Linking the past and present: Reconstructing the dragonfly and damselfly family tree

Date:
October 29, 2021
Source:
University of Tsukuba
Summary:
Researchers used transcriptomics (a type of gene sequencing)
calibrated using information from the fossil record to create the
first phylogenetic reconstruction of the insect order Odonata
(dragonflies and damselflies), covering 105 species. This
reconstruction of the evolutionary history allowed robust
estimations of the species divergence time (or first appearance,
around 200 million years ago) and the timing of evolutionary
changes, such as the development of egg-laying organs.



FULL STORY ==========================================================================
Many people hate insects, but the iridescent colors and elegant flying
style of dragonflies and damselflies have made them firm favorites
worldwide. They have been around in some form for hundreds of millions
of years, but the evolutionary history of these relics of prehistoric
life has been poorly understood -- until now.


==========================================================================
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.

"This is the first transcriptome-based phylogenetic reconstruction of
the order Odonata," says one of the authors of the study Professor
Ryuichiro Machida. "We analyzed a total of 2,980 protein-coding
genes in 105 species, covering all but two of the order's families."
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.

"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." 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.

========================================================================== Story Source: Materials provided by University_of_Tsukuba. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Manpreet Kohli, Harald Letsch, Carola Greve, Olivier Be'thoux,
Isabelle
Deregnaucourt, Shanlin Liu, Xin Zhou, Alexander Donath, Christoph
Mayer, Lars Podsiadlowski, Simon Gunkel, Ryuichiro Machida,
Oliver Niehuis, Jes Rust, Torsten Wappler, Xin Yu, Bernhard
Misof, Jessica Ware. Evolutionary history and divergence
times of Odonata (dragonflies and damselflies) revealed
through transcriptomics. iScience, 2021; 103324 DOI: 10.1016/
j.isci.2021.103324 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211029114012.htm

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