Bulb Mite Research Articles

Population growth rate of dry bulb mite, Aceria tulipae (Acariformes: Eriophyidae), on agriculturally important plants and implications for its taxonomic status

Dry bulb mite (DBM), Aceria tulipae, is an economically important mite with a worldwide distribution and a broad host range. As a generalist, it is the most important eriophyoid mite attacking bulbous plants such as garlic, onion and tulip. To date, DBM has been recorded on host plants belonging to the families Liliaceae, Amaryllidaceae, Melanthiaceae and Asparagaceae. However, a precise understanding of DBM host range is lacking as it is largely based on casual records of mites on plants, some of which may include accidental hosts. Moreover, the possible existence of cryptic species has not been considered. In this study the hypothesis that DBM may be a complex of distinct genetic lineages or cryptic species was tested by comparing the common barcode sequence marker mtDNA COI of specimens from several populations originating from the Netherlands and Poland. The population growth rate of DBM on seven agriculturally important plant species and on various parts of the garlic plant was also experimentally assessed in the laboratory. The results did not support the first hypothesis, and indicated that DBM populations originating from Poland and the Netherlands shared essentially the same genome. In addition, they indicated that DBM reached the highest population growth rate on leek and also displayed high growth rates on garlic, chive and red onion, whereas white onion and wheat were not colonized by the mites. Answering the question of whether DBM is a single polyphagous species rather than a complex of cryptic lineages is of particular importance since the misidentification of pests may lead to ineffective control strategies. Moreover, improved knowledge of DBM host range is essential for assessing risk to crops.

Mixed evidence for the erosion of intertactical genetic correlations through intralocus tactical conflict

Alternative reproductive tactics, whereby members of the same sex use different tactics to secure matings, are often associated with conditional intrasexual dimorphisms. Given the different selective pressures on males adopting each mating tactic, intrasexual dimorphism is more likely to arise if phenotypes are genetically uncoupled and free to evolve towards their phenotypic optima. However, in this context, genetic correlations between male morphs could result in intralocus tactical conflict (ITC). We investigated the genetic architecture of male dimorphism in bulb mites (Rhizoglyphus echinopus) and earwigs (Forficula auricularia). We used half-sibling breeding designs to assess the heritability and intra/intersexual genetic correlations of dimorphic and monomorphic traits in each species. We found two contrasting patterns; F.auricularia exhibited low intrasexual genetic correlations for the dimorphic trait, suggesting that the ITC is moving towards a resolution. Meanwhile, R.echinopus exhibited high and significant intrasexual genetic correlations for most traits, suggesting that morphs in the bulb mite may be limited in evolving to their optima. This also shows that intrasexual dimorphisms can evolve despite strong genetic constraints, contrary to current predictions. We discuss the implications of this genetic constraint and emphasize the potential importance of ITC for our understanding of intrasexual dimorphisms.

Isolation of Serratia marcescens involved in chitin degradation in the bulb mite Rhizoglyphus robini

There is an increasing awareness of the importance of the microbiome of arthropods to understand their host’s biology. In the bulb mite, Rhizoglyphus robini, associated bacteria have been found to be involved in its chitinolytic abilities. The bulb mite, a plant pest feeding on below-ground parts of mostly Liliaceae crops, prefers fungus-infested plants. Moreover its fitness is higher when feeding on a fungal food source than when feeding on non-infected plants. In this study we isolated a chitinolytic bacterium from mite homogenate and identified it molecularly as Serratia marcescens (Bizio 1823), which is a model organism for chitin degradation. Precise identification of the bacterium can be important for the development of biological control programs of the mite as well as for further studies investigating Serratia marcescens and its chitinolytic machinery.

