Animal personalities are characterized by consistent behavior within individuals linked to consistently variable behavior among individuals in a population across time and contexts. Genetic determination, transgenerational effects, and personal experience are major pathways shaping animal personalities. Among these pathways, little attention has been paid to environmental factors in the parental generation affecting offspring personality. Here we tested the effects of the maternal diet on offspring personality in the plant-inhabiting predatory mite Amblyseius swirskii. Mated females and males, whose mothers were fed during egg production on cattail pollen, spider mites, or thrips, were subjected to a battery of 3 to 5 tests each for exploration, activity, and boldness. Movement activity was assessed in the mites' familiar environment. Exploration was quantified by the latency to leave and reach novel sites or objects. Boldness was evaluated by residence in risky and benign sites. On average, offspring from spider mite-fed mothers were the most active and those from pollen-fed mothers were the shiest. Offspring from thrips-fed mothers were more repeatable in activity than offspring from pollen- and spider mite-fed mothers. Consistently little and highly active personalities produced more eggs than flexible types. Only offspring from pollen-fed mothers were repeatable in boldness. Taken together, our study suggests that the maternal diet critically influences both mean behavioral trait expression and behavioral repeatability of offspring. The ability of mothers to respond to short-term diet changes during internal egg formation allows to adaptively adjust the behavior and personalities of daughters and sons within local and regional groups.

Plant defense systems such as induced resistance (IR; induced by herbivores) and induced systemic resistance (ISR; induced by beneficial rhizobacteria) are modulated by overlapping signaling pathways within plants. Both ISR and IR are systemic and may involve the production of toxic, antifeedant and/or repellent compounds, and/or reduce nutrient availability, which may in consequence affect plant usability and palatability for later arriving herbivores. The combined effects of ISR and IR on different herbivores sharing the same plant and plant performance have been rarely addressed. Here, we assessed the effects of three plant-growth-promoting rhizobacteria (PGPR), Azotobacter chroococcum, Azospirillum brasilense and Pseudomonas brassicacearum, on the defense response and physiology of strawberry plants upon sequential attack by two herbivores with different feeding modes, two-spotted spider mites Tetranychus urticae and cotton aphids Aphis gossypii. Attack of strawberry plants by spider mites and aphids adversely affected the abundance of the later arriving herbivore, mediated by the host plant’s defense system. First-attacking spider mites exerted much stronger adverse effects on later attacking aphids than first-attacking aphids on later attacking spider mites. In absence of PGPR inoculation, the herbivores, especially first-attacking spider mites, severely impaired host plant physiology and productivity. PGPR inoculation increased the plant`s capacity to mount a stronger phenolic response upon attack by spider mites and aphids, indicating a priming-like enhancement of inducible defense. In consequence, the abundances of both herbivores were lower on PGPR-inoculated plants compared to chemically fertilized and control plants. Overall, our study suggests that PGPR inoculation ameliorates the plant damage caused by sequentially attacking herbivores. Additionally, the PGPRs improve the physiology and productivity, and favorably balance the nutritional state, of strawberry plants.

The two-spotted spider mite, Tetranychus urticae Koch, is a significant pest in strawberry cultivation worldwide, causing substantial crop damage and economic losses. Biological control using predatory mites such as Amblyseius swirskii Athias-Henriot and Neoseiulus californicus (McGregor) is an essential component of integrated pest management (IPM) strategies. However, the efficacy of these natural enemies can be negatively affected by acaricide applications. This study assessed the sublethal effects of two acaricides; bromopropylate, a synthetic agent, and GC-Mite, a botanical formulation, on the life history and population growth parameters of A. swirskii and N. californicus feeding on T. urticae in strawberry crops. Acute toxicity assays demonstrated that both predatory mites exhibited significantly lower susceptibility to these acaricides than T. urticae, with A. swirskii showing the greatest resistance. Perinatal exposure to LC25 residue of bromopropylate and GC-Mite prolonged immature development, reduced adult longevity, and decreased fecundity in both predatory mite species. N. californicus experienced more pronounced negative effects, including marked declines in survival rates and reproductive output, whereas A. swirskii displayed greater resilience and more stable reproductive potential. Population growth parameters, such as the intrinsic rate of increase (r) and net reproductive rate (R0), declined significantly under acaricide treatments, with bromopropylate producing stronger adverse effects than GC-Mite. These results emphasize the relative compatibility of GC-Mite within IPM programs due to its lower toxicity to beneficial predatory mites. Careful selection and application of acaricides that minimize harm to natural enemies are crucial for sustainable management of T. urticae in strawberry cultivation.

