Floral Resources Research Articles

Quantifying the production of plant pollen at the farm scale.

Plant pollen is rich in protein, sterols and lipids, providing crucial nutrition for many pollinators. However, we know very little about the quantity, quality and timing of pollen availability in real landscapes, limiting our ability to improve food supply for pollinators. We quantify the floral longevity and pollen production of a whole plant community for the first time, enabling us to calculate daily pollen availability. We combine these data with floral abundance and nectar measures from UK farmland to quantify pollen and nectar production at the landscape scale throughout the year. Pollen and nectar production were significantly correlated at the floral unit, and landscape level. The species providing the highest quantity of pollen on farmland were Salix spp. (38%), Filipendula ulmaria (14%), Rubus fruticosus (10%) and Taraxacum officinale (9%). Hedgerows were the most pollen-rich habitats, but permanent pasture provided the majority of pollen at the landscape scale, because of its large area. Pollen and nectar were closely associated in their phenology, with both peaking in late April, before declining steeply in June and remaining low throughout the year. Our data provide a starting point for including pollen in floral resource assessments and ensuring the nutritional requirements of pollinators are met in farmland landscapes.

Effect of floral resources and mealybug honeydew on the longevity of the parasitoid, Anagyrus fusciventris

ABSTRACT The effect of floral resources and mealybug honeydew on the longevity of Anagyrus fusciventris (Girault) (Hymenoptera: Encyrtidae), a parasitoid of both the longtailed (Pseudococcus longispinus Targioni Tozzetti) and citrophilus mealybugs (P. calceolariae Maskell) (Hemiptera: Pseudococcidae) in New Zealand, was investigated in the laboratory. A. fusciventris longevity was significantly increased by the provision of sugar solution, buckwheat (Fagopyrum esculentum) and alyssum (Lobularia maritima) flowers, and P. calceolariae honeydew compared with water alone. Female A. fusciventris provided with buckwheat survived 17 days longer than females provisioned with water alone.

Larval diet of the carpenter bee Xylocopa (Neoxylocopa) cearensis (Hymenoptera: Apidae: Xylocopini) from Delta do Parnaíba Environmental Protection Area

The genus Xylocopa Latreille, 1802 (Apidae: Xylocopini) Latreille includes efficient pollinating bees that visit a wide range of botanical species. Although several studies have investigated their interactions with plants in dune ecosystems, there is still a limited understanding of these bee communities in coastal environments. This study aimed to characterize the larval diet of Xylocopa (Neoxylocopa) cearensis Ducke, 1910 by analyzing pollen from their nests to assess the presence of specialization or generalization in relation to botanical species. The research was carried out in coastal sandbanks of the Delta do Parnaíba Environmental Protection Area, Tutóia, Maranhão-BR, over a 12-month. The natural nests were inventoried by active searches and, when possible, transported to the Federal University of Maranhão. Pollen samples were collected from 19 brood cells of 12 nests in total. All the nests were found on branches of Anacardium occidentale L. Using the cetolysis method, 21 types of pollen were recognized, representing 14 botanical families. Three of those types of pollen were considered to be Frequent pollen, Mouriri cearensis Huber (35.44%), Chamaecrista ramosa (Vogel) H. S. Irwin & Barneby (32.80%) and Myrcia multiflora (Lam.) DC (27.05%). Based on these results, X. cearensis can be characterized as a polylectic species that demonstrates adaptability. These floral resources serve as essential protein sources for the nutrition of their brood, highlighting the importance of these plant species in supporting their reproductive success. This study provides useful information that can serve as a reference for future research on other Xylocopa species in similar ecosystems.

Hedgerow Gardens Provide Floral Resources for Diverse Insect Visitors to Avocado Fowers in Southern California

Hedgerow Gardens Provide Floral Resources for Diverse Insect Visitors to Avocado Fowers in Southern California

Hedgerow Gardens Provide Floral Resources for Diverse Insect Visitors to Avocado Flowers in Southern California

Hedgerow Gardens Provide Floral Resources for Diverse Insect Visitors to Avocado Flowers in Southern California

Landscape fragmentation constrains bumblebee nutritional ecology and foraging dynamics

