Phylogenetic analysis of partial sequences of elongation factor 1 alpha identifies major groups of lice (Insecta : Phthiraptera)

As a first attempt to use molecular data to resolve the relationships betwe en the four suborders of lice and within the suborder Ischnocera, we sequen ced a 347-bp fragment of the elongation factor l alpha gene of 127 lice (In secta: Phthiraptera) as well as outgroup taxa from the order Psocoptera. A number of well-supported monophyletic groups were found but the relationshi ps among many of these groups could not be resolved. While it is probable t hat multiple substitutions at high divergences and ancient radiation over a short period of time have contributed to the problem, we attribute most of this lack of resolution to the high ratio of taxa to characters. Neverthel ess, the sequence data unequivocally support a number of important relation ships that are at variance with the conclusions of morphological taxonomy. These include the sister group relationship of Chelopistes and Oxylipeurus, two lice occupying different ecological niches on the same host, which hav e previously been assigned to different families. These results provide evi dence in support of the hypothesis that lice have speciated in situ on the host in response to niche specialization and that this has given rise to co nvergent morphologies in the-lice: of different host groups which share sim ilar ecological niches. We discuss our attempts to overcome the limitations of this large data set, including the use of leaf stability analysis, a ne w method for analyzing the stability of taxa in a phylogenetic tree, and ex amine a number of hypotheses of relationships based on both traditional tax onomy and host associations. (C) 2001 Academic Press.