Maternal effects are key drivers of offspring phenotypic plasticity, influencing traits such as survival, growth, and behavior. Maternal age at oviposition is an intrinsic factor governing such effects, which often exerts negative impacts on offspring traits. However, in the thelytokous predatory mite Amblyseius herbicolus, offspring of older mothers exhibit increased growth efficiency and reduced prey consumption. The proximate mechanisms of this inverse Lansing effect remain elusive, but this conservative offspring' foraging strategy may reflect an anticipatory maternal response to mitigate intraspecific competition among later-produced offspring. Here, we investigated how maternal age at oviposition and maternal rearing density influence offspring foraging strategies. Eggs (ie offspring) were collected from mothers maintained under low- and high-density conditions and classified as Young or Old based on maternal age at oviposition. Offspring were then assessed for immature survival under low prey availability, prey consumption, predation incidence, latency to attack prey, and superfluous killing. Offspring of older mothers showed reduced prey consumption and lower predation incidence, whereas offspring of high-density mothers had higher survival under prey limitation. Maternal density partially modulated age-related effects. Our findings highlight the role of maternal effects in shaping adaptive foraging strategies and demonstrate that maternal influences can induce risk-averse behavioral changes in response to ecological conditions. Both intrinsic and extrinsic maternal factors shape offspring behavioral strategies, and maternal age, in particular, can serve as a dynamic source of variation influencing predator-prey interactions and population dynamics.

Abstract Offspring phenotypes are often influenced by maternal age at reproduction. However, the persistence of such effects across multiple generations remains poorly understood, especially in rare cases where offspring of older mothers exhibit enhanced performance. Using the predatory mite Amblyseius herbicolus , we experimentally tested whether maternal age at reproduction influences offspring life history across two generations under contrasting dietary conditions. We found that grandmaternal (F 0 ) and maternal (F 1 ) age affected offspring (F 2 ) developmental time and body size, but not hatching success, survival, or oviposition. The effect of maternal age on body size depended on grandmaternal age, suggesting that grandmaternal age mediates how mothers adjust offspring provisioning. Diet strongly influenced offspring traits but showed limited interaction with age effects. To our knowledge, this is the first study to demonstrate the persistence of an inverse Lansing effect across generations, whereby enhanced immature development is maintained without detectable trade-offs in reproduction or adult survival. These results identify maternal age as a key driver of transgenerational phenotypic variation, with important implications for population dynamics and responses to environmental change at the population level.

Following the international trade and use of bamboo as exotic ornamentals, several species of bamboo spider mites (Stigmaeopsis spp.) have invaded the Americas and Europe, and their distribution is expanding, particularly across Europe. These mites construct dense silk nests that serve as effective defences against natural enemies, posing challenges for biological control. We evaluated the predatory performance of two commercially available phytoseiid mites native to the Americas and Europe, Phytoseiulus persimilis and Neoseiulus cucumeris, in comparison with Typhlodromus bambusae, a natural enemy of Stigmaeopsis spp. in their native Asian range. Stigmaeopsis spp. show nest size variation among species. For instance, S. longus typically builds larger nests than S. celarius. To consider this difference, we conducted experiments with both species, using nests aged 0, 24, or 72 h to reflect differences in silk density. T. bambusae consistently exhibited high predation on both adult females and eggs across all nest ages. In contrast, P. persimilis showed limited predation, particularly when more elaborate woven nests were present, suggesting difficulty penetrating or entering these structures. N. cucumeris exhibited moderate but variable predation: some individuals preyed on adult females at rates comparable to T. bambusae, and a few also successfully attacked eggs, even in well-developed nests. These findings suggest that nest architecture and silk density strongly influence predator access, and behavioural variation may allow some N. cucumeris individuals to overcome such barriers. Evaluating predator efficacy under varying nest structures offers a useful framework for assessing their potential in managing exotic spider mite invasions.

Background Animal personalities are characterized by within-individual consistency linked to among-individual variability. Personality expression is often dependent on major life history events such as mating and the onset of reproduction. Here, we hypothesized that in facultatively polyandrous animals, multiple mating increases the females’ assets (i.e., residual reproductive value — RRV), due to direct and/or indirect benefits. Based on the predictions of the asset protection principle, higher RRV should promote behaviors that reduce the risk of fitness loss and hence mediate behavioral repeatability displayed in groups. Methods We tested our hypothesis in group-living predatory mites, Phytoseiulus persimilis . Predatory mite females were presented with one or two mates, and their postmating repeatability in activity and sociability was evaluated in groups composed of females of the same and mixed mating types. Results Mating frequency had little effect on activity patterns but pronounced effects on sociability traits. Polyandrous females were on average more sociable as well as more repeatable in sociability than monandrous females. These behavioral shifts reflect strategies to mitigate inter-individual conflicts within groups to enhance asset protection. Conclusions Our study suggests that the mating frequency can critically influence female personality expression after mating and highlights the importance of considering mate-related variables in animal personality research.

