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1. Globally, conversion of natural habitat to agricultural land is a primary driver of declines in critical ecosystem services, including pollination. However, exotic species are often well-adapted to human-modified environments and could compensate for ecosystem services that are lost when native species decline. 2. We measured pollination services (pollen delivery to stigma) provided by wild insects to a mass flowering crop, choi Brassica rapa at 12 sites across a gradient of increasing agricultural land use (agricultural expansion) in New Zealand. 3. We found that pollination services increased as the proportion of agricultural land in the surrounding landscape increased; pollination from exotic species exceeded the loss of pollination from native species. However, pollination service delivery became increasingly dominated by a few exotic fly species that were active throughout the day, compared to native species, which had more constrained activity patterns. 4. Synthesis and applications. The best way to ensure continued sufficient crop pollination is to protect and restore diverse natural habitats on or around farms, as species-rich pollinator communities are relatively resilient to further environmental change. However, we show that where human-driven disturbance has caused loss of native pollinator species, exotic pollinators can maintain sufficient pollination. Therefore, in areas where native species loss cannot easily be reversed, decisions about pesticide use and habitat provision that foster populations of beneficial exotic species are likely to maintain pollination service delivery, at least in the short term. This highlights the need for land managers to identify the pollinator communities that are present on their farms, whether native or exotic, and make decisions to support these important communities accordingly.

Worldwide, anthropogenic change is causing biodiversity loss, disrupting many critical ecosystem functions. Most studies investigating the relationship between biodiversity and ecosystem functioning focus on species richness, predominantly within the context of productivity-related functions. Consequently, there is limited understanding of how other biodiversity measures, such as species evenness (the distribution of abundance among species), affect complex multitrophic functions such as pollination. We explore the effect of species evenness on the ecosystem function of pollination using a controlled experiment with selected plants and insects in flight cages. We manipulated the relative abundances of plant and pollinator species, while holding species richness, composition, dominance order, and total abundance constant. Then, we tested how numerical species evenness affected network structure and consequently, seed production, in our artificial communities. Contrary to our expectation, numerical dominance in plant communities increased complementarity in pollinator use (reduced pollinator sharing) among plant species. As predicted by theory, this increased complementarity resulted in higher seed production for the most dominant and rare plant species in our cages. Our results show that in a controlled experimental setting, numerical species evenness can alter important aspects of plant–pollinator networks and plant reproduction, irrespective of species richness, composition, and total abundance. Extending this understanding of how species evenness affects ecosystem functioning to natural systems is crucial as anthropogenic disturbances continue to alter species’ abundances, likely disrupting ecosystem functions long before extinctions occur.

Functional traits are the primary biotic component driving organism influence on ecosystem functions; in consequence, traits are widely used in ecological research. However, most animal trait-based studies use easy-to-measure characteristics of species that are at best only weakly associated with functions. Animal-mediated pollination is a key ecosystem function and is likely to be influenced by pollinator traits, but to date no one has identified functional traits that are simple to measure and have good predictive power. Here, we show that a simple, easy to measure trait (hairiness) can predict pollinator effectiveness with high accuracy. We used a novel image analysis method to calculate entropy values for insect body surfaces as a measure of hairiness. We evaluated the power of our method for predicting pollinator effectiveness by regressing pollinator hairiness (entropy) against single visit pollen deposition (SVD) and pollen loads on insects. We used linear models and AIC model selection to determine which body regions were the best predictors of SVD and pollen load. We found that hairiness can be used as a robust proxy of SVD. The best models for predicting SVD for the flower species and were hairiness on the face and thorax as predictors (  = 0.98 and 0.91 respectively). The best model for predicting pollen load for . was hairiness on the face (  = 0.81). We suggest that the match between pollinator body region hairiness and plant reproductive structure morphology is a powerful predictor of pollinator effectiveness. We show that pollinator hairiness is strongly linked to pollination-an important ecosystem function, and provide a rigorous and time-efficient method for measuring hairiness. Identifying and accurately measuring key traits that drive ecosystem processes is critical as global change increasingly alters ecological communities, and subsequently, ecosystem functions worldwide.

