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2 Posts tagged with the systematics tag
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Large centipedes and larger datasets

 

Dr Greg Edgecombe, Department of Earth Sciences, NHM

 

27th January - 4.00 pm

 

Earth Sciences Seminar Room (Basement, WEB 05, formerly Mineralogy Seminar Room)

                                         

Scolopendromorpha includes the largest and most fiercely predatory centipedes, totalling more than 700 species.  Subjected to phylogenetic analysis since the late 1990s, early studies drew on small sets of external morphological characters, mostly those used in classical taxonomic works.

 

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Scolopendra gigantea

 

In order to bolster the character sample, new anatomical data were worked up by systematically sampling the group’s diversity in order to formulate new characters from understudied structures/organ systems. Simultaneously, targeted sequencing of a few markers for a small (but growing) number of species provided the first molecular estimates of phylogeny.  These have resulted in stable higher-level relationships that predict a single origin of blindness in three lineages that share this trait, and are now backed up by transcriptomic datasets with high gene occupancy. Explicit matrices of morphological characters and fossils coded as terminal taxa remain vital to “total evidence” dating/tip dating of the tree.

 

More information on attending seminars at http://www.nhm.ac.uk/research-curation/news-events/seminars/

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Different ideas of the relationship between the crustacea (crabs, barnacles, copepods and others) and insects have been discussed at length over the past century. The emergence of more and better DNA information is allowing the evolutionary relationships to be explored and clarified.


Ronald Jenner (Zoology) co-authored a first phylogenomic test of the recent hypothesis of a sister group relationship between hexapods (insects) and remipede crustaceans. Numerous data and testing of different interpretations led the authors to robustly find hexapods and remipedes as sister groups.


Remipede crustaceans were first described as Carboniferous fossils in the 1950s (around 310 million years old).  However, living species have been discovered since 1979, living only in underground aquifers connected to the sea. They are slow-moving with relatively basic segmented body plans, but can have specialised characteristics such as poison fangs and advanced sense of scent, important for securing prey in their unusual habitat.

 

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A Remipede from Mexico

 

The paper looks at the idea of the Pancrustacea - a large group containing both crustaceans and insects.  The data support the idea that the Pancrustacea can be divided into two major groups.  In the first are the marine decapods (crabs, prawns and lobsters), barnacles and copepods.  In the second group are found the freshwater Branchiopoda (such as the familar waterflea Daphnia), the Remipedes and the insects.  This supports the insects as a part of the Pancrustacea, possibly as part of a subgroup that moved from shallow marine environments to specialist freshwater, groundwater and terrestrial habitats.

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von Reumont, B. M., Jenner, R. A., Wills, M. A., Dell’Ampio, E., Pass, G., Ebersberger, I., Meyer, B., Koenemann, S., Iliffe, T. M., Stamatakis, A., Niehuis, O., Meusemann, K. and Misof, B. Early online. Pancrustacean phylogeny in the light of new phylogenomic data: support for Remipedia as the sister group of Hexapoda. Molecular Biology and Evolution (doi:10.1093/molbev/msr270)  Abstract