The Lansing effect predicts a decline in offspring performance with increasing maternal age. Maternal age and diet can influence offspring development and fitness via maternal effects, but how these two factors interact remains poorly understood. We examined how maternal age at oviposition and dietary conditions affect offspring developmental plasticity in a thelytokous predatory mite ( Amblyseius herbicolus ). Mothers were provided either a restricted or abundant prey diet, and their offspring were exposed to varying prey availability and monitored for hatching success, survival to adulthood, developmental time, size at maturity, and prey consumption. We addressed two main questions: How does maternal age affect offspring developmental time and size at maturity and does maternal diet modify the effect of maternal age on offspring? Our results suggest an inverse Lansing effect. Offspring of older mothers showed increased survival and reduced prey consumption without any compromise in terms of size at maturity. Interactions were found between maternal diet and age on offspring prey consumption and developmental plasticity. Notably, offspring from older, diet-restricted mothers achieved the best overall performance during development. Our study demonstrates that maternal age and diet jointly shape offspring development, and highlights the importance of incorporating maternal age into studies of maternal effects and phenotypic plasticity. ### Competing Interest Statement The authors have declared no competing interest.

The idea of individual niche specialization suggests that individuals should diversify in their realized niches to mitigate inter-individual conflict. We tested the hypothesis that parental and early-life diet experiences drive individual foraging specialization and animal personality formation in plant-inhabiting predatory mites Phytoseiulus persimilis and Phytoseiulus macropilis. Both species are specialized predators of herbivorous spider mites. Adult females and males, whose parents had been exposed to either prey eggs or mobile prey, and/or who themselves had experienced either eggs or mobile prey during juvenile development, were tested for their prey life stage preference, and exploration and activity patterns. Parental and/or personal experience of a given prey life stage exerted species- and sex-dependent effects on the adult predators' mean and individual foraging phenotypes, with parental plus early-life effects being the strongest. Repeatability in activity and exploration was linked to prey life stage preference, pointing at co-variation of personality formation and individualized foraging niches.

Animal personalities are characterized by intra-individual consistency and consistent inter-individual variability in behaviour across time and contexts. Personalities abound in animals, ranging from sea anemones to insects, arachnids, birds, fish and primates, yet the pathways mediating personality formation and expression remain elusive. Social conditions during the early postnatal period are known determinants of mean behavioural trait expressions later in life, but their relevance in shaping personality trajectories is unknown. Here, we investigated the consequences of early social isolation on adult personality expression in plant-inhabiting predatory mites Phytoseiulus persimilis. These mites are adapted to live in groups. We hypothesized that transient experience of social isolation early in life, that is, deprivation of any social contact during a sensitive window in the post-hatching phase, has enduring adverse effects on adult personality expression. Newly hatched mites were transiently reared in isolation or in groups and tested as adults for repeatability of various within-group behaviours, such as movement patterns and mutual interactions including sociability, defined as the propensity to associate and interact benignly with conspecifics, and activity patterns when alone. Groups composed of individuals with the same or different early-life experiences were repeatedly videotaped and individual behaviours were automatically analysed using AnimalTA. Social experiences early in life had persistent effects on mean behavioural traits as well as adult personality expression, as measured by intraclass correlation coefficients (indicating repeatability). On average, isolation-reared females moved at higher speeds, meandered less, kept greater distances from others and had fewer immediate neighbours than group-reared females. Group-reared females were highly repeatable in inter-individual distance, moving speed, meandering and area explored, whereas isolation-reared females were repeatable only in the number of immediate neighbours. Activity, quantified as the proportion of time spent moving within groups, was only repeatable in group-reared females, whereas activity, quantified as the proportion of time spent moving when alone, was only repeatable in females reared in isolation. Strikingly, also the early-life experiences of male mates influenced personality expression of mated females, with isolation-reared males boosting the repeatability of behavioural traits of group-reared females. Overall, our study provides evidence that a transient phase of social isolation during a critical period early in life has lasting effects that extend into adulthood, impairing adult personality expression. These effects should cascade upward, changing the phenotypic composition and diversity within populations. This paper is the first to show for any animal that early-life social isolation disrupts adult personality expression.image

The theory of individual niche specialization posits that members of local groups should diversify in their realized individual diet niches to alleviate inter-individual food competition and ensuing conflicts (Bolnick et al. 2003). Here we tested the hypothesis that early life experiences co-shape individual specialization in diet niches and animal personality expression in the omnivorous plant-inhabiting predatory mite Amblyseius swirskii.

