Life history and habitat explain variation among insect pest populations subject to global change

Walter, Jonathan A.; Ives, Anthony R.; Tooker, John F.; Johnson, Derek M.

doi:10.1002/ecs2.2274

Cited by 21 publications

(25 citation statements)

References 71 publications

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“…geographical space) to be represented as the sum of many sine waves of different frequency. In a similar fashion, temporal patterns in pest populations were characterized using a combination of wavelet analyses and autoregressive moving-average model fitting (Walter et al 2018). The wavelet and spectral analyses estimate the amount of variation in a time series attributable to a particular frequency (scale) at a particular point in time.…”

Section: Methodsmentioning

confidence: 99%

“…For example, in a 14-yr time series of moth light trap data from an alder carr undisturbed forest (where no successional trends were expected), both positive and negative trends were found in many more species than expected by chance (Lepš et al 1998). Similarly, in analyses of various time series of agricultural and forest pest insect populations in the United States Walter et al (2018) found that half of the time series exhibited a long-term trend. Thus, synchrony values can also be affected by these trends.…”

Section: Introductionmentioning

confidence: 95%

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Accounting for long‐term directional trends on year‐to‐year synchrony in species fluctuations

et al. 2019

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What determines the stability of communities under environmental fluctuations remains one of the most debated questions in ecology. Scholars generally agree that the similarity in year‐to‐year fluctuations between species is an important determinant of this stability. Concordant fluctuations in species abundances through time (synchrony) decrease stability while discordance in fluctuations (anti‐synchrony) should stabilize communities. Researchers have interpreted the community‐wide degree of synchrony in temporal fluctuations as the outcome of different processes. However, existing synchrony measures depend not only on year‐to‐year species fluctuations, but also on long‐term directional trends in species composition, for example due to land‐use or climate change. The neglected effect of directional trends in species composition could cause an apparent increase in synchrony that is not due to year‐to‐year fluctuations, as species that simultaneously increase (or decrease) in abundance over time will appear correlated, even if they fluctuate discordantly from year to year. The opposite pattern is also conceivable, where different species show contrasting trends in their abundances, thus overestimating year‐to‐year anti‐synchrony. Therefore, trends in species composition may limit our understanding of potential ecological mechanisms behind synchrony between species. We propose two easily implementable solutions, with corresponding R functions, for testing and accounting for the effect of trends in species composition on overall synchrony. The first approach is based on computing synchrony over the residuals of fitted species trends over time. The second approach, applicable to already existing indices, is based on three‐terms local variance, i.e. computing variance over three‐years‐long, movable windows. We demonstrate these methods using simulations and data from real plant communities under long‐term directional changes, discussing when one approach can be preferred. We show that accounting for long‐term temporal trends is necessary and that separation of effect of trends and year‐to‐year fluctuation provides a better understanding of ecological mechanisms and their connections with ecological theory.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Accounting for long‐term directional trends on year‐to‐year synchrony in species fluctuations

et al. 2019

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“…Because synchronous local patterns are amplified in the area‐wide total (Schindler et al ., ), these synchronous fluctuations can manifest as intermittent or periodic outbreaks, particularly for relatively abundant species like corn earworm, true armyworm, and forage looper. State‐wide population fluctuations of beet armyworm, celery looper, corn earworm, dingy cutworm, and forage looper were characterised as cyclic in a separate analysis (Walter et al ., ), and spatial synchrony probably magnifies the negative impacts of cyclic outbreaks. Although its overall abundance declined, due in part to the introduction of Bt corn (Bohnenblust et al ., ), corn earworm remained relatively abundant throughout the study period, and its populations have become increasingly synchronous since the 1990s.…”

Section: Discussionmentioning

confidence: 99%

“…Climate and weather, by which we distinguish between, respectively, long‐term and short‐term changes in atmospheric conditions, have long been recognised as important factors regulating insect populations (Andrewartha and Birch ), and in recent decades concerns have emerged that climate change may increase the frequency and severity of damaging insect outbreaks (Cannon ; Logan et al ., ; Gregory et al ., ; Björkman et al ., ). Documented responses of insect pest populations to climate change vary widely (Johnson et al ., ; Haynes et al ., ; Ouyang et al ., ), however, ostensibly due in part to differences in life history and physiology (Walter et al ., ). Identifying which environmental variables drive population fluctuations, and how, is a first step towards predicting pest outbreaks in a changing climate.…”