Habitat fragmentation is modifying landscapes and the distribution of floral resources, possibly shaping pollinator resource acquisition, which is an issue of global concern for pollinator health and urbanization sustainability. Here, in different urban parks contrasting in terms of local features and surrounding urban matrix, we aimed to clarify how fragmentation and local flower availability shape bumblebee foraging dynamics by characterizing several components: the nutritional content and plant composition of collected pollen pellets, the trip length and the plant-nutrition association along a fragmentation gradient. We found mostly negative linear or non-linear relationships between nutritional quality and fragmentation, tight plant composition-nutrition associations interpretable as low access to alternative resources, and longer foraging time in smaller green areas, showing that urban green area fragmentation limits nutritional resource accessibility. However, flower local richness improved the collection of beneficial nutrients as proteins and polyphenols, thus potentially rescuing negative landscape effects. This study illuminates the link between landscape and local features and the nutritional ecology of pollinators, a key aspect for understanding pollinator foraging dynamics. The findings of the study can provide valuable guidelines for policy makers and stakeholders involved in the management and ecological restoration planning for urban green areas and even for outlining mitigation measures in urban contexts.

Managed honeybee hives negatively affect the reproduction of native plants in a dryland nature reserve

Abstract The honeybee, Apis mellifera, stands out for its positive image due to its contribution to crop pollination and honey production, which facilitated its widespread distribution. However, large apiaries resulting in high honeybee densities could increase pollination frequency while increasing competition for floral resources, ultimately affecting native plant fitness. We studied the impact of managed honeybee hives on pollination and reproductive success of native plants in Villavicencio Nature Reserve, Mendoza, Argentina. During the flowering peak, we studied pollination and reproduction of three native plant species (Larrea divaricata, L. cuneifolia and Zuccagnia punctata) near and far from the hives. We estimated pollen deposition on flower stigmas, pollen tubes developed in flower pistils, fruit set, seed set and seed viability. We found that the honeybee hives had a positive effect on the reproduction of the self‐compatible species, L. divaricata. For the self‐incompatible species, results differed among species: Hives had positive effects on the pollination and negative effects on the reproduction of L. cuneifolia, while they had negative effects on the reproduction of Z. punctata. Synthesis and applications. Beekeeping is increasingly turning to natural areas in search of better quality honey; however, increased honeybee abundance in the field could influence the reproduction of native plants. Our results show that the introduction of managed hives negatively affected the reproduction of self‐incompatible native plants. This result allows us to make several recommendations for conservation and management actions concerning beekeeping in natural areas, regarding the among‐year rotation of the location of hives, the number of hives per site, and the need to monitor the reproduction of self‐incompatible species.

Assessing important floral resources supporting two species of Exomalopsis (Apidae) in agricultural cultivation areas: insights from pollen load analysis

Assessing important floral resources supporting two species of Exomalopsis (Apidae) in agricultural cultivation areas: insights from pollen load analysis

Organic compost belowground and floral diversity aboveground interactively shape beneficial insects in urban gardens

Abstract Plant diversity aboveground can exert top‐down pressure on herbivores by attracting predatory insects, while organic soil amendments rich in beneficial microbes can limit herbivores from the bottom‐up by enhancing plant defensive chemistry. Aboveground and belowground forces always operate simultaneously to shape herbivore pressure, but understanding how they interact is a longstanding and persistent challenge. Here, we examine how organic composts mediate the effects of plant diversity across trophic levels, using zucchini plants (Cucurbita pepo) as a study system. Over two field seasons, we manipulated vermicompost treatments in 18 experiments in school gardens that varied in surrounding plant and floral resource diversity and measured responses of insect herbivores and their natural enemies. Vermicompost strengthened a positive relationship between flower richness and foliar‐feeding omnivores, suggesting that robust reservoirs of omnivores at flower‐rich sites mounted stronger responses to compost‐treated host plants. Predators increased with flower richness, but were not affected by vermicompost. Net outcomes of vermicompost and plant diversity were neutral for herbivores. Synthesis and applications. Altogether, our results reveal that bottom‐up factors protecting plants are modified by their environmental context, and may more effectively attract natural enemies in landscapes with diverse floral resources. Therefore, we recommend augmentation of biodiversity aboveground (i.e. floral resources) together with biodiversity belowground (organic soil amendments) to strengthen crop protection.