Animal personalities are defined by within-individual consistency, and consistent among-individual variation, in behavior across time and/or contexts. Here we hypothesized that brief early-life experience of intraguild predation (IGP) risk has enduring phenotypic effects on personality expression in boldness and aggressiveness in later life. We tested our hypothesis in predatory mites Phytoseiulus persimilis, which are IG predators with ontogenetic role reversals, i.e., they are potential IG prey during early life but IG predators as adults. Adult P. persimilis females, which had experienced IGP risk early in life or not, were subjected to three tests each for boldness and aggressiveness. IGP-experienced individuals were on average bolder and more aggressive. Boldness was moderately repeatable, aggressiveness was weakly repeatable. Strikingly, early-life IGP experience shifted the within-group personality composition toward consistently bold and aggressive personalities. Phenotypic adjustment of personality expression was adaptive, as indicated by the positive correlation between personality scores and egg production.

The development rate of the predatory ladybird, Stethorus gilvifrons (Mulsant), fed on Tetranychus urticae Koch, was determined at 15, 20, 25, 27, 30, 34, and 38 °C. The total development time from egg to adult emergence for females was estimated to be 61.4, 31.6, 14.4, 13.3, 12.5, and 11.7 days, respectively. The development time decreased with increasing temperature from 15 to 34 °C, but all eggs failed to hatch at 38 °C. The lower temperature threshold (T0) for the entire development period and the thermal constant (K) for female S. gilvifrons were estimated to be 11.64 °C and 194.50 degree-days (DD) using the common linear model, and 11.96 °C and 187.87 DD using the Ikemoto and Takai model, respectively. Data were fitted to 20 non-linear development rate models and the thermal thresholds (Tmin and Tmax) and optimal temperature (Topt) were estimated. Among non-linear models, the Briere-2 and Ikemoto and Takai linear model provided adequate descriptions of the temperature-dependent development of S. gilvifrons. The upper-temperature threshold was estimated to be about 44 °C using the Logan-10 non-linear model. The estimated thermal development characteristics can be used to predict the occurrence and the population dynamics, as well as to improve the mass rearing and release, of S. gilvifrons for the biological control of T. urticae.

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The ladybird, Stethorus gilvifrons (Mulsant) (Coleoptera: Coccinellidae), is an important predator of two-spotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), in southeastern Europe and western and southwestern Asia, such as Iran, India, and Turkey. To enhance forecasting the occurrence and performance of this predator in natural control and improve its usage in biological control, we evaluated and compared four non-linear oviposition models, i.e., Enkegaard, Analytis, Bieri-1, and Bieri-2. The models were validated by using data of age-specific fecundity of female S. gilvifrons at six constant temperatures (15, 20, 25, 27, 30, and 34 °C). All four models provided good fit quality to age-dependent oviposition at 15 to 30 °C (R2 0.67 to 0.94; R2adj 0.63 to 0.94) but had a poor fit at 34 °C (R2 0.33 to 0.40; R2adj 0.17 to 0.34). Within temperatures, the best performing models were Bieri-1 (R2), Bieri-2 (R2adj), and Analytis (RSS) at 15 °C, Bieri-1 at 27 °C, and Analytis at 20, 25, and 30 °C. Analytis was the best suited model across the wide temperature range tested (from 15 to 30 °C). The models presented here allow for prediction of the population dynamics of S. gilvifrons in field and greenhouse crops in temperate and subtropical climates.

Intense mate competition favors the evolution of extraordinary mating strategies such as the ability of males to identify premature females that are close to becoming mature and associate with them until they are sexually receptive (dubbed precopulatory mate guarding). Owing to possible take-overs by rival males, precopulatory guarding is a high-risk, time- and energy-intensive strategy. Here, we provide experimental evidence that guarding spider mite males undress females by actively removing the exuvia during ecdysis to adult; females undressed by guarding males eclose faster than unguarded females. Such behavior is adaptive because it maximizes the guard's chances of being the first mate.

