Memory duration is positively correlated with host fruit preference and offspring performance in a polyphagous frugivore

Abstract

Understanding how polyphagous herbivores optimise foraging for multiple hosts remains unclear: prior experiences with hosts and the modification of subsequent behaviours (referred to in the broad sense as learning) have been proposed as one potential mechanism. A critical feature of learning is the effect of reward value, with learning and memory positively linked with reward quality. However, the links between host plant quality for offspring, prior experience and memory have not been researched in herbivorous insects. No‐choice and dual‐choice olfactometer assays were conducted to determine how prior oviposition experience on nine different fruits affected host preference, response times and the duration of altered response times (over subsequent days) in the polyphagous frugivore, Bactrocera tryoni (Froggatt). In no‐choice tests, the average time naïve B. tryoni took to respond to the different fruit odours differed and was directly correlated to larval host quality; for example, naïve females responded fastest to guava, a high‐quality larval host, and slowest to blueberry, a poor host. However, B. tryoni experienced on fruits for 24 h responded significantly faster to all fruits equally, regardless of fruit type. The duration of the experience‐based responses was directly correlated with fruit quality, with females displaying the longest response retention when experienced on high‐quality fruits and the shortest on low‐quality fruits. For B. tryoni, we demonstrate that the host responses following prior experience are influenced by the quality of a host plant for offspring survival.

Does memory help optimise fruit fly foraging at the landscape level?

“…2) Memory of oviposition experience is based on the work of Silva et al (2020). This research identified two main processes that occur when a fruit fly experiences various hosts in which it oviposits.…”

“…This behaviour was incorporated into the model by using a matrix of the results of the probability of preference for the different hosts. The host quality ranking was determined by the percent survival of the offspring in (Silva et al, 2020). The rules of this behaviour are outlined in fig.…”

“…Research into insect experience and memory has largely been focused on the hymenopteran order in the insects and therefore the majority of IBM's that include insect memory belong this group (Becher et al, 2016;Dubois et al, 2021). Whereas in the generalist herbivores, where an evolved response to host quality choice is more likely than an instant 'reward' (Silva et al 2020) there are few examples where memory have been incorporated into IBM's (Potting et al, 2005;Guttal et al, 2012).For generalist herbivorous insects, who discriminate between a broad range of hosts with varying qualities within and between hosts, it is hypothesised that they are at a disadvantage as the ability to remember such a broad host range is neurologically challenging (Bernays, 2001). Though a recent hypothesis "the sequential cues hypothesis" by Silva and Clarke (2020b) puts forward a potential solution to the difficulty of a broad diet breadth.…”

“…The larvae are restricted to the fruit that the females oviposit into. Females have an innate ability to rank hosts in which to oviposit, and this is correlated to larval survival (Balagawi et al, 2005;Silva et al, 2020). Recently it has been shown that prior oviposition experience modifies host choice (Silva and Clarke, 2020a;Silva et al, 2020).…”

“…Females have an innate ability to rank hosts in which to oviposit, and this is correlated to larval survival (Balagawi et al, 2005;Silva et al, 2020). Recently it has been shown that prior oviposition experience modifies host choice (Silva and Clarke, 2020a;Silva et al, 2020). If a female experiences oviposition into a poor host, then the following day, she is more likely to lay eggs in that poor host even if there are good quality hosts available nearby.…”