Landscape-wide floral resource deficit enhances the importance of diverse wildflower plantings for pollinators in farmlands

Pollinators are declining rapidly, largely due to land conversion and intensification of agriculture. To mitigate their crisis, low-disturbance habitats, such as sown wildflower plantings, could promote pollinators by restoration of their resources. However, comprehensive knowledge is lacking on how landscape context, spatial configuration and age of wildflower plantings, seasonality and flower composition affect pollinator communities, especially from East-Central Europe. To understand these effects, we established diverse native wildflower plantings within heterogeneous and homogeneous agricultural landscapes, by two spatial configurations: one large field or three smaller strips, in Hungary. We sampled floral resources and wild pollinator insects (wild bees, hoverflies, butterflies), in early and mid-summer, for two years after establishment. Flower resources of the sown plant species increased continuously, and were complemented at high rate by flowering plant species from the soil seed bank, especially in the first year. Both flower abundance and diversity increased the abundance of pollinators, highlighting the important role of using diverse seed mixtures. Wild bee abundance and species richness increased year by year and season by season, while butterfly abundance also demonstrated a yearly increase after establishment. Hoverfly abundance and species richness, however, showed an opposite trend, possibly due to the inter-annual variation. Wild bee and butterfly abundance was higher in the heterogeneous than in the homogeneous landscapes. We did not observe any significant local effects of spatial configuration itself on pollinator populations. Wildflower plantings were particularly attractive for wild bees in flower-poor (homogeneous) landscapes during the flower-poor (mid-summer) period of the year. This can be explained by the increased contrast in flower resources between the wildflower plantings and the surrounding landscape, and highlights the importance of wildflower plantings in such conditions. Our results emphasise that to support pollinators effectively, future wildflower plantings should be maintained for multiple years, aim to maximise floral diversity and ensure continuously available flower resources throughout the entire season. They can be facilitated by i) using diverse seed mixtures of native flowering plants, ii) particularly focusing on plants that bloom during the crucial mid-summer period, iii) allowing the plant species to grow and bloom from the soil seed bank, and iv) using management techniques, which help to extend the flowering season. Further results from the upcoming years and similar long-term and landscape-scale experimental studies are needed to understand all the benefits and ecological processes of diverse native wildflower plantings especially in understudied European regions.

The Diversity of Butterflies (Insecta Lepidoptera) and Floral Resources of District Haridwar, Uttarakhand, India: A Systematic Checklist

The Diversity of Butterflies (Insecta Lepidoptera) and Floral Resources of District Haridwar, Uttarakhand, India: A Systematic Checklist

Floral resource partitioning of coexisting bumble bees: Distinguishing species-, colony-, and individual-level effects.

Resource partitioning is considered a key factor in alleviating competitive interactions, enabling coexistence among consumer species. However, most studies have focused on resource partitioning between species, ignoring the potentially critical role of intraspecific variation in resource use. We investigated floral resource partitioning across species, colonies, and individuals in a species-rich bumblebee community in the diversification center of bumblebees. We used a total of 10,598 bumblebees belonging to 13 species across 5 years in the Hengduan Mountains of southwest China. First, we evaluated the influence of a comprehensive set of floral traits, including both those related to attractiveness (flower color and shape) and rewards (pollen, sugar ratio, nectar volume, sugar concentration, and amino acid content) on resource partitioning at the species level in bumblebee-plant networks. Then, we explored intraspecific resource partitioning on the colony and individual levels. Our results suggest that bumblebee species differ substantially in their use of the available floral resources, and that this mainly depends on flower attractiveness (floral color and shape). Interestingly, we also detected floral resource partitioning at the colony level within all commonest bumblebee species evaluated. In general, floral resource partitioning between bumblebee individuals decreased with species- and individual-level variation in body size (intertegular span). These results suggest that bumblebee species may coexist via the flexibility in their preferences for specific floral traits, which filters up to support the co-occurrence of high numbers of species and individuals in this global hotspot of species richness.

Effects of Various Nectar and Pollen Plants on the Survival, Reproduction, and Predation of Neoseiulus bicaudus.

