Coiling directions in the planktonic foraminifer Pulleniatina: A complex eco-evolutionary dynamic spanning millions of years

Cross-disciplinary information for understanding macroevolution

Many different macroevolutionary models can produce the same observations. Despite efforts in building more complex and realistic models, it may still be difficult to distinguish the processes that have generated the biodiversity we observe. In this opinion we argue that we can make new progress by reaching out across disciplines, relying on independent data and theory to constrain macroevolutionary inference. Using mainly paleontological insights and data, we illustrate how we can eliminate less plausible or implausible models, and/or parts of parameter space, while applying comparative phylogenetic approaches. We emphasize that such cross-disciplinary insights and data can be drawn between many other disciplines relevant to macroevolution. We urge cross-disciplinary training, and collaboration using common-use databases as a platform for increasing our understanding.

The relationship between volcanism and global climate changes in the Tropical Western Pacific over the mid-Pleistocene transition: Evidence from mercury concentration and isotopic composition

Volcanoes are a significant component of the Earth system, influencing the interaction between oceans and the atmosphere over large spatial and temporal scales. Being a volcanically dynamic region, the Tropical Western Pacific (TWP) can significantly impact variations in global climate. However, high-resolution continuous records of volcanic activity in this region are lacking, resulting in significant uncertainties regarding the coupling between the deep earth, climate changes, and atmospheric CO₂ in the TWP. To address this issue, mercury (Hg) levels, isotopic compositions, and Hg/total organic carbon (Hg/TOC) ratios were determined at site U1486 to track volcanic activity throughout the mid-Pleistocene transition (MPT) from 1.3 Myr to 0.6 Myr. Our results of anomalously high Hg concentrations and Hg/TOC ratios provide evidence of time-varying volcanism throughout the MPT. Mercury isotopes in the Hg-enriched sediments were characterized by near-zero Δ¹⁹⁹Hg values, which is consistent with volcanism acting as the primary source of Hg to the sediments. Spectral analysis of the Hg/TOC ratio showed significant periodicity at ~100 kyr and ~ 23 kyr as well as a weaker signal at ~41 kyr consistent with Milankovitch cycles. A cross spectral analysis of Hg/TOC and the LR04 δ¹⁸O stack record suggests that the peak in volcanism lags the temperature minimum by ~6 kyr, and occurs prior to the δ¹⁸O minimum known as the glacial termination by ~14 ± 2 kyr. The records of volcanic activity in this site are also consistent with a prominent rise in atmospheric CO₂ and negative excursion of benthic carbon isotopes throughout the MPT. This study provides direct sedimentary evidence in the TWP of the feedback between volcanic activity, climate change and atmospheric CO₂.

Diachroneity Rules the Mid-Latitudes: A Test Case Using Late Neogene Planktic Foraminifera across the Western Pacific

Planktic foraminifera are commonly used for first-order age control in deep-sea sediments from low-latitude regions based on a robust tropical–subtropical zonation scheme. Although multiple Neogene planktic foraminiferal biostratigraphic zonations for mid-latitude regions exist, quantification of diachroneity for the species used as datums to test paleobiogeographic patterns of origination and dispersal is lacking. Here, we update the age models for seven southwest-Pacific deep-sea sites using calcareous nannofossil and bolboform biostratigraphy and magnetostratigraphy, and use 11 sites between 37.9° N and 40.6° S in the western Pacific to correlate existing planktic foraminiferal biozonations and quantify the diachroneity of species used as datums. For the first time, northwest and southwest Pacific biozones are correlated and compared to the global tropical planktic foraminiferal biozonation. We find a high degree of diachroneity in the western Pacific, within and between the northwest and southwest regions, and between the western Pacific and the tropical zonation. Importantly, some datums that are found to be diachronous between regions have reduced diachroneity within regions. Much work remains to refine regional planktic foraminiferal biozonations and more fully understand diachroneity between the tropics and mid-latitudes. This study indicates that diachroneity is the rule for Late Neogene planktic foraminifera, rather than the exception, in mid-latitude regions.