摘要
The basic life cycle of Foraminifera has long been recognized as alternation between sexual and asexual generations;a common modification is several successive asexual generations.Production and release of flagellated gametes also has been documented as the basic sexual-reproductive mode in extant lineages.Research on population dynamics,local spatial distributions,and biogeography of Amphistegina spp.and Heterostegina depressa have been augmented by culture studies over the past 50years,providing insights that have been widely used in paleoecological and paleoenvironmental interpretations.Hypotheses are proposed suggesting how stages in the life cycle might contribute to understanding biogeographic and evolutionary trends commonly observed in large benthic foraminifers.Recruitment of sexually-produced cryptobiotic propagules,followed by successive asexual generations(schizogeny),can potentially establish viable,locally-adapted populations within literally years,consistent with the concepts of both allopatric speciation and reticulate evolution associated with isolation and reconnection of local basins.The review concludes with the recommendation that future studies utilizing genomics,proteonomics,geochemistries,scanning technologies,and other approaches can promote greater understanding of both modern and fossil larger benthic foraminiferal lineages.
