Galls on galls: A hypergall‐inducing midge and its parasitoid community

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THE SCIENTIFIC NATURALIST
Galls on galls: A hypergall-inducing midge and its
parasitoid community
Quinlyn Baine | Emily E. Casares | Evangelina Carabotta |
Vincent G. Martinson | Ellen O. Martinson
Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA
Correspondence
Ellen O. Martinson
Email: emartinson@unm.edu
Handling Editor: John Pastor
KEYWORDS: Aciurina, Cecidomyiidae, chamisa, ecosystem engineer, endogall, Ericameria, inquiline, rabbitbrush, Rhopalomyia
Insect-induced plant galls are parasitic structures that
display forms and pigments not seen in the normal devel-
opment of the host plant (Redfern, 2011). In western
North America, Aciurina bigeloviae (Cockerell 1890)
(Diptera, Tephritidae) (hereafter Aciurina) (Figure 1A,B)
induces a large (~9–13 mm in diameter), densely haired,
spherical gall on Ericameria nauseosa var. graveolens
(Nuttall) Reveal & Schuyler (Asteraceae), also known
as rubber rabbitbrush or chamisa (Figure 1C). Aciurina
females oviposit into leaf buds where the larva hatches
and remains within the stem of the rabbitbrush through-
out the summer. In early fall, the larva induces growth of
the external gall structure, where it consumes the highly
nutritive tissue that develops in the interior of the gall.
Aciurina emerges in early spring after overwintering in
the gall as a larva (Figure 2).
While the primary function of a gall is to provide protec-
tion and nutrition to the offspring of the gall inducer, these
predictable structures are exploited by a variety of associ-
ated organisms to obtain needed resources (i.e., nutrition
and shelter) (Harper et al., 2004;Redfern,2011;Stone&
Schönrogge, 2003). The majority of gall-associated species
fall into three functional guilds: parasitoid, predator, and
inquiline (Stone et al., 2002). Parasitoids and predators
feed directly on the larvae of the primary galler. In con-
trast, inquilines (e.g., beetles, mites, midges, wasps) are
specialist herbivores that feed on galled plant tissue
(Askew et al., 2013; Ward et al., 2020).
Gall-associated inquilines generally feed on tissue
modified by the primary galler (Ward et al., 2020); however,
a rarely observed subset of inquilines induce a hypergall,
which is a secondary gall that forms on previously
galled plant tissue (Ferraz & Monteiro, 2003;Hawkins&
Goeden, 1982;Pénzesetal.,2012;Wardetal.,2020).
Hypergallers modify the original gall structure into a
further specialized chamber for nourishment and protec-
tion, which distinguishes hypergallers from other inqui-
lines. Some previous studies refer to hypergallers as
“endogallers”because the secondary gall is completely
surrounded by original galled tissue (Ferraz & Monteiro,
2003; Hawkins & Goeden, 1982; Pénzes et al., 2012; Ward
et al., 2020). However, we propose “hypergaller”as a
more inclusive term for secondary galler that can form
independent structures that protrude into the primary
galler’s chamber or externally from the original gall.
We have found only six hypergalling groups in the cur-
rent literature (Appendix S1: Section S2), the majority of
which are limited to a single study or a brief mention
(Ferraz & Monteiro, 2003;Gagné,1989;Hawkins&
Goeden, 1982; Headrick & Goeden, 1997; Pénzes et al.,
2012; Solinas & Bucci, 1982;Wardetal.,2020). These
groups include hypergalling wasps, scales, and midges on
a variety of primary gallers. Some hypergallers are
indirectly lethal to the primary gallers because growth
of the hypergall can extend into the primary galler’s
central chamber, compressing the primary galler larva
Received: 10 November 2022 Revised: 1 February 2023 Accepted: 2 February 2023
DOI: 10.1002/ecy.4018
Ecology. 2023;104:e4018. https://onlinelibrary.wiley.com/r/ecy © 2023 The Ecological Society of America. 1of6
https://doi.org/10.1002/ecy.4018