An assessment of the value of nuclear and mitochondrial genes in elucidating the origin and evolution of Isotoma klovstadi Carpenter (Insecta, Collembola)

In order to infer the origin and the evolution of Antarctic Collembola, a c orrect phylogenetic analysis depicting relationships among Antarctic and no n-Antarctic species is required. A preliminary assessment of the value of D NA sequences in reconstructing phylogenetic relationships among the Antarct ic Isotoma klovstadi and other non-Antarctic species was carried out by seq uencing one mitochondrial gene (Cytochrome c oxidase, subunit II) and two n uclear genes (a fragment of the 28S rDNA and the Elongation Factor-1 alpha) . Estimates of base composition heterogeneity revealed that in the two prot ein-coding genes (COII and EF-1 alpha) 3rd codon position sites are composi tionally very heterogeneous and the analysis of these two genes was therefo re performed only on 1st and 2nd codon position sites. Phylogenetic analyse s using Maximum Likelihood, Maximum Parsimony and Minimum Evolution reveale d that the COII and the EF-1 alpha genes are more suitable than the D3 frag ment for the reconstruction of phylogenetic relationships within the Family Isotomidae to which Isotoma and several other genera of Antarctic Collembo la belong.