Multiple evolutionary routes of the single polar capsule in species (Myxozoa; Myxobolidae).

Kudo, 1933 is a species rich genus of Myxosporea, sharing many morphological similarities with species of but the former possesses a single polar capsule, and the latter has two. Based on molecular phylogenetic analyses, this single distinguishing feature is not monophyletic, and members of are intermixed with species, calling into question the validity of genus . The occurrence of two polar capsules in a small proportion of spores as observed in this study suggests that these species have the capacity to express this -like trait, clouding the distinction of these two genera further. Herein, using the most comprehensive data set to date, we explored the phylogenetic relationships of to other myxobolids, to investigate the evolutionary history of the genus and the origins of single polar capsule in this group. The phylogenetic analyses and statistical tests of topology revealed as a strongly supported polyphyletic lineage, clustering in five distinct branches within clade. Ancestral state reconstruction for polar capsule number showed that species have evolved from myxosporean species with two polar capsules at least four times, which could be classified in three possible evolutionary pathways. The polyphyly of and the multiple evolutionary origins of single polar capsule of demonstrate that the distinction of this genus from is largely for convenience, and does not reflect their evolutionary history.