Jan‐Hendrik Dudenhöffer

Biotic resistance to plant invasion is driven by competition with the resident vegetation and antagonistic interactions with other biota in the community, but how these mechanisms operate after invasion control remains poorly understood. We assessed whether the resistance to reinvasion by lodgepole pine ( Pinus contorta ) and to secondary invasion by radiata pine ( Pinus radiata ) and Douglas fir ( Pseudotsuga menziesii ) differs between uninvaded grassland and sites where P. contorta had been controlled. We set up a factorial field experiment in the New Zealand High Country combining animal exclusion and vegetation removal treatments in grassland areas and previously controlled stands of P. contorta . Seeds of all three conifer species were sown in two cohorts, and we monitored seedling emergence, survival and resulting establishment over an 18 month period. Seedling emergence and survival were differently influenced by animal access and resident vegetation, and the effects differed between habitats. Animal access reduced seedling emergence, particularly in controlled pine stands, showing early consumer‐driven biotic resistance. In the grassland, intact vegetation increased seedling emergence, suggesting facilitation under stressful conditions, while no such effect occurred in the controlled pine stands. In contrast, seedling survival was consistently lower in the presence of vegetation across both habitats, showing biotic resistance driven by plant competition. The resulting seedling establishment was lowest in open and undisturbed plots in controlled pine stands, indicating increased biotic resistance as a buffer against reinvasion and secondary invasion. Our results show that the components of biotic resistance following invasion control can shift over time and can be modified by the legacy of the primary invader. Consumers primarily limit establishment during the early seed‐to‐seedling transition and plant competition thereafter, together finally providing resistance against reinvasion and secondary invasion. These findings highlight that post‐control legacies can impact habitat invasibility, with implications for the prioritisation of non‐native conifer management. Synthesis and applications . Post‐control areas are less vulnerable to reinvasion when vegetation structure and consumer communities are maintained. Managers should prioritise preventing establishment in uninvaded grasslands, while using grazing and retaining woody debris to strengthen natural biotic resistance and improve long‐term, cost‐effective invasive conifer control.

The use of animal symbolism or names is a common practice in advertising and branding. Businesses use animals to project attributes of their brand and thus contribute to public familiarity with the species. In New Zealand, birds are arguably the most prominent animals in national conservation priorities and citizen science activities. This fact reflects New Zealand's unique biogeography and the historic lack of terrestrial mammals. Here we explore the frequency with which bird names have been used in business branding over the last 70 years and examine the trend in the relative use of native, non‐native or generic names. We quantified the use of bird names in New Zealand businesses using the New Zealand Business Register, which provides details of ca. 1.6 million businesses. We identified the most frequent generic and specific names used between 1950 and 2022. We further explored associations between specific bird groups and business sectors. The prevalence of bird names in New Zealand business branding was generally low, with an increase from approximately 0.3% in the 1950s, trebling to about 1% of all registered businesses in recent years. The representation of native species within businesses that use bird names has increased from approximately 25% in the 1950s to more than 50% today. Aside from the kiwi, the most common bird names used by businesses were generic, for example, eagle, swan, or falcon. However, of those names that could be related to a known species, 83% referred to a species native to New Zealand. We detected non‐random associations between bird groups and specific business sectors. For example, raptors were overrepresented in business names from the construction, public administration and safety sectors. We provide an empirical case study on the commercially oriented usage of animal names for business branding. The increased use of bird names over time and associations between specific bird groups and business sectors may indicate socio‐cultural attributes linked to particular bird characteristics. The identification of trends and patterns could be the basis for further investigation into relationships between a species' familiarity and public perceptions, with consequent relevance to species conservation. Read the free Plain Language Summary for this article on the Journal blog.

