hrvatski

Molekularno-filogenetske analize sekvenci mitohondrijskog gena za citokrom oksidazu I (COI)

Phylogenetics is the study of evolutionary relationships among organisms or genes. One of the phylogenetic studies purposes is to reconstruct evolutionary ties between organisms and the other one is to estimate the time of divergence between organisms since they last shared a common ancestor. To illustrate the evolutionary relationships among a group of organisms we use and construct phylogenetic trees. Phylogenetic relationships within the suborder Tricladida are not jet fully understood. In Ball’s proposal some uncertainties were left open, one of them being the closer similarities in eye structure between the Dugesiidae and the land planarians (Terricola) than between Dugesiidae and the non-dugesiid members of the Paludicola (Ball 1981). Analyses of freshwater planarians were based on DNA sequence variation of mitochondrial gene for cytochrome oxidase I (COI). Phylogenetic studies were carried out using maximum likelihood, maximum parsimony and bayesian methods. Maximum likelihood (ML) is one commonly used method for reconstructing trees. To perform maximum likelihood method we used two programs - Modeltest 3.7 (Posada and Crandal 1998) and PAUP 4 beta 10 (Swoford 2001). The first step is to find a model of evolution that fits the DNA changes in the aligned sequences that are being used. In this analysis we used Akaike information criteria (AIC). Resulting phylogenetic tree was visualizated using Treeview 1.6.6. (Page 2001). To perform maximum parsimony method we used PAUP 4 beta 10 (Swoford 2001). We used nexus format file of COI sequences. Statistical support for the tree was evaluated by bootstrapping. One more commonly used method in phylogenetic analyses is Bayesian analysis. We performed it using Mr. Bayes 3.1.1. (Huelselbeck i Ronquist 2003) program. To root our phylogenetic trees we used Bdelloura candida as an outgroup. Results of this phylogenetic research contribute to our better understanding of relations between this group of organisms.

planarije; COI; Bayesian analiza; maximum likelihood; maximum parsimony

nije evidentirano