John S. Terblanche

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Verified

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• PhD
• Professor (Full) at Stellenbosch University

Climate change is altering the abundance and geographic distributions of insects, with potential consequences for human health, sustainable agriculture, and ecosystem function. How insects will be affected during their routine movements by climate-change-associated warming remains poorly understood. Here, we therefore review the potential impacts o...

Heatwaves are increasing in frequency and intensity due to climate change, pushing animals beyond physiological limits. While most studies focus on survival limits, sublethal effects on fertility tend to occur below lethal thresholds, and consequently can be as important for population viability. Typically, male fertility is more heat-sensitive tha...

Harmonia axyridis is an invasive beetle (Coleoptera: Coccinellidae), native to Asia, that has established on four continents beyond its native range and was first observed in South Africa in 2001. Using microsatellite data and a comprehensive geographic coverage of international (17 locations) and South African (14 locations) beetle samples, we inf...

Global trade in fresh fruit and vegetables, intensification of human mobility, and climate change facilitate fruit fly (Diptera: Tephritidae) invasions. Life-history traits, environmental stress response, dispersal stress, and novel genetic admixtures contribute to their establishment and spread. Tephritids are among the most frequently intercepted...

Mechanisms aimed at recovering from heat-induced damages are closely associated with the ability of ectotherms to survive exposure to stressful temperatures. Autophagy, a ubiquitous stress-responsive catabolic process, has recently gained renewed attention as one of these mechanisms. By increasing the turnover of cellular structures as well as the...

Larvicides are widely used for mosquito control, but resistance development complicates efforts. We investigated the interplay between insecticide resistance and environmental stress in Aedes albopictus, Culex pipiens pipiens, and Culex pipiens molestus. Mosquitoes were selected for resistance to diflubenzuron and Bacillus thuringiensis subsp. isra...

This study evaluates the potential of quantum dots (QDs) as a marking method for Mediterranean fruit flies (Ceratitis capitata) (Medfly) in comparison to traditional fluorescent powder. As a highly destructive pest impacting a wide variety of fruit crops, an effective marking technique is essential for improving the biological understanding and man...

Thermal performance curves (TPCs) have become an important part of the thermal biologists’ toolbox in understanding how organisms may respond to temperature variation. The aim of this study was to investigate how temperature affects the locomotion of soil arthropods (Collembola and Acari), and explore how these responses might influence the potenti...

BACKGROUND Adult trapping is essential for detecting, monitoring, and controlling fruit fly pests (Diptera: Tephritidae), its efficacy depends on both biotic and abiotic factors. Although efficient commercial trapping systems exist, capturing major invasive tephritid pests remains challenging. This study investigated whether sex, thermal history, t...

The Polyphagous Shot Hole Borer (PSHB; Euwallacea fornicatus, Coleoptera: Curculionidae: Scolytinae) is an invasive and destructive tree pest. To assess whether thermal acclimation influences E. fornicatus locomotion performance (i.e., induced plastic responses) that may influence invasion potential, beetles were acclimated to three temperatures...

Here, we present novel high quality genome assemblies for five invasive tephritid species of agricultural concern: Ceratitis capitata, C. quilicii, C. rosa, Zeugodacus cucurbitae and Bactrocera zonata (read depths between 65 and 78x). Three assemblies (C. capitata, C. quilicii and Z. cucurbitae) were scaffolded with chromosome conformation data and...

Knowing how environmental conditions affect performance traits in pest insects is important to improve pest management strategies. It can be informative for monitoring, but also for control programs where insects are mass‐reared, and field‐released. Here, we investigated how adult thermal acclimation in sterile Bactrocera dorsalis affects dispersal...

Efficient water balance is key to insect success. However, the hygric environment is changing with climate change; although there are compelling models of thermal vulnerability, water balance is often neglected in predictions. Insects survive desiccating conditions by reducing water loss, increasing their total amount of water (and replenishing it)...

To celebrate its centenary year, Journal of Experimental Biology (JEB) commissioned a collection of articles examining the past, present and future of experimental biology. This Commentary closes the collection by considering the important research opportunities and challenges that await us in the future. We expect that researchers will harness the...

Background Thermal history may induce phenotypic plasticity in traits that affect performance and fitness. One type of plastic response triggered by thermal history is acclimation. Because flight is linked to movement in the landscape, trapping and detection rates, and underpins the success of pest management tactics, it is particularly important t...

