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INTRODUCTION
Investigation of the relationship between parasite phylogeny and various biological traits can provide two important types of information. It serves as a background for understanding a parasite's evolutionary history, including evolution of the host-parasite interaction, and it indicates markers suitable for diagnostic and/or taxonomic purposes.
An immense amount of data and analyses were produced during the last few years for various groups of parasites (Page, 1996a; Barta et al. 1997; Hoberg et al. 1997; Proctor, 1999; Jousson et al. 2000; Paterson et al. 2000; Johnson and Clayton, 2001; Nieberding et al. 2004, 2005; Banks et al. 2006) including apicomplexan taxa, such as Adelina, Atoxoplasma, Cyclospora, Goussia, gregarines, etc. (Carreno et al. 1999, Eberhard et al. 1999, Barta et al. 2001, Jirk et al. 2002, Leander et al. 2006, Schrenzel et al. 2005, Kopecná et al. 2006). Within coccidia, attention has been mainly given to the evolution of Sarcocystidae, the tissue cyst-forming coccidia with a typically heteroxenous life-cycle. A number of studies investigated the phylogenetic significance of specificity to intermediate and definitive hosts, or affinity to various tissues (Votýpka et al. 1998; Dolezel et al. 1999; Slapeta et al. 2003). For example, the species of the genus Sarcocystis were suggested to co-evolve with their final, rather than intermediate, hosts (Dolezel et al. 1999; Holmdahl et al. 1999; Slapeta et al. 2003). Based on this finding, the final host is supposed to represent an ancestral type of the host within Sarcocystidae (Barta, 1989; Tenter et al. 1992).
Paradoxically, only few studies have been devoted to the largest group of coccidia, the monoxenous parasites of the genus Eimeria Schneider, 1875. Thus, evolution of various traits within this genus, such as morphology, host-specificity or pathogenicity, remains very unclear. Since Eimeria are typically parasites with extremely narrow host spectra, analysis of the dependence between phylogeny and host-specificity is relatively straightforward. The molecular data currently available show significant correlation between phylogenetic relationships and host-specificity; the genus splits into well-formed lineages, such as livestock-specific or fowl-specific species. This pattern, however, is not universal. For example, with an increasing number of available sequences, it became clear that rodent-associated fauna is composed of species from several lineages. While each of these lineages itself is...