Mesostigmatid Mites Research Articles

Myrmecophily among mesostigmatid mites

AbstractAnt nests are biodiversity hot spots, concentrating resources from a wide area that can be exploited by other organisms, known as myrmecophiles. The mite order Mesostigmata includes a wide range of lineages that have become myrmecophiles with many species reliant on ant nests for at least part of their development. The nature of the associations is quite variable, including predators of smaller arthropods in the nest (close to the ancestral lifestyle of these mites), scavengers, kleptoparasites, parasites, and parasitoids. A few mite species show extreme modifications of morphological and/or developmental patterns, others show almost none. Some host specificity is common but one-on-one host specialization is rare or poorly tested. Phoresy on the ants is common, but the target ant caste varies with the goal of phoresy. In general, the diversity of mesostigmatid mites in the nest of a given ant species is affected by habitat conditions along with a range of life history characteristics of the ants, including factors such as body size, colony size, colony founding mode, social parasitism, and nest density. Unfortunately, the life history of the majority of mites associated with ants is still unknown.

Environmental role of different‐aged pine and oak stands growing on post‐agricultural and forest lands in forming the Mesostigmata mites communities

AbstractReclamation of agricultural soil and forest succession after afforestation proceeds slowly and at many levels. Therefore, the history of land use is recorded in the soil's physical, chemical and ecological parameters for many decades. This process depends on time and the form of afforestation, which primarily includes tree species. In our study, we analyzed differences in the physical and chemical characteristics of pine and oak stands on forest and post‐agricultural land at 22, 42 and 62 y/o. Our study revealed that 14 of 24 examined parameters (litter pH, soil pH, litter thickness, soil organic matter, Corg, bulk density, C/N ratio, soil moisture, soil K, Mg and Mn content, N and Ca litter content, Mg litter content) differed significantly among examined habitats (land use, stand age and tree species). We calculated the abundance, species richness and diversity of the mite communities (Acari, Mesostigmata) for each habitat type. In total, 6730 mites were classified into 72 taxa (60 species, 11 genera and one taxon as family). The highest abundance was recorded in 42 y/o. oak stands on post‐agricultural land, while the lowest is in 22 y/o. pine and oak stands on post‐agricultural land. The highest species richness and diversity were recorded in the oldest oak stand on post‐agricultural land. In contrast, the lowest diversity was recorded in the youngest oak and pine stands on post‐agricultural land. Our results demonstrate that the negative impact of the agricultural history of land use weakens over time and provides a better understanding of land use history on the relations between the soil environment and soil fauna, including mesostigmatid mite assemblages.

Investigation of honey bee colonies in terms of mesostigmatid mites in Turkey

Turkey is in an essential geographic position for transmitting honey bee diseases from Asia to Europe. This study investigated Tropilaelaps mercedecae and Euvarroa sinhai, a potential risk for European beekeeping, for the first time throughout Turkey. In addition, the situation of varoasis has been comprehensively revealed. In total, 1199 colonies in 401 apiaries were examined in 40 provinces of Turkey. About 200 workers and a 10-cm2 honeycomb with capped brood cells were collected from each hive. While Tropilaelaps and Euvarroa species were not found, varroasis was detected in all 40 provinces. The prevalences were recorded at 69.3 ± 2.7 (95%CI) in apiaries and 45.5 ± 2.4 (95%CI) in hives. All of the investigated samples were Varroa destructor Korean (K) haplotypes. At the end of the study, it was determined that varroasis was still endemic and spread throughout the country with a slight increase. Also, Tropilaelaps sp, a severe danger for European beekeeping, is not yet found in Apis mellifera colonies in Turkey.

Impact of land use history and soil properties on soil mite communities (Acari, Mesostigmata) inhabiting stands growing on post‐agricultural land

