Introduction

Polyploidy, or whole-genome duplication (with or without hybridization), is widespread in flowering plants and has occurred at least once in the evolutionary history of all angiosperms1,2,3,4,5. Polyploid plants often diverge from diploid counterparts in phenotypic characteristics, including changes in morphological and physiological traits that may influence organismal fitness6,7,8,9. Such phenotypic divergence is often thought to arise from the increase in genome size and chromosome copies, which can fuel phenotypic and functional innovations as well as genomic diversification and versatility10,11,12,13,14,15. As such, polyploids are often hypothesized to have an increased ability to withstand abiotic stress and biotic antagonism (e.g., competitive interactions)3,5,10,11,15,16. While recent studies have shown evidence for polyploid advantage in competitive interactions in a handful of polyploid complex systems9,17,18,19,20,21,22, notable exceptions exist22,23. It remains largely unknown whether the hypothesized polyploid advantage holds across various environmental conditions, particularly in the novel environments of the Anthropocene. These novel environmental conditions, including exposure to new pollutants like engineered nanoparticles, are likely to alter the nature and strength of species interactions24,25,26,27. Therefore, understanding species interactions in these novel environments is essential for predicting the future interactive dynamics of polyploid and diploid plants.

One of the emerging environmental threats in the Anthropocene arises from engineered nanoparticles28,29,30,31,32. Nanoparticles, with unique properties such as nanoscale size (1–100 nm), large relative surface area, novel physiochemical attributes, and high reactivity, have revolutionized various industries (e.g., electronics, cosmetics, medicine, and agriculture), leading to an annual global production of millions of metric tons30,31,33,34,35. Through production, use, disposal, runoff, and atmospheric deposition, thousands of metric tons of engineered nanoparticles are discharged into terrestrial and aquatic ecosystems each year35. This increasing accumulation poses a threat to ecosystem functioning by adversely affecting plants, microbes, and animals29,31,32,36,37,38. The negative impacts on organisms can arise through various mechanisms, such as nanoscale size facilitating entry into cells, interference with cell division, DNA damage, and induction of cell death36,39,40. Aggregation on cell surfaces can disrupt nutrient transport40,41, while inherent material characteristics, particularly heavy metals, can lead to the creation of harmful reactive oxygen species and biomolecule oxidation36,39,41,42. Notably, toxicity levels may differ between bulk and nano forms of a material. If the toxic effects are mainly attributed to material effects, organisms exposed to both bulk and nano forms may experience similar levels of toxicity. However, if toxicity primarily arises from nanoscale effects, organisms exposed to nanoparticles are expected to experience stronger toxicity compared to those exposed to the bulk counterparts. For example, copper oxide (CuO) nanoparticles have been shown to exhibit toxicity to plants and animals at doses ten times lower than those required for CuO bulk particles41. Given their common application in agricultural and environmental remediation as fertilizers and pesticides, CuO nanoparticles have been extensively investigated in a variety of key crops. These include, for example, rice (Oryza sativa), maize (Zea mays), wheat (Triticum aestivum), soybean (Glycine max), cotton (Gossypium hirsutum), spinach (Spinacia oleracea), zucchini (Cucurbita pepo), sweet potato (Ipomoea batatas), and alfalfa (Medicago sativa)43,44,45,46,47,48,49. While these previous studies have revealed adverse effects of nanoparticles on individual organisms, such as reduced plant germination, nutrient uptake, and biomass50, it remains largely unknown how nanoparticle exposure influences species interactions24,25,26,27, especially in wild plants.

