Resolvendo a incongruência filogenética para articular a homologia e a evolução fenotípica: um estudo de caso de Nematoda

quinta-feira, janeiro 28, 2010

Resolving phylogenetic incongruence to articulate homology and phenotypic evolution: a case study from Nematoda

Erik J. Ragsdale* and James G. Baldwin

-Author Affiliations

Department of Nematology, University of California, Riverside, CA 92521, USA

*Author for correspondence (


Modern morphology-based systematics, including questions of incongruence with molecular data, emphasizes analysis over similarity criteria to assess homology. Yet detailed examination of a few key characters, using new tools and processes such as computerized, three-dimensional ultrastructural reconstruction of cell complexes, can resolve apparent incongruence by re-examining primary homologies. In nematodes of Tylenchomorpha, a parasitic feeding phenotype is thus reconciled with immediate free-living outgroups. Closer inspection of morphology reveals phenotypes congruent with molecular-based phylogeny and points to a new locus of homology in mouthparts. In nematode models, the study of individually homologous cells reveals a conserved modality of evolution among dissimilar feeding apparati adapted to divergent lifestyles. Conservatism of cellular components, consistent with that of other body systems, allows meaningful comparative morphology in difficult groups of microscopic organisms. The advent of phylogenomics is synergistic with morphology in systematics, providing an honest test of homology in the evolution of phenotype.

Caenorhabditis elegans   comparative morphology   evolution of novelty  congruence  plant parasitism


Received December 7, 2009.
Accepted January 6, 2010.
© 2010 The Royal Society