Section: Introductionmentioning

confidence: 97%

Weather and regional crop composition variation drive spatial synchrony of lepidopteran agricultural pests

Walter

Sheppard

Venugopal

et al. 2019

Ecological Entomology

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1. Spatial synchrony, the tendency for temporal population fluctuations to be correlated across multiple locations at regional scales, is common and contributes to the severity of outbreaks and epidemics, but is little studied in agricultural pests.2. This study analysed spatial synchrony from 1974 to 2008 in 16 lepidopteran agricultural pests in Maryland, U.S.A., and investigated whether pest synchrony is driven by interannual variability in seasonal weather and the areas planted in different crop types.3. Lepidopteran pests exhibited high degrees of spatial synchrony, which was driven by environmental variation, a phenomenon known as the Moran effect. Region-wide variation in the areas planted in major crops drove spatially synchronous abundance fluctuations in more than half of studied species. The combination of weather and crop composition explained large fractions of synchrony in black cutworm, corn earworm, European corn borer, and spotted cutworm populations. Other pests, including forage looper and variegated cutworm, displayed a high degree of spatial synchrony, but without dependence on the tested drivers.4. The study finding that synchronous variation in the area planted in different crop types contributed to synchronous pest abundance fluctuations suggests that strategies to reduce synchrony in changes in crop type across a region could reduce the severity of pest outbreaks and enhance the stability of agricultural systems.

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“…In the US, declines have been 76 documented in populations of several wild bee species, butterflies in Ohio and lowland 77 California, and the migratory monarch butterfly (12)(13)(14)(15), while beekeepers sustain losses of > 78 40% of their managed honey bee colonies annually (16). There is also evidence that populations 79 of some insect pests are declining (17,18). 80…”

Section: Significance Statement 49mentioning

confidence: 99%

Rising insecticide potency outweighs falling application rate to make US farmland increasingly hazardous to insects

et al. 2019

Preprint

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28Each year, millions of kilograms of insecticides are applied to crops in the US. While insecticide 29 use supports food, fuel, and fiber production, it can also threaten non-target organisms, a concern 30 underscored by mounting evidence of widespread insect decline. Nevertheless, answers to basic 31 questions about the spatiotemporal patterns of insecticide use remain elusive, due in part to the 32 inherent complexity of insecticide use, and exacerbated by the dispersed nature of the relevant 33 data, divided between several government repositories. Here, we integrate these public datasets 34 to generate county-level annual estimates of total 'insect toxic load' (honey bee lethal doses) for 35 insecticides applied in the US between 1997-2012, calculated separately for oral and contact 36 toxicity. To explore the underlying drivers of the observed changes, we divide insect toxic load 37 into the components of extent (area treated) and intensity (application rate x potency). We show 38 that while contact-based insect toxic load remained relatively steady over the period of our 39 analysis, oral-based insect toxic load increased roughly 9-fold, with reductions in application rate 40 outweighed by disproportionate increases in potency (toxicity/kg) and increases in extent. This 41 pattern varied markedly by region, with the greatest increases seen in Heartland and Northern 42Great Plains regions, likely driven by use of neonicotinoid seed treatments in corn and soybean. 43In this "potency paradox," US farmland has become more hazardous to insects despite lower 44 volumes of insecticides applied, raising serious concerns about insect conservation and 45 highlighting the importance of integrative approaches to pesticide use monitoring. 46 47 48 the potency (toxicity/kg) of insecticides applied and in the area treated; the volume of 56 insecticides applied declined. Toxic load increased most dramatically in regions where 57 neonicotinoid seed treatments for field crops are commonly used. 58 59 395

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Life history and habitat explain variation among insect pest populations subject to global change

Cited by 21 publications

References 71 publications

Accounting for long‐term directional trends on year‐to‐year synchrony in species fluctuations

Accounting for long‐term directional trends on year‐to‐year synchrony in species fluctuations

Weather and regional crop composition variation drive spatial synchrony of lepidopteran agricultural pests

Rising insecticide potency outweighs falling application rate to make US farmland increasingly hazardous to insects

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