While polyploids are often hypothesized to exhibit competitive dominance over diploids7,9, the impact of nanoparticles on the competitive interactions between polyploids and diploids remains unclear. The dynamics of plant–plant interactions, in terms of both nature and magnitude, can vary under different environmental conditions51,52,53,54. According to the stress gradient hypothesis (SGH), the magnitude of competition may decrease and potentially shift towards facilitation in more stressful environments51,52. SGH also suggests that the type of stress experienced can influence species interactions53. While increased resource stress (e.g., water or nutrient deficiency) often reduces the magnitude of competition, increased non-resource stress (e.g., cold, heat, salinity) may lead to shifts from competition to facilitation53,54. In this study, we aim to investigate how CuO nanoparticles influence the interactions between polyploids and diploids. We evaluate the nature and intensity of plant–plant interactions using the relative interaction index (RII)55. Owing to, for example, the genomic and phenotypic novelty and versatility of polyploidy7,9, we hypothesize that polyploids are likely competitively dominant (Fig. 1). As a result, in polyploids, the competitive effect of diploids on polyploids (RII8x,2x, 2x and 8x refer to diploids and octoploids, respectively) is expected to be weaker than the effect of polyploids on polyploids (RII8x,8x > RII8x,2x). Conversely, in diploids, the competitive effect of polyploids on diploids (RII2x,8x) is expected to be stronger than the effect of diploids on diploids (RII2x,8x > RII2x,2x). Stress induced by nanoscale effects is expected to reduce intraploidy competition (RII8x,8x and RII2x,2x) and interploidy competition (RII8x,2x and RII2x,8x), as opposed to exposure to bulk particles and control conditions (in the absence of the two forms of the material; Fig. 1a,b). However, if stress is attributed to material effects, rather than nanoscale effects, the reduction in competition is expected to be similar between exposure to nanoparticles and bulk particles (Fig. 1c,d). In the absence of stress from nanoparticles or bulk particles, competition is expected to be similar across conditions (Fig. 1e,f). On the other hand, as CuO is often used as fertilizers 56, competition may be increased due to factors such as increased plant sizes (Fig. 1g,h). However, if polyploidy leads to, for example, genomic instability and slower metabolism10,12, polyploids may be competitively inferior (diploid dominance: RII8x,2x > RII8x,8x and RII2x,8x < RII2x,2x; Fig. S1) or competitively similar to diploids (competitive symmetry: RII8x,8x = RII8x,2x and RII2x,8x = RII2x,2x; Fig. S2). Their competitive interactions may be weakened due to nanoscale effects or material effects, or strengthened due to fertilization effects (Figs. S1 and S2).

Fig. 1
figure 1

Hypotheses of competitive interactions between polyploids and diploids in response to nanoparticles. (a-f) Plant–plant interactions between ploidy levels are quantified using the relative interaction index (RII), where RII < 0 indicates competition and RII > 0 indicates facilitation. If polyploids (8x, octoploid as an example) are stronger competitors, the competitive effect of polyploids on polyploids (RII8x,8x) is expected to be stronger than the effect of diploids on polyploids (RII8x,2x), resulting in stronger intraploidy than interploidy competitions, RII8x,8x > RII8x,2x. In contrast, diploids are expected to be more affected by interploidy competition (RII2x,8x) than intraploidy competition (RII2x,2x), leading to RII2x,8x > RII2x,2x. The intraploidy and interploidy competitions may, nevertheless, change under non-resource stress (e.g., nanoparticles and bulk particles of the material). The stress gradient hypothesis (SGH) predicts reduced competition with increased stress. (a, b) If the stress is caused by nanoscale effects rather than material effects, a reduction in competition is expected under nanoparticles (NPs), in contrast to bulk particles (Bulk) and the control (Control) where no nanoparticles or bulk particles are introduced. (c, d) If the stress is caused by material effects, a reduction in competition is expected to be similar under both nanoparticles and bulk particles, relative to the control. (e, f) However, competition may remain unchanged if nanoparticles and bulk particles are not the primary sources of stress that influences plant–plant interactions. (g, h) On the other hand, if nanoparticles and bulk particles provide fertilization, intraploidy and interploidy competitions may increase due to reasons such as increased plant sizes.

