scholarly journals Supplemental Material: Stress in the tropics? Impact of a latitudinal seawater δ18O gradient on Middle Jurassic temperature reconstructions at low latitudes

2020 ◽  
Author(s):  
Matthias Alberti ◽  
et al.
Keyword(s):  
Middle Jurassic ◽  
Additional Information ◽  
Low Latitudes ◽  
Temperature Reconstructions ◽  
The Tropics

Geochemical datasets and additional information on materials, methodology, and results.<br>

Stress in the tropics? Impact of a latitudinal seawater δ18O gradient on Middle Jurassic temperature reconstructions at low latitudes

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1210-1215 ◽  
Author(s):  
Matthias Alberti ◽  
Yael Leshno ◽  
Franz T. Fürsich ◽  
Yael Edelman-Furstenberg ◽  
Nils Andersen ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Absolute Temperature ◽  
Time Interval ◽  
Global Trends ◽  
Tropical Water ◽  
Western Asia ◽  
Low Latitudes ◽  
Temperature Reconstructions ◽  
Stable Oxygen ◽  
The Tropics

Abstract Previous stable oxygen isotope records of calcitic fossils (δ18Oshell) from Europe have been interpreted to reflect strong climatic perturbations throughout the Jurassic, but it is unknown whether they reflect global trends because data from other regions are sparse. Here, we use bivalve and brachiopod shells from western Asia and northern Africa to examine seawater temperatures at low latitudes as well as latitudinal temperature gradients in the Middle Jurassic. Our results include the first absolute temperature estimates for most of the study areas and this time interval. Furthermore, we acknowledge a latitudinal gradient in δ18O values of seawater (δ18Osea) that leads to more realistic temperature reconstructions of tropical water temperatures, which were underestimated by earlier methods. Following this approach, δ18Oshell values translate into average equatorial water temperatures during the Middle Jurassic several degrees higher than today (as high as 34–35 °C). Such high temperatures cause environmental stress, probably explaining previously documented low diversities of low-latitudinal ecosystems (e.g., coral reefs) during this time interval. A comparison with literature data raises doubts over whether previously published European temperature curves are truly representative of global patterns. Instead, they might reflect the complex paleogeography of European basins influenced by regional and/or short-term changes in δ18Osea values.

A revision of Xinjiangchelys oshanensis (Ye, 1973), and new material from the Middle Jurassic of Lufeng, Yunnan Province, China

2015 ◽  
Vol 186 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Haiyan Tong ◽  
Zhiming Dong ◽  
Tao Wang
Keyword(s):  
Middle Jurassic ◽  
Yunnan Province ◽  
Shell Morphology ◽  
Single Specimen ◽  
Systematic Revision ◽  
Additional Information ◽  
New Material

Abstract Xinjiangchelys oshanensis (Ye, 1973) was originally described as Plesiochelys oshanensisYe, 1973 from the Jurassic Upper Lufeng series of Eshan, Yunnan Province, China. The species was based on a single specimen (IVPP V4444), a damaged shell with articulated carapace and plastron. This species was later referred to as Xinjiangchelys? oshanensis and X. oshanensis respectively, but has never been revised and often overlooked in the studies of Asian Mesozoic turtles. In this paper, we provide the systematic revision of X. oshanensis (Ye, 1973) after new restoration of the specimen. Five additional shells from the Middle Jurassic Chuanjie Formation of Lufeng, Yunnan Province, China are referred to this species. Our study confirms the validity of the species and its assignment to the genus Xinjiangchelys. The study of the new material completes the shell morphology of X. oshanensis and provides additional information about its age.

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.

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 Colonial ascidians strongly preyed upon, yet dominate the substrate in a subtropical fouling community

2019 ◽  
Vol 286 (1899) ◽  
pp. 20190396 ◽  
Author(s):  
Laurel Sky Hiebert ◽  
Edson A. Vieira ◽  
Gustavo M. Dias ◽  
Stefano Tiozzo ◽  
Federico D. Brown
Keyword(s):  
Interactive Effects ◽  
Southeastern Brazil ◽  
Fouling Communities ◽  
Colonial Species ◽  
Predation Intensity ◽  
Low Latitudes ◽  
Predation Treatment ◽  
The Tropics ◽  
Colonial Ascidians ◽  
Solitary Species

Higher diversity and dominance at lower latitudes has been suggested for colonial species. We verified this pattern in species richness of ascidians, finding that higher colonial-to-solitary species ratios occur in the tropics and subtropics. At the latitudinal region with the highest ratio, in southeastern Brazil, we confirmed that colonial species dominate space on artificial plates in two independent studies of five fouling communities. We manipulated settlement plates to measure effects of predation and competition on growth and survivorship of colonial versus solitary ascidians. Eight species were subjected to a predation treatment, i.e. caged versus exposed to predators, and a competition treatment, i.e. leaving versus removing competitors, to assess main and interactive effects. Predation had a greater effect on growth and survivorship of colonial compared to solitary species, whereas competition did not show consistent patterns. We hypothesize that colonial ascidians dominate at this subtropical site despite being highly preyed upon because they regrow when partially consumed and can adjust in shape and space to grow into refuges. We contend that these means of avoiding mortality from predation can have large influences on diversification patterns of colonial species at low latitudes, where predation intensity is greater.

scholarly journals Obliquity forcing of low-latitude climate

2015 ◽  
Vol 11 (10) ◽  
pp. 1335-1346 ◽  
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 ◽  
Tropical Circulation ◽  
Low Latitude ◽  
Low Latitudes ◽  
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 palaeoclimate 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 idealized 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, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.

scholarly journals New Information on the Madagascan Middle Jurassic Sauropod Lapparentosaurus madagascariensis

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 498
Author(s):  
Miky Lova Tantely Raveloson ◽  
Neil D. L. Clark ◽  
Armand H. Rasoamiaramana
Keyword(s):  
Middle Jurassic ◽  
Hind Limb ◽  
Axial Skeleton ◽  
Systematic Position ◽  
Full Description ◽  
Neural Spine ◽  
Additional Information ◽  
New Information ◽  
Bone Fragments ◽  
The Common

The systematic position of the Middle Jurassic sauropod Lapparentosaurus madagascariensis is not fully understood due to a lack of useful anatomical detail. Despite many new bone fragments from the axial skeleton, post-cranial skeleton, and a hind limb having been previously unearthed, its systematic position has not yet been satisfactorily established. Although this Malagasy taxon is only recognised by two autapomorphies located in the scapula and coracoid, two features of the neural spine, which are reported here, provide additional information on the common autapomorphies shared with the British genus Cetiosaurus. A full description of the femur and neural spine helps to determine some aspects of its relationship to other similar taxa. Remains of Lapparentosaurus madagascariensis have been recovered from mixed facies that may have been deposited in a shallow water lagoon during a transgressive period in the Isallo IIIb subunit in the Majunga Basin.

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