Neoseiulus bicaudus is a predatory mite species that could potentially be used for the biological control of spider mites and thrips. Floral resources can provide excellent habitats and abundant nutrients for natural enemies. The objective of this experiment was to evaluate the effects of eight floral resources on the longevity, fecundity, and predation ability of N. bicaudus. Among the considered plants, Cnidium monnieri led to the highest longevity (24 days) and fecundity (13.8 eggs) of N. bicaudus, while Tagetes erecta resulted in the lowest longevity (7 days) and fecundity (0.1 eggs) observed in the predatory mites. By comparing the effects of three nectar and pollen plants on the predation of predatory mites, it was observed that N. bicaudus still exhibited a type II functional response to Tetranychus turkestani. In the presence of pollen, the predation efficacy (a/Th) of N. bicaudus exhibited a lower value, compared to that in the absence of pollen (Control: a/Th = 24.00). When pollen was supplied, the maximum consumption (1/Th) of predatory mites was higher than in its absence (Control: 1/Th = 9.90 d-1), with the highest value obtained in the presence of B. officinalis pollen (B. officinalis: 1/Th = 17.86 d-1). The influence coefficient of predation of N. bicaudus on T. turkestani in the presence of pollen was compared in the presence of three nectar and pollen plants: Cnidium monnieri, Centaurea cyanus, and Borago officinalis. At low prey densities, the influence coefficient of C. cyanus exceeded that of B. officinalis, and the overall influence coefficient values were negative (i.e., the presence of pollen reduced predatory mite feeding on T. turkestani). They exhibited similar values at high prey densities, and all of the influence coefficient values were close to 0 (i.e., the presence of pollen had no effect on predatory mite feeding on T. turkestani). The findings revealed that diverse plant species exert differential impacts on N. bicaudus, with some influencing its lifespan and others affecting its reproductive capabilities. Furthermore, the presence of nectar and pollen plants had a significant impact on predatory mite feeding on T. turkestani at low prey densities; however, this effect diminished as the prey density increased. Therefore, we recommend planting C. monnieri, C. cyanus, and B. officinalis in the field to ensure an ample population of predatory mites. The obtained results hold significant implications for the utilization of nectar and pollen plants in eco-friendly pest management strategies within agricultural contexts.

Bees and their interactions with flowering plants in disturbed and semi-natural settings

A knowledge of bee populations is scarce, particularly in sub-Saharan Africa, where human-induced changes appear to have a considerable negative effect on wild bees. The goal of the study was to assess the abundance, diversity, and richness of bees and their interactions (or visitation) with flowering plants in disturbed and semi-natural habitats in Tanzania. Bees were sampled using sweep nets and pan traps whereas bee-plant interaction and floral abundance were visually assessed. We show that semi-natural habitats are crucial places for bees to forage and nest, as their richness, diversity, and species composition were higher than disturbed habitats. The study areas in semi-natural habitats also had a higher number of bee visits compared to the disturbed habitats. The lower number of bees found in disturbed habitats implies that human-caused alterations have a negative impact on foraging resources and bee communities. Furthermore, we recorded more than 400 bee-plant interactions and high floral abundance in semi-natural habitats compared to disturbed habitats. However, in both disturbed and semi-natural habitats, there was a positive relationship between floral abundance and bee abundance. This reveals that floral resources have a significant impact on bee abundance and their visitation. Our findings demonstrate further that, if natural environments are disturbed and floral resources are depleted, bee populations may decline. Therefore, habitat management, whether disturbed or semi-natural, is critical for the survival of bees.

Declining potential nectar production of the herb layer in temperate forests under global change

Abstract Wild pollinators are crucial for ecosystem functioning and human food production and often rely on floral resources provided by different (semi‐) natural ecosystems for survival. Yet, the role of European forests, and especially the European forest herb layer, as a potential provider of floral resources for pollinators has scarcely been quantified. In this study, we measured the potential nectar production (PNP) of the forest herb layer using resurvey data across 3326 plots in temperate forests in Europe, with an average time interval of 41 years between both surveys in order to assess (i) the importance of the forest herb layer in providing nectar for wild pollinators, (ii) the intra‐annual variation of PNP, (iii) the overall change in PNP between survey periods and (iv) the change in intra‐annual variation of PNP between survey periods. The PNP estimates nectar availability based on the relative cover of different plant species in the forest herb layer. Although PNP overestimates actual nectar production, relative differences amongst plots provide a valid and informative way to analyse differences across time and space. Our results show that the forest herb layer has a large potential for providing nectar for wild pollinator communities, which is greatest in spring, with an average PNP of almost 16 g sugar/m2/year. However, this potential has drastically declined (mean plot‐level decline >24%). Change in light availability, associated with shifts in canopy structure and canopy composition, is the key driver of temporal PNP changes. Synthesis. Our study shows that if management activities are carefully planned to sustain nectar‐producing plant species for wild pollinators, European forest herb layers and European forests as a whole can play key roles in sustaining wild pollinator populations.