Intense male competition for access to females has often led to the evolution of alternative reproductive tactics (ARTs) such as sneaking, female mimicking, and satellite behavior. In many cases, which tactic a male expresses will depend upon intrinsic condition and/or environmental factors. Parental effects are also expected to play a critical role in ART expression when the parental environment is predictive of the offspring environment. Such parental effects on ARTs have remained largely unexplored. Here, we investigated maternal effects associated with operational sex ratio (OSR) on male ARTs (fighter and sneaker) in two-spotted spider mites Tetranychus urticae . In this mite species, mothers can anticipate the future male competition intensity (the future OSR) based upon the present OSR. To adjust local mate competition (LMC) among sons, mothers produce proportionally more sons under female-biased OSR and vice versa. We manipulated the maternal OSR and found that changes in maternal OSR did not alter the sneaker: fighter ratio among sons, but sneaker sons from mothers that experienced female-biased OSR started to guard females more quickly. Sneakers stay motionless on the dorsum of molting females, which is an advantageous position for mating with the emerging adult, and appear to deceive rival fighter males because they are not challenged. Earlier guarding by sneakers is advantageous for securing matings under intense male competition—as would be anticipated from the female-biased maternal OSR. We conclude that mothers anticipate the level of male competition in the next generation and influence their sons’ mating behavior accordingly. Significance statement In response to intense male competition for access to females, males often evolve alternative reproductive tactics (ARTs) such as sneaking behavior. Parental effects are widespread and expected to play an important role in the determination of offspring’s ARTs when the parental environment is predictive of the offspring environment. We focus on operational sex ratio (OSR) as a predictor of male competition intensity in the next generation and found that female-biased OSR in the parental generation induces earlier guarding by sneaker sons in two-spotted spider mites. Mothers produce proportionally more sons under female-biased OSR, resulting in intense male competition in the next generation, and improve the odds of early guarding sneakers. Overall, our study suggests that spider mite mothers adjust their sons’ mating behavior by anticipating the intensity of male competition in the next generation from the present OSR.

Plants mediate interactions between below- and above-ground microbial and animal communities. Microbial communities of the rhizosphere commonly include mutualistic symbionts such as mycorrhizal fungi, rhizobia and free-living plant growth-promoting rhizobacteria (PGPR) that may influence plant growth and/or its defense system against aboveground pathogens and herbivores. Here, we scrutinized the effects of three PGPR, Azotobacter chroococcum, Azospirillum brasilense, and Pseudomonas brassicacearum, on life history and population dynamics of two-spotted spider mites, Tetranychus urticae, feeding on aboveground tissue of strawberry plants, and examined associated plant growth and physiology parameters. Our experiments suggest that these three species of free-living rhizobacteria strengthen the constitutive, and/or induce the direct, anti-herbivore defense system of strawberry plants. All three bacterial species exerted adverse effects on life history and population dynamics of T. urticae and positive effects on flowering and physiology of whole strawberry plants. Spider mites, in each life stage and in total, needed longer time to develop on PGPR-treated plants and had lower immature survival rates than those fed on chemically fertilized and untreated plants. Reduced age-specific fecundity, longer developmental time and lower age-specific survival rates of mites feeding on rhizobacteria treated plants reduced their intrinsic rate of increase as compared to mites feeding on chemically fertilized and control plants. The mean abundance was lower in spider mite populations feeding on PGPR-treated strawberries than in those feeding on chemically fertilized and untreated plants. We argue that the three studied PGPR systemically strengthened and/or induced resistance in above-ground plant parts and enhanced the level of biochemical anti-herbivore defense. This was probably achieved by inducing or upregulating the production of secondary plant metabolites, such as phenolics, flavonoids and anthocyanins, which were previously shown to be involved in induced systemic resistance of strawberry plants. Overall, our study emphasizes that PGPR treatment can be a favorable strawberry plant cultivation measure because providing essential nutrients needed for proper plant growth and at the same time decreasing the life history performance and population growth of the notorious herbivorous pest T. urticae.

Transgenerational effects abound in animals. While a great deal of research has been dedicated to the effects of maternal stressors such as diet deficiency, social deprivation or predation risk on offspring phenotypes, we have a poor understanding of the adaptive value of transgenerational effects spanning across multiple generations under benign conditions and the relative weight of multigenerational effects. Here we show that grandparental and parental diet experiences combine with personal early-life learning to form adaptive foraging phenotypes in adult plant-inhabiting predatory mites Amblyseius swirskii . Our findings provide insights into transgenerational plasticity caused by persistent versus varying conditions in multiple ancestral generations and show that transgenerational effects may be adaptive in non-matching ancestor and offspring environments.