The evolutionary patterns of divergence of seven euhirudinean families were investigated by cladistic analysis of 33 euhirudinean species. Oligochaetes, Acanthobdella peledina, and branchiobdellidans were included as outgroup taxa. Cladistic analysis employed 1.8 kb of nuclear 18S ribosomal DNA and 651 bp of mitochondrial cytochrome c oxidase subunit I in addition to morphological data. The use of two molecular data sets, one nuclear gene and one mitochondrial gene, as well as morphological data combined historical information evolving under a variety of different constraints and therefore was less susceptible to the biases that could confound the use of only one type of data. Results suggest that the nuclear 18S rDNA gene yields a meaningful historical signal for determining higher level relationships. The more rapidly evolving CO-I gene was informative for recent or local areas of the evolutionary hypothesis, such as within-family relationships. Analyses combining all data from the three character sets yielded one most-parsimonious tree. Most of the higher taxa in recent leech systematics were well corroborated in the resulting topology. However, these results suggested paraphyly of the order Rhynchobdellida, which contradicts the presence of a proboscis as a synapomorphy. The medicinal leech family Hirudinidae was polyphyletic because Haemadipsidae and Haemopidae each have a hirudinid ancestor. In addition, all but one of the genera within the family Erpobdellidae must be either abandoned or renamed. Unusual findings included compelling evidence of historical plasticity in bloodfeeding behavior, having been lost at least four times in the course of euhirudinean evolution. Biogeographic patterns supported a New World origin for Arhynchobdellida. � 1999 Academic Press

The aim of this paper is to assess the monophylyof the Annelida. Also, recent cladistic analyses of metazoan taxa, using a variety of data, have shown incongruities with regards to annelids and associated taxa that should be resolved. The Platyhelminlhes is selected as the taxon to root our minimal length trees and polarise our characters in a parsimony analysis: ingroup taxa being

To go from any page to the next page, or previous page, you can click the 'next page', or 'previous page', arrow at the top of the screen but it is more convenient to use the 'page down', or 'page up ' keys on the bottom right of your keyboard. These keys have the advantage that they can be used if you adopt 'Full screen' viewing, when the menus are no longer shown. You can also use the scroll bar to the right of the page. The monograph begins with a table of Contents. This allows you to go to any topic by clicking on it in the list. However, it is suggested that on a first reading you may wish to proceed page by page through the text, using the 'page down' key. At some points in the text, green wording will allow you to skip text or