AbstractDecades of agriculture in a former—type of ecosystem, for example, deciduous forests—result in severe habitat degradation. The planted tree species encounter harsh conditions due to physically and chemically transformed soil environments. In addition, afforestation itself significantly modifies the upper soil horizons. It may impact the soil fauna communities, including mites from the Mesostigmata order (Mesostigmata = Gamasida). Due to their sensitivity, mesostigmatid mites are good bioindicators of changes in the soil. A decrease in the density, species richness, and diversity of mites indicates disturbances in the soil environment and may confirm the impact of agricultural practice on the soil environment. Our research aim was to examine the impact of soil properties and land use history on the mesostigmatid mite communities in stands growing on forest and post‐agricultural lands. These sites were afforested with different tree species (Betula pendula Roth., Fagus sylvatica L., Pinus sylvestris L., and Quercus robur L.). Thus, 21 research plots were established on forest and post‐agricultural land, each on rusty soils considered to be one of the most common in Central European forests. We collected a total of 567 soil samples during three sampling sessions in spring and autumn for soil Mesostigmata investigation. We also described the soil profile on each plot and collected soil and litter samples to measure pH, litter thickness, soil organic matter, bulk density, soil moisture, soil organic carbon, and elements content. Our study revealed that 16 out of 30 environmental parameters differed between habitat types. A total of 1355 mites were classified into 58 taxa (50 species and 8 genera). The most numerous species were Veigaia nemorensis (165 ind.; 12.2% of all mesostigmatid mites), Zercon peltatus (156; 11.5%), and Paragamasus conus (141; 10.4%). The highest abundance was recorded in birch stands on forest land, whereas the lowest abundance for oak stands growing on post‐agricultural land. Interestingly, in oak stands we recorded both the highest diversity of mite communities (forest land) and the lowest on post‐agricultural land. Furthermore, our study showed that post‐agricultural land and Na content in forest litter affected the abundance, species richness, and diversity of mesostigmatid mite communities. Species richness was additionally affected by tree species, that is, pine and oak. Our research indicated that long‐term agricultural practice negatively affected the density, species richness, and diversity of Mesostigmata communities 20 years after afforestation.

Bottom-up effects of nematode prey on soil predatory mites (Acari: Mesostigmata)

Pest suppression is one of the desirable functions of a healthy soil. Predatory Mesostigmata soil mites, with their high degree of omnivory, are one of the most remarkable groups performing this beneficial role. Food web bottom-up effects are important for the fitness of these predators, which ultimately affects their potential as biocontrol agents. In below-ground systems, free-living nematodes (FLN) are an important diet for mites, providing essential nutrients such as omega 3 long-chain polyunsaturated fatty acids (ω3-LC PUFAs). Here we assess the food quality of nematodes for the maintenance of predator fitness, i.e. development, reproduction and lipid content. We selected two mite species, different in size and morphology, collected from vegetable crops in Israel. Additionally, five species of FLN were isolated from the same fields. Additionally, one plant-parasitic species, common across arable sites in Israel, and maintained on tomato as host, was tested. Depending on species and trophic group, nematodes varied in fatty acid profile, and both mite species generally reflected the fatty acid pattern of their diet. All nematode species were able to produce ω3-LC PUFA de novo, except the bacterial feeder Acrobeloides bodenheimeri, which had the highest proportion of ω6-PUFA. Interestingly, the latter lacking ω3-LC PUFA, was the best diet for both mites. Macrocheles aff. scutatus, a medium-sized mite with a holodorsal shield, fed and developed on all nematodes except the entomophilious Oscheius tipulae. It was able to complete its development feeding on the plant parasitic Meloidogyne incognita, yet the reproduction was almost zero. The smaller and slender Protogamasellopsis zaheri, with a split dorsal shield, developed and reproduced with all nematodes, with M. incognita as an intermediate diet. Our results demonstrate that nematode species vary in their nutritional quality as prey. However, food quality is predator species dependent, likely affecting biocontrol efficacy. Besides ω3-LC PUFA, ω6-PUFA can play an important role in the reproductive and developmental parameters of mesostigmatid mites; yet, other factors such as nematode size and behaviour have to be considered.

Large-scale experimental warming reduces soil faunal biodiversity through peatland drying

