Hymenoptera

Ward, Anna K. G., Busbee, Robert W., Chen, Rachel A., Davis, Charles K., Driscoe, Amanda L., Egan, Scott P., Goldberg, Bailey A. R., Hood, Glen Ray, Jones, Dylan G., Kranz, Adam J., Meadely-Dunphy, Shannon A., Milks, Alyson K., Ott, James R., Prior, Kirsten M., Sheikh, Sofia I., Shzu, Shih-An, Weinersmith, Kelly L., Zhang, Linyi, Zhang, Y. Miles & Forbes, Andrew A., 2022, Borneosa aspera, Zoological Studies 61 (57), pp. 1-30 : 12-15

( Hymenoptera : Chalcidoidea: Torymidae : Toryminae )

6,338 individuals (mean = 111.2, range 1–2,378) reared from 57 gall types ( Table S1).

Summary of Natural History: Torymus wasps are primarily Holarctic in their distribution and there are more than 300 named species, though not all of them attack oak gall wasps ( Grissell 1995). Hosts are almost always insects in a concealed location, but from diverse orders. In the Nearctic, two species groups contain all of the oak gall-associated species. The fullawayi species group consists primarily of species that attack insects in cynipid oak galls ( Grissell 1976). Species in the tubicola group have a more diverse range of hosts, but several specialize on oak galls or on galls on other plant hosts ( Grissell 1976).

Most female Torymus have a long ovipositor (in some species, the ovipositor is more than the length of their body) that helps them attack hosts in concealed and otherwise protected locations. There is some evidence for apparent intraspecific variation in ovipositor length in some species, both between generations and within the same generation ( Eady 1958; Askew 1965), which may result in a larger than expected host range for any given species. In the Palearctic, oak gall associated species range between one and 41 host records ( Askew et al. 2013). The Nearctic species Torymus tubicola (Osten Sacken) is also described as a particularly generalist species, with more than 30 named oak gall hosts across the United States ( Grissell 1976; Noyes 2022). However, as for Ormyrus and Synergus some of the apparently generalist Torymus species in both the Palearctic ( Kaartinen et al. 2010) and Nearctic may harbor cryptic species.

Relationship to galler phylogeny: Torymus wasps have been reared from gallers across the Nearctic oak gall wasp phylogeny ( Ward et al. 2022), including from all four Palearctic lineages ( Fig. 5a ). Like Ormyrus , the genus houses essentially ubiquitous parasitoids in the oak gall system.

a) b)

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Biogeography and oak tree section: We reared Torymus from galls in all three floristic regions ( Fig. 5b ) and from all three oak sections ( Fig. 5c ). Torymus are also known from galls on oaks in section Protobalanus in California ( Grissell 1976).

Tree organ and gall size: Torymus wasps were found in association with galls on all six organ types ( Fig. 5d ). They emerged more often from large and medium sized galls than from small (> 5 mm) galls ( Fig. 5e ). Though our collections were exclusive to aboveground galls, Torymus have also been reared from root galls ( Forbes et al. 2016).

Co-occurrence with other natural enemies: Torymus were reared from the same gall types producing Eurytoma wasps significantly more often than predicted (P = 0.0200). Conversely, Torymus were significantly less likely to be reared from the same gall types as Ceroptres wasps ( Fig. 5f; P = 0.0003). Previous work has shown that Torymus wasps can emerge from the same individual galls as other insects, though these other insects are usually either known or suspected inquilines (e.g., Synergus , Brasema ), or suspected parasites of inquilines (e.g., Allorhogas Gahan ) ( Hall 2001).

Additional Notes: The implication from the current Torymus taxonomic organization ( Grissell 1976) and from molecular phylogeny of family Torymidae ( Janšta et al. 2018) is that oak galls have been colonized two or more times, such that gall-associated Torymus are para- or polyphyletic. Any future phylogenetic assessment of Torymus coevolution with oak galls should therefore endeavor to include non-gall associated taxa.

Figures

Fig. 5. Summary of data for Torymus collected from Nearctic galls. For full explanation of figure details, refer to figure 1 legend. a) Associations of Torymus with the Nearctic oak gall wasp phylogeny (Fig. S1). b) Gall types from which Torymus were reared in the Californian (blue), Mexican and Central American (orange), and Eastern North American (green) floristic provinces. c) Associations of Torymus with trees in sections Quercus (Q), Lobatae (L), and Virentes (V). d) Association of Torymus with gall types on different oak tissues. e) proportion of gall types of three size categories (“small” <0.5 mm; “medium”, “large”> 20 mm) from which Torymus were reared. f) Results of probabilistic co-occurrence analysis for Torymus against seven other common associates. Yellow = significantly less likely to co-occur; blue = significantly more likely to co-occur; gray = no difference from probabilistic expectations. g) Torymus lateral habitus.