Mechanistic description of population dynamics using dynamic energy budget theory incorporated into integral projection models

Summary Integral projection models (IPMs) provide a powerful approach to investigate ecological and rapid evolutionary change in quantitative life‐history characteristics and population dynamics. IPMs are constructed from functions that describe the demographic rates – survival, growth and reproduction – in relation to the characteristics of individuals and their environment. Currently, however, demographic rates are estimated using phenomenological regression models that lack a mechanistic representation of the biological processes that give rise to observed demographic variation. This lack of mechanistic underpinning limits the ability of the model to predict future dynamics under novel environmental conditions because the model ingredients pertain to current environmental conditions only. Here, we use dynamic energy budget (DEB) theory to construct DEB‐IPMs based on a mechanistic representation of individual life‐history trajectories. We derive the demographic functions describing growth and reproduction from a simple DEB growth model. The functions describing mortality and the association between parent and offspring characteristics do not follow DEB theory and hence are estimated from individual‐level observations. We apply the DEB‐IPM to two contrasting systems: the small, fast‐reproducing bulb mite Rhizoglyphus robini and the large, slow‐reproducing reef manta ray Manta alfredi. In both cases, predictions of population growth rate, lifetime reproductive success and generation time agree with empirical observations. In case of the bulb mite, predictions and observations even agree across different feeding conditions. If the DEB energetics model is accepted as describing growth and reproduction, DEB‐IPMs can be parameterised using easy‐to‐collect life cycle information (growth rate, length at birth, maturation and old age) making them suitable for data‐deficient species. Because species differ only in these DEB parameters, comparative studies of character and population dynamics between species are straightforward, particularly since DEB‐IPMs can be extended to include population feedback on resources, of which we give an example. Most crucially, because DEB theory specifies growth and reproduction rates as explicitly dependent on environmental conditions such as food availability or temperature, DEB‐IPMs provide a mechanistic platform to investigate the biological processes that determine joint change in phenotypic characters, life‐history traits, population size and community structure.

Transcriptomics of Intralocus Sexual Conflict: Gene Expression Patterns in Females Change in Response to Selection on a Male Secondary Sexual Trait in the Bulb Mite.

Intralocus sexual conflict (IASC) prevents males and females from reaching their disparate phenotypic optima and is widespread, but little is known about its genetic underpinnings. In Rhizoglyphus robini, a mite species with alternative male morphs, elevated sexual dimorphism of the armored fighter males (compared to more feminized scramblers males) was previously reported to be associated with increased IASC. Because IASC persists if gene expression patterns are correlated between sexes, we compared gene expression patterns of males and females from the replicate lines selected for increased proportion of fighter or scrambler males (F- and S-lines, respectively). Specifically, we tested the prediction that selection for fighter morph caused correlated changes in gene expression patterns in females. We identified 532 differentially expressed genes (FDR < 0.05) between the F-line and S-line males. Consistent with the prediction, expression levels of these genes also differed between females from respective lines. Thus, significant proportion of genes differentially expressed between sexually selected male phenotypes showed correlated expression levels in females, likely contributing to elevated IASC in F-lines reported in a previous study.

Control of the Bulb Mite, Rhizoglyphus robini Claparede, on Chinese Chive by Hot Water Irrigation of Soil

Control of the Bulb Mite, <i>Rhizoglyphus robini</i> Claparede, on Chinese Chive by Hot Water Irrigation of Soil

Life History Consequences of the Facultative Expression of a Dispersal Life Stage in the Phoretic Bulb Mite (Rhizoglyphus robini).

Life history traits play an important role in population dynamics and correlate, both positively and negatively, with dispersal in a wide range of taxa. Most invertebrate studies on trade-offs between life history traits and dispersal have focused on dispersal via flight, yet much less is known about how life history trade-offs influence species that disperse by other means. In this study, we identify effects of investing in dispersal morphology (dispersal expression) on life history traits in the male dimorphic bulb mite (Rhizoglyphus robini). This species has a facultative juvenile life stage (deutonymph) during which individuals can disperse by phoresy. Further, adult males are either fighters (which kill other mites) or benign scramblers. Here, in an experiment, we investigate the effects of investing in dispersal on size at maturity, sex and male morph ratio, and female lifetime reproductive success. We show that life history traits correlate negatively with the expression of the dispersal stage. Remarkably, all males that expressed the dispersal life stage developed into competitive fighters and none into scramblers. This suggests that alternative, male reproductive strategies and dispersal should not be viewed in isolation but considered concurrently.