Modelling foraging strategies of honey bees as agents in a dynamic landscape representation

Introduction: Both intrinsic colony mechanisms and external environmental variables affect the honey bee colony development rates and response and a key aspect of this is the use of resources within the landscape by honey bees. Although several models have been developed to explore the foraging behaviour of bees, none fully considered the spatial and temporal dynamics of landscape resources and the role of the colony in the process. Methodology: Here, we introduce a new honey bee foraging model being developed as a part of the ApisRAM honey bee colony model. Based on agent-based modelling, we used a dynamic ALMaSS landscape model enhanced with floral resource modelling to assess the impacts of weather conditions and resource availability on the possible foraging behaviour of honey bees. Several possible mechanisms (defined, based on honey bee traits) for scouting and foraging were investigated, separately for nectar and pollen collection, including prioritising foraging polygons for nectar foraging according to their distance to the colony, the quality or the energetic efficiency and, for pollen foraging, according to their distance to the colony and pollen quantity. Results: If model foraging bees prioritised the polygons, based on their distance from the colony, the number of unsuccessful flights increased compared to other tested strategies and the total amount of sugar collected showed a high variability. Contrary to expectations, the energetic efficiency strategy did not provide the colony with the highest amount of sugar. Overall, the tested strategies provide different outcomes on the collection of resources, the number of performed flights and their success rate, evidencing that the model's outcome at the colony level arises from the individual types of behaviour. Conclusions and Relevance: Variability in the mass of collected nectar and pollen was found mostly when scout bees applied the distance strategy. This higher variability in sugar collection means that model bees were not able to find the most profitable foraging sites at the landscape level, but only at the local level. Other strategies showed less dependence on the surrounding landscape (i.e. quality or random), but it comes at a cost (i.e. lower production for both nectar and pollen collection). These outputs help us evaluate which strategies could be used for future model development and confirm the models' ability to create dynamic responses. These responses at the colony level were only possible thanks to the implementation of a dynamic landscape model and dynamic spatiotemporal resource model, as well as implementing a social communication mechanism for bees to share information about the resources. Plant nectar production and quality information is essential to predict honey bee foraging distribution. In future model development, the implementation of pollen quality should also be explored to evaluate if it influences the overall pollen collection.

Ecological intensification: multifunctional flower strips support beneficial arthropods in an organic apple orchard

AbstractFlower strips are a fundamental part of agri-environment schemes in the Common Agricultural Policy (CAP). Although vegetation is central for many arthropod groups, a few studies have evaluated the effects of flower strip structural and functional attributes on arthropod communities. In this study, we explored the relationship between flower strip attributes and the abundance of different arthropod functional groups in annual flower strips located in an organic apple orchard. We surveyed plant and arthropod communities in 30 1 m × 6 m plots. In each plot, we collected data on species composition and vegetation structure (e.g., total cover, density, number of floral displays). For each plant species, we also retrieved data on leaf palatability and nutritional value. Arthropods were collected using sweep netting technique. Structural and functional attributes of the flower strip revealed a crucial role in regulating arthropod abundance, which however depended on the specific arthropod functional group. We identified three main attributes (plant species richness, composition, and vegetation density) of flower strips that should be considered when implementing multifunctional flower strips. Specifically, plant species richness to ensure complementarity of resources and niches, plant species composition to ensure complementary floral resources, and vegetation density to ensure sheltering microhabitats and suitable microclimatic conditions and to increase the density of floral resources. Our results suggest that by considering structural and functional attributes of flower strips, it is possible to design multifunctional flower strips with greater effectiveness as measures for ecological intensification.