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To evaluate the influence of CuO nanoparticles, one of the widely used nanoparticles35, on interactions between polyploids and diploids, we competed diploid and polyploid plants with intraploidy or interploidy individuals under exposure to CuO nanoparticles and bulk particles in axenic microcosms. We aimed to test the outlined hypotheses (Fig. 1; Figs. S1 and S2), by addressing three questions: (1) Do polyploids exhibit competitive dominance over diploids? (2) Does the impact of nanoparticle exposure on intraploidy and interploidy interactions align with predictions from the stress gradient hypothesis? (3) What mechanisms underlie the impact of nanoparticles on species interactions, specifically examining nanoscale effects versus material effects? The answers to these questions will fill a critical knowledge gap in understanding how nanoparticle exposure alters competitive dynamics between species, specifically the nature and strength of intraploidy and interploidy interactions in plants.

Methods

Experimental design

To examine intraploidy and interploidy interactions, we focused on diploid (2x) Fragaria viridis and octoploid (8x) Fragaria virginiana, two closely related wild strawberry species7,57. Both species are perennial herbaceous plants found across diverse temperate habitats including woodlands, meadows, grasslands, disturbed sites, and agricultural fields58. F. viridis is widely distributed across Europe, while F. virginiana is native to North America but overlaps with F. viridis in parts of its range. F. viridis is thought to contribute to one of the four subgenomes of F. virginiana, as well as to the other octoploids including F. chiloensis and the cultivated strawberry (F. × ananassa), although this remains a subject of ongoing debate59,60. The collections were part of a worldwide achene collection of Fragaria conducted during 2013–20147,61 with permits obtained, and species have been identified previously7,8,57,61. Aseptic propagation of the plants was conducted in Murashige and Skoog Basal medium with vitamins and sucrose (PhytoTech Labs, Lenexa, Kansas) within glass culture tubes (25 mm × 150 mm) before the start of the competition experiment. The basic unit of the competition experiment consisted of five plant combinations (Fig. 2): diploid growing alone (2x), diploid growing with intraploidy level (2x–2x), diploid and polyploid growing together (2x–8x), polyploid growing with intraploidy level (8x–8x), and polyploid growing alone (8x). The competition experiment was conducted under a completely randomized design with stress treatments (CuO nanoparticles, ‘NPs’; CuO bulk particles, ‘Bulk’; and control), each replicated five times: 5 plant combinations × 3 stress treatments × 5 replicates, resulting in 75 total experimental microcosms.

Fig. 2
figure 2

Summary of experimental design. The basic unit of the competition experiment consists of five plant combinations: diploid growing alone (2x), diploid growing with intraploidy level (2x–2x), diploid growing with polyploid (2x–8x), polyploid growing with intraploidy level (8x–8x), and polyploid growing alone (8x). Each competition unit was replicated five times per treatment: the control (no copper oxide nanoparticles or bulk particles), copper oxide (CuO) nanoparticles, and CuO bulk particles. The experiment used a completely randomized design.

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Before the start of the experiment, individual microcosms (55 mL glass tubes, 25 mm × 150 mm) were filled with 4 g Sunshine Redi-Earth Plug & Seedling Potting Mix (Sun Gro Horticulture, Agawam, Massachusetts) that comprises peat moss, vermiculite, dolomitic limestone, and 4 mL of deionized (DI) water. These microcosms were autoclaved three times for 45 min each time. Then, CuO nanoparticles (particle size < 50 nm; Sigma Aldrich, St. Louis, Missouri) or CuO bulk particles (particle size ~ 2000 nm, Alfa Aesar; VWR International, Radnor, Pennsylvania), suspended in 1 mL of autoclaved DI water, was added into the NPs treatment (resulting in a final concentration of 100 ppm in microcosms, i.e., 100 mg kg-1 wet soil) and the Bulk treatment (100 ppm), respectively. While exceeding the naturally occurring copper levels in soil (2–50 mg Cu per kg dry weight)62 , this concentration remains lower than those observed in copper polluted soils63. Additionally, it is comparable to concentrations used in nano-phytotoxicity studies of CuO and other metal (and oxide) nanoparticles36,37. For the control treatment, 1 mL of autoclaved DI water was added. Following the preparation of microcosms, diploid and polyploid plants were axenically transferred into individual microcosms. The microcosms were capped, and plants were grown at 24 ºC and 16-h days in a growth room. To minimize the potential influence of microenvironmental variation, microcosms were randomized daily within and across microcosm racks. We ended the experiment after three weeks, because axenic microcosms without additional added water could experience increased evaporation over time. In this study, we measured the height of individual plants in the microcosms at both the beginning and end of the experiment.

