SEXUAL REPRODUCTION IN THE PERONOSPOROMYCETES (CHROMISTAN FUNGI)

An overview of sexual reproduction in the Peronosporomycetes leads to the recognition of constant features and variable traits. Variation in characters is accorded different weighting depending on its use for t axonomic identification or phylogenetic systematics. The phylogenetic significance of features of gametangial morphogenesis, such as vacuola tion and the patterns of nuclear meioses and abortions, can be related to morphological characters such as the persistence of periplasm and oogonial and oospore wall deposition. The cellular reorganization occu rring in the oogonium and oospores, particularly in relation to the po ssible functions of the dense body vesicle system and the glucan, phos phate, and lipid oospore reserves, may be critical for the internal mo rphology of the mature oospore and its function. Such differences are valuable for morphometric analysis, which lends itself to new identifi cation procedures. The ecological implications of these differences in the production of oogonia and oospores are considered; sexual reprodu ction (its frequency or absence) may be crucial for successful life-hi story strategies in biodiversity.