Reproductive strategy of a woodwasp with no fungal symbionts, Xeris spectrum (Hymenoptera: Siricidae)

Abstract

Experiments were conducted to elucidate the reproductive strategy of the siricid woodwasp, Xeris spectrum, which carries no substantial symbiotic fungi in its body, in a comparison with the life cycles of two fungus-carrying siricid woodwasp species, Sirex nitobei and Urocerus japonicus, by considering ecological traits such as seasonal patterns of occurrence, spatial distribution of emergence on a tree, and oviposition activities. Part of the X. spectrum populations emerged in spring, during May and June, while others emerged in summer, during August and September, simultaneously with other siricid fungus-carrying woodwasps. The vertical distribution pattern of X. spectrum emergence holes on the trunk closely coincided with the emergence hole pattern of S. nitobei. X. spectrum laid few eggs on fresh logs, old logs, or on logs inoculated with potato dextrose agar, whereas on logs inoculated with Amylostereum chailletii or A. areolatum, X. spectrum females oviposited no less than 30%, on average, of their potential eggs. Moreover, the oviposition sites on these logs were concentrated near the Amylostereum inoculation positions. These results indicate that X. spectrum has evolved a life history that utilizes fungal symbionts of other woodwasp species without itself possessing any symbiotic fungus. Moreover, X. spectrum has evolved a dual reproductive system in that (1) some adults emerge in summer during the same emergence period as the fungus-carrying woodwasps and thereby oviposit on host trees already inoculated with fungi, and (2) other adults emerge the next spring and oviposit on trees that were inoculated with fungi a year earlier.

Community Composition and Phenology of Native Siricidae (Hymenoptera) Attracted to Semiochemicals in Minnesota

“…1). Annual variation such as this is not undocumented; in Japan, X. spectrum emergence varied nine-fold between study years and U. japonicus (F. Smith) was only captured in one of 2 yr (Fukuda and Hijii 1997). Conversely, populations of S. juvencus, U. cressoni, and U. albicornis were relatively consistent from 2006 to 2008 in our study (Fig.…”

“…1). Within the year, a late summer peak in Siricidae abundance is common (Fukuda and Hijii 1997, McIntosh et al 2001, Smith and Schiff 2002, Costello et al 2008) with X. spectrum being the only exception. This species, which does not carry symbiotic fungi, emerges earlier than most other siricids (Fukuda and Hijii 1997, Fig .…”

“…fungi and tend to oviposit in areas that were inoculated previously with a wood decay fungus by another siricid (Fukuda and Hijii 1997). Hymenopteran parasitoids Schiff 2002, Long et al 2009) and host resistance (Morgan 1968) are agents that contribute to natural population control of native Siricidae in North America.…”

Post-disaster Forest Management and Bark Beetle Outbreak in Tatra National Park, Slovakia

“…Woodwasp larvae can digest sapwood with low nutritional quality with the aid of symbiosis (Kukor and Martin 1983). In the earlier study, we clarified that a woodwasp with no fungal symbionts, Xeris spectrum can utilize the fungal symbionts of other woodwasp species without possessing any symbiotic fungi of its own (Fukuda and Hijii 1997). Moreover, the larvae of funguscarrying woodwasp species cannot develop on living trees.…”

Anthropogenic effects on interaction outcomes: examples from insect-microbial symbioses in forest and savanna ecosystems

“…At this point, the wasps also introduce a phytotoxic mucus that affects the defense mechanisms of the tree which is important for the establishment of both the wasp and the fungus (Coutts 1969). Only one genus of Siricidae, Xeris, do not have mycangia, but rather infect wood that has previously been colonized by Amylostereum following attack by other siricids or wounding (Fukuda and Hijii 1997). The fungus is thought to facilitate the tunneling of developing wasp larvae by physically softening the wood by causing white-rot.…”