Control of the Bulb Mites, Rhizoglyphus robini Claparede and Sancassania spp. on Chinese Chive by Rotary Tilling in Winter

Control of the Bulb Mites, <i>Rhizoglyphus robini</i> Claparede and <i>Sancassania</i> spp. on Chinese Chive by Rotary Tilling in Winter

Effects of variation in nutrition on male morph development in the bulb mite Rhizoglyphus robini.

In male dimorphic species, growth influences morph expression and thereby the reproductive success of males. However, how variation in nutritional conditions affects male morph development and whether males can compensate for lost growth is poorly known. Here, we performed an experiment where males of the bulb mite (Rhizoglyphus robini)-which are fighters, able to kill other mites, or benign scramblers-were offered high quality food during the larval stage, but food of high or low quality during the protonymph and tritonymph (=final) stage. When food quality was low during the latter two stages, males matured smaller, later and were more likely to be a scrambler than when food quality was high. We found no evidence for compensatory growth: when males had low quality food only during the protonymph stage, they matured at the same age, but grew at a slower rate and matured at a smaller size than males that had high quality food throughout ontogeny. Furthermore, males that experienced this transient period of low food quality were less likely to mature as a fighter. Interestingly, scrambler increase in body size during the protonymph and tritonymph stages was always lower than that of fighters. Given the strong link between adult size and fitness, combined with the different development times and life histories of the male morphs, the lack of ability to compensate for a transient period of food deprivation during ontogeny is likely to have consequences for the dynamics of bulb mite populations.

SELECTION FOR ALTERNATIVE MALE REPRODUCTIVE TACTICS ALTERS INTRALOCUS SEXUAL CONFLICT

Intralocus sexual conflict (IASC) arises when fitness optima for a shared trait differ between the sexes; such conflict may help maintain genetic variation within populations. Sex-limited expression of sexually antagonistic traits may help resolve the conflict, but the extent of this resolution remains a subject of debate. In species with alternative male reproductive tactics, unresolved conflict should manifest more in a more sexually dimorphic male phenotype. We tested this prediction in the bulb mite (Rhizoglyphus robini), a species in which aggressive fighters coexist with benign scramblers. To do this, we established replicated lines in which we increased the proportion of each of the alternative male morphs using artificial selection. After approximately 40 generations, the proportion of fighters and scramblers stabilized at >0.9 in fighter- and scrambler-selected lines, respectively. We then measured several female fitness components. As predicted by IASC theory, female fecundity and longevity were lower in lines selected for fighters and higher in lines selected for scramblers. This finding indicates that sexually selected phenotypes are associated with an ontogenetic conflict that is not easily resolved. Furthermore, we suggest that IASC may be an important mechanism contributing to the maintenance of genetic variation in the expression of alternative reproductive tactics.

Neoseiulus paspalivorus, a predator from coconut, as a candidate for controlling dry bulb mites infesting stored tulip bulbs

The dry bulb mite, Aceria tulipae, is the most important pest of stored tulip bulbs in The Netherlands. This tiny, eriophyoid mite hides in the narrow space between scales in the interior of the bulb. To achieve biological control of this hidden pest, candidate predators small enough to move in between the bulb scales are required. Earlier experiments have shown this potential for the phytoseiid mite, Neoseiulus cucumeris, but only after the bulbs were exposed to ethylene, a plant hormone that causes a slight increase in the distance between tulip bulb scales, just sufficient to allow this predator to reach the interior part of the bulb. Applying ethylene, however, is not an option in practice because it causes malformation of tulip flowers. In fact, to prevent this cosmetic damage, bulb growers ventilate rooms where tulip bulbs are stored, thereby removing ethylene produced by the bulbs (e.g. in response to mite or fungus infestation). Recently, studies on the role of predatory mites in controlling another eriophyoid mite on coconuts led to the discovery of an exceptionally small phytoseiid mite, Neoseiulus paspalivorus. This predator is able to move under the perianth of coconuts where coconut mites feed on meristematic tissue of the fruit. This discovery prompted us to test N. paspalivorus for its ability to control A. tulipae on tulip bulbs under storage conditions (ventilated rooms with bulbs in open boxes; 23°C; storage period June-October). Using destructive sampling we monitored predator and prey populations in two series of replicated experiments, one at a high initial level of dry bulb mite infestation, late in the storage period, and another at a low initial dry bulb mite infestation, halfway the storage period. The first and the second series involved treatment with N. paspalivorus and a control experiment, but the second series had an additional treatment in which the predator N. cucumeris was released. Taking the two series of experiments together we found that N. paspalivorus controlled the populations of dry bulb mites both on the outer scale of the bulbs as well as in the interior part of the bulbs, whereas N. cucumeris significantly reduced the population of dry bulb mites on the outer scale, but not in the interior part of the bulb. Moreover, N. paspalivorus was found predominantly inside the bulb, whereas N. cucumeris was only found on the outer scale, thereby confirming our hypothesis that the small size of N. paspalivorus facilitates access to the interior of the bulbs. We argue that N. paspalivorus is a promising candidate for the biological control of dry bulb mites on tulip bulbs under storage conditions in the Netherlands.