Statistical analyses

We quantified plant–plant interactions using the relative interaction index (RII)55 that ranges between -1 and 1. A negative RII indicates competition (with more negative values reflecting stronger competition), while a positive RII indicates facilitation (with higher positive values reflecting stronger facilitation). The RII compares plant growth with competitors (Bw) and without competitors (Bo): RII = (Bw – Bo)/(Bw + Bo). In this study, we assessed plant growth using changes in plant height over the course of the experiment as a proxy, given that plant growth in the microcosms was primarily vertical. In addition, we opted for this non-destructive measurement rather than biomass harvesting to minimize the handling of heavy metal and nanoparticles in the microcosms. For each ploidy combination (2x–2x, 2x–8x, 8x–8x; Fig. 2), Bw represented plant growth of each diploid or polyploid plant growing with intraploidy or interploidy competitors in individual microcosms. Bo was plant growth of the diploid or polyploid growing alone, averaged across replicated microcosms in each treatment (Fig. 2). As plant growth (Bw and Bo) can be negative due to changes in physiological processes (e.g., metabolism, carbon assimilation, turgor loss) under stress, these estimates were converted to positive values for estimating RII. This was done by subtracting the lowest value of Bw and Bo under each treatment, separately for diploids and polyploids. These estimates of RII, based on plant growth, were robust and strongly correlated with RII estimates based on final plant height (Pearson’s correlation r = 0.62, P < 0.001; Fig. S3). In this study, we focused on RII estimates based on plant growth rather than final plant height to avoid the potential influence of initial plant height variation among treatments and plants, despite efforts to homogenize plant sizes at the start of the experiment.

To evaluate the hypothesized intraploidy and interploidy competitive effects (Fig. 1), we conducted linear mixed models (LMMs) with RII as the response variable using R v4.2.264. The predictors included competition type (intraploidy and interploidy), treatment (control, NPs, and Bulk), and their interactions. The random effect of microcosm ID was included unless its inclusion affected model fitting (Table S1). The analyses were carried out separately for polyploids (8x–8x, 2x–8x) and diploids (2x–2x, 2x–8x). Statistical significance (type III sums of squares), least-squares means (LS means) of predictors, and planned contrasts of intraploidy vs. interploidy interactions and treatment effects within the models were assessed using packages emmeans65 and phia66.

Results

In polyploids, consistent with the stress gradient hypothesis (Fig. 1), the competitive interaction between polyploids (RII8x,8x) was significantly lowered and shifted towards facilitation under the NPs treatment relative to the control (LS mean contrast: NPs, RII8x,8x = 0.26; control, RII8x,8x = -0.06; F = 8.3, df = 1, P = 0.006; Fig. 3a and Fig. S4; Table S1). Such reduction in the intraploidy competition of polyploids was caused by nanoscale effects (Fig. 1a) rather than material effects (Fig. 1c). This was because unlike the NPs treatment, the Bulk treatment increased competition compared to the control (LS mean contrast: Bulk, RII8x,8x = -0.34; control, RII8x,8x = -0.06; F = 6.3, df = 1, P = 0.016). Similar to the intraploidy competition of polyploids (RII8x,8x), the competitive effect of diploids on polyploids (RII8x,2x) was also lowered under the NPs treatment (LS mean contrast: NPs, RII8x,2x = 0.50; control, RII8x,2x = 0.10; F = 6.6, df = 1, P = 0.014; Fig. 3a). Overall, the nature of interactions (RII8x,8x× and RII8x,2x) shifted from neutrality under the control to facilitation under the NPs treatment, and to competition under the Bulk treatment (Fig. 3a).

