Aphid–Buchnera–Ant symbiosis; or why are aphids rare in the tropics and very rare further south?

2016 ◽  
Vol 107 (2-3) ◽  
pp. 297-310 ◽  
Author(s):  
Evgeny Perkovsky ◽  
Piotr Wegierek
Keyword(s):  
Northern Hemisphere ◽  
Late Cretaceous ◽  
Buchnera Aphidicola ◽  
Ant Colonies ◽  
Ant Predation ◽  
Low Latitudes ◽  
Extinction Event ◽  
Steep Decline ◽  
Cretaceous Terrestrial Revolution ◽  
The Tropics

ABSTRACTAt least since the Cretaceous Terrestrial Revolution, the geographical distribution of aphids, particularly in the Northern Hemisphere, has been strongly affected by the low thermal tolerance of their obligatory bacterial symbiont, Buchnera aphidicola, which was why the aphids switched to obligate parthenogenesis in low latitudes. Hormaphidids and greenideids penetrated into the tropics only after the Oligocene strengthening of climate seasonality, and specialisations of the tropical representatives of these families did not allow them to spread further south (in the case of cerataphidines), or only allowed in few cases (in the case of greenideids).Aphids suffered from the Mesozoic–Cenozoic boundary extinction event much more strongly than other insects. The extinction was roughly coincidental with the establishment of the tight symbiosis of aphids with formicine and dolichoderine ants, which was accompanied by the flourishing of all three groups.In the Cretaceous, all of the representatives of extant and subfamilies occupied positions that were subordinate to Armaniinae and Sphecomyrminae. Prior to large ant colonies evolving their efficient ant–aphid mutualism, the aphids remained unprotected before the growing ant predation. The origin of the aphid trophobiosis with large colonies of Formicinae and Dolichoderinae has resulted in the steep decline of aphids left beyond that ant–aphid symbiotic network. By at least the basal Eocene (unlike the Late Cretaceous), ant proportions in the entomofauna increased sharply, and evident dominants emerged. Even now, aphid milkers from small colonies (hundreds of specimens) never protect their symbionts, and homopteran-tending ants are more likely to be dominant, with large colonies of 104–105 workers.The mutualistic ant–aphid system failed to cross the tropical belt during the Cenozoic because of Buchnera's low heat tolerance. As a result, the native southern temperate aphid fauna consists now of seven genera only, five of which are Late Cretaceous relicts. Some of them had relatives in Late Cretaceous amber of the Northern Hemisphere.

scholarly journals Interannual variability of precipitable water

1996 ◽  
Vol 14 (4) ◽  
pp. 464-467 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Precipitable Water ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Zonal Winds ◽  
Low Latitudes ◽  
Linear Trends

Abstract. The 12-month running means of the surface-to-500 mb precipitable water obtained from analysis of radiosonde data at seven selected locations showed three types of variability viz: (1) quasi-biennial oscillations; these were different in nature at different latitudes and also different from the QBO of the stratospheric tropical zonal winds; (2) decadal effects; these were prominent at middle and high latitudes and (3) linear trends; these were prominent at low latitudes, up trends in the Northern Hemisphere and downtrends in the Southern Hemisphere.

scholarly journals Obliquity forcing of low-latitude climate

2015 ◽  
Vol 11 (1) ◽  
pp. 221-241 ◽  
Author(s):  
J. H. C. Bosmans ◽  
F. J. Hilgen ◽  
E. Tuenter ◽  
L. J. Lourens
Keyword(s):  
High Latitude ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Rotational Axis ◽  
Low Latitude ◽  
Low Latitudes ◽  
Paleoclimate Records ◽  
Induced Changes ◽  
The Tropics

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical paleoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, implying that this gradient may be used to explain obliquity signals in low-latitude paleoclimate records instead of the classic 65° N summer insolation curve.

scholarly journals Emission location dependent ozone depletion potentials for very short-lived halogenated species

2010 ◽  
Vol 10 (6) ◽  
pp. 16277-16305
Author(s):  
I. Pisso ◽  
P. H. Haynes ◽  
K. S. Law
Keyword(s):  
Northern Hemisphere ◽  
Ozone Depletion ◽  
Degradation Products ◽  
Stratospheric Ozone ◽  
Surface Emission ◽  
Spatial And Seasonal Variation ◽  
Geographical Regions ◽  
Simplifying Assumptions ◽  
Hemisphere Winter ◽  
The Tropics