Wheat curl mite and dry bulb mite: untangling a taxonomic conundrum through a multidisciplinary approach

Two economically important eriophyoid mites, Aceria tosichella (wheat curl mite; WCM) and Aceria tulipae (dry bulb mite; DBM), were frequently confounded in the world literature until the late 20th Century. Their morphological similarity and ambiguous data from plant-transfer and virus-transmission trials contributed to this confusion. Until recently, there was a general lack of knowledge about the existence of species complexes and it was not possible to accurately genotype tested mites. In the present study, two WCM genotypes of divergent host specificity (MT-1 and MT-2) and one DBM genotype were tested for the acceptance of Poaceae, Amarylidaceae, and Liliaceae species that were reported or suspected as hosts of WCM or DBM. The MT-1 lineage colonized all tested plants. Onion- and garlic-associated DBM populations did not colonize tulip and wild garlic, suggesting that host-acceptance variability exists within A. tulipae s.l. Morphometric analysis did not discriminate closely-related MT-1 and MT-2 genotypes but completely separated both WCM genotypes from DBM based on the larger overall body size of the latter. Three morphological traits combined to discriminate between the DBM and MT-1 genotypes, both of which can infest Amarylidaceae bulbs. In total, these combined DNA sequence, host-acceptance, morphometrical results unambiguously separated two WCM and one DBM genotypes. Similar studies on additional lineages of both WCM and DBM should ultimately dispel previous taxonomic confusion between these two species.

Life-History Differences Favor Evolution of Male Dimorphism in Competitive Games

Many species exhibit two discrete male morphs: fighters and sneakers. Fighters are large and possess weapons but may mature slowly. Sneakers are small and have no weapons but can sneak matings and may mature quickly to start mating earlier in life than fighters. However, how differences in competitive ability and life history interact to determine male morph coexistence has not yet been investigated within a single framework. Here we integrate demography and game theory into a two-sex population model to study the evolution of strategies that result in the coexistence of fighters and sneakers. We incorporate differences in maturation time between the morphs and use a mating-probability matrix analogous to the classic hawk-dove game. Using adaptive dynamics, we show that male dimorphism evolves more easily in our model than in classic game theory approaches. Our results also revealed an interaction between life-history differences and sneaker competitiveness, which shows that demography and competitive games should be treated as interlinked mechanisms to understand the evolution of male dimorphism. Applying our approach to empirical data on bulb mites (Rhizoglyphus robini), coho salmon (Oncorhynchus kisutch), and bullhorned dung beetles (Onthophagus taurus) indicates that observed occurrences of male dimorphism are in general agreement with model predictions.

A Survey on Cut Flower Cultivar Trends and Horticultural Status of Lilies (Lilium Hybrids) in South Korea

