Clonal dynamics and life history evolution in the jellyfish Aurelia aurita

rganisms with more than one stage or phase have complex life cycles. As a model system for the evolution of a complex life history, I studied a marine jellyfish, Aurelia aurita, which has sessile polypoid and pelagic medusoid phases. The polyp creates both new polyps and sexual medusae through clonal replication. The natural replication of genotypes allowed me to address three inter-related questions: (1) To what extent can phenotypic plasticity account for observed differences in life history among individuals? (2) Are sexual and asexual characters characters in the life history correlated? and (3) What is the significance of variation in fitness of clones across environments? I replicated six sibling polyp clones across three feeding regimes to test whether clones differed in growth rates and budding patterns, and found significant genotypic variation in growth and tissue allocation, in addition to significant effects of feeding treatment. A significant genotype-by-environment interaction indicated plasticity in growth. Given variation in clone formation, I compared allocation to the sexual stage (medusae) with allocation to the asexual stage (polyps), using 40 lineages. The rate at which buds were produced was negatively correlated with tissue volume allocated to juvenile medusae at each reproductive event. However, size of medusae and timing of reproduction add complexity: some lineages make small numbers of small medusae frequently whereas others make larger numbers of large medusae less frequently. Clones which make medusae frequently tend to bud frequently. Correlations were...