A laboratory population of <i>Tisbe furcata</i> (Copepoda, Harpacticoida) with a 35-generation history of stable population size was examined for life history adaptations to demographic stationarity. Survival and fecundity schedules and individual fitness parameters were measured; a standard being provided by three accessions of the wild source population. <i>Tisbe furcata</i> responded to density regulation by increasing its potential net reproductive rate, R<sub>o</sub> This result is in agreement with the theory of fitness in age-structured populations, though in contradiction with intuitions based on the <i>r-K</i>paradigm. The physiological mechanisms through which R<sub>o</sub> is raised are... |