| Abstract: | Asexual reproduction, a rare trait among cestodes in general, occurs in the “larval” (metacestode) stage of species of the family Taeniidae. The distribution of this trait among taeniid species is not consistent with an ecological hypothesis of current environmental predictability. We therefore chose a subset of the family and studied their phylogenetic relationships by Wagner parsimony analysis as a test of historical influences on asexual reproduction. We produced a consensus tree based on four 50-step trees with consistency indices of 0.38. Given these hypothetical relationships, we found that asexual reproduction either arose or was lost multiple times. Moreover, this consensus tree is incongruent with both definitive and intermediate host phylogenies, and asexual reproduction does not correlate with host transfers inferred from these phylogenies. Developmental and phylogenetic constraints on asexual reproduction therefore appear to have been minimal. Given current information, neither historical constraint nor explanations invoking adaptation based on environmental predictability can account for life-history variation in these cestodes. |