This study investigated trends in lily (Lilium hybrids) cultivars and challenges for growing cut lily flowers using a survey of producers in the South Korean lily industry. A questionnaire requested information on various topics including the total growing area, length of farming experience, cultivars grown, factors considered when purchasing bulbs, cultivation systems, horticultural practices, disease and pest problems, and horticultural problems. The survey targeted the membership of the Korea Lily Producer Association and the number of respondents corresponded to 43% of all lily farmers in the country. Oriental-Trumpet (OT) hybrid ‘Yelloween’ and Oriental hybrids ‘Siberia’, ‘Medusa’, and ‘Sorbonne’ were mainly cultivated in South Korea. The main flower colors were yellow, white, and pink. Factors considered in choosing cultivars were the prices of bulbs and cut flowers affecting income of the farm. More than 90% of respondents used soil culture in a greenhouse to grow cut flowers. There were various horticultural practices used from planting to harvest. The main pests harming bulb and flower productivity were fungus gnat (Bradysia difformis) and bulb mite (Rhizoglyphus robini), and the most common horticultural problem was leaf scorch. Overall, the survey suggested that the stable production of lily bulb with low cost and high quality was required and practical techniques should be developed for increasing the cut lily production efficiency. In addition, the pests, diseases, and horticultural problems in the given local environmental conditions should be considered when breeding new cultivars and developing production technology.

No Evidence for Reproductive Isolation through Sexual Conflict in the Bulb Mite Rhizoglyphus robini

Sexual conflict leading to sexual antagonistic coevolution has been hypothesized to drive reproductive isolation in allopatric populations and hence lead to speciation. However, the generality of this speciation mechanism is under debate. We used experimental evolution in the bulb mite Rhizoglyphusrobini to investigate whether sexual conflict promotes reproductive isolation measured comprehensively to include all possible pre- and post-zygotic mechanisms. We established replicate populations in which we either enforced monogamy, and hence removed sexual conflict by making male and female evolutionary interests congruent, or allowed promiscuity. After 35 and 45 generations of experimental evolution, we found no evidence of reproductive isolation between the populations in any of the mating systems. Our results indicate that sexual conflict does not necessarily drive fast reproductive isolation and it may not be a ubiquitous mechanism leading to speciation.

Biological aspects and life table parameters of predator gamasid ascid mite, Blattisocius dentriticus (Berlese) (Acari:Gamasida: Ascidae)

The gamasid ascid mite, Blattisocius dentriticus (Berlese) (Gamasida: Ascidae) was reared at 30 + 2 °C and 80+ 5 % R.H. on four different foods (the acarid astigmatid mite, Rhizoglyphus robini (Claparede), two different fungi (Fusarium moniliforme, Botrytis allii) and larvae of Musca domesticate Linnaeus. The main objective in this study was to examine the possibilities of using gamasid predator mite, B. dentriticus to fed on different foods. Also the obtained result clear that the lowest incubation period of B.dentreticus was noticed for resulted females and males fed on immature of acarid bulb mite (1.3 & 0.95 days), but the longest period recorded when the female and male individuals fed on the fungus F. moniliforme (3.7 & 2.6 days). From the obtained data also, it could be observed that the duration of life cycle for both sexes was affected by the type of food employed. However, adult longevity of B .dentriticus was influenced by the kind of food employed for female, this period lasted (22.2, 36.8, 32.2 and 24.8) days when the individuals fed on aforementioned foods. These periods changed to (19.2, 30, 25.8 and 21.6 days) for males which fed on the tested foods, respectively. The current study indicated that immature of astigmatid mite, R. robini proved to be the most favorable food as it gave the highest reproduction rate (47.8 eggs). On the contrary, the fungus F. moniliforme resulted in the least number of deposited B.dentritucus eggs with an average of (26 eggs). During the total time (life span) of the predatory mite, B.dentreticus, the total number of the tested consumed prey was significantly differed. The number was (80.2 and119 prey) when the predatory mite males and females fed on amixtures of acarid mite R. robini , respectively. While the number of consumed preys was (77, 113.4 prey) when predatory mite fed on M.domesticae larvae, respectively. The calculated life table parameters were, Mean generation time (T) was (10.35, 26.81, 20.4 and14.85) days. The doubling time (DT) was (2.34, 0.0753, 5.23 and 3.483 times). Finite rate of increase (λ) e rm was (1.34, 1.09, 1.14 and1.22) times/female/day. Gross reproductive rate (GRR) was (29.58, 12.45, 18.5 and 22.43) times/female/day. It could be generally concluded that immatures of bulb mite, R.robini was the most suitable food for the development and reproduction of predator gamasid mite,B.dentriticus.

