Platyhelminth phylogenetics - a key to understanding parasitism?

Littlewood, D. T. J., Cribb, T. H., Olson, P. D. and Bray, R. A. (2001) Platyhelminth phylogenetics - a key to understanding parasitism?. Belgian Journal of Zoology, 131 1: 35-46.

Author Littlewood, D. T. J.
Cribb, T. H.
Olson, P. D.
Bray, R. A.
Title Platyhelminth phylogenetics - a key to understanding parasitism?
Journal name Belgian Journal of Zoology   Check publisher's open access policy
ISSN 0777-6276
Publication date 2001
Sub-type Article (original research)
Volume 131
Issue 1
Start page 35
End page 46
Total pages 12
Place of publication Belgium
Publisher Royal Belgium Zoological Society
Collection year 2001
Language eng
Subject C1
300508 Parasitology
780105 Biological sciences
Abstract The comparative method, the inference of biological processes from phylogenetic patterns, is founded on the reliability of the phylogenetic tree. In attempting to apply the comparative method to the understanding of the evolution of parasitism in the phylum Platyhelminthes, we have highlighted several points we consider to be of value along with many problems. We discuss four of these topics. Firstly, we view the group at a phylum level, in particular discussing the importance of establishing the sister taxon to the obligate parasite group, the Neodermata, for addressing such questions as the monophyly, parasitism or the endo or ectoparasitic nature of the early parasites. The variety of non-congruent phylogenetic trees presented so far, utilising either or both morphological and molecular data, gives rise to the suggestion that any evolutionary scenarios presented at this stage be treated as interesting hypotheses rather than well-supported theories. Our second point of discussion is the conflict between morphological and molecular estimates of monogenean evolution. The Monogenea presents several well-established morphological autapomorphies, such that morphology consistently estimates the group as monophyletic, whereas molecular sequence analyses indicate paraphyly, with different genes giving different topologies. We discuss the problem of reconciling gene and species trees. Thirdly, we use recent phylogenetic results on the tapeworms to interpret the evolution of strobilation, proglottization, segmentation and scolex structure. In relation to the latter, the results presented indicate that the higher cestodes are diphyletic, with one branch difossate and the other tetrafossate. Finally, we use a SSU rDNA phylogenetic tree of the Trematoda as a basis for the discussion of an aspect of the digenean life-cycle, namely the nature of the first intermediate host. Frequent episodes of host-switching, between gastropod and bivalve hosts or even into annelids, are indicated.
Keyword Zoology
Platyhelminthes
Parasitism
Phylogenetics
Monogenea
Cestoda
Digenea
Gene Trees
Life-history Evolution
Evolution
Eucestoda
Origin
Perspectives
Turbellaria
Tricladida
Morphology
Tapeworms
Cestoidea
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemistry and Molecular Biosciences
 
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Created: Tue, 14 Aug 2007, 15:16:47 EST