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Bryozoans are widespread aquatic colonial animals living both in the sea (sea mats) and fresh waters, with an extensive marine fossil record over almost 500 million years. Collaborating research groups in the NHM Departments of Zoology and Palaeontology represent arguably the strongest concentration of bryozoan research expertise anywhere in the world.

 

NaturalHistoryMuseum_026159_IA.jpg

 

Wilbertopora woodwardi (Brydone) from the Upper Cretaceous Chalk, Hampshire

 

Andrea Waeschenbach (NERC Postdoctoral Fellow, Zoology), Paul Taylor (Palaeontology) and Tim Littlewood (Zoology) have had accepted for publication the most comprehensive molecular phylogeny of bryozoans to date, using mitochondrial and ribosomal genes.

 

This has resulted in a well supported topology (the shape of the phylogenetic tree), providing unambiguous evidence for the interrelationship of the taxonomic classes.  It also provides strong evidence that several presently recognized taxonomic units at various hierarchical levels are each in fact of more than one origin in evolutionary terms - they are non-monophyletic (a monophyletic group has a single ancestor)

 

Using this topology, the work tried to establish the likely larval form and strategy of the ancestral bryozoans, but this gave ambiguous results.  It seems most likely that multiple shifts have occurred between different types of larval nutrition – dependency on yolk provided to the egg (lecithotrophy) and feeding by the bryozoan larva on phytoplankton (planktotrophy).

 

This result, combined with their long fossil record, promises bryozoans to be a suitable phylum to studying links between reproductive strategy and large scale evolutionary patterns, such as speciation rates. This paper is a significant contribution for assessing the interrelationships in a relatively neglected group that offers much promise as an evolutionary model. This work was funded by NERC (NE/E015298/1).

 

Waeschenbach, A., Taylor, P.D., Littlewood, D.T.J. (2011) A molecular phylogeny of bryozoans, Molecular Phylogenetics and Evolution. http://dx.doi.org/10.1016/j.ympev.2011.11.011

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