il ' ii - Northern Research Station - USDA Forest Service

GALL MIDGES INFESTING CHENOPODIACEAE:
BIOLOGY AND TAXONOMY
Netta Dorchin
Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel t
Abstract.---Gall midges (Cecidomyiidae) are dominant among the relatively few insect
taxa that are known to infest plants of the beet family (Chenopodiaceae). More than 300
gall midge species have been reported from chenopod hosts, and about 115 species of
Chenopodiaceae are known to be hosts for gall midges. This extensive speciation of gall
midges on chenopods is demonstrated by current data on plant-midge relationships, with
special focus on the Lasiopterini, which is the largest group involved, and a possible
, _ explanation for this evolutionary process is discussed. Taxonomic difficulties conceming
the Lasiopterini are also reviewed.
CHENOPODS AS HOSTS FOR GALL MIDGES
Chenopodiaceae is a cosmopolitan family of plants,
Atriplex
23%(300)
mainly distributed in the deserts of central Asia, the Anabasis
Middle East, Africa, Australia and in south American 3.2%(42)
prairies. The family comprises about 100 genera and Suaeda
1,300 species, with the most prominent genera being 7.7%(100)
Anabasis, Atriplex, Salsola, Suaeda and Haloxylon, Haloxylon Salsola
together comprising more than 600 species worldwide 2%(25) 12%(150)
(Mabberly 1997) (fig. l a). Chenopods are annual or A
perennial herbaceous plants, shrubs, or rarely, trees, often
dominating a variety of harsh biotopes such as salines Atriplex
and deserts, where almost no other plants grow. It is in 10%(12)Anabasis
these biotopes that chenopods form the characteristic 9%(11)
landscape of salt marshes, Irano-turanian prairies, and Suaeda
.sand dunes. Among the several anatomical and physi- 11%(13)
ological adaptations that enable chenopods to grow in
these extreme conditions, the best studied are their means Haloxylon Salsola
• for plant disposing of excess salts: concentrating them in 6%(7) 21%(24)
, its tissues or excreting them through epidermal salt-
B
secreting hairs or salt glands (Mozafar and Goodin 1970,
Waisel 1972). These mechanisms possibly also play a !
. role in the unpalatability of chenopods to most insects. Figure 1.--Five prominent genera within the
. Chenopodiaceae. A. number of species (total no. It
. While other arthropods seldom infest chenopods, more 1300), B. number of host species (total no. 117).
than 300 cecidomyiid species are exclusive chenopod
feeders, and the great majority of them are gall formers. 1997). In that study, I screened 41 out of the 76 cheno-
More than 100 species ofChenopodiaceae are known to pod species of Israel, and found 28 of them to be hosts of
be hosts of gall midges, and about 60 percent of them gall midges. Seven of these plants were not previously
belong to one of the five prominent genera mentioned known to be hosts. Out of these 28 hosts 55 species of
above (Anabasis, Atriplex, Salsola, Suaeda, and gall midges were reared, most of which are probably
Haloxylon, fig. 1b). However, many additional cheno- undescribed. The number of gall midge species per host
pod-infesting gall midges and chenopod hosts are still averaged 2 in that study. However, the number of gall
, awaiting discovery, as is indicated by a recent research midge species infesting a given host varies greatly
on the chenopod-infesting gall midges in Israel (Dorchin among the hosts, with many hosts yielding only one gall
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