501
resulting from appearance of the parasitoid guild. One outcome of the MMPR, host
specialization, is not necessarily associated with clade diversification among parasitoids, as the evolution of host breadth proceeded from specialist to generalist in
Tachinidae, the most diverse clade of dipteran parasitoids.
11.10 An Outlook Toward the Future
Hopefully, this contribution will set the stage for further exploration into the paleobiology and evolutionary biology of parasites and parasitoids. Six major questions
are posed to spark future work in this fascinating field.
1. What specific feature or features render the parasite life habit an evolutionary
cul-de-sac when compared to the evolutionarily more successful parasitoid
life habit?
2. Can other evidence be marshalled to understand the vertebrate host identities of
the several “giant” flea lineages from the mid Mesozoic?
3. How does the evolutionary transformation from parasitism to parasitoidism
occur? Are there modes in which nonparasitic modes of feeding evolve directly
into parasitoidic modes of feeding without going through a parasite stage?
4. Are there biological factors determining why some orders undergo one or two
originations of the parasitoid life habit (e.g., Strepsiptera, Hymenoptera),
whereas other orders undergo many more such originations (e.g., Coleoptera,
Diptera)?
5. What accounts for the spectacular increase in taxonomic diversity of parasitoid
clades such as Strepsiptera, Eremoneura, Proctotrupomorpha and Aculeata, during the past 170–120 million years? Are such increases explained by innovations
such as triungulin or planidium larval stage, a telescopic ovipositor or an elongate drilling ovipositor?
6. Does the postulated transformation of mid-Mesozoic food webs from those initially driven by primary-producers to subsequent ones driven by efficient parasitoid consumers leave other ecological effects on terrestrial ecosystems?
Much of the deep-time history of predation, parasitism and parasitoidism remains
unknown. These six questions will be best answered through interdisciplinary collaboration by paleoecologists, entomologists knowledgeable in fossil and modern
insect groups, taphonomists, food-web specialists and others that can pool their
knowledge in solving issues of common interest.
Acknowledgements We are grateful to Kenneth De Baets and John Huntley for the invitation to
provide this review. We thank two reviewers for constructive evaluations of this contribution.
Jennifer Wood assembled the figures; Jon Eizyk ably secured copyright permissions for reproduction of the figures. The Smithsonian Institution Libraries provided facilities and interlibrary loan
articles essential for the completion of this review. Kevin Johnson and Sandra Schachat provided
valuable feedback. We thank David Smith and Matthew Buffington for access to Hymenoptera
specimens that were examined for the Stephanoidea and Evanioidea studies. The Paleobiology
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution
resulting from appearance of the parasitoid guild. One outcome of the MMPR, host
specialization, is not necessarily associated with clade diversification among parasitoids, as the evolution of host breadth proceeded from specialist to generalist in
Tachinidae, the most diverse clade of dipteran parasitoids.
11.10 An Outlook Toward the Future
Hopefully, this contribution will set the stage for further exploration into the paleobiology and evolutionary biology of parasites and parasitoids. Six major questions
are posed to spark future work in this fascinating field.
1. What specific feature or features render the parasite life habit an evolutionary
cul-de-sac when compared to the evolutionarily more successful parasitoid
life habit?
2. Can other evidence be marshalled to understand the vertebrate host identities of
the several “giant” flea lineages from the mid Mesozoic?
3. How does the evolutionary transformation from parasitism to parasitoidism
occur? Are there modes in which nonparasitic modes of feeding evolve directly
into parasitoidic modes of feeding without going through a parasite stage?
4. Are there biological factors determining why some orders undergo one or two
originations of the parasitoid life habit (e.g., Strepsiptera, Hymenoptera),
whereas other orders undergo many more such originations (e.g., Coleoptera,
Diptera)?
5. What accounts for the spectacular increase in taxonomic diversity of parasitoid
clades such as Strepsiptera, Eremoneura, Proctotrupomorpha and Aculeata, during the past 170–120 million years? Are such increases explained by innovations
such as triungulin or planidium larval stage, a telescopic ovipositor or an elongate drilling ovipositor?
6. Does the postulated transformation of mid-Mesozoic food webs from those initially driven by primary-producers to subsequent ones driven by efficient parasitoid consumers leave other ecological effects on terrestrial ecosystems?
Much of the deep-time history of predation, parasitism and parasitoidism remains
unknown. These six questions will be best answered through interdisciplinary collaboration by paleoecologists, entomologists knowledgeable in fossil and modern
insect groups, taphonomists, food-web specialists and others that can pool their
knowledge in solving issues of common interest.
Acknowledgements We are grateful to Kenneth De Baets and John Huntley for the invitation to
provide this review. We thank two reviewers for constructive evaluations of this contribution.
Jennifer Wood assembled the figures; Jon Eizyk ably secured copyright permissions for reproduction of the figures. The Smithsonian Institution Libraries provided facilities and interlibrary loan
articles essential for the completion of this review. Kevin Johnson and Sandra Schachat provided
valuable feedback. We thank David Smith and Matthew Buffington for access to Hymenoptera
specimens that were examined for the Stephanoidea and Evanioidea studies. The Paleobiology
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution