October 19, 2007

The Evolutionary Ecology of Aging in C. elegans

E. P. Caswell-Chen
Associate Dean for Graduate Programs
Professor and Nematologist
Department of Nematology
University of California, Davis

 Abstract:  The nematode Caenorhabditis elegans is a widely used model organism for studies of developmental genetics, aging, and biodemography; however, relatively little is known about its ecology and natural history. When starved, C. elegans adults retain progeny internally, leading to the death of the parent.  It appears that such behavior enhances juvenile survival to the long-lived dauer stage, and we have interpreted this as a form of facultative vivipary.  To understand the fitness consequences of extended life span and surivival in long-lived mutants, we monitored survival and reproduction of large cohorts of worms, and quantified the fitness consequences of increased longevity relative to reproduction and survival.  Analyses revealed that fitness costs in clk-1 and daf-2 mutants are consistent with the theory of antagonistic pleiotropy for the evolution of senescence.  Since the standard lab strain of C. elegans  arose from the progeny of a single hermaphrodite, we investigated the life span and biodemography of wild-caught C. elegans.  In comparing lab and wild worms, we observed differences in important demographic properties that are consistent with the hypothesis that the lab strain N2 has adapted to laboratory conditions.  We have used age-based matrix projection models to assess the selection gradient, or force of selection, on life span relative to demographic traits as they might be expressed under conditions more natural than those observed in the lab.