A
bstract
The LHCb collaboration has recently presented their result on
R
K
= ℬ(
B
+
→
K
+
μ
+
μ
−
)
/
ℬ(
B
+
→
K
+
e
+
e
−
) for the dilepton invariant mass bin
m
ℓℓ
2
= 1 − 6 GeV
2
(
ℓ
=
μ, e
). ...The measurement shows an intriguing 2
.
6
σ
deviation from the Standard Model (SM) prediction. In view of this, we study model independent New Physics (NP) explanations of
R
K
consistent with other measurements involving
b
→
sℓ
+
ℓ
−
transition, relaxing the assumption of lepton universality. We perform a Bayesian statistical fit to the NP Wilson Coefficients and compare the Bayes Factors of the different hypotheses in order to quantify their goodness-of-fit. We show that the data slightly favours NP in the muon sector over NP in the electron sector.
A
bstract
We attempt to explain recent anomalies in semileptonic
B
decays at LHCb via a composite Higgs model, in which both the Higgs and an SU(2)
L
-triplet leptoquark arise as pseudo-Goldstone ...bosons of the strong dynamics. Fermion masses are assumed to be generated via the mechanism of partial compositeness, which largely determines the leptoquark couplings and implies non-universal lepton interactions. The latter are needed to accommodate tensions in the
b
→
sμμ
dataset and to be consistent with a discrepancy measured at LHCb in the ratio of
B
+
→
K
+
μ
+
μ
−
to
B
+
→
K
+
e
+
e
−
branching ratios. The data imply that the leptoquark should have a mass of around a TeV. We find that the model is not in conflict with current flavour or direct production bounds, but we identify a few observables for which the new physics contributions are close to current limits and where the leptoquark is likely to show up in future measurements. The leptoquark will be pair-produced at the LHC and decay predominantly to third-generation quarks and leptons, and LHC13 searches will provide further strong bounds.
Type specimens are permanently preserved biological specimens that fix the usage of species names. This method became widespread from 1935 onwards and is now obligatory. We used DNA sequencing of ...types and more recent collections of wild and cultivated melons to reconstruct the evolutionary history of the genus Citrullus and the correct names for its species. We discovered that the type specimen of the name Citrullus lanatus, prepared by a Linnaean collector in South Africa in 1773, is not the species now thought of as watermelon. Instead, it is a representative of another species that is sister to C. ecirrhosus, a tendril‐less South African endemic. The closest relative of the watermelon instead is a West African species. Our nuclear and plastid data furthermore reveal that there are seven species of Citrullus, not four as assumed. Our study implies that sweet watermelon originates from West, not southern Africa as previously believed, and that the South African citron melon has been independently domesticated. These findings affect and explain numerous studies on the origin of these two crops that led to contradictory results because of the erroneous merging of several distinct species.
Changes in the growing-season lengths of temperate trees greatly affect biotic interactions and global carbon balance. Yet future growing-season trajectories remain highly uncertain because the ...environmental drivers of autumn leaf senescence are poorly understood. Using experiments and long-term observations, we show that increases in spring and summer productivity due to elevated carbon dioxide, temperature, or light levels drive earlier senescence. Accounting for this effect improved the accuracy of senescence predictions by 27 to 42% and reversed future predictions from a previously expected 2- to 3-week delay over the rest of the century to an advance of 3 to 6 days. These findings demonstrate the critical role of sink limitation in governing the end of seasonal activity and reveal important constraints on future growing-season lengths and carbon uptake of trees.
Sex Chromosomes in Land Plants Ming, Ray; Bendahmane, Abdelhafid; Renner, Susanne S
Annual review of plant biology,
01/2011, Letnik:
62
Journal Article
Recenzirano
Sex chromosomes in land plants can evolve as a consequence of close linkage between the two sex determination genes with complementary dominance required to establish stable dioecious populations, ...and they are found in at least 48 species across 20 families. The sex chromosomes in hepatics, mosses, and gymnosperms are morphologically heteromorphic. In angiosperms, heteromorphic sex chromosomes are found in at least 19 species from 4 families, while homomorphic sex chromosomes occur in 20 species from 13 families. The prevalence of the XY system found in 44 out of 48 species may reflect the predominance of the evolutionary pathway from gynodioecy towards dioecy. All dioecious species have the potential to evolve sex chromosomes, and reversions back from dioecy to various forms of monoecy, gynodioecy, or androdioecy have also occurred. Such reversals may occur especially during the early stages of sex chromosome evolution before the lethality of the YY (or WW) genotype is established.
The Evolution of Mutualistic Dependence Chomicki, Guillaume; Kiers, E. Toby; Renner, Susanne S
Annual review of ecology, evolution, and systematics,
11/2020, Letnik:
51, Številka:
1
Journal Article
Recenzirano
While the importance of mutualisms across the tree of life is recognized, it is not understood why some organisms evolve high levels of dependence on mutualistic partnerships, while other species ...remain autonomous or retain or regain minimal dependence on partners. We identify four main pathways leading to the evolution of mutualistic dependence. Then, we evaluate current evidence for three predictions: (
a
) Mutualisms with different levels of dependence have distinct stabilizing mechanisms against exploitation and cheating, (
b
) less dependent mutualists will return to autonomy more often than those that are highly dependent, and (
c
) obligate mutualisms should be less context dependent than facultative ones. Although we find evidence supporting all three predictions, we stress that mutualistic partners follow diverse paths toward-and away from-dependence. We also highlight the need to better examine asymmetry in partner dependence. Recognizing how variation in dependence influences the stability, breakdown, and context dependence of mutualisms generates new hypotheses regarding how and why the benefits of mutualistic partnerships differ over time and space.
Age estimation from molecular sequences has emerged as a powerful tool for inferring when a plant lineage arrived in a particular area. Knowing the tenure of lineages within a region is key to ...understanding the evolution of traits, the evolution of biotic interactions, and the evolution of floras. New analytical methods model change in substitution rates along individual branches of a phylogenetic tree by combining molecular data with time constraints, usually from fossils. These ‘relaxed clock’ approaches can be applied to several gene regions that need not all have the same substitution rates, and they can also incorporate multiple simultaneous fossil calibrations. Since 1995, at least 100 plant biogeographic studies have used molecular-clock dating, and about a fifth has used relaxed clocks. Many of these report evidence of long-distance dispersal. Meta-analyses of studies from the same geographic region can identify directional biases because of prevailing wind or water currents and the relative position and size of landmasses.
Ant–plant symbioses involve over 110 ant species in five subfamilies that are facultative or obligate occupants of stem, leaf or root domatia formed by hundreds of ant-plant species. The phylogenetic ...distribution and geological ages of these associations, and the frequency of gains or losses of domatium, are largely unknown.
We compiled an up-to-date list of ant domatium-bearing plants, estimated their probable true number from model-based statistical inference, generated dated phylogenies that include c. 50% of ant-plant lineages, and traced the occurrence of domatia and extrafloral nectaries on a 1181-species tree, using likelihood and Bayesian methods.
We found 681 vascular plants with domatia (159 genera in 50 families) resulting from minimally 158 inferred domatium origins and 43 secondary losses over the last 19 Myr. The oldest African ant–plant symbioses are younger than those in Australasia and the Neotropics. The best statistical model suggests that the true number of myrmecophytes may approach 1140 species.
The phylogenetic distribution of ant-plants shows that domatia evolved from a range of pre-adapted morphological structures and have been lost frequently, suggesting that domatia have no generalizable effect on diversification. The Miocene origin of ant–plant symbioses is consistent with inferred changes in diet and behaviour during ant evolution.
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