Flight-reproduction trade-offs, such that more mobile individuals sacrifice reproductive output (e.g., fecundity) or incur fitness costs, are well-studied in a handful of wing-dimorphic model systems. However, these trade-offs have not been systematically assessed across reproduction-related traits and taxa in wing monomorphic species despite havin...

The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), holds an impressive record of successful invasion events promoted by globalization in fruit trade and human mobility. In addition, C. capitata is gradually expanding its geographic distribution to cooler temperate areas of the Northern Hemisphere. Cold tolerance of C. capitata...

In many pests, insecticide efficacy is dependent on environmental conditions, including ambient temperature. However, it remains unknown if thermal history alters sub-lethal effects to potentially enhance or reduce pesticide resistance in the false codling moth (FCM) Thaumatotibia leucotreta. Here, using FCM, a pest of economic importance in South...

Variation in geographical range size among closely related species may result from differences in physiological traits, such as desiccation tolerance, that enable these species to interact with their environment or adapt to new surroundings. We tested the hypothesis that insect species with a broader geographical range have either a higher basal de...

The False Codling Moth (FCM) (Meyrick) (Thaumatotibia leucotreta; Lepidoptera: Tortricidae) is a highly polyphagous, major agricultural pest indigenous to sub-Saharan Africa. With growing international trade there is increasing concern about introducing this pest into other countries. In South Africa, FCM poses a risk to multiple crops, and is curr...

1. Fire is an important cause of disturbance which directly shapes many ecosystems worldwide. While the effect of fire on the distribution and regeneration of plant species has been widely documented, little is known on how phytophagous insects are reacting to these disturbances. 2. This study explores the survival strategies of various weevil spe...

Acari, as with other small arthropods, are most commonly introduced to new areas as contaminants of agricultural trade. The biosecurity risk of such trade is managed by national and regional biosecurity systems, a chief aim of which is to prevent the introduction of agricultural and environmental pests. However, agricultural contaminants are introd...

Climate warming is considered to be among the most serious of anthropogenic stresses to the environment, because it not only has direct effects on biodiversity, but it also exacerbates the harmful effects of other human‐mediated threats. The associated consequences are potentially severe, particularly in terms of threats to species preservation, as...

Insects have the ability to readily adapt to changes in environmental conditions, however the strength of local environmental adaptation signals under divergent conditions and the occurrence of trait inertia after relaxation of selection, remains poorly understood, especially for traits of climate stress resistance (CSR) and their phenotypic plasti...

Extreme temperature events are increasing in frequency and intensity due to climate change. Such events threaten insects, including pollinators, pests and disease vectors. Insect critical thermal limits can be enhanced through acclimation, yet evidence that plasticity aids survival at extreme temperatures is limited. Here, using meta-analyses acros...

Biotic interactions can modulate the responses of organisms to environmental stresses, including diet changes. Gut microbes have substantial effects on diverse ecological and evolutionary traits of their hosts, and microbial communities can be highly dynamic within and between individuals in space and time. Modulations of the gut microbiome composi...

Females and males have divergent strategies of energy investment, so the thermal preference of each sex in insects may differ because energetic conversion of metabolic reserves is dependent on temperature. We determined the thermal preference of virgin, sexually mature Mediterranean fruit flies, Ceratitis capitata, and found that males preferred a...

The ambrosia beetle Euwallacea fornicatus (Polyphagous Shot Hole Borer; PSHB), native to Asia, was documented in South Africa for the first time in 2012. Death of susceptible host trees is caused by blocking of xylem tissues by the mutualistic plant-pathogenic fungus, Fusarium euwallaceae and extensive tunnelling by the beetles into the sapwood. Wi...

Cold acclimation may enhance low temperature flight ability, and salt loading can alter an insects’ cold tolerance by affecting their ability to maintain ion balance in the cold. Presently however, it remains unclear if dietary salt impacts thermal acclimation of flight ability in insects. Here, we examined the effect of a combination of dietary sa...

The relative costs and benefits of thermal acclimation for manipulating field performance of pest insects depend upon a number of factors including which traits are affected and how per- sistent any trait changes are in different environments. By assessing plastic trait responses of Ceratitis capitata (Mediterranean fruit fly) across three distinct...

Insects are mass-reared for release for biocontrol including the sterile insect technique. Insects are usually reared at temperatures that maximize the number of animals produced, are chilled for handling and transport, and released into the field, where temperatures may be considerably different to those experienced previously. Insect thermal biol...