Abstract. We present trajectory-based estimates of Ozone Depletion Potentials (ODPs) for very short-lived halogenated source gases as a function of surface emission location. The ODPs are determined by the fraction of source gas and its degradation products which reach the stratosphere, depending primarily on tropospheric transport and chemistry, and the effect of the resulting reactive halogen in the stratosphere, which is determined by stratospheric transport and chemistry, in particular by stratospheric residence time. Reflecting the different timescales and physico-chemical processes in the troposphere and stratosphere, the estimates are based on calculation of separate ensembles of trajectories for the troposphere and stratosphere. A methodology is described by which information from the two ensembles can be combined to give the ODPs. The ODP estimates for a species with a 20 d lifetime, representing a compound like n-propyl bromide, are presented as an example. The estimated ODPs show strong geographical and season variation, particularly within the tropics. The values of the ODPs are sensitive to the inclusion of a convective parametrization in the trajectory calculations, but the relative spatial and seasonal variation is not. The results imply that ODPs are largest for emissions from South and South-East Asia during Northern Hemisphere summer and from the Western Pacific during Northern Hemisphere winter. Large ODPs are also estimated for emissions throughout the tropics with also non-negligible values extending into northern mid-latitudes particularly in the summer. These first estimates, which include some simplifying assumptions, show larger ODP values than previous studies, particularly over Southern Asia, suggesting that emissions of short-lived halogen source gases in certain geographical regions could have a significant impact on stratospheric ozone depletion.

scholarly journals The Annual Cycle of the Axial Angular Momentum of the Atmosphere

2005 ◽  
Vol 18 (6) ◽  
pp. 757-771 ◽  
Author(s):  
Joseph Egger ◽  
Klaus-Peter Hoinka
Keyword(s):  
Angular Momentum ◽  
Northern Hemisphere ◽  
Annual Cycle ◽  
Lower Troposphere ◽  
Mass Term ◽  
Friction Torque ◽  
Hadley Cell ◽  
Trade Winds ◽  
Latitude Belt ◽  
The Tropics

Abstract Earlier analyses of the annual cycle of the axial angular momentum (AAM) are extended to include mass flows and vertical transports as observed, and to establish angular momentum budgets for various control volumes, using the European Centre for Medium-Range Forecasts (ECMWF) Re-Analyses (ERA) for the years 1979–92, transformed to height coordinates. In particular, the role of the torques is examined. The annual cycle of the zonally averaged angular momentum is large in the latitude belt 20° ⩽ |ϕ| ⩽ 45°, with little attenuation in the vertical up to a height of ∼12 km. The oscillation of the mass term (AAM due to the earth’s rotation) dominates in the lower troposphere, but that of the wind term (relative AAM) is more important elsewhere. The cycle of the friction torque as related to the trade winds prevails in the Tropics. Mountain torque and friction torque are equally important in the extratropical latitudes of the Northern Hemisphere. The annual and the semiannual cycle of the global angular momentum are in good balance with the global mountain and friction torques. The addition of the global gravity wave torque destroys this agreement. The transports must be adjusted if budgets of domains of less than global extent are to be considered. Both a streamfunction, representing the nondivergent part of the fluxes, and a flux potential, describing the divergences/convergences, are determined. The streamfunction pattern mainly reflects the seasonal shift of the Hadley cell. The flux potential links the annual oscillations of the angular momentum with the torques. It is concluded that the interaction of the torques with the angular momentum is restricted to the lower troposphere, in particular, in the Tropics. The range of influence is deeper in the Northern Hemisphere than in the Southern Hemisphere, presumably because of the mountains. The angular momentum cycle in the upper troposphere and stratosphere is not affected by the torques and reflects interhemispheric flux patterns. Budgets for the polar as well as for the midlatitude domains show that fluxes in the stratosphere are important.

