Are parasitoids serving as the conduit for the spread of
endosymbionts?
Parasitoids can serve as a driving force for the horizontal transfer of
endosymbionts (Haine, Pickup, & Cook, 2005) as their lifestyle entails
close cellular and tissue contact with their host. Horizontal transfer
involving parasitoids is generally unidirectional (from host to
parasitoid) because they usually end up killing the host. But
parasitoids can also act as phoretic vectors (Ahmed et al., 2015; Gehrer
& Vorburger, 2012) and can transmit Wolbachia by sequential
probing of infected and uninfected hosts. Moreover, horizontal transfers
can also happen between parasitoids if infected and uninfected larval
parasitoids share the same host (Huigens, De Almeida, Boons, Luck, &
Stouthamer, 2004). Such habits can also facilitate multiple infections
if parasitoids infecting same host have different endosymbiont
infections. As these multiple infections come in close contact, they can
undergo recombination. Such parasitoid-mediated horizontal transfer
could be an explanation for the distribution of A supergroupWolbachia infections in our sampling. Out of the 17Wolbachia A supergroup STs found, nine STs were found in
morphospecies which are parasitoid wasps (Hymenoptera). Seven STs were
found from Platygastridae and one each from Bethylidae and Diapriidae
(Table 1). Therefore, the comparatively higher incidence of
recombination in Wolbachia supergroup A infections could be due
to their presence in parasitoid hosts (Mascarenhas et al., 2016).
Similarly, predators and parasites can also be conduits for the spread
of endosymbionts as speculated by predation of infectedArmadillidium vulgare by uninfected Porcellio dilatatus(Le Clec’h et al., 2013) and predatory mite Metaseiulus
occidentalis and its prey, Tetranychus urticae (Hoy &
Jeyaprakash, 2005). In soil arthropod community, we also observed
incidences of Wolbachia recombination amongst predators.Wolbachia F supergroup ST-552, infecting morph0148 (Araneae-Zelotes ), had a fragment of gatB gene similar to A
supergroup ST-544 infecting morph0076 (Araneae- Orthobula ). Also,fbpA gene of ST-544 was found to have probably recombined with
ST-570 infecting Morph0375 (Coleoptera- Monolepta sp. ). Apart
from such trophic interactions within the community, if any member of a
community interacts with individuals of other community then it is
likely to spread endosymbionts from one community to other.