Complex response in size-related traits of the bulb mites (Rhizoglyphus robini) in elevated thermal conditions - an experimental evolution approach

Temperature is a key environmental factor affecting almost all aspects of life history in ectotherms. Theory predicts that they grow faster, reach smaller sizes and produce smaller offspring when temperature increases. In addition, temperature changes, through their effects on metabolism, may also influence the expression of alternative reproductive phenotypes (ARPs) in ectotherms. Although many studies have investigated the phenotypic plasticity of life history traits in relation to temperature change, little is known about how those traits and phenotypic plasticity may evolve together. In our study we subjected bulb mites (non-model, soil organisms that normally experience rather stable thermal conditions) to experimental evolution in two temperature treatments: control (24°C) and elevated (28°C). After 18 generations, we measured adult body size, egg size and development time of both treatments at control as well as at elevated temperatures (test temperatures). Thus, we were able to detect genetic changes (the effects of selection temperature) and environmental effects (the effects of test temperature). We also observed the ARP expression throughout the experimental evolution. Our results revealed quite complex patterns of life history in traits response to temperature. Mites developed faster and reached smaller sizes at increased temperature, but evolutionary responses to increased temperature were not always parallel to the observed phenotypic plasticity. Additionally, despite smaller body sizes, females laid larger eggs at higher temperature. This effect was more pronounced in animals evolving at elevated temperature. Evolution at increased temperature also affected ARP expression, with the proportion of armored fighters decreasing from generation to generation. We propose that this could be the consequence of temperature sensitivity of the cost-to-benefits ratio of expressing ARPs.

Control of the Bulb Mites, Rhizoglyphus robini Claparede by Heating Chinese Chive Seedlings on Plug-tray with Hot-water

Control of the Bulb Mites, <i>Rhizoglyphus robini</i> Claparede by Heating Chinese Chive Seedlings on Plug-tray with Hot-water

Genetic Characterization of North American Populations of the Wheat Curl Mite and Dry Bulb Mite

The wheat curl mite, Aceria tosichella Keifer, transmits at least three harmful viruses, wheat streak mosaic virus (WSMV), high plains virus (HPV), and Triticum mosaic virus (TriMV) to wheat (Triticum aestivum L.) throughout the Great Plains. This virus complex is considered to be the most serious disease of winter wheat in the western Great Plains. One component of managing this disease has been developing mite resistance in wheat; however, identification of mite biotypes has complicated deployment and stability of resistance. This biotypic variability in mites and differential virus transmission by different mite populations underscores the need to better understand mite identity. However, A. tosichella has a history of serious taxonomic confusion, especially as it relates to A. tulipae Keifer, the dry bulb mite. Molecular techniques were used to genetically characterize multiple A. tosichella populations and compare them to populations of A. tulipae. DNA from these populations was polymerase chain reaction amplified and the ribosomal ITS2 region sequenced and compared. These results indicated limited variability between these two species, but two distinct types within A. tosichella were found that corresponded to previous work with Australian mite populations. Further work using sequencing of several mitochondrial DNA genes also demonstrated two distinct types of A. tosichella populations. Furthermore, the separation between these two A. tosichella types is comparable to their separation with A. tulipae, suggesting that species scale differences exist between these two types ofA. tosichella. These genetic differences correspond to important biological differences between the types (e.g., biotypic and virus transmission differences). In light of these differences, it is important that future studies on biological response differences account for these mite differences.

Mating system affects population performance and extinction risk under environmental challenge.

Failure of organisms to adapt to sudden environmental changes may lead to extinction. The type of mating system, by affecting fertility and the strength of sexual selection, may have a major impact on a population's chances to adapt and survive. Here, we use experimental evolution in bulb mites (Rhizoglyphus robini) to examine the effects of the mating system on population performance under environmental change. We demonstrate that populations in which monogamy was enforced suffered a dramatic fitness decline when evolving at an increased temperature, whereas the negative effects of change in a thermal environment were alleviated in polygamous populations. Strikingly, within 17 generations, all monogamous populations experiencing higher temperature went extinct, whereas all polygamous populations survived. Our results show that the mating system may have dramatic effects on the risk of extinction under environmental change.