Prey-Mediated Effects of Drought on the Consumption Rates of Coccinellid Predators of Elatobium abietinum

Abstract

Climate change in the UK is predicted to cause an increase in summer drought events. Elatobium abietinum is an important pest of Sitka spruce (Picea sitchensis), causing defoliation of trees, and is predicted to become more abundant in response to climatic change, reducing spruce productivity. Populations are also moderated by invertebrate predators, though the extent to which this might be modified under a changing climate is unclear. Elatobium abietinum is preyed upon by the coccinellid species Aphidecta obliterata (a spruce specialist) and Adalia bipunctata (a generalist), populations of which naturally occur in spruce plantations. This study sought to investigate the effect of different intensities and frequencies of drought on the consumption rate of the aphids by the two coccinellids. In Petri dish trials, severe drought stress increased the consumption rates of 3rd instar aphids by both adult and larval coccinellids. Moderate intermittent stress tended to result in a reduced consumption rate for larval coccinellids only, suggesting an age-dependent response. The findings of this study suggest that, under drought conditions, a prey-mediated effect on predator consumption, and, therefore, biocontrol efficacy, is likely, with drought intensity and frequency playing an important role in determining the nature of the response.

Implications of animal water balance for terrestrial food webs

“…Instead, food web ecologists often focused on effects of variable moisture from the bottom-up, via effects on plants, with energy or nutrients driving food web responses (e.g. [22][23][24][25][26][27][28]). For instance, Banfield-Zanin and Leather [24] recently found increased per capita consumption of aphids by lady beetles when aphids were reared on drought-stressed spruce trees, which led to smaller aphids.…”

“…[22][23][24][25][26][27][28]). For instance, Banfield-Zanin and Leather [24] recently found increased per capita consumption of aphids by lady beetles when aphids were reared on drought-stressed spruce trees, which led to smaller aphids. Other studies have documented significant bottom-up effects from precipitation associated with ENSO cycles [26,[29][30][31].…”

Coexistence between similar invaders: The case of two cosmopolitan exotic insects

“…Our findings documented that lady beetle activity and thus, the interactions between these two dominant species were strongly related to temperatures via daily degree day accumulation, and to a lesser extent, precipitation accumulation. Warmer temperatures affect lady beetles directly by increasing metabolism and rates of egg and larval development, but also require higher rates of prey consumption (Banfield-Zanin and Leather 2016, Speights and Barton 2019). Although warmer temperatures are generally associated with increased activity, there is evidence that increased temperatures may cause high mortality of eggs, larvae, and some adults above a heat stress threshold (Acar et al 2001, Knapp and Nedvěd 2013, Auad et al 2014).…”

“…Responses of aphids are often species-specific but warming temperatures and milder winters generally shift aphid phenology such that early season flight activity occurs sooner in the season (Bell et al 2015, Wu et al 2020). Under laboratory simulated drought conditions, aphids tended to be less nutritious and smaller in size, requiring higher consumption rates by lady beetle species to meet dietary requirements (Banfield-Zanin and Leather 2016). Therefore, climate change may lead to directional shifts in species phenology and the timing of trophic interactions such that predatory-prey interactions may become more synchronous or asynchronous, with implications for biological control.…”

Aphidophagous ladybirds (Coleoptera: Coccinellidae) and climate change: a review

“…Elevated carbon dioxide can increase aphid consumption and ladybird growth rate (Srinivasa Rao et al ., 2018) or have a negligible effect (Chen et al ., 2007). The effect of water availability on aphid consumption appears to vary with drought intensity (Banfield‐Zanin & Leather, 2016). When combined together with variation in host plant and aphid responses, outcomes are highly specific to the system under examination.…”