Boreal peatlands are important ecosystems for carbon cycling because they store 1/3 of the world’s terrestrial carbon in only ∼3% of the global landmass. This high carbon storage capacity makes them a key potential mitigation strategy for increased carbon emissions induced by global climate warming. In high-carbon storage systems like peatlands, soil faunal communities are responsible for secondary decomposition of organic matter and nutrient cycling, which suggests they play an important role in the carbon cycle. Experiments have shown that warming can affect plant and microbial communities in ways that potentially shift peatlands from carbon sinks to sources. Although previous studies have found variable effects of climate change manipulations on soil communities, warming is expected to affect soil community composition mainly through reductions in moisture content, whereas elevated CO2 atmospheric concentrations are expected to only indirectly and weakly do so. In this study we used a large-scale peatland field-based experiment to test how soil microarthropod (oribatid and mesostigmatid mite, and collembolan species abundance, richness and community composition) respond to a range of experimental warming temperatures (between 0°C and +9°C) crossed with elevated CO2 conditions over 4 years in the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment. Here we found that warming significantly decreased surface peat moisture, which in turn decreased species microarthropod richness and abundance. Specifically, oribatid and mesostigmatid mite, collembolan, and overall microarthropod richness significantly decreased under lower moisture levels. Also, the abundance of microarthropods increased under higher moisture levels. Neither warming nor elevated [CO2] affected microarthropods when analysed together or separate, except for the richness of mesostigmatids that significantly increased under warming. At the community level, communities varied significantly over time (except collembolans), and moisture was an important driver explaining community species composition. While we expect that the cumulative and interactive effects of the SPRUCE experimental treatments on soil faunal biodiversity will continue to emerge, our results already suggest effects are becoming more observable over time. Taken together, the changes belowground indicate potential changes on carbon and nitrogen cycles, as microarthropods are important players of soil food webs.

Does Gamasid mites (Acari, Mesostigmata) observed in oil palm and rubber plantations can be used as indicators of tropical secondary forest soil transformation?

The aim of the study was to assess modifications in the community of soil mesostigmatid mites’, as indicator of environment stability with land-use change across 2–4 texturally distinct soils in La Mé and Grand Lahou, Côte d’Ivoire. The fieldwork was carried out in humid period on two study sites: 1– rubber landscape (secondary forest, 7-, 12- and 25-year-old rubber plantations) and 2– oil palm landscape (secondary forest, 13-, 20- and 39-year-old oil palm plantations). Three sampling stands were established in each land-use type and age class, for a total of 24 sampling stands. On each sampling stands, soil cores for Gamasid mite’s extraction were taken at 10 cm soil depth through a 40–50 m transect. Our findings highlighted a drop of mesostigmatid mites’ density (–49% and –52%), species richness (–41% and –40%), and diversity (–35% and –49%), respectively after conversion of the secondary forests into rubber and oil palm plantations. The soil with clayey sandy and clayey textures favored the development of the mesostigmatid mites, particularly in the abundance and species richness of Uropodina. However, the soil with sandy clayey textures improved the abundance and species richness of Gamasina. The mesostigmatid mites’ community was degraded in sandy-textured soils. In light of the Maturity Index values, a better quality of soil and environment was detected in the secondary forests compared to plantations. The results also suggest that the mesostigmatid mites’ community influence the soil nutrients and probably plant productivity indirectly by influencing the populations of their prey.

Soil arthropod responses to subsoil manuring in irrigated vegetable and rainfed grain production

Diverse soil biology is being increasingly recognised as important for productive soils. Subsoil manuring – the process of placing organic materials underground using a modified deep ripper – has been used to improve the structure and productivity of texture contrast soils. Using soil arthropods as indicator species, this study investigated the soil biology responses of the subsoil manuring approach. Different organic materials were placed in the upper zone of a clay subsoil at field sites used for irrigated vegetable and rainfed grain production. Soil samples were taken from the topsoil and from the depth of organic material placement and processed to extract soil arthropods. Of three suborders of soil arthropods recorded, mesostigmatid mites showed the most notable increases in abundance in response to subsoil manuring. The placement of organic materials at depth resulted in elevated abundance of soil arthropods at depths that are not the normal habitat of these organisms. Abundance and richness were both suppressed under irrigated production compared to rainfed, although it is acknowledged that a number of management practice differences between the two production systems could contribute to the differences observed.

Restoring management practices in Tuscan organic vineyards and impact on soil mesostigmatid mites

Soil fauna actively contributes to drive crucial processes of energy and nutrient cycling in agricultural systems, to influence the quality of crops and pest incidence. Soil tillage can be absolutely considered as one of the most influential agricultural manipulations of soil structure and has a profound influence on soil biology and its provision of ecosystem services. Understanding the effects of different tillage intensities is of interest not only to the scientific community but also to farmers, practitioners, policymakers, and agricultural consultants. As the long-term evidence in degraded vineyard soils, EU and FAO highly recommend inter-row practices basing on sustainable managements and good agronomic practices (GAPs) to re-install soil functionality. In this study, we aimed at evaluating effects of different GAP practices that can improve soil recovering on some soil quality indicators, with emphasis to edaphic mesostigmatid mites.

