Variation in life history responses of Tetrahymena thermophila under variable resource conditions


Resource availability is one of the determining factors driving the evolution of organisms. Aquatic microbes are often exposed to “feast-and-famine” conditions, where resources abound at certain times, interspersed by long periods of resource scarcity. According to life history theory, natural selection should shape organisms to optimize resource allocation into different life history traits such as reproduction, survival or dispersal to guarantee the maximum number of surviving offspring in the next generation, where the schedule of resource allocation strongly depends on the prevailing environmental context. Here we look for intraspecific variation in life history traits among different clonal lines of the ciliate Tetrahymena thermophila, coming from different geographic locations and differing histories of lab domestication. We characterized a set of 44 clones of T. thermophila in terms of important life history traits such as growth rate and maximum density under resource abundance, survival under resource depletion, short and long-distance dispersal abilities and sociality. Additionally, morphological features such as cell size and shape and their plasticity were measured. Strains differed significantly in almost all the measured life history traits, indicating substantial intraspecific variation. Importantly, we also found significant co-variation among clonal lines in these traits and an indication of certain trade-offs, for example between survival and the frequency of long-distance dispersal morphs produced by different lineages. To understand the present variation, we furthermore studied whether the co-variation patterns among clonal lines is contingent on the genetic relatedness of the different clones or rather related to their history (i.e. lab domestication versus recent field collection). The associations of life history traits and their co-variation will be discussed with regard to the predictions of certain theoretical models (e.g. ruderal species).

11th INTECOL Congress
London, UK
Frank Pennekamp
Postdoctoral researcher in ecology