Local floral abundance influences bumble bee occupancy more than urban‐agricultural landscape context

Abstract Loss of natural habitat due to increases in agricultural extent raises the question of whether human‐dominated landscape types can support biodiversity, particularly for declining insect pollinators. Compared to more rural agricultural landscapes, urban areas may confer benefits for bumble bee populations by providing stable and diverse floral resources. However, disentangling the effects of local‐ and landscape‐scale characteristics on bumble bee populations in human‐modified landscapes is challenging. Here, we assessed bumble bee occupancy using a repeated transect sampling design conducted during the summers of 2019 and 2020 within the metropolitan area of Madison, WI, and the surrounding agricultural landscape. We fit hierarchical occupancy models to estimate the detection (p) and occupancy () probabilities relative to local habitat quality (floral abundance and floral richness) and landscape (agricultural‐urban gradient) features for eight bumble bee species. We hypothesised that bumble bees were more likely to occupy urban areas, serving as refugia, relative to agricultural sites. We found that the detection probability of all bumble bee species was seasonal and influenced by maximum floral abundance at survey sites, independent of the surrounding land cover type. After accounting for species‐specific detection probabilities, the effect of urbanisation on bee occupancy was weak, and no species were less likely to occupy urban than rural agricultural areas. Our findings suggest that bumble bee occupancy is associated with a ‘honeypot effect’ where local resource availability, in the form of higher floral abundance, is most important in limiting the occupancy of bumble bees across urban and agricultural landscapes.

Land-use affects pollinator-specific resource availability and pollinator foraging behaviour.

Land-use management is a key factor causing pollinator declines in agricultural grasslands. This decline can not only be directly driven by land-use (e.g., habitat loss) but also be indirectly mediated through a reduction in floral resource abundance and diversity, which might in turn affect pollinator health and foraging. We conducted surveys of the abundance of flowering plant species and behavioural observations of two common generalist pollinator species, namely the bumblebee Bombus lapidarius and the syrphid fly Episyrphus balteatus, in managed grasslands of variable land-use intensity (LUI) to investigate whether land-use affects (1) resource availability of the pollinators, (2) their host plant selection and (3) pollinator foraging behaviour. We have found that the floral composition of plant species that were used as resource by the investigated pollinator species depends on land-use intensity and practices such as mowing or grazing. We have also found that bumblebees, but not syrphid flies, visit different plants depending on LUI or management type. Furthermore, LUI indirectly changed pollinator behaviour via a reduction in plot-level flower diversity and abundance. For example, bumblebees show longer flight durations with decreasing flower cover indicating higher energy expenditure when foraging on land-use intensive plots. Syrphid flies were generally less affected by local land use, showing how different pollinator groups can differently react to land-use change. Overall, we show that land-use can change resource composition, abundance and diversity for pollinators, which can in turn affect pollinator foraging behaviour and potentially contribute to pollinator decline in agricultural grasslands.

Standardising bee sampling: A systematic review of pan trapping and associated floral surveys.

The use of coloured pan traps (bee bowls, Moericke traps) for sampling bees (and other pollinators) has continuously increased over the last two decades. Although a number of methodological studies and conceptual frameworks offer guidance on standardised sampling, pan trap setups vary widely in characteristics even when optimised for capturing bees. Moreover, some uncertainty persists as to how local flower abundance and diversity influence sampling. We systematically reviewed peer-reviewed studies that used pan traps for bee collection and that were listed in the Web of Science core collection. To gauge methodological variation, we identified a set of relevant methodological criteria and assessed the studies accordingly. For obtaining evidence that pan trap samples and floral environment around traps are correlated, we screened the relevant studies for such correlations. While some aspects of pan trapping (e.g., trap coloration and elevation) were similar in the majority of studies, other aspects varied considerably (e.g., trap volume/diameter and sampling duration). Few studies used floral abundance and/or diversity as an explanatory variable in their analyses of bee samples. Among these studies, we found a considerable variation in key aspects of floral survey methods, such as time and space between vegetation surveys and pan trap sampling, abundance measures (quantitative, semi-quantitative and presence-absence), and processing of raw data prior to analysis. Often studies did not find any correlation between the floral environment and bee samples. Reported correlations varied markedly across studies, even within groups of studies applying a similar method or analysing a similar group of bees. Our synthesis helps to identify key issues of further standardisation of pan trap methodology and of associated floral surveys. In addition to the few aspects that have been standardised over the past decades, we suggest methodological direction for future research using pan traps as a better standardised method for the collection of wild bees. We encourage further studies to illuminate if and how varying floral resources around traps bias bee samples from pan traps. More generally, our synthesis shows that trapping methodologies should be reviewed regularly when their use increases to ensure standardisation.