Diversity of phytoseiid mite (Acari: Mesostigmata) fauna from Andaman & Nicobar Islands, India

The highly biodiverse group of mesostigmatid mites belonging to the family of Phytoseiidae are globally recognized as potential predators of small soft-bodied arthropods and destructive mite pests owing to their high searching capacity, good adaptability to a wide range of climatic regimes from arctic to tropics, short life cycle (1 week approx.), high multiplication capability (40–60 offspring per female) with high feeding potential. Phytoseiid mites that are commercially exploited as efficient biocontrol agents are regarded as farmers’ friends as they play a pivotal role in managing the pest population below the economic injury level to ensure a safe and sustainable pattern of food production system keeping aside hazardous chemicals. At present, the global scientific communities are deeply involved with this group of mites and due to their higher attention, the number of nominal phytoseiid species has increased from 34 in 1950 to more than 2500 in 2021.

Reducing tillage intensity benefits the soil micro‐ and mesofauna in a global meta‐analysis

AbstractSoil fauna drives crucial processes of energy and nutrient cycling in agricultural systems, and influences the quality of crops and pest incidence. Soil tillage is the most influential agricultural manipulation of soil structure, and has a profound influence on soil biology and its provision of ecosystem services. The objective of this study was to quantify through meta‐analyses the effects of reducing tillage intensity on density and diversity of soil micro‐ and mesofaunal communities, and how these effects vary among different pedoclimatic conditions and interact with concurrent management practices. We present the results of a global meta‐analysis of available literature data on the effects of different tillage intensities on taxonomic and functional groups of soil micro‐ and mesofauna. We collected paired observations (conventional vs. reduced forms of tillage/no‐tillage) from 133 studies across 33 countries. Our results show that reduced tillage intensity or no‐tillage increases the total density of springtails (+35%), mites (+23%), and enchytraeids (+37%) compared to more intense tillage methods. The meta‐analyses for different nematode feeding groups, life‐forms of springtails, and taxonomic mite groups showed higher densities under reduced forms of tillage compared to conventional tillage on omnivorous nematodes (+53%), epedaphic (+81%) and hemiedaphic (+84%) springtails, oribatid (+43%) and mesostigmatid (+57%) mites. Furthermore, the effects of reduced forms of tillage on soil micro‐ and mesofauna varied with depth, climate and soil texture, as well as with tillage method, tillage frequency, concurrent fertilisation, and herbicide application. Our findings suggest that reducing tillage intensity can have positive effects on the density of micro‐ and mesofaunal communities in areas subjected to long‐term intensive cultivation practices. Our results will be useful to support decision making on the management of soil faunal communities and will facilitate modelling efforts of soil biology in global agroecosystems.HIGHLIGHTSGlobal meta‐analysis to estimate the effect of reducing tillage intensity on micro‐ and mesofaunaReduced tillage or no‐tillage has positive effects on springtail, mite and enchytraeid densityEffects vary among nematode feeding groups, springtail life forms and mite subordersEffects vary with texture, climate and depth and depend on the tillage method and frequency

Linked seasonality between a phoretic mite and its moth fly host (Parasitiformes: Mesostigmata and Diptera: Psychodidae)

Phoresy is a widespread phenomenon in mites. It allows mesostigmatid mites that are associated with ephemeral habitats such as mammal dung to travel fast on larger animals that can detect a proper habitat from a greater distance. To address the gap in knowledge on phoresy in these mites, we examined host specificity in phoretic Mesostigmata associated with psychodid species and studied temporal dynamics to see if phoretic life cycles are synchronized with the host life cycle. Using a field collection of more than 2500 moth flies (Psychodidae) from eight localities in Norway, we found three out of 29 species carrying phoretic mites of two species: deutonymphs of Trachygamasus ambulacralis were phoretic on female Psychoda phalaenoides and both sexes of Psychoda grisescens, and adults of Iphidozercon gibbus were phoretic on females of Psychoda satchelli. All flies were species with larval development in vertebrate dung. Abundances of P. phalaenoides and T. ambulacralis were highly correlated, probably due to the two species exhibiting similar seasonal variations in abundance; both were significantly seasonal with a peak in August and September. Thus, T. ambulacralis infestation levels on P. phalaenoides appeared similar throughout the season. We discuss the implications for the life histories of the mites in question. Trachygamasus ambulacralis is first time recorded from Norway.

Which soil properties affect soil mite (Acari, Mesostigmata) communities in stands with various shares of European ash (Fraxinus excelsior L.)?

