Asexual multiplication of larval parasitic worms: a predictor of adult life-history traits in Taeniidae?

The hypothesis that asexual multiplication inside the intermediate host and adult life-history traits within the final host are independent is tested among Cestoda. Using phylogenetic relationships among the Cestoda species, we can show that asexual multiplication appears to have been lost and recovered several times throughout Taeniidae evolution; this allows a comparison of the adult life-history traits of species with and without asexual multiplication at the larval stage. The adult trait considered is the size of the parasite, since numerous life-history traits, such as fecundity and longevity, are correlated with size. If adult traits are independent of whether the larval stage reproduced asexually or not, we expect no difference in the adult size of the proliferative (i.e. with asexual multiplication) and non-proliferative species. The results are inconsistent with this hypothesis. In contrast, species with asexual multiplication in the intermediate host seem to have smaller adult size, reflecting a trade-off. We propose that ecological factors involving intraspecific and interspecific competition in the final host might be responsible for this trade-off. The role of these parameters in the evolution of life-history traits and more precisely in the acquisition of asexual multiplication is investigated with comparative analysis and discussed in the context of host-parasite interactions.