the polarity of synaptic plasticity.
Abstract: Activation of N-methyl-d-aspartate subtype glutamate receptors (NMDARs) is required for long-term potentiation (LTP) and long-term depression (LTD) of excitatory synaptic transmission at hippocampal CA1 synapses, the proposed cellular substrates of learning and memory. However, little is known about how activation of NMDARs leads to these two opposing forms of synaptic plasticity. Using hippocampal slice preparations, we showed that selectively blocking NMDARs that contain the NR2B subunit abolishes the induction of LTD but not LTP. In contrast, preferential inhibition of NR2A-containing NMDARs prevents the induction of LTP without affecting LTD production. These results demonstrate that distinct NMDAR subunits are critical factors that determine the polarity of synaptic plasticity.
1,116 citations
Authors
Showing all 90682 results
Name | H-index | Papers | Citations |
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Gordon H. Guyatt | 231 | 1620 | 228631 |
John C. Morris | 183 | 1441 | 168413 |
Douglas Scott | 178 | 1111 | 185229 |
John R. Yates | 177 | 1036 | 129029 |
Deborah J. Cook | 173 | 907 | 148928 |
Richard A. Gibbs | 172 | 889 | 249708 |
Evan E. Eichler | 170 | 567 | 150409 |
James F. Sallis | 169 | 825 | 144836 |
Michael Snyder | 169 | 840 | 130225 |
Jiawei Han | 168 | 1233 | 143427 |
Michael Kramer | 167 | 1713 | 127224 |
Bruce L. Miller | 163 | 1153 | 115975 |
Peter A. R. Ade | 162 | 1387 | 138051 |
Marc W. Kirschner | 162 | 457 | 102145 |
Kaj Blennow | 160 | 1845 | 116237 |