Invasive alien trees can alter the biotic and abiotic properties of invaded ecosystems. Even after intensive control programmes, areas can be prone to reinvasion by the same species or secondary invasion by other species. One key factor that might determine reinvasion or secondary invasion is soil and litter legacy effects of the primary invader. Alien conifers are a prominent case of invaders with the potential to create lasting soil and litter legacy effects. In New Zealand, lodgepole pine (Pinus contorta) is considered the most problematic invasive conifer species posing a threat to biodiversity, farming productivity and landscape values. We assessed if soil and litter microbiome legacies of controlled P. contorta invasions can facilitate the reinvasion by conspecifics and potential secondary invasion by the two most abundant commercially planted alien conifer species (Pinus radiata, Pseudotsuga menziesii). We grew plants in a sterile background soil inoculated with live or sterile soil and litter samples sourced from uninvaded grassland and stands of P. contorta that had been controlled by herbicide 2 years previously. Our experimental design aimed to disentangle the total observed legacy effect into its components of soil and litter microbiome‐mediated effects and their potential interaction on seedling establishment and early growth of the primary invader and the potential secondary invaders. We found an overall negative legacy effect of P. contorta invasion on its own performance, whereas P. menziesii and P. radiata were neutrally or even positively affected, respectively. This was mainly driven by the individual effect of the soil microbiome. In contrast, seedling establishment was positively affected by the physical litter component but negatively affected by the litter microbiome. Thereby, the soil and litter microbiome‐mediated components can interact creating non‐additive effects. Synthesis. Our results suggest an increased risk of secondary invasion by other alien conifers after control of P. contorta. The complex interactions of soil and litter effects on plant performance highlight the importance of simultaneously considering multiple dimensions of legacy effects and their possible interactions. Paying attention to such interactions may help to better understand reinvasion and secondary invasion processes and inform post‐invasion management practices.

Summary: Plant–soil feedback (PSF) is a standing concept helping to explain plant species coexistence. Accumulating evidence suggests that PSF depends on the environmental context. One particularly impactful disruption of the environmental context is the invasion of alien species into a community. While PSF between native and non‐native species has been linked to invasion success, the effect of an invader on PSF between resident plants has received little attention. We explored how Pinus contorta (lodgepole pine) invasion impacts PSF between four resident grasses (two native and two non‐native species). We grew the plants in live soil to condition species‐specific soil communities, followed by a response phase where the plants were grown in conspecific and heterospecific soil. Both phases were performed with soil from uninvaded, invaded, or controlled invasion areas. Pairwise PSF between the species in uninvaded soil was negative and became neutral to positive in invaded soil. This effect persisted even after P. contorta removal. Our results suggest a destabilizing effect of P. contorta invasion on the coexistence of the resident grasses, benefitting non‐natives over natives. This work exemplifies an overlooked mechanism by which an invader can alter interactions between resident species and adds a novel dimension to the context dependence of PSF.

Caffeine is a widely occurring plant defence chemical that occurs in the nectar of some plants, e.g. Coffea or Citrus spp., where it may influence pollinator behaviour to enhance pollination. Previous laboratory work found inexperienced bumblebees (Bombus terrestris) located new food sources emitting a learned floral odour more consistently if they had been fed caffeine in association with the odour and a food reward. Inexperienced bees primed with caffeine also made more initial visits to target robotic flowers emitting the target odour, compared to control bees or those primed with odour alone. We tested whether these behaviours could be replicated under semi-field conditions in strawberry crops, to improve crop pollination and hence marketable yield. In three trials in mini-polytunnels, odour/caffeine-primed and control bumblebee colonies were allowed to forage on strawberry crops with nectar-rich distractor flowers present. Some small effects of caffeine priming were observed (a slight increase in the proportion of visits to the target flowers in one trial), but after controlling for polytunnel identity, the priming treatment did not influence crop yield and quality. While caffeine priming of commercial bumblebee colonies may have potential to improve pollination in crops, further research is needed to optimise the system for in-field use.

Plant invasions are a widespread and recurring phenomenon that cause significant economic and environmental damage. Invasive alien conifers are weeds that are not only costly to manage, but consistently reinvade after management efforts. Understanding how many seeds survive to germinate is a key part in understanding the weed life cycle puzzle. Here we investigated the contribution that seed predators have on reducing invasive alien conifer seed survival across both invaded and uninvaded habitats in Aotearoa New Zealand. We combined quantitative and qualitative experiments to measure seed predation across invaded and uninvaded habitats, as well as to identify which fauna are the most prolific seed predators. We utilised ex-situ empirical evidence with in-situ observations to provide realistic impacts from different seed predator species. We found that introduced mammals, particularly rodents, were the primary seed predators of invasive conifers. Seed predation pressure was highest in herbicide treated invasive alien conifer forests, indigenous beech forests, and managed pasture containing grazing livestock. Indigenous tussock areas support fewer vertebrate seed predators and as a result are particularly vulnerable to conifer invasion. The majority of seed predation occurs within the first two weeks post-dispersal. These results suggest that introduced mammal control operations, which are essential to protect endemic New Zealand species, will likely result in increasing invasive conifer populations by reducing seed predation pressure. Seed predation varies greatly between habitats, suggesting invasion and reinvasion rates are higher in ungrazed areas of lower forest density that support fewer introduced mammals.

