Evolution of centric diatoms inferred from patterns of oogenesis and spermatogenesis

Centric diatoms have three patterns of oogenesis and four patterns of spermatogenesis, yielding a combination of seven patterns. The evolution of these combinations was inferred from differences in character states of the meiotic patterns observed in oogenesis and spermatogenesis. Furthermore, we have inferred the evolutionary relationships among centric diatoms based on the evolution of these combinations, the data on occurrence of combinations and a molecular phylogenetic tree. Our results suggested that the last common ancestor of extant diatoms was a bipolar or multipolar centric diatom with the most primitive among extant oogenetic/spermatogenic combinations. Our results also suggested that ancestors of the radial centrics and pennates would have diverged, in that order, from a bipolar or multipolar centric diatom with the most primitive among extant oogenetic/spermatogenic combinations.