Fig. 3
figure 3

Responses of intraploidy and interploidy interactions to copper oxide nanoparticles (NPs) and bulk particles (Bulk). (a, b) The least-squares mean (LS mean) and 1 SE of the relative interaction index (RII) are plotted for (a) polyploids and (b) diploids. Significant contrasts in LS means are denoted: ***P < 0.001; **P < 0.01; *P < 0.05; †P = 0.070. For statistical details, see Table S1.

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Unlike polyploids, diploids did not experience facilitation under the NPs treatment (LS mean: RII2x,2x = -0.04, 95% CI = -0.26–0.17; RII2x,8x = -0.20, 95% CI = -0.47–0.08) nor competition under the Bulk treatment (LS mean: RII2x,2x = -0.13, 95% CI = -0.34–0.09; RII2x,8x = -0.13, 95% CI = -0.41–0.15; Fig. 3b and Fig. S4).

In examining the competitive asymmetry between polyploids and diploids, we found no strong evidence for the hypothesis of polyploid competitive dominance (RII8x,8x > RII8x,2x and RII2x,2x < RII2x,8x; Fig. 1). In polyploids, the overall trend followed the hypothesis (RII8x,8x > RII8x,2x), but the contrasts of means were not statistically significant across treatments (all P > 0.05; Fig. 3a). In diploids, the interactions were mostly neutral (Fig. 3b).

Discussion

This study provides, to our knowledge, the first demonstration of how nanoparticles influence species interactions between polyploid and diploid plants. By quantifying both intraploidy and interploidy interactions, our results revealed a shift towards facilitation in the polyploid under nanoparticle exposure. This shift was driven by nanoscale effects rather than material effects. In contrast, the diploid exhibited neutral plant–plant interactions under both nanoparticle and bulk particle exposure. These contrasting interaction dynamics in the polyploid and diploid translated into observable differences in growth responses across treatments (Fig. S4).

Intraploidy and interploidy competitions weakened under nanoparticles in the polyploid

The overall trend of intraploidy and interploidy interactions followed the prediction that polyploids were limited more by individuals of their own than by diploids (Fig. 1 and Fig. S4), though the mean difference was not statistically significant due to variation among microcosms. This pattern aligns with findings in other polypoid species complex, including the autotetraploid perennial grass Dactylis glomerata under field conditions17, the allotetraploid annual grass Brachypodium hybridum in a dry field locality19, and the allotetraploid perennial herbaceous Chrysanthemum indicum under both well-watered and drought conditions9. However, in Chamerion angustifolium, an autotetraploid perennial herb, intraploidy and interploidy competitions remained similar across well-watered and drought conditions22. Unlike previous studies that involved higher plant densities, such as two to eight plants per pot9, six plants in varying pot sizes19, or up to 36 plants per pot17, our microcosm experiment was designed to assess interactions between only two individuals of the same or different ploidy levels. This minimal competition design67 was employed to accommodate the size of microcosms. Since competition is density dependent9,54, increasing the number of competing individuals is expected to intensify competition, leading to much stronger intraploidy than interploidy competitions in the polyploid.