Simple Summary In two separate experiments, we examined how (1) developmental temperature and (2) transport conditions influenced the low-temperature performance and flight ability of false codling moth (FCM) adults. In experiment 1, larvae were exposed to a control (constant 25 °C), a cold treatment (constant 15 °C) or a fluctuating thermal regime...

Simple Summary Despite being essential for growth, insects cannot synthesize sterols. Naturally, sterols are obtained from insects’ host plants, but in artificial diets are sometimes missing or not optimal, leading to reduced growth. By adding 1.0 g of stigmasterol, and a combination of 0.2 g each of cholesterol and stigmasterol to two standard min...

Agricultural biosecurity interventions are aimed at minimizing introductions of harmful non‐native organisms to new areas via agricultural trade. To prioritize such interventions, historical data on interceptions have been used to elucidate which factors determine the likelihood that a particular import is carrying a harmful organism. Here we use a...

Understanding of the morphological and physiological correlates of competitive behaviours can provide important insights into the ecology of competition, home range size and resource consumption. Here, we first estimated and defined sexual dimorphism in a poorly studied African cerambycid species, Cacosceles newmannii. We then assessed morphologica...

To forecast climate change impacts across habitats or taxa, thermal vulnerability indices (e.g., safety margins and warming tolerances) are growing in popularity. Here, we present their history, context, formulation, and current applications. We highlight discrepancies in terminology and usage, and we draw attention to key assumptions underpinning...

Developmental and adult thermal acclimation can have distinct, even opposite, effects on adult heat resistance in ectotherms. Yet, their relative contribution to heat-hardiness of ectotherms remains unclear despite the broad ecological implications thereof. Furthermore, the deterministic relationship between heat-knockdown and recovery from heat st...

Historic approaches to understanding biological responses to climate change have viewed climate as something external that happens to organisms. Organisms, however, at least partially influence their own climate experience by moving within local mosaics of microclimates. Such behaviors are increasingly being incorporated into models of species dist...

DNA barcoding has been succesfully used for bio-surveillance of forest and agricultural pests in temperate areas, but has few applications in the tropics and particulary in Africa. Cacosceles newmannii (Coleoptera: Cerambycidae) is a Prioninae species that is locally causing extensive damage in commercially-grown sugarcane in the KwaZulu-Natal Prov...

Quantifying insect respiratory structures and their variation has remained challenging due to their microscopic size. Here we measure insect tracheal volume using X-ray micro-tomography (μCT) scanning (at 15 μm resolution) on living, sedated larvae of the cerambycid beetle Cacosceles newmannii across a range of body sizes. In this paper we provide...

Quantifying insect respiratory structures and their variation has remained challenging due to their microscopic size. Here we measure insect tracheal volume using X-ray micro-tomography (µCT) scanning (at 15 µm resolution) on living, sedated larvae of the cerambycid beetle Cacosceles newmannii across a range of body sizes. In this paper we provide...

Trait–environment interactions have contributed to the remarkable plant radiations in the Cape Floristic Region (CFR) of southern Africa. Whether such interactions have also resulted in the diversification of the invertebrate fauna, independently of direct associations with plants is, however, not clear. One candidate where this may be the case is...

Understanding sources of variation in animal thermal limits is critical to forecasting ecological responses to climate change. Here, we estimated upper and lower thermal limits, and their capacity to respond to thermal acclimation, in several species and populations of diving beetles (Dytiscidae) from diverse geographic regions representative of va...

An outbreak of Cacosceles newmannii (Coleoptera: Cerambycidae) was detected for the first time on sugarcane (Saccharum spp.) in 2015 in KwaZulu‐Natal, South Africa. Although primary host plants of this native species remain unknown, these are central to testing hypotheses concerning the outbreak. We hypothesized that this species has undergone a ho...

Biosecurity interception records are crucial data underlying efforts to predict and manage pest and pathogen introductions. Here we present a dataset containing information on imported plant products inspected by the South African Department of Agriculture's laboratories between 1994 and 2019 and the contaminant organisms found on them. Samples wer...

How respiratory structures vary with, or are constrained by, an animal’s environment is of central importance to diverse evolutionary and comparative physiology hypotheses. To date, quantifying insect respiratory structures and their variation has remained challenging due to their microscopic size, hence only a handful of species have been examined...

The establishment success of a population is a function of abiotic and biotic factors and introduction dynamics. Understanding how these factors interact has direct consequences for understanding and managing biological invasions and for applied ecology more generally. Here we use a mesocosm approach to explore how the size of founding populations...

