Meeting Abstract

S2.9  Sunday, Jan. 4  What can 18S rDNA do for copepod phylogeny and classification? HUYS, R*; LLEWELLYN-HUGHES, J; British Museum r.huys@nhm.ac.uk

No group of plants or animals on Earth exhibits the range of morphological diversity as seen among the extant Crustacea. This is best demonstrated by the Copepoda, which by virtue of their immense vertical distribution are also arguably the most abundant metazoans. Their current position of world predominance can be attributed to two principal, recurrent, radiation events, i.e. their major habitat shift into the marine plankton, and the evolution of parasitism. Given their moderately high host specificity in conjunction with the incredible spectrum of potential marine hosts, it is highly conceivable that parasitic copepods significantly outnumber their free-living counterparts in species diversity. Their successful colonization or utilization of virtually every metazoan phylum has generated a great diversity in copepod body morphology, which is arguably unparalleled among the Crustacea. Families such as the Monstrillidae and Thaumatopsyllidae demonstrate how extremely powerful natural selection can be in shaping morphology to meet functional needs so that distantly related taxa may appear uncannily similar. Here I will show how small subunit ribosomal sequence data (18S rDNA) can help resolving controversial issues that had reached a temporary impasse in the phylogeny and classification of the symbiotic copepods, such as the placement of the Thaumatopsyllidae, the paraphyly of the Cyclopoida and the origin of parasitism in freshwater. I will demonstrate how the use of such data can lead to the discovery of previously overlooked morphological characters and how they impact on the ordinal level classification of the Copepoda.