Within food webs, vectors of plant pathogens interact with individuals of other species across multiple trophic levels, including predators, competitors, and mutualists. These interactions may in turn affect vector-borne pathogens by altering vector fitness and behavior. Predators, for example, consume vectors and reduce their abundance, but often spur movement of vectors as they seek to avoid predation. However, a general framework to predict how species interactions affect vectors of plant pathogens, and the resulting spread of vector-borne pathogens, is lacking. Here we developed a mathematical model to assess whether interactions such as predation, competition, and mutualism affected the spread of vector-borne plant pathogens with nonpersistent or persistent transmission modes. We considered transmission mode because interactions affecting vector–host encounter rates were expected to most strongly affect nonpersistent pathogens that are transmitted with short feeding bouts; interactions that affect vector feeding duration were expected to most strongly affect persistent pathogens that require long feeding bouts for transmission. Our results show that interactions that affected vector behavior (feeding duration, vector–host encounter rates) substantially altered rates of spread for vector-borne plant pathogens, whereas those affecting vector fitness (births, deaths) had relatively small effects. These effects of species interactions were largely independent of transmission mode, except when interactions affected vector–host encounter rates, where effects were strongest for nonpersistent pathogens. Our results suggest that a better understanding of how vectors interact with other species within food webs could enhance our understanding of disease ecology.

Two main mechanisms may buffer ecosystem functions despite biodiversity loss. First, multiple species could share similar ecological roles, thus providing functional redundancy. Second, species may respond differently to environmental change (response diversity). However, ecosystem function would be best protected when functionally redundant species also show response diversity. This linkage has not been studied directly, so we investigated whether native and exotic pollinator species with similar traits (functional redundancy) differed in abundance (response diversity) across an agricultural intensification gradient. Exotic pollinator species contributed most positive responses, which partially stabilized overall abundance of the pollinator community. However, although some functionally redundant species exhibited response diversity, this was not consistent across functional groups and aggregate abundances within each functional group were rarely stabilized. This shows functional redundancy and response diversity do not always operate in concert. Hence, despite exotic species becoming increasingly dominant in human-modified systems, they cannot replace the functional composition of native species.

Background. Pollinators, which provide the agriculturally and ecologically essential service of pollination, are under threat at a global scale. Habitat loss and homogenisation, pesticides, parasites and pathogens, invasive species, and climate change have been identified as past and current threats to pollinators. Actions to mitigate these threats, e.g., agri-environment schemes and pesticide-use moratoriums, exist, but have largely been applied post-hoc. However, future sustainability of pollinators and the service they provide requires anticipation of potential threats and opportunities before they occur, enabling timely implementation of policy and practice to prevent, rather than mitigate, further pollinator declines. Methods. Using a horizon scanning approach we identified issues that are likely to impact pollinators, either positively or negatively, over the coming three decades. Results. Our analysis highlights six high priority, and nine secondary issues. High priorities are: (1) corporate control of global agriculture, (2) novel systemic pesticides, (3) novel RNA viruses, (4) the development of new managed pollinators, (5) more frequent heatwaves and drought under climate change, and (6) the potential positive impact of reduced chemical use on pollinators in non-agricultural settings. Discussion. While current pollinator management approaches are largely driven by mitigating past impacts, we present opportunities for pre-emptive practice, legislation, and policy to sustainably manage pollinators for future generations.

Reported declines of pollinator populations around the world have led to increasing concerns about the consequences for pollination as a critical ecosystem function and service. Pollination could be maintained through compensation if remaining pollinators increase their contribution or if novel species are recruited as pollinators, but empirical evidence of this compensation is so far lacking. Using a natural experiment in New Zealand where endemic vertebrate pollinators still occur on one offshore island reserve despite their local extinction on the adjacent North Island, we investigated whether compensation could maintain pollination in the face of pollinator extinctions. We show that two recently arrived species in New Zealand, the invasive ship rat (Rattus rattus) and the recent colonist silvereye (Zosterops lateralis; a passerine bird), at least partly maintain pollination for three forest plant species in northern New Zealand, and without this compensation, these plants would be significantly more pollen-limited. This study provides empirical evidence that widespread non-native species can play an important role in maintaining ecosystem functions, a role that needs to be assessed when planning invasive species control or eradication programmes.