Metabolic rate, and the flexibility thereof, is a complex trait involving several inter-linked variables that can influence animal energetics, behavior, and ultimately, fitness. Metabolic traits respond readily to ambient temperature variation, in some cases increasing relative or absolute energetic costs, while in other cases, depending on the org...

The fitness consequences of thermal plasticity of functional traits of insects, and the life stages at which these responses manifest, remain a subject of much debate. Here, we examine whether a short-term exposure to cold, medium or warm fluctuating temperature regimes during development (larval or adult) affects adult performance, thermal toleran...

Quantifying intraspecific variation in heat tolerance is critical to understand how species respond to climate change. In a previous study, we recorded variability in critical thermal maxima (CTmax) by 3 °C among populations of small Iberian lizard species, which could substantially influence predictions of climate-driven activity restriction. Here...

1. Neochetina eichhorniae is the most widely established biocontrol agent on water hyacinth populations around South Africa. However, some N. eichhorniae populations have failed to adequately control their host population, specifically those exposed to cold conditions. 2. The aim of this study was to determine whether two climatically distinct popu...

Specific trait–environment interactions have led to globally unusual botanical radiations in the Cape Floristic Region (CFR) of South Africa. Yet it is unclear whether such interactions have similarly resulted in the diversification of the fauna independently of associations with plants. We explore this question for the Collembola genus Seira, whic...

Acclimation and other forms of plasticity that can increase stress resistance feature strongly in discussions surrounding climate change impacts or vulnerability projections of insects and other ectotherms. There is interest in compiling databases for assessing the adequacy of acclimation for dealing with climate change. Here we argue that the natu...

South Africa has a rich history of managing invasive alien animal populations. This chapter explores examples of animal control projects, their resourcing and degree of success or failure. Out of 1023 alien animal species present in South Africa, 80 are designated for compulsory control or eradication in national legislation, and 24 are currently b...

Although it is well known that insects are sensitive to temperature, how they will be affected by ongoing global warming remains uncertain because these responses are multifaceted and ecologically complex. We reviewed the effects of climate warming on 31 globally important phytophagous (plant‐eating) insect pests to determine whether general trends...

Temperature has a profound impact on insect fitness and performance via metabolic, enzymatic or chemical reaction rate effects. However, oxygen availability can interact with these thermal responses in complex and often poorly understood ways, especially in hypoxia-adapted species. Here we test the hypothesis that thermal limits are reduced under l...

What makes some species successful invaders while others fail, and why some invaders have major impacts in invaded ecosystems are pivotal questions that are attracting major research effort. The increasing availability of high resolution, georeferenced stable isotope landscapes (‘isoscapes’), coupled with the commercialization of stable isotope‐enr...

Bactrocera dorsalis (Hendel) and Ceratitis capitata (Wiedemann) are highly polyphagous fruit fly species and important pests of commercial fruit in regions of the world where they are present. In South Africa, B. dorsalis is now established in the north and northeastern parts of the country. B. dorsalis is currently absent in other parts of the cou...

Larvae of a long horn beetle were found for the first time feeding on sugarcane in the Entumeni district of KwaZulu-Natal in 2015. This beetle was later identified as Cacosceles newmannii (Thomson) (Coleoptera: Cerambycidae: Prioninae: Cacoscelini). The larvae of this beetle cause significant damage to sugarcane, resulting in important economic los...

The recent shift of the indigenous longhorn beetle Cacosceles newmannii (Coleoptera: Cerambycidae) into sugarcane of KwaZulu-Natal has resulted in widespread concern surrounding its pest status and further potential for spread and damage in sugarcane crops. Although historically widespread in many biomes in southern Africa, C. newmannii is though...

Thermal flight performance curves (TFPCs) may be a useful proxy for determining dispersal on daily timescales in winged insect species. Few studies have assessed TFPCs across a range of species under standard conditions despite that they may be useful in predicting variation in performance, abundance or geographic range shifts with forecast climate...

Background: Data on the current species diversity from the Drosophilidae family in South Africa is limited or outdated. Objectives: Using haphazard, limited trapping for a different study, we serendipitously report on and document Drosophilidae species in two distinct regions (representing a sub-tropical and a Mediterranean climate region) of Sout...

Cacosceles newmannii (Coleoptera: Cerambycidae) is an emerging pest of sugarcane in South Africa. The larvae of this cerambycid beetle live within the sugarcane stalk and drill galleries that considerably reduce sugar production. To provide an alternative to chemical control, entomopathogenic nematodes and fungus were investigated as potential biol...