Consistent with the stress gradient hypothesis, intraploidy and interploidy competitions in the polyploid weakened under nanoparticle stress, shifting towards facilitation. This pattern aligns with a limited but growing body of research on nanoparticle effects on species interactions24,25,26,27, where reduced competition under nanoparticle exposure has also been noted. For example, competition between freshwater green microalgae decreased under CuO nanoparticles, promoting species coexistence27. In ciliate protozoans, interactions between Tetrahymena pyriformis and Loxocephalus sp. shifted from competition to facilitation of Loxocephalus under cerium oxide (CeO2) nanoparticles24. In plants, the competitive effect of the invasive annual herbaceous Amaranthus retroflexus on the native Amaranthus tricolor weakened under silver (Ag) nanoparticles25. Similarly, the competitive effect of the native perennial grass Thinopyrum junceum on the invasive creeping succulent Carpobrotus sp. in a coastal dune ecosystem decreased under titanium dioxide (TiO2) nanoparticles26. The broad taxonomic range and diverse nanoparticle types in these studies, including our own, underscore the commonality of nanoparticles in weakening species competitions across biological kingdoms.

The reduction in competition observed under CuO nanoparticles, but not bulk particles, suggests that the impact was attributable to nanoscale effects. In this study, the polyploid showed sensitivity to CuO NPs when grown in isolation (Fig. S4). However, the presence of neighbors likely mitigated nanoparticle stress through processes such as reduced nanoparticle uptake per plant, increased nanoparticle aggregation, or alterations in nanoparticle surface properties mediated by neighboring individuals. This led to reduced competition and a shift towards facilitation in the polyploid. In contrast, CuO bulk particles tended to benefit the polyploid (resulting in larger plant sizes) when grown in isolation (Fig. S4), likely due to increased nutrient availability, as copper is an essential micronutrient. As a result, both intraploidy and interploidy competitions in the polyploid intensified under bulk particles. Notably, the only other study on CuO NP effects on species competition, which examined freshwater green microalgae27, did not include bulk particles, preventing a direct comparison between nanoscale and material effects. The distinct effects of CuO NPs and bulk particles on species interactions likely stem from differences in toxicity. Previous studies have shown that CuO NPs exhibit stronger toxicity than bulk particles on individual organisms. For example, the aquatic plant Lemna minor experienced a significant decline in fresh biomass within 96 h of exposure to 10 mg/L CuO NPs, whereas a significant decrease occurred only at 150 mg/L CuO bulk particles68. Similarly, bok choy (Brassica rapa) exhibited a significant decrease in leaf dry weight and foliar area at 75 mg/L CuO NPs when grown in soil for 70 days, whereas a comparable decrease occurred only at 150 to 300 mg/L CuO bulk particles69. However, exceptions exist; for example, maize (Zea mays) seedlings exhibited greater reduction in shoot height and higher root cell membrane injury at 8 mM CuO bulk particles than at the same concentration of CuO NPs when grown in water for 6 days49, due to higher copper accumulation in roots under CuO bulk particles and nanoparticle aggregation reducing CuO NP toxicity. Overall, the varied outcomes of CuO NP and bulk particle exposure across studies highlight the context dependency of their effects, influenced by factors such as particle concentration (low vs. high), environmental matrix (aquatic vs. soil), experimental duration (short vs. long term), interaction level (individual organisms vs. species interactions), species characteristics (e.g., wild vs. cultivated), and prior exposure history (naïve vs. pre-exposed).

Intraploidy and interploidy interactions were neutral under nanoparticles in the diploid

Unlike the polyploid, intraploidy and interploidy interactions in the diploid remained largely neutral under both CuO NPs and bulk particles. The diploid showed low sensitivity to CuO NPs when grown in isolation (Fig. S4), suggesting that the potential benefits of growing with neighbors to alleviate nanoparticle stress may not be evident in the diploid. In contrast, CuO bulk particles tended to benefit the diploid when grown in isolation (Fig. S4). Yet, in the closed-system microcosms, where substantial evaporation occurred, the potential benefits of growing with neighbors, such as enhanced moisture retention through surface covering, might have been offset by competition from larger plants stimulated by CuO bulk particles.

