  Character evolution that affects ecological community interactions often
occurs contemporaneously with temporal changes in population size, potentially
altering the very nature of those dynamics. Such eco-evolutionary processes may
be most readily explored in systems with short generations and simple genetics.
Asexual and cyclically parthenogenetic organisms such as microalgae,
cladocerans, and rotifers, which frequently dominate freshwater plankton
communities, meet these requirements. Multiple clonal lines can coexist within
each species over extended periods, until either fixation occurs or a sexual
phase reshuffles the genetic material. When clones differ in traits affecting
interspecific interactions, within-species clonal dynamics can have major
effects on the population dynamics. We first consider a simple predator-prey
system with two prey genotypes, parameterized with data on a well-studied
experimental system, and explore how the extent of differences in defense
against predation within the prey population determine dynamic stability versus
instability of the system. We then explore how increased potential for
evolution affects the community dynamics in a more general community model with
multiple predator and multiple prey genotypes. These examples illustrate how
microevolutionary "details" that enhance or limit the potential for heritable
phenotypic change can have significant effects on contemporaneous
community-level dynamics and the persistence and coexistence of species.
