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ASEXUAL REPRODUCTION IN CESTODES (CYCLOPHYLLIDEA: TAENIIDAE): ECOLOGICAL AND PHYLOGENETIC INFLUENCES
Janice Moore1, Daniel R Brooks2
1Department of Zoology, Colorado State University, Fort Collins, CO, 80523.
Summary
Asexual reproduction in tapeworms (Taeniidae) is rare and its distribution doesn't fit environmental predictability. Phylogenetic analysis suggests this trait evolved or was lost multiple times, independent of host evolution.
Area of Science:
- Parasitology
- Evolutionary Biology
- Molecular Phylogenetics
Background:
- Asexual reproduction is uncommon in cestodes, but occurs in the larval metacestode stage of the Taeniidae family.
- The distribution of asexual reproduction within Taeniidae does not align with ecological hypotheses based on environmental predictability.
Purpose of the Study:
- To investigate the historical influences on the evolution of asexual reproduction in Taeniidae.
- To test whether phylogenetic relationships explain the occurrence of asexual reproduction in this tapeworm family.
Main Methods:
- Phylogenetic analysis using Wagner parsimony was performed on a subset of the Taeniidae family.
- A consensus phylogenetic tree was constructed from four 50-step trees with consistency indices of 0.38.
Main Results:
- The phylogenetic tree indicated that asexual reproduction arose or was lost multiple times within the Taeniidae.
- The inferred tapeworm phylogeny was incongruent with both definitive and intermediate host phylogenies.
- Asexual reproduction did not correlate with host transfers indicated by the phylogenies.
Conclusions:
- Developmental and phylogenetic constraints on asexual reproduction appear minimal in Taeniidae.
- Neither historical evolutionary constraints nor adaptation to environmental predictability fully explain the life-history variation in asexual reproduction observed in these cestodes.
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