European ash (Fraxinus excelsior L.) is an important tree species and a critical component of European forests. Its share has gradually decreased due to the global climate crisis or fungal diseases. Therefore, it may influence dependent plant communities and soil organisms. Hence, we aimed to describe soil properties among different habitats where ash may grow and assess how these habitats affect abundance, species richness, and diversity of soil mite (Mesostigmata) communities. The study was conducted in eight stands (western Poland) grouped in four habitats differing in terms of soil conditions and stand species composition. Stands represented: (1) optimal habitats for ash growth with >90 % ash in the tree layer, (2) optimal habitats without ash in the tree layer, (3) suboptimal habitats with >60 % ash and co-dominance of Quercus robur L., and (4) transformed habitats with >60 % ash and co-dominance of Pinus sylvestris L. Soil environments within the research plots (circular plot area in each stand = 400 m2) were characterized by the description of the soil profile and 17 soil parameters provided for each of 72 soil samples. Mesostigmatid mites were extracted from 72 additionally collected samples into Berlese-Tullgren funnels, then mounted on slides and classified to species or genus levels.In total, 362 mites were classified into 39 taxa. The most numerous taxa were Paragamasus sp. (13.0 % of all mites), Oodinychus ovalis (C. L. Koch) (11.3 %), and Paragamasus runcatellus (Berlese) (8.6 %). We found that decreasing nitrate‑nitrogen was accompanied by increasing mite abundance, species richness, and diversity. Furthermore, mesostigmatid mite abundance and species richness increased with increasing soil pH. Although soil moisture, pH of forest litter, magnesium, calcium, potassium, total nitrogen, and C/N mass ratio differed between all habitats, they did not affect Mesostigmatid abundance, species richness, and diversity. Nevertheless, analysis of variance conducted for the Canonical Correspondence Analysis model showed that habitat and pH of forest litter significantly impacted the community species composition of mesostigmatid mites. Our study provides a better understanding of the habitat requirements of soil mesostigmatid mites and, therefore, leads to improving the use of mesostigmatid mite taxa as effective bioindicators of soil and environmental quality.

Diversity and distribution of ectoparasite taxa associated with Micaelamys namaquensis (Rodentia: Muridae), an opportunistic commensal rodent species in South Africa.

South Africa boasts a rich diversity of small mammals of which several are commensal and harbour parasites of zoonotic importance. However, limited information is available on the parasite diversity and distribution associated with rodents in South Africa. This is particularly relevant for Micaelamys namaquensis (Namaqua rock mouse), a regionally widespread and locally abundant species that is often commensal. To address the paucity of data, the aims of the study were to record the ectoparasite diversity associated with M. namaquensis and develop distribution maps of lice and mites associated with M. namaquensis and other rodents in South Africa. Micaelamys namaquensis individuals (n = 216) were obtained from 12 localities representing multiple biomes during 2017–2018. A total of 5591 ectoparasites representing 5 taxonomic groups – fleas, lice, mesostigmatid mites, chiggers and ticks was recorded. These consisted of at least 57 taxa of which ticks were the most speciose (20 taxa). Novel contributions include new host and locality data for several ectoparasite taxa and undescribed chigger species. Known vector species were recorded which included fleas (Ctenocephalides felis, Dinopsyllus ellobius and Xenopsylla brasiliensis) and ticks (Haemaphysalis elliptica, Rhipicephalus appendiculatus and Rhipicephalus simus). Locality records indicate within-taxon geographic differences between the 2 louse species and the 2 most abundant mite species. It is clear that M. namaquensis hosts a rich diversity of ectoparasite taxa and, as such, is an important rodent species to monitor in habitats where it occurs in close proximity to humans and domestic animals.

Temperature and precipitation affect seasonal changes in mite communities (Acari: Mesostigmata) in decomposing litter of broadleaved and coniferous temperate tree species

