COPEPOD REPRODUCTIVE STRATEGIES - LIFE-HISTORY THEORY, PHYLOGENETIC PATTERN AND INVASION OF INLAND WATERS

Life-history theory predicts that different reproductive strategies sh ould evolve in environments that differ in resource availability, mort ality, seasonality, and in spatial or temporal variation. Within a pop ulation, the predicted optimal strategy is driven by tradeoffs that ar e mediated by the environment in which the organisms live. At the same time, phylogenetic history may circumscribe natural selection by dict ating the range of phenotypes upon which selection can act, or by limi ting the range of environments encountered. Comparisons of life-histor y patterns in related organisms provide a powerful tool for understand ing both the nature of selection on life-history characters and the di versity of life-history patterns observed in nature. Here, we explore reproductive strategies of the Copepoda, a well defined group with man y phylogenetically independent transitions from free-living to parasit ic life styles, from marine to inland waters, and from active developm ent to diapause. Most species are iteroparous annuals, and most (with the exception of some parasitic taxa) develop through a relatively res tricted range of life-history stages (nauplii and copepodids, or some modification thereof). Within these bounds, we suggest that there may be a causal relationship between the success of numerous copepod taxa in inland waters and the prevalence of either diapause or parasitism w ithin these groups. We hypothesize that inland waters are more variabl e spatially and temporally than marine habitats, and accordingly, we i nterpret diapause and parasitism as mechanisms for coping with environ mental variance. (C) 1998 Elsevier Science B.V. All rights reserved.