Climate change can alter species coexistence through changes in biotic interactions. By describing reciprocal interactions between plants and soil microbes, plant–soil feedback (PSF) has emerged as a powerful framework for predicting plant species coexistence and community dynamics, but little is known about how PSF will respond to changing climate conditions. Hence, the context dependency of PSF has recently gained attention. Water availability is a major driver of all biotic interactions, and it is expected that precipitation patterns will change with ongoing climate change. We tested how soil water content affects PSF by conducting a full factorial pairwise PSF experiment using eight plant species common to southeastern United States coastal prairies under three watering treatments. We found coexistence-stabilizing negative PSF at drier-than-average conditions shifted to coexistence-destabilizing positive PSF under wetter-than-average conditions. A simulation model parameterized with the experimental results supports the prediction that more positive PSF accelerates the erosion of diversity within communities while decreasing the predictability in plant community composition. Our results underline the importance of considering environmental context dependency of PSF in light of a rapidly changing climate.

Summary: Phytochemicals are used often in vitro and in vivo in cancer research. The plant hormones jasmonates (JAs) control the synthesis of specialized metabolites through complex regulatory networks. JAs possess selective cytotoxicity in mixed populations of cancer and normal cells. Here, direct incubation of leaf explants from the non‐medicinal plant Arabidopsis thaliana with human breast cancer cells, selectively suppresses cancer cell growth. High‐throughput LC‐MS identified Arabidopsis metabolites. Protein and transcript levels of cell cycle regulators were examined in breast cancer cells. A synergistic effect by methyljasmonate (MeJA) and by compounds upregulated in the metabolome of MeJA‐treated Arabidopsis leaves, on the breast cancer cell cycle, is associated with Cell Division Cycle 6 (CDC6), Cyclin‐dependent kinase 2 (CDK2), Cyclins D1 and D3, indicating that key cell cycle components mediate cell viability reduction. Bioactives such as indoles, quinolines and cis‐(+)‐12‐oxophytodienoic acid, in synergy, could act as anticancer compounds. Our work suggests a universal role for MeJA‐treatment of Arabidopsis in altering the DNA replication regulator CDC6, supporting conservation, across kingdoms, of cell cycle regulation, through the crosstalk between the mechanistic target of rapamycin, mTOR and JAs. This study has important implications for the identification of metabolites with anti‐cancer bioactivities in plants with no known medicinal pedigree and it will have applications in developing disease treatments

Species‐rich plant communities can induce unique soil biotic legacy effects through changing the abundance and composition of soil biota. These soil legacy effects can cause feedbacks to influence plant performance. In addition, soil biota can induce (defensive) secondary metabolites in shoots and roots and thus affect plant–herbivore interactions. We hypothesize that plant diversity‐driven soil biotic legacy effects elicit changes in the shoot and root metabolome. We tested this hypothesis by establishing an experiment with four plant species. We grew plants in a sterile substrate inoculated with soil conditioned by different plant species communities: (a) monocultures of either of the four species, (b) the four species in a mixture, (c) an eight species mixture including all four species or (d) a sterile inoculum. After at least 8 weeks in the field, we estimated shoot herbivory. At the same time, we took root and shoot samples for metabolomics analyses by liquid chromatography quadrupole time‐of‐flight mass spectrometry. We found that shoot and root metabolomes of all plants grown in sterile soil differed significantly from those grown in living soil. The plant metabolomes in living soils differed by species and tissue. Across all species, shoots displayed a greater richness of secondary metabolites than roots. The richness of secondary metabolites differed by species and among living soils. The conditioning species richness significantly affected the Shannon diversity of secondary metabolites in Centaurea jacea. Shoot herbivory positively correlated with the richness and Shannon diversity of secondary metabolites in Leucanthemum vulgare. We detected multiple metabolites that together explained up to 88% of the variation in herbivory in the shoots of C. jacea and Plantago lanceolata. Synthesis. Our findings suggest that plant diversity‐driven shifts in soil biota elicit changes in the composition and diversity of shoot and root secondary metabolites. However, these plant responses and their effect on shoot herbivores are species‐specific. Tracking changes in plant secondary chemistry in response to soil biotic legacy effects will help to understand the mechanisms that govern species‐specific plant–plant and plant–herbivore interactions.

Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield-related ecosystem services can be maintained by few abundant species or rely on high richness remains unclear. Using a global database from 89 crop systems, we partition the relative importance of abundance and species richness for pollination, biological pest control and final yields in the context of on-going land-use change. Pollinator and enemy richness directly supported ecosystem services independent of abundance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.