Phylogenetic utility and evidence for multiple copies of elongation factor-1 alpha in the spider genus Habronattus (Araneae : Salticidae)

In the continuing quest for informative genes for use in molecular systemat ics, the protein-coding gene Elongation factor-1 alpha (EF-1 alpha) has rap idly become one of the most prevalent "single-copy" nuclear genes utilized, particularly in arthropods. This paper explores the molecular evolutionary dynamics and phylogenetic utility of EF-1 alpha in the salticid spider gen us Habronattus. As has been reported for other arthropod lineages, our stud ies indicate that multiple (two) copies of EF-1 alpha exist in Habronattus. These copies differ in intron structure and thus in size, making it possib le to easily separate PCR amplification products. We present data for an in tronless EF-1 alpha copy for three Habronattus species. The presence of non sense mutations and generally elevated rates of amino acid change suggest t hat this copy is evolving under relaxed functional constraints in Habronatt us. A larger taxon sample (50 species plus outgroups) is presented for an E F-1 alpha copy that includes both intron and exon regions. Characteristics of both regions suggest that this is a functional, orthologous copy in the species sampled. Maximum-likelihood relative-rate comparisons show that exo n third codon sites are evolving more than 100 times as fast as second codo n sites in these sequences and that intron sites are evolving about twice a s fast as exon third sites. In combination, the, EF-1 alpha data provide ro bust, species-level phylogenetic signal that is largely congruent with morp hologically well supported areas of Habronattus phylogeny. The recovery of some novel clades, and the unexpected fragmentation of others, suggests are as requiring further phylogenetic attention.