Odonata Timetree; Exponentially Increased Base Substitution Rate Toward The Recent and Within the Carboniferous

Using BEAST v1.X, we constructed a credible timetree of 115 specimens of Odonata and five species of Ephemeroptera (Paleoptera; Pterygota) and two species of Archaeognatha and three species of Zygentoma (Apterygota). 88 specimens we ourselves analyzed were collected from the Ryukyu islands, Taiwan, Japan, and China, and the resting sequence data were mostly from whole mitochondrial data found in GenBank / DDJB. The combined gene (not concatenated gene) analysis of the mitochondrial COI (795 bp), COII (548 bp), and 16S rRNA (517 bp), and the nuclear 28S rRNA (825 bp) were performed. Using the calibration function of BEAST v1.X, the timetree was constructed by applying a 1.55 Ma geological event (isolation of the Ryukyu islands from China), in addition to chronologically robust fossil dates ranging from 400 Ma for Archaeognatha, 300 Ma for Ephemeroptera, and 200 Ma for Odonata and to 1.76 Ma for Calopterygidae, for a total of 13 calibration points (event: 6, fossil: 12; Quaternary 7, pre Quaternary 11). The resultant timetree showed that molecular clock was not uniformly progressed, and the base substitution rate has exponentially increased from ca. 20 Ma to the Recent by over an order of magnitude. Our new and attractive finding indicates that the Quaternary severe climatic change including a start of glacial and interglacial cycle might have resulted in the extensive radiation and speciation of Odonata, and consequently increased the biodiversity. C4 pores generated in the Miocene effectively decreased atmospheric CO2, and triggered the Quaternary glaciation. Another peak of base substitution rate was found in the Carboniferous time around 320 Ma, and this may be analogous to the late Paleozoic icehouse. This glaciation has been triggered by the development of terrestrial plants to form thick coal layers, because this process also reduced the atmospheric CO2.

Cicada timetree by BEAST v1.X verified the recently and exponentially increasing base substitution rates

Following the recent publication of global cicada phylogenetic trees by Marshall et al. (2018), Łukasik et al. (2018), and Simon et al. (2019), we developed a new dated tree incorporating mostly endemic east Asian cicada data for totally 113 specimens, using the mostly advanced BEAST v1.X software applied the relaxed clock model. Fossil calibrations as old as Triassic were adopted after Moulds (2018), and a Quaternary geological event calibration was adopted following Osozawa et al. (2012), applying the calibration function of BEAST. Our timetree suggests that Tettigarctidae had cicada basal lineage as old as 200 Ma, and Derotettiginae was next as old as 100 Ma. Tibicininae was a sister of the resting Cicadidae, and Tettigomyiinae, Cicadettinae, and Cicadina started simultaneous branching and radiation around 40 Ma. We made a base substitution rate vs age diagram based on the timetree using the BEAST function, and it strongly suggested an exponential increase of base substitution rate approaching the present. The consequent increased cicada biodiversity including generation of cryptic species might have been driven by the generation and spreading of C4 grasses and the following Quaternary glaciations and severe environmental change.

Post-Triassic Spermatophyta Timetree Adding the Quaternary Radiated Asarum Wild Gingers

BackgroundAngiospermae radiation was known as the mid-Cretaceous event, but adaptive radiation of Asarum is also expected in the Quaternary. In order to know such the Angiospermae evolutionary history through the time, we constructed a whole Spermatophyta timetree employing BEAST v1. X associated with robust fossil calibration function.ResultsWe successfully and precisely dated the Spermatophyta phylogeny, and the Angiospermae topology was concordant to the APG system. Using another function of BEAST, we discovered the exponential increase in base substitution rate in recent geologic time, and another rise of rate at the mid-Cretaceous time. These increasing events correspond to the Quaternary and mid-Cretaceous Angiospermae radiations.ConclusionsA probable cause of the recently increasing rate and the consequent radiation was ultimately generation of C4 grasses, reduction of atomospheric CO2, and the start of the Quaternary glacial period. Mid-Cretaceous event was explained by co-radiation with insect beetles as the food plant.