Monophyletic ApocritaOrussidae as sister group

• Chalinus braunsi • Photograph copyright Simon van Noort (Iziko)

The lack of robustness of the basal lineages of the Apocrita make inferring the groundplan biology problematic. Dowton &

Austin (2001)

Generalists Ectoparasitoids attacking hosts concealed in

wood

Stephanidae

• Foenatopus• Photograph copyright Simon van Noort (Iziko)

Stephanidae

• Share a number of morphological characteristics with orussids

• Idiobiont ectoparasitoids from start to finish

• Permanently paralyze host, oviposit on it

• No cocoon

Megalyridae

• Megalyridea capensis• Photograph copyright Simon van Noort (Iziko)

Megalyridae

• Presumed idiobiont ectoparasitoids of larval hosts

• Best studied species on cerambycids in wood

• Early Jurassic

• No subgenual organs?

• No cocoons

Aulacidae and Ibaliidae

• Attack hosts deeply buried in wood

• Oviposit in host eggs

• Koinobiont endoparasitoids

• Cocoons/No cocoons

• If ancestral biology = generalist ectoparasitoid attacking deeply concealed xylophagous and/or mycophagous hosts

• Then diversification of attack strategies on these hosts facilitated successful colonization of hosts in other habitats

Diversification of attack strategies on deeply

concealed hosts is suggested by the biologies of orussids,

stephanids, megalyrids, aulacids, and ibaliids, among

others

Subgenual Organs

• Substrate-borne vibrations

• Orussids (Vilhelmsen et al. 2001) and stephanids

• Xoridines and Labena

Detection of substrate-borne vibrations

• Makes for easy transition from the ancestral log– To stems and twigs– To other habitats with concealed hosts– Xanthopimpla on stems of stout grasses

Chemoreception

• Alternative/supplementary strategy for host location

• Ibaliidae and perhaps Aulacidae– Detection of symbiotic fungi in oviposition

hole

Chemoreception

• Host specificity through detection of host-associated odor cues (kairomones)

What Drives Diversification?(more questions than answers)

• Host stage attacked

• Koinobiosis

• Competition or Predator Avoidance?

• Synovigeny

Getting Inside

• Oviposition in the host egg– Ibaliid pathway to koinobiont endoparasitism

• Gradual internalization of parasitoid egg– Attaching to inside of cuticle instead of

outside (M. Shaw 1983)

• Changes in venom gland proteins

Oviposition in the Host Egg

• A commonly employed strategy

• Idiobiont egg parasitoids

• Koinobiont egg-larval parasitoids

• Mymaridae

Transitions

• Abundant evidence for repeated forays into an endoparasitic lifestyle

• And a variety of ways for doing so

• The Challenge– Does the endo to ectoparasitoid transition

ever occur, and if so, how is it achieved, biologically speaking