Key messageWe identified the effect of microclimatic conditions on soil mite communities (Mesostigmata) during the decomposition of broadleaved and coniferous litter. The abundance, species richness, and diversity of mite communities decreased from spring to autumn regardless of litter quality and was related to changes in temperature and precipitation.ContextLitter decomposition is one of the fundamental soil-supporting processes in terrestrial ecosystems. However, there is still a lack of knowledge on some general patterns of the relationships between litter quality (tree species), microclimate, and structure of soil mite assemblages.AimsThe study aimed to analyze the impact of climatic conditions (temperature and precipitation) on mesostigmatid mite communities in the litter of 11 tree species through the vegetation season.MethodsThe experiment tested litter decomposition of 11 different tree species (693 litterbags), for seven consecutive months (April-October) under homogenous Scots pine (Pinus sylvestris L.) canopy monocultures in common garden conditions. Soil mites were extracted in Tullgren funnels.ResultsMesostigmatid mite abundance was positively correlated with the temperature of the sampling month and negatively with the temperature of the previous month. Species richness depended on the sampling month temperature. Changes in litter mass loss in late autumn (after litterfall) and overwinter were important for colonization of litterbags by soil mesostigmatid mites in the following spring.ConclusionsChanges in climatic conditions, i.e., temperature and precipitation between the sampling months (during the following vegetation period), may cause significant changes in mesostigmatid mite abundance and thus may impact ecosystem functions. The winter period is important for mesostigmatid mite abundance in the following vegetation period.

Responses of soil-inhabiting mesostigmatid mites to deforestation and disturbance in oak (Quercus brontii) forests of southwestern Iran

The impacts of deforestation on edaphic mesostigmatid mites were investigated in oak forests of Lordegan, southwestern Iran, from April to October. A total of twenty-one species belonging to eighteen genera and ten families were collected and identified. The Shannon-Wiener, Simpson, Jaccard's and Margalef biodiversity indices were used for data analyses. Among the collected species, Antennoseius bacatus with 29% and Sessilunchus hungaricus with 16% relative abundance were the most abundant and dominant species in human-disturbed and natural forests, respectively. The estimated values were higher in natural oak forest than in disturbed and cultivated habitat. Significant differences were observed in soil nitrogen content and soil organic carbon between the two habitats, but not in pH values. Significant effects of sampling time and habitat were found on all four indices, but the effect of their interactions on these indices was not significant. It can be concluded that the changes in soil quality that resulted from deforestation may have a major role in reducing the soil mite density and related diversity indices in disturbed forests.

Some new records of mesostigmatid mites (Acari: Mesostigmata) associated with greenhouse plants from Iran

During 2018-2019, fauna of mesostigmatic mites (Acari: Mesostigmata) associated with greenhouse plants were collected and identified in Rasht region, Guilan Province, Northern Iran. Totally, 62 species belonging to 36 genera and 17 families were collected and identified. Among them, 6 species Cilliba sellnicki (Hirschmann & Zirngiebl-Nicol, 1964), Epicrius canestrinii (Haller, 1881), Vulgarogamasus trouessarti (Berlese, 1892), Rhodacarellus epigynalis Sheals, 1956, Gamasolaelaps excisus (Koch, 1879) and Proctolaelaps holoventris Moraes et al., 2016 are new record for mite’s fauna of Iran.

Does litter decomposition affect mite communities (Acari, Mesostigmata)? A five-year litterbag experiment with 14 tree species in mixed forest stands growing on a post-industrial area

Decomposition and topsoil microclimate, mainly humidity and soil temperature, affects the availability of nutrients, as well as the edaphon structure, including soil mites, springtails, nematodes, insects and oligochaetes. Soil arthropod decomposers are the food base for predators in the soil trophic chains, including mesostigmatid (gamasid) mites. The aim of our study was to describe the succession of mesostigmatid assemblages on decomposed litter of 14 tree species in mixed stands growing on a reclaimed post-mining site. We hypothesized that litter species would significantly affect the gamasid abundance, species richness and diversity. Moreover, we hypothesized that mesostigmatid abundance, species richness and diversity would be higher in deciduous litter compared to pioneer Scots pine litter. Additionally, along with the decomposition process, the gamasid diversity, species richness and abundance would be significantly affected by soil temperature and differ among collection dates, with the lowest values at the beginning and the end, and with the highest values in the middle of the study period. In December 2011, 1389 litterbags (mesh size = 1 mm) containing leaf litter (initial dry mass = 8.004–10.772 g) were placed on research plots and collected after 3, 6, 9, 13, 19, 25, 31, 37, 43 and 58 months after the experiment started. We determined the percentage litter mass loss for each sample and mean soil temperature on each research plot. Soil microarthropods were extracted from litterbag samples using Berlese-Tullgren funnels, and mesostigmatid mites were selected using a stereomicroscope. The mites were identified to genus and/or species level including developmental stages, using a microscope with high magnification and acarological keys. In total, 19,296 gamasid mites were selected and classified into 52 taxa. The dominant species were Trachytes aegrota (C.L. Koch) (49.9% of all gamasid mites found), Veigaia nemorensis (C.L. Koch) (8.9%) and Gamasellodes bicolor (Berlese) (7.7%). We found that time of litterbag sampling did not affect abundance, species richness and diversity of gamasid mites. Moreover, litter species affected species richness and diversity of gamasid mite assemblages, however, abundance was affected when calculated per sample, but not when calculated per dry litter mass. Additionally, we found that mean soil temperature and percentage litter mass loss also significantly affected abundance and species richness, however, the impact on diversity was insignificant. Our results may help to better understand of the importance of soil fauna that has a decisive impact on soil-forming processes on degraded areas. Results could also help to choose the right tree species to improve revitalization of degraded areas by creating better conditions for edaphic fauna, including species not directly involved in the decomposition process.