The distinct interaction dynamics between the diploid and polyploid under CuO NPs and bulk particles may have several reasons, such as differences in sensitivity to moisture stress, nanoparticle stress, and dosage effects. In this study, the polyploid exhibited negative growth under the control condition, likely due to its higher sensitivity to moisture stress than the diploid in the axenic closed-system microcosms (Fig. S4). Therefore, unlike the diploid, the polyploid was less likely to benefit from neighbor-mediated moisture retention, as this benefit may not outweigh competition for water under CuO bulk particles. Previous studies have observed differences in sensitivity to moisture stress between diploids and polyploids, with polyploids often showing higher tolerance to water deficits7,9,17,19. Unlike these studies conducted in the presence of soil microbiomes, our axenic study excluded potential benefits conferred by microbial symbionts in mitigating moisture stress. Symbiotic microbes, such as arbuscular mycorrhizal fungi and actinobacteria, are known to enhance plant performance under water deficit by facilitating water uptake and access, as well as by producing antioxidant enzymes that mitigate oxidative stress70,71. This exclusion might contribute to the higher sensitivity to moisture stress in the polyploid if it relies more on microbial symbionts for better stress tolerance than the diploid. While this aspect requires further investigation, differences in associated microbial communities between diploids and polyploids have been observed in Fragaria72.

Furthermore, diploids and polyploids can differ in sensitivity to copper stress. For example, in the annual herbaceous Matricaria chamomilla, diploids were more sensitive than colchicine-induced autotetraploids within seven days of exposure to 60 µM CuCl273 and within 24 h of exposure to 120 µM CuCl274 under hydroponic conditions. Similarly, diploid Arabidopsis thaliana was more sensitive than autotetraploid lines within 14 days of exposure to 50–100 µM of CuCl2 in axenic petri dish experiments75. Such ploidy difference in tolerance to copper stress was often attributed to higher copper accumulation in tissues in diploids than polyploids73,74,75. Different from the previous studies, in this study, we found that the diploid was not sensitive to CuO NPs, unlike the polyploid (Fig. S4), likely due to the shorter shoots of the diploid with less surface area for interactions with CuO NPs. While using a widely accepted experimental dosage of 100 ppm CuO NPs and bulk particles, which has been shown to induce toxicity in various plant species36,37, it is important to recognize the potential for heightened stress in the diploid at higher CuO NP concentrations. Moreover, elevated CuO bulk particle levels may reduce the observed benefits in both the diploid and polyploid, thereby reshaping their interaction dynamics. A deeper mechanistic understanding of ploidy-specific responses to nanoparticle stress, dosage dependence, and the resulting impacts on diploid–polyploid interactions remains an important direction for future research.

Conclusions

Our findings demonstrate that nanoparticles influence species interactions within a polyploid species complex. Using an axenic experiment, we isolated the direct effects of nanoparticles on plant–plant interactions, minimizing confounding impact from environmental or symbiotic microbes, whose interactions with nanoparticles31,37,38 could otherwise obscure these effects. Future studies should integrate both axenic and microbe-present conditions to disentangle direct and indirect nanoparticle impacts. Despite the advantages of axenic microcosms, our approach has some limitations. Further research is needed to elucidate: (1) how nanoparticle effects on species interactions vary with competitor density and exposure intensity, (2) short-term versus long-term consequences, and (3) the extent to which controlled experimental findings translate to natural ecosystems. Moreover, while the polyploid originated from multiple diploid progenitors, we focused on only one diploid progenitor. If responses to nanoparticles vary among the subgenome lineages, our findings may reflect not only whole-genome duplication but also partly lineage-specific characteristics inherited from F. viridis. Expanding studies to other species pairs within the polyploid complex and across different polyploid systems will be crucial for broader generalizations. By examining established diploids and polyploids, our study captures the combined effects of whole-genome duplication and polyploidy-enabled adaptation in response to nanoparticles. To disentangle these effects, similar tests in natural or synthetic neopolyploids across diverse taxa are needed in both wild and domesticated plants, in the face of growing nanotechnology in agriculture and other industries35,56. Together, these efforts will enhance our understanding of the potential off target impacts of nanoparticles on organisms and communities, offering critical insights for environmental and organismal conservation efforts.