Symbiont Spillover from Invasive to Native Woodwasps

Abstract

Hosts and their associated microbes are being increasingly introduced around the world, which can lead to novel host/microbe associations via new sympatries. Woodwasps (Hymenoptera: Siricidae) are able to utilize wood for its nutrients due to obligate mutualistic associations with white rot fungi in the genus Amylostereum and when invasive woodwasps are introduced to new areas, their symbionts accompany them. There is increasing evidence that woodwasp-fungus associations previously believed to be highly specific are actually flexible. We show that in North America, both Urocerus albicornis and Urocerus cressoni, which develop in trees in the Pinaceae, usually use Amylostereum chailletii but sometimes carry an Amylostereum areolatum strain putatively introduced to North America by the invasive woodwasp Sirex noctilio. Symbiont spillover from invasive to native hosts is a source of new host/introduced symbiont associations that could result in changes in microbes and host fitness with the potential to impact communities.

First record of the invasive woodwasp, Urocerus albicornis (Hymenoptera: Siricidae), from a local forest in Japan

“…The invasive woodwasp, U . albicornis, has a symbiotic relationship with the fungi Amylostereum areolatum and A. chailletii (Castrillo et al, ; Hajek et al, ), while the native woodwasp U. antennatus is associated with A . laevigatum (Tabata & Abe, ; Tabata et al, ).…”

“…laevigatum (Tabata & Abe, ; Tabata et al, ). Hajek et al () demonstrated symbiont spillover from an invasive woodwasp Sirex noctilio to native woodwasp Urocerus spp. in North America, presumably via horizontal transmission during sequential use of the same wood for larval development.…”

“…The invasive woodwasp, U. albicornis, has a symbiotic relationship with the fungi Amylostereum areolatum and A. chailletii (Castrillo et al, 2015;Hajek et al, 2018), while the native woodwasp U. antennatus is associated with A. laevigatum (Tabata & Abe, 1999;Tabata et al, 2012). Hajek et al (2018) Ibaliidae) is a natural enemy of U. albicornis in North America (Champlain, 1922). Similarly, Ibalia leucospoides ssp.…”

“…Many species of woodwasps (horntails) (Hymenoptera: Siricidae) are forest pests that attack a wide range of trees (Morgan, 1968;Schiff et al, 2012). Most siricid woodwasp species carry symbiotic fungi in their mycangia, and the fungi are transferred into host trees during oviposition (Hajek, Harris, & Bittner, 2018;Kuramitsu et al, 2019;Tabata, Miyata, & Maeto, 2012). Immature woodwasps feed on liquids from the fungi-infected part of wood (Thompson, Bodart, McEwen, & Gruner, 2014).…”

Symbionts mediate oviposition behaviour in invasive and native woodwasps

“…Preference for this fungal strain by S. nigricornis in the present study is consistent with the fact that larvae of this native Sirex are known to develop in the same trees as S. noctilio (Long et al ., ; Ryan et al ., ; Hajek et al ., ) and horizontal transmission of Amylostereum between Sirex species appears to occur within trees (Hajek et al ., ; Wooding et al ., ). Sirex species were previously considered specific to single Amylostereum species (Talbot, ; Gilbertson, ), although studies of Sirex and Urocerus have demonstrated flexibility in the Amylostereum species being carried (Wooding et al ., ; Fitza et al ., ; Hajek et al ., ), in particular by two Sirex native to North America, including S. nigricornis (Hajek et al ., ; Olatinwo et al ., ). Although relatively little is understood about the biology and behaviour of S. nigricornis , flexibility in symbiont use could be advantageous now that the competitive S. noctilio is present.…”