Varroa destructor is a honey bee ( Apis mellifera ) parasite identified as one of the leading causes of overwintering colony loss in New Zealand. It has been shown that a naturally occurring heritable trait, “ Varroa Sensitive Hygiene” (VSH), confers an advantage to colonies by increasing behaviours that limit the survival and reproduction of Varroa mites. The SNP 9–9224292 is an adenine/guanine (A/G) polymorphism on chromosome 9 of Apis mellifera where the G allele was observed to be associated with VSH behaviour in North American honey bees. In this study, we sought to determine if selection for the G allele of SNP 9–9224292 could decrease Varroa mite infestation of New Zealand honey bee ( Apis mellifera ligustica ) colonies. We genotyped queens and tracked their colonies over summer before measuring Varroa levels at the point of autumn Varroa treatment. The mean Varroa population level in colonies headed by queens that carry two copies of VSH associated G allele of SNP 9–9224292 was 28.5% (P<0.05) lower compared with colonies headed by queens with two copies of non-VSH associated A alleles. Although a significant reduction in mite infestation was achieved in treatment colonies, conventional Varroa treatment was still required for adequate Varroa control. Considering the open mating of queens used and a lack of drift control in this study, this VSH SNP shows promise for marker assisted selection of New Zealand honey bees when aiming for innate Varroa control traits.

Many crop plants rely on insect pollination, particularly insect-pollinated crops which are functionally dioecious. These crops require insects to move pollen between separate plants which are functionally male or female. While honey bees are typically considered the most important crop pollinator species, many other insects are known to visit crops but the pollination contribution of the full diversity of these flower visitors is poorly understood. In this study, we examine the role of diverse insect pollinators for two kiwifruit cultivars as model systems for dioecious crops: Actinidia chinensis var. deliciosa ‘Hayward’ (a green-fleshed variety) and A. chinensis var. chinensis ‘Zesy002’ (a gold-fleshed variety). In our round-the-clock insect surveys, we identified that psychodid flies and mosquitoes were the second and third most frequent floral visitors after honey bees ( Apis mellifera L), but further work is required to investigate their pollination efficiency. Measures of single-visit pollen deposition identified that several insects, including the bees Leioproctus spp. and Bombus spp. and the flies Helophilus hochstetteri and Eristalis tenax , deposited a similar amount of pollen on flowers as honey bees ( Apis mellifera ). Due to their long foraging period and high pollen deposition, we recommend the development of strategies to boost populations of Bombus spp., Eristalis tenax and other hover flies, and unmanaged bees for use as synergistic pollinators alongside honey bees.

Approximately one-third of our food globally comes from insect-pollinated crops. The dependence on pollinators has been linked to yield instability, which could potentially become worse in a changing climate. Insect-pollinated crops produced via hybrid breeding (20% of fruit and vegetable production globally) are especially at risk as they are even more reliant on pollinators than open-pollinated plants. We already observe a wide range of fruit and seed yields between different cultivars of the same crop species, and it is unknown how existing variation will be affected in a changing climate. In this study, we examined how three hybrid carrot varieties with differential performance in the field responded to three temperature regimes (cooler than the historical average, average, and warmer that the historical average). We tested how temperature affected the plants' ability to set seed (seed set, pollen viability) as well as attract pollinators (nectar composition, floral volatiles). We found that there were significant intrinsic differences in nectar phenolics, pollen viability, and seed set between the carrot varieties, and that higher temperatures did not exaggerate those differences. However, elevated temperature did negatively affect several characteristics relating to the attraction and reward of pollinators (lower volatile production and higher nectar sugar concentration) across all varieties, which may decrease the attractiveness of this already pollinator-limited crop. Given existing predictions of lower pollinator populations in a warmer climate, reduced attractiveness would add yet another challenge to future food production.