Shifting daylength regimes associated with range shifts alter aphid‐parasitoid community dynamics

Abstract

With climate change leading to poleward range expansion of species, populations are exposed to new daylength regimes along latitudinal gradients. Daylength is a major factor affecting insect life cycles and activity patterns, so a range shift leading to new daylength regimes is likely to affect population dynamics and species interactions; however, the impact of daylength in isolation on ecological communities has not been studied so far. Here, we tested for the direct and indirect effects of two different daylengths on the dynamics of experimental multitrophic insect communities. We compared the community dynamics under “southern” summer conditions of 14.5‐hr daylight to “northern” summer conditions of 22‐hr daylight. We show that food web dynamics indeed respond to daylength with one aphid species (Acyrthosiphon pisum) reaching much lower population sizes at the northern daylength regime compared to under southern conditions. In contrast, in the same communities, another aphid species (Megoura viciae) reached higher population densities under northern conditions. This effect at the aphid level was driven by an indirect effect of daylength causing a change in competitive interaction strengths, with the different aphid species being more competitive at different daylength regimes. Additionally, increasing daylength also increased growth rates in M. viciae making it more competitive under summer long days. As such, the shift in daylength affected aphid population sizes by both direct and indirect effects, propagating through species interactions. However, contrary to expectations, parasitoids were not affected by daylength. Our results demonstrate that range expansion of whole communities due to climate change can indeed change interaction strengths between species within ecological communities with consequences for community dynamics. This study provides the first evidence of daylength affecting community dynamics, which could not be predicted from studying single species separately.

The impact of artificial light at night on nocturnal insects: A review and synthesis

“…Several studies have noted an influx of predatory and scavenging arthropods into lit areas (Davies, Bennie, & Gaston, ; Šustek, ), though this response appears to be taxon‐specific (Eccard, Scheffler, Franke, & Hoffmann, ; Manfrin et al, ; Meyer & Sullivan, ; van Grunsven, Jähnichen, Grubisic, & Hölker, ). Broad‐spectrum LED lights in combination with urban heat reduced pea aphid populations by increasing visibility and lengthening the activity period of their visually oriented coccinellid predators (Miller et al, ); however, in similar experiments, bright illumination decreased or did not affect rates of parasitism by parasitoid wasps (Kehoe et al, ; Sanders et al, , see Sanders, Kehoe, Cruse, Veen, & Gaston, ). The introduction of artificial light and noise causes parasitic frog‐biting midges to be unable to locate and feed from their túngara frog hosts (McMahon, Rohr, & Bernal, ).…”

“…Even low‐level ALAN increases perceived day length (Kyba, Ruhtz, Fischer, & Hölker, ), and could thereby induce seasonal polyphenism in stink bugs (Niva & Takeda, ) and aphids (Hardie, ; Sanders et al, ), or alter the calling songs of katydids (Whitesell & Walker, ). Low‐level ALAN is known to accelerate development in a range of insect taxa (Kehoe, Cruse, Sanders, Gaston, & Veen, , van Geffen, Grunsven, Ruijven, Berendse, & Veenendaal, , but see Durrant, Botha, Green, & Jones, ), with varying effects on fitness.…”

Prey–predator phenological mismatch under climate change

“…However, such expectation is less obvious for less tightly interactive systems such as preys and predators and to date it has mostly been described in a nutritional ecology context showing qualitative mismatches resulting from asynchronies between developmental stages of interacting organisms [45,46]. Nevertheless, some examples on the disruption of trophic interactions due to phenological asynchrony between primary and secondary consumers have been documented, such as among birds and insects [9,47] or host-parasitoid systems [48]. When asymmetric shifts in developmental rate or voltinism create asynchrony, new environmental constraints appear that can in turn drive the plastic response or the evolution of interacting species phenology toward resynchronization.…”

Orb-weaving spiders are fewer but larger and catch more prey in lit bridge panels from a natural artificial light experiment

“…Artificial light at night (ALAN) is an increasingly widespread pollutant that has considerable physiological and behavioral effects on wildlife, making it an urgent, worldwide conservation concern (Longcore & Rich, 2004;Hölker et al, 2010;Gaston et al, 2013;Falchi et al, 2016). Exposure to ALAN can alter circadian rhythms (Chittka, Stelzer & Stanewsky, 2013), inhibit reproduction (Bebas, Cymborowski & Giebultowicz, 2001;Van Geffen et al, 2015), accelerate development (Van Geffen et al, 2015;Kehoe et al, 2018), and lead to increased mortality (Eisenbeis, 2006).…”