Processing food (e.g. ingestion, digestion, assimilation) requires energy referred to as specific dynamic action (SDA) and is at least partially fuelled by oxidation of the nutrients (e.g. proteins and lipids) within the recently ingested meal. In ectotherms, environmental temperature can affect the magnitude and/or duration of the SDA, but is like...

• In sterile insect technique programmes, temperatures experienced by insects during rearing and handling, along with cool temperatures after release, can negatively affect performance and activity levels. Phenotypic plasticity (trait modifications caused by prior stress exposure) can offset these effects but is poorly understood in many species an...

Oxygen- and capacity-limited thermal tolerance (OCLTT) is a controversial hypothesis claiming to explain variation in, and mechanistically determine, animal thermal limits. The lack of support from Insecta is typically argued to be a consequence of their high performance respiratory systems. However, no studies have reported internal body oxygen le...

Terrestrial insects are responding to ongoing climate change. While these responses have been primarily linked to rising temperatures, insects are sensitive to desiccation, and the impacts of altered precipitation regimes remain relatively unexplored. Here, we develop a mechanistic model of survival and performance responses to both temperature and...

The recent host shift of the indigenous longhorn beetle Cacosceles newmannii (Coleoptera: Cerambycidae) from indigenous vegetation onto sugarcane in the KwaZulu-Natal Province of South Africa has resulted in widespread concern surrounding its pest status due to severe crop damage and significant economic losses for growers. This dramatic host shift...

Dispersal is a central requirement of a successful sterile insect release programme, but field-released false codling moth (FCM) typically suffer from poor dispersal ability, especially at low ambient temperatures. Here we test the hypothesis that poor activity and dispersal in FCM is caused by delayed or perturbed recovery of ion and/or water home...

Phytophagous insect pests strongly affect the productivity and profitability of agriculture and forestry. Despite the well-known sensitivity of insects to abiotic effects such as temperature, their potential responses to ongoing climate change remain unclear. Here we compile and review documented climate change responses of 31 of the globally most...

The spatial scale at which climate and species’ occupancy data are gathered, and the resolution at which ecological models are run, can strongly influence predictions of species performance and distributions. Running model simulations at coarse rather than fine spatial resolutions, for example, can determine if a model accurately predicted the dist...

The recent invasion of the indigenous longhorn beetle Cacosceles newmannii (Coleoptera: Cerambycidae) into sugarcane of KwaZulu-Natal has resulted in widespread concern surrounding its pest status and further potential for spread and damage in surrounding sugarcane crops. Its dramatic host shift from indigenous vegetation can be attributed to sever...

The recent shift of the indigenous longhorn beetle Cacosceles newmannii (Coleoptera: Cerambycidae) into sugarcane of Kwa-Zulu Natal has resulted in widespread concern surrounding its pest status and further potential for spread and damage in sugarcane crops. Although historically widespread in many biomes in southern Africa, C. newmannii is though...

Insects exchange respiratory gases using an astonishing diversity of patterns. Of these, discontinuous gas exchange cycles (DGCs) have received the most study, but there are many other patterns exhibited intraspecifically and interspecifically. Moreover, some individual insects transition between patterns based on poorly understood combinations of...

Traits of thermal sensitivity or performance are typically the focus of species distribution modelling. Among-population trait variation, trait plasticity, population connectedness and the possible climatic covariation thereof are seldom accounted for. Here, we examine multiple climate stress resistance traits, and the plasticity thereof, for a glo...

There is tremendous diversity of interactions between plants and other species. These relationships range from antagonism to mutualism. Interactions of plants with members of their ecological community can lead to a profound metabolic reconfiguration of the plants' physiology. This reconfiguration can favour beneficial organisms and deter antagonis...

Developing a general management framework for monitoring and reporting biological invasions in agricultural contexts is crucial to assist in the planning and execution of intervention and control strategies. Here we make use of a diverse range of data sets for economically significant South African agricultural fruit fly pests to offer several pote...

The exotic aphid Sipha flava (Forbes) (Homoptera: Aphididae) has recently become a pest of concern for sugarcane farmers in the Mazabuka region of Zambia. The steady decline in sugarcane yields has led to the need for investigation into the spatial-temporal dynamics of S. flava outbreaks, its population dynamics and invasion potential. Field survey...

Starvation is common among wild animal populations, and many individuals experience repeated bouts of starvation over the course of their lives. Although much information has been gained through laboratory studies of acute starvation, little is known about how starvation affects an animal once food is again available (i.e. during the refeeding and...