Large‐scale migration synchrony between parasitoids and their host

Abstract

Abstract. 1. Parasitoids are a valuable group for conservation biological control. In their role as regulators of aphid pests, it is critical that their lifecycle is synchronised with their hosts in both space and time. This is because a synchronised parasitoid community is more likely to strengthen the overall conservation biological control effect, thus damping aphid numbers and preventing potential outbreaks. One component of this host-parasitoid system was examined, that of migration, and the hypothesis that peak summer parasitoid and host migrations are synchronised in time was tested.2. Sitobion avenae Fabricius and six associated parasitoids were sampled from 1976 to 2013 using 12.2-m suction-traps from two sites in Southern England. The relationship between peak weekly S. avenae counts and their parasitoids was quantified.3. Simple regression models showed that the response of the peak parasitoids to the host was positive: generally, more parasitoids migrated with increasing numbers of aphids. Further, when averaged over time, the parasitoid migration peak date corresponded with the aphid migration peak. The co-occurrence of the peaks was between 51% and 64%. However, the summer peak in aphid migration is not steadily shifting forward with time unlike spring first flights of aphids. Cross-correlation analysis showed that there were no between-year lagged effects of aphids on parasitoids.4. These results demonstrate that the peak in migration phenology between host and parasitoid is broadly synchronised within a season. Because the threshold temperature for flight (> 12 ∘ C) was almost always exceeded in summer, the synchronising agent is likely to be crop senescence, not temperature. Studies are needed to assess the effects of climate change on the mismatch potential between parasitoids and their hosts.

The impact of climate change on wheat insect pests: current knowledge and future trends

“…Using a model that incorporated aphid and parasitoid responses, Hoover and Newman (2004) showed that climate change should not alter biological control of cereal aphids. Consistent with this, based on suction trap samples from 1976 to 2013 from two sites in Southern England, simple regression models showed that the peak parasitoid abundance was correlated with peak aphid abundance in this record (Perez-Rodriguez et al, 2015). Together, and based on the reports so far, there is little evidence that parasitism of aphids will be disrupted by climate change.…”

“…Data sets of pest abundance or pest injury in wheat systems might exist that have yet to be analysed in conjunction with historical climate records. Several of the publications cited in Table 1, although relatively recent, draw upon such archival records (Bell et al, 2014;Brabec et al, 2014;Woli et al, 2014;Huang et al, 2015;Perez-Rodriguez et al, 2015). Where such historical records are lacking, they should be initiated without delay to enable projections as climate change progresses.…”

“…Examples in which such effects have been examined rigorously are rare, including those specifi cally focused on cereal systems. As reviewed above, for aphids, data and models available suggest that parasitism will not be disrupted by climate change (Hoover and Newman, 2004;Dong et al , 2013;Perez-Rodriguez et al , 2015). On the other hand, the study of cereal leaf beetle (Evans et al, 2012) suggests warming trends could strongly reduce larval parasitism of this pest.…”

Molecular ecology of insect pests of agricultural importance: the case of aphids

“…braconids) are seen to function somewhat differently from predation by generalist arthropod predators such as ladybirds and spiders (Snyder & Ives, 2003). Analysis of samples from 1976 to 2013 from the RIS archive revealed a positive regulation of parasitoid braconid populations in response to their aphid host S. avenae (Perez-Rodriguez et al, 2015). There was also a broad synchronisation of the migration time of the parasitoids and that of the aphid within a season.…”

Different genetic structures revealed resident populations of a specialist parasitoid wasp in contrast to its migratory host

“…Seasonal migration of herbivorous insects to new habitats, which provides “enemy‐free space”, has been considered as one of the avoidance behaviors that have evolved in the host in response to parasitism (Chapman, Reynolds, & Wilson, ). However, parasitoids may evolve to synchronize migration with their hosts (Pérez‐Rodríguez, Shortall, & Bell, ), and even ahead of their hosts (Bortolotto, Júnior, & Hoshino, ). For instance, some Aphidiinae parasitoids show long‐range dispersal in egg and larval stages through host flight as well as through active dispersal by adult parasitoids (Bortolotto et al., ; Derocles, Plantegenest, Chaubet, Dedryver, & Le Ralec, ).…”