Evolutionary conservatism will limit responses to climate change in the tropics

2021 ◽  
Vol 17 (10) ◽  
Author(s):  
Ethan B. Linck ◽  
Benjamin G. Freeman ◽  
C. Daniel Cadena ◽  
Cameron K. Ghalambor
Keyword(s):  
Thermal Tolerance ◽  
Species Turnover ◽  
Tropical Species ◽  
Evolutionary Divergence ◽  
Closely Related Species ◽  
Tropical Mountains ◽  
Low Latitudes ◽  
Parapatric Speciation ◽  
The Tropics

Rapid species turnover in tropical mountains has fascinated biologists for centuries. A popular explanation for this heightened beta diversity is that climatic stability at low latitudes promotes the evolution of narrow thermal tolerance ranges, leading to local adaptation, evolutionary divergence and parapatric speciation along elevational gradients. However, an emerging consensus from research spanning phylogenetics, biogeography and behavioural ecology is that this process rarely, if ever, occurs. Instead, closely related species typically occupy a similar elevational niche, while species with divergent elevational niches tend to be more distantly related. These results suggest populations have responded to past environmental change not by adapting and diverging in place, but instead by shifting their distributions to tightly track climate over time. We argue that tropical species are likely to respond similarly to ongoing and future climate warming, an inference supported by evidence from recent range shifts. In the absence of widespread in situ adaptation to new climate regimes by tropical taxa, conservation planning should prioritize protecting large swaths of habitat to facilitate movement.

scholarly journals Reassessing the Effect of Cloud Type on Earth’s Energy Balance in the Age of Active Spaceborne Observations. Part II: Atmospheric Heating

2019 ◽  
Vol 32 (19) ◽  
pp. 6219-6236 ◽  
Author(s):  
Yun Hang ◽  
Tristan S. L’Ecuyer ◽  
David S. Henderson ◽  
Alexander V. Matus ◽  
Zhien Wang
Keyword(s):  
Northern Hemisphere ◽  
Meridional Overturning Circulation ◽  
Regional Warming ◽  
Atmospheric Heating ◽  
Stratocumulus Clouds ◽  
Meridional Overturning ◽  
Subtropical Oceans ◽  
The Tropics ◽  
Global Mean

Abstract The role of clouds in modulating vertically integrated atmospheric heating is investigated using CloudSat’s multisensor radiative flux dataset. On the global mean, clouds are found to induce a net atmospheric heating of 0.07 ± 0.08 K day−1 that derives largely from 0.06 ± 0.07 K day−1 of enhanced shortwave absorption and a small, 0.01 ± 0.04 K day−1 reduction of longwave cooling. However, this small global average longwave effect results from the near cancellation of much larger regional warming by multilayered cloud systems in the tropics and cooling from stratocumulus clouds in subtropical oceans. Clouds are observed to warm the tropical atmosphere by 0.23 K day−1 and cool the polar atmosphere by −0.13 K day−1 enhancing required zonal heat redistribution by the meridional overturning circulation. Zonal asymmetries in the occurrence of multilayered clouds that are more frequent in the Northern Hemisphere and stratocumulus that occur more frequently over the southern oceans also leads to 3 times as much cloud heating in the Northern Hemisphere (0.1 K day−1) than the Southern Hemisphere (0.04 K day−1). These findings suggest that clouds very likely make the strongest contribution to the annual mean atmospheric energy imbalance between the hemispheres (2.0 ± 3.5 PW).

On the Role of Atmospheric Teleconnections in Climate

2008 ◽  
Vol 21 (12) ◽  
pp. 2990-3001 ◽  
Author(s):  
Anastasios A. Tsonis ◽  
Kyle L. Swanson ◽  
Geli Wang
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
Recent Application ◽  
The North ◽  
The Pacific ◽  
Atmospheric Teleconnections ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The Tropics

Abstract In a recent application of networks to 500-hPa data, it was found that supernodes in the network correspond to major teleconnection. More specifically, in the Northern Hemisphere a set of supernodes coincides with the North Atlantic Oscillation (NAO) and another set is located in the area where the Pacific–North American (PNA) and the tropical Northern Hemisphere (TNH) patterns are found. It was subsequently suggested that the presence of atmospheric teleconnections make climate more stable and more efficient in transferring information. Here this hypothesis is tested by examining the topology of the complete network as well as of the networks without teleconnections. It is found that indeed without teleconnections the network becomes less stable and less efficient in transferring information. It was also found that the pattern chiefly responsible for this mechanism in the extratropics is the NAO. The other patterns are simply a linear response of the activity in the tropics and their role in this mechanism is inconsequential.

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