The evolution of senescence in natural populations of guppies (Poecilia reticulata): a comparative approach

Model organisms like Drosophila melanogaster or Caenorhabditis elegans have revealed genes that influence senescence and the evolvability of senescenc e. We are interested instead in evaluating why and how senescence evolves i n natural populations. To do so, we are taking the ecological geneticist's perspective of comparing natural populations that differ in factors that ar e predicted to influence the evolution of senescence and are evaluating whe ther senescence has evolved in the predicted fashion. We are also manipulat ing the environment to evaluate more directly the evolution of senescence. Guppies (Poecilia reticulata) are found in streams throughout the Northern Range mountains of Trinidad. Natural populations experience large differenc es in mortality rate as a consequence of the predators with which they co-o ccur. We have already shown, both with comparative studies and manipulation s of the distribution of guppies and their predators, that the early life h istory evolves very rapidly in response to these differences in mortality. For example, high adult mortality rates select for individuals that develop more rapidly, produce their first litter of young at more of their availab le resources to reproduction for the remainder of their lives. These change s were predicted by independently derived theory. Aspects of this same theo ry also predict how the late life history and senescence should evolve. Spe cifically, theory predicts that the populations that experience low mortali ty rates should also experience delayed senescence and longer life spans re lative to those that experience high mortality rates. We are currently eval uating these predictions with representstives from two high mortality tion and two low-predation environments. Our presentation will focus on our pilo t study, which evaluated life span, lifetime reproduction, and the patterns of aging in our laboratory populations. We will also report on the progres s in our ongoing comparative studies of senescence in natural populations. (C) 2001 Elsevier Science Tnc, AV rights reserved.