Trichostrongyloid Nematodes and their Vertebrate Hosts: Reconstruction of the Phylogeny of a Parasitic Group

Abstract

Publisher Summary This chapter introduces trichostrongyloid nematodes as a model for discussing the reconstruction of the phylogeny of a parasitic group. Morphological and biological characters are studied and assessed for their relative phylogenetic importance. On the basis of morphological characters and their presumed evolution, trichostrongyloids are divided into 14 families and 24 subfamilies. The evolutionary trends of each character are analyzed and used to construct a classification that recognizes different phylogenetic lines. A parasitic line may become isolated from its ancestral forms by passing from one host group to another; the isolation may be followed by the evolutionary radiations of variable importance. In the Trichostrongyloidea, the most important characters from a phylogenetic point of view are those of the caudal bursa and synlophe. Using these characters, a number of different evolutionary lines become evident and the degree of evolution of the different genera composing each of those lines can be assessed. The chapter also presents a phylogenetic tree of the Trichostrongyloidea.