Convergent evolution is the independent origination, as the result of natural selection, of a given phenotype in organisms subjected to similar environmental conditions. The widespread extent of convergent evolution across the tree of life continues to be unveiled by emerging molecular phylogenetic studies. In this regard, the phylum Bryozoa is no exception. Bryozoans are aquatic, mostly sessile, animals, that form colonies composed of discrete morphological and functional units called zooids. The extent of polymorphic zooidal diversity within this phylum is rivaled only by that found in siphonophores and some athecate cnidarians, yet, soft-bodied cnidarians have a trivial fossil record; the rich bryozoan fossil record, on the other hand, enables us to trace morphological features through geological time. In this talk I will illustrate how recent advances in molecular phylogenetics have thrown up some unexpected results in this group, where key traits have been shown to have evolved convergently, thus, raising considerable implications for the taxonomic classification of living and fossil species. The ease by which morphological and functional features appear and disappear throughout the phylogeny suggests that these transitions may be the result of a few easy to manipulate gene regulatory switches. Because these discrete morphological and functional units are produced by the same genetic individual, bryozoans providing a rich testing ground to study differential gene expression in different polymorphs which is hoped to provide some insights into the genetic basis of division of labour and the underlying genetic mechanisms of morphological evolution.
Dr Andrea Waeschenbach
Researcher, Molecular systematics
Life Sciences Department, Invertebrates
Natural History Museum
Cromwell Road
London
SW7 5BD
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