DOI: 10.5061/dryad.s3b66h9
title: Data from: Facultative bacterial endosymbionts shape parasitoid food webs in natural host populations: a correlative analysis

description: 1.Facultative bacterial endosymbionts can protect their aphid hosts from
 natural enemies such as hymenopteran parasitoids. As such, they have the
 capability to modulate interactions between aphids, parasitoids and
 hyperparasitoids. However, the magnitude of these effects in natural aphid
 populations and their associated parasitoid communities is currently
 unknown. Moreover, environmental factors such as plant fertilization and
 landscape complexity are known to affect aphid‐parasitoid interactions but
 it remains unclear how such environmental factors affect the interplay
 between aphids, parasitoids and endosymbionts. 2.Here, we tested whether
 facultative endosymbionts confer protection to parasitoids in natural
 populations of the English grain aphid, Sitobion avenae, and if this is
 affected by plant fertilization and landscape complexity. Furthermore, we
 examined whether the effects of facultative endosymbionts can cascade up
 to the hyperparasitoid level and increase primary‐hyperparasitoid food web
 specialization. 3.Living aphids and mummies were collected in fertilized
 and unfertilized plots within 13 wheat fields in Central Germany. We
 assessed the occurrence of primary parasitoid, hyperparasitoid and
 endosymbiont species in aphids and mummies using a newly established
 molecular approach. 4.Facultative endosymbiont infection rates were high
 across fields (~80 %), independent of whether aphids were parasitized or
 un‐parasitized. Aphid mummies exhibited a significantly lower share of
 facultative endosymbiont infection (~38 %). These findings suggest that
 facultative endosymbionts do not affect parasitoid oviposition behavior,
 but decrease parasitoid survival in the host. Facultative endosymbiont
 infection rates were lower in mummies collected from fertilized compared
 to unfertilized plants, indicating that plant fertilization boosts the
 facultative endosymbiont protective effect. Furthermore, we found strong
 evidence for species‐specific and negative cascading effects of
 facultative endosymbionts on primary and hyperparasitoids, respectively.
 Facultative endosymbionts impacted parasitoid assemblages and increased
 the specialization of primary‐hyperparasitoid food webs: these effects
 were independent from and much stronger than other environmental factors.
 5.The current findings stongly suggest that facultative endosymbionts act
 as a driving force in aphid‐parasitoid‐hyperparastioid networks: they
 shape insect community composition at different trophic levels and
 modulate, directly and indirectly, the interactions between aphids,
 parasitoids and their environment.
description: The molecular detection
 and identification of facultative endosymbionts and parasitoids in field
 collected Sitobion avenaeThe molecular detection
 and identification of facultative endosymbionts and parasitoids in field
 collected Sitobion avenae. Positive and negative detections are
 represented as “1” and “0”, respectively. Spaces are replaced using
 “_”.Ye et
 al. Original data.csv