Edaphic mesostigmatid mites (Acari: Mesostigmata) and thrips (Insecta: Thysanoptera) in rose cultivation and secondary vegetation areas in the Bogotá plateau, Colombia

ABSTRACT Soil mesostigmatid mites include predator species with potential as biological control agents. Their use for that purpose in rose crops in Colombia is highly desirable, to complement pest management strategies. The first step for their use in a program is to know their identity. The objectives of this study were: to determine the species of non-Uropodina Mesostigmata present in rose fields and the surrounding secondary vegetation of fields in the Bogotá plateau, relating their occurrence to soil characteristics; and to determine the fluctuation of the density of those mites and of thrips in selected areas of that plateau. The study was conducted between August 2015 and December 2016 in four rose fields in greenhouses at Nemocon, Tocancipa, Cogua and Guasca, and patches of secondary vegetation next to the latter two localities. Twenty soil samples were taken every two months from each area. Complementary samplings were conducted at irregular frequencies in a rose field and a patch of secondary vegetation of other region (Facatativa) and in two patches of high Andean vegetation (La Calera, Soacha). Ninety-six species were found. In both rose cultivation and natural vegetation, Parasitidae and Laelapidae were the dominant families throughout the study, but high proportions of Veigaiidae and Blattisociidae were also observed in secondary vegetation. Twenty-five thrips species were found, distributed in six genera (Thripidae). Mite species composition was compatible with that of temperate areas of other parts of the world, given the high elevation of study sites (2460–2777 m), despite its location close to the equator. Three of the species collected have been commercialized as biological control agents in other countries. A significant and positive correlation was found between mite density and organic matter content and pH level. The study showed a great diversity of Mesostigmata in the Bogota plateau (altogether, 96 species), at least eight of which new to science and several in need of better taxonomic characterization.

Surrounding the swollen roots of sweetpotato with a decomposing band of an organic amendment enhances nematode-suppressive services and reduces damage caused by root-knot nematode

A previous field trial showed that marketable yield increased and root-knot nematode populations declined when the swollen roots of sweetpotato were surrounded by a sawdust-based amendment. Further evidence that such amendments provide worthwhile levels of nematode control was obtained in this study. Customised pots filled with an organic amendment or amended soil were kept in a greenhouse or buried in the field for various times and then the nematode-control potential of various treatments was assessed by surrounding the pots with soil infested with Meloidogyne incognita. Swollen root production generally increased, and root-knot nematode populations consistently declined, when sawdust was used as an amendment. The addition of an organic nitrogen source generally improved the level of control. Laboratory and greenhouse assays confirmed that amended soils were biologically suppressive, as root-knot nematode numbers were lower and fewer galls were produced in soil containing decomposing amendments than in soil or sand that had been heated to kill the soil biota. A predatory nematode morphologically similar to Clarkus papillatus was one of the suppressive agents as numbers were very high in some experiments. Mesostigmatid mites in the family Laelapidae and genera Sejus, Protogamasellus, Holaspulus and Gamasiphis were also contributing, while an acarid mite (Rhizoglyphus robini) occurred in high numbers and was observed devouring root-knot nematode juveniles on agar plates. Nematophagous fungi were also involved as three species of nematode-trapping fungi (Arthrobotrys musiformis, A. thaumasia and A. oligospora) and an unidentified fungus that captures nematodes on bulbous hyphal extensions were consistently isolated from amended soils. These results suggest that sawdust-based amendments enhance the nematode-suppressive services provided by a wide range of predators.