Saturday, 30 October 2021

Evolution News - Here Be Dragonflies!

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Aeshna cyanea
Source: Wikipedia
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Aeshna grandis
Source: Wikipedia
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Anax junius
Source: Wikipedia
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Ischnura senegalensis
Source: Wikipedia
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Libellula quadrimaculata
Source: Wikipedia
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Sympetrum flaveolum
Source: Wikipedia
Linking the Past and Present: Reconstructing the Dragonfly and Damselfly Family Tree - University of Tsukuba

Scientist from Japan have succeeded in doing what Creationists insist is impossible because it doesn't happen. They have shown the evolution and relationships between the different members of the insect order, Odonata, which includes all living and extinct dragonflies and damselflies, surely amongst the most beautiful of insects. For those unsure of the difference, damselflies tend to be smaller and more dainty and rest with their wings together over their backs, while dragonflies are generally larger, more robust and faster flying, and hold their wings horizontally, like those of an aeroplane when at rest. They are the only insects capable of flying backwards.

The scientists constructed a fanily tree for the order Odorata, by conducting a detailed analysis of the transcriptome - the collection of RNA in cells which are transcriptions of the functional DNA and mapping this onto the fossil record. Because this technique indirectly analyses only the active DNA, it gives a better evolutionary relationship between species and allows detailed timing of species divergence to be estimated.

As the University of Tsukuba research news item explains:
This is the first transcriptome-based phylogenetic reconstruction of the order Odonata. We analyzed a total of 2,980 protein-coding genes in 105 species, covering all but two of the order's families.

A robust and reliable phylogenetic reconstruction is essential for dependable estimates of species divergence times," explains Machida. "Different fossil calibration schemes can be applied, but these can greatly impact the range of estimated dates. We used a comprehensive fossil dataset combining newly assessed fossils with data from the literature to produce a well-resolved and robustly time-calibrated phylogeny for Odonata.

Professor Ryuichiro Machida, co-author
Sugadaira Montane Research Center
University of Tsukuba, Sugadaira Kogen Ueda, Nagano, Japan
In newly published study, researchers including a member of the University of Tsukuba have applied transcriptomics, a type of gene sequencing, to reconstruct the phylogeny of the insect order Odonata. By calibrating this sequencing using the fossil record, they have been able to determine when dragonflies and damselflies first emerged.

Transcriptomics is the study of the collection of ribonucleic acid (RNA)—known as the transcriptome—that is present in a cell at any given time. This RNA contains a wealth of information and can be used to determine relationships among different members of a species. Understanding these relationships is essential for reconstructing evolutionary histories, or phylogenies, which are essentially like a family tree in a genetic sense.

[…]

There are thousands of living (extant) species of Odonata, but few have been analyzed in a phylogenetic context, and most species have been identified or differentiated on the basis of physical characteristics, such as wing patterns or larvae appearance. Although comparing appearances can be useful for extant species, it's not always as helpful when trying to reconstruct evolutionary histories—that's where transcriptomics and fossil calibration are useful.

[…]

This reconstruction provides the most comprehensive divergence time estimates for Odonata to date, meaning the researchers were able to determine when dragonflies and damselflies first appeared (around 200 million years ago). They were even able to estimate the time at which certain evolutionary characteristics developed, such as ovipositors (tube-shaped organs for laying eggs). Species that once flourished but have since died out were also identified. Given that these species can now only be identified in the fossil record, transcriptomics and phylogenetic reconstructions provide a unique opportunity to better understand the connections between extant and extinct species. Studies of a similar nature could shed light on equally obscured genetic histories for other species.
In the summary of their paper published recently in iscience, the authors say:
Graphical Abstract
Highlights
  • Evolutionary relationships of dragonflies and damselflies are unraveled using transcriptomes.
  • Earliest flying insects – dragonflies, damselflies, and their extinct ancient relatives – date back to Permian period.
  • Both extant dragonflies and damselflies started diverging in the Triassic period.

Summary

Dragonflies and damselflies are among the earliest flying insects with extant representatives. However, unravelling details of their long evolutionary history, such as egg laying (oviposition) strategies, is impeded by unresolved phylogenetic relationships particularly in damselflies. Here we present a transcriptome-based phylogenetic reconstruction of Odonata, analyzing 2,980 protein-coding genes in 105 species representing nearly all the order’s families. All damselfly and most dragonfly families are recovered as monophyletic. Our data suggest a sister relationship between dragonfly families of Gomphidae and Petaluridae. According to our divergence times estimates, both crown-Zygoptera and -Anisoptera arose during the late Triassic. Egg laying with a reduced ovipositor apparently evolved in dragonflies during the late Jurassic/early Cretaceous. Lastly, we also test the impact of fossil choice and placement particularly of the extinct fossil species, Triassolestodes asiaticus, and Proterogomphus renateae on divergence time estimates. We find placement of Proterogomphus renateae to be much more impactful than Triassolestodes asiaticus.



Copyright: © 2021 The authors. Published by Elsevier B.V.
Open access
Reprinted under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license (CC BY-NC-ND 4.0)
Once again we see scientists casually refuting creationism simply by showing the evidence. In this case, there is clear and consistent fossil and genomic evidence that all living and extinct dragonflies and their close relatives, damselflies, have a common ancestor which lived around 200 million years ago, and that members of that order have diversified over time exactly as the Theory of Evolution says they will.

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