Oribatid mites in urban zones of West Berlin

Summary A comparison is made between oribatid fauna (Acari, Oribatida) in the urban regions of West Berlin and forest areas. There are characteristic species compositions living in urban soils, in epilithic moss cushions or on the bark of trees. The urban environment obviously causes a change in the species pattern in these types of habitats and minimizes the number of species in central urban regions. The most important regional factors are probably relative aridity, air pollution and habitat isolation, showing a similar increasing tendency from sub-urban to central regions of West Berlin. The effects of air pollution (SO2) on moss-inhabiting oribatid mites are analysed in 13 sites of the urban district of West Berlin. The use of moss- and bark-dwelling mites as bioindicators of air pollution is discussed.Soil oribatids might be useful bioindicators of soil pollution in further research.Dedicated to the late Prof. Dr. M.S. Ghilarov     

Effects of repeated drought on soil microarthropod communities in the northern Chihuahuan Desert

 Soil microarthropods were sampled in plots centered on creosotebushes (Larrea tridentata) and in plots centered on mesquite (Prosopis glandulosa) coppice dunes. Nine plots in each area were covered by rain-out shelters with greenhouse plastic roofs which excluded natural rainfall and nine plots received natural rainfall. There were differences in the abundance of several mite taxa in soils from the mesquite coppice dune plots. Some taxa (Stigmaeidae, Nanorchestidae, and Entomobryidae) occurred in significantly lower numbers in the soils of the drought plots. Other taxa (Tarsonemidae and Cunaxidae) were more abundant in the drought plots in the mesquite coppice dunes. There were no significant differences in the abundance of any of the dominant taxa of soil microarthropods in the drought and control plots centered on creosotebush. In the creosotebush habitat, there were significantly fewer Prostigmata in the plots exposed to drought. In an area with both creosotebush and mesquite, there were no significant differences in microarthropod population responses to drought and in recovery from drought. The differences in responses of soil microarthropods to drought in creosotebush and mesquite habitats are attributed to the differences in soil stability, litter accumulations, and microclimate associated with the shrubs. Received: 29 December 1997     

Responses of oribatid mite communities to summer drought: The influence of litter type and quality

A litterbag experiment was used to study the impact of extended periods of summer drought on the structure of oribatid mite communities (Acari, Oribatida) developing in two litter types (beech, spruce) of two qualities (fresh, pre-incubated). Within each litter type, litter quality determined species composition and densities and, in turn, this determined the impact of drought upon the oribatid mite communities. In both litter types, drought had a greater impact on community development in the pre-incubated compared to the fresh litter. In the short-term perspective of the present study, oribatid mite communities in beech litter were less sensitive to summer drought than those in spruce litter. This was partly due to the presence of site-specific, drought-tolerant species but seemed also strongly related to differences in the decomposition patterns between the litter types. Marked changes in densities and composition of oribatid communities after only one period of summer-drought suggest that there is a potential for a significant alteration of oribatid community structure in both litter types if climatic changes persist.     

Species diversity and metal accumulation in oribatid mites (Acari, Oribatida) of forests affected by a metallurgical plant

A study was made of oribatid mite communities and their responses to metal contamination derived from the Kosogorsky metallurgical plant located in the Tula District, Russia. Mite communities were sampled in three different seasons in four sites at different distances from the smelter. Concentrations of zinc, copper, cadmium, lead and iron were measured in ten mite species. The data show that the mite community as a whole is quite tolerant to the metal contamination caused by the Kosogorsky plant. At the polluted sites some species typical for nutrient-rich soils appeared, but community structure and species diversity were not seriously affected by metal contamination. In general, oribatid mites accumulated metals to very high internal concentrations. Average Cu, Cd, Pb and Fe concentrations did not differ significantly between species, but Zn did, and its level was associated with the mode of feeding of the species. Microphytophagous species, feeding exclusively on fungi, accumulated zinc in higher concentrations than other mites. This study illustrates the potential for bioindication by the little studied but species-rich group of soil oribatids.     

Diversity of soil mites (Acari: Oribatida,Mesostigmata) along a gradient of land use types in New York

This study explored the relationship between landscape-level factors (land use type) and the diversity of soil mites (Acari: Oribatida, Mesostigmata) at a within-site scale, using diversity measures including point diversity (local species diversity within a single sampling point), patterns of species turnover among the sampling points, and alpha diversity (total species richness in a habitat). The land use types included corn fields, intensive short-rotation forestry plantations, two types of abandoned agricultural fields, and hardwood forests.Land use type was identified as a significant factor influencing both small-scale (within individual soil cores) and site-scale diversity of Oribatida, which increased in the order “corn → willow → abandoned fields → forests”. There was no statistical relationship between land use type and abundance or diversity of Mesostigmata.Using a bootstrapping method to generate “random” communities, we found that all land use types had significantly more diverse patterns of species abundance than was expected by chance. On the other hand, the patterns of presence/absence of species were less diverse than expected by chance. Local site factors were significant in driving the patterns of diversity of soil mites at the site scale; land use type was less important. The overall structure of Oribatida and Mesostigmata assemblages was significantly related to land use type. We conclude that soil communities respond to land management on both local scales and habitat-wide scales.     

The ecology of extinction: population fluctuation and decline in amphibians

Even among widespread species with high reproductive potentials and significant dispersal abilities, the probability of extinctions should be correlated both with population size variance and with the extent of population isolation. To address how variation in demographic characteristics and habitat requirements may reflect on the comparative risk of species decline, I examined 617 time series of population census data derived from 89 amphibian species using the normalized estimate of the realized rate of increase, ΔN, and its variance. Amphibians are demonstrably in general decline and exhibit a great range of dispersal abilities, demographic characteristics, and population sizes. I compared species according to life-history characteristics and habitat use. Among the populations examined, census declines outnumbered increases yet the average magnitudes for both declines and increases were not demonstrably different, substantiating findings of amphibian decline. This gives no support for the idea that amphibian population sizes are dictated by regimes featuring relatively rare years of high recruitment offset by intervening years of gradual decline such that declines may outnumber increases without negative effect. For any given population size, those populations living in large streams or in ponds had significantly higher variance than did populations of completely terrestrial or other stream-dwelling amphibians. This could not be related to life-history complexity as all the stream-breeding species examined have larvae and all of the wholly terrestrial species have direct development without a larval stage. Variance in ΔN was highest amongst the smallest populations in each comparison group. Estimated local extinction rates averaged 3.1% among pond-breeding frogs, 2.2% for pond-breeding salamanders, and negligible for both stream-breeding and terrestrial direct-developing species. Recoveries slightly exceeded extinctions among European pond-breeding frogs but not among North American pond-breeding frogs. Less common species had greater negative disparities between extinctions and recoveries. Species with highly fluctuating populations and high frequencies of local extinctions living in changeable environments, such pond- and torrent-breeding amphibians, may be especially susceptible to curtailment of dispersal and restriction of habitat.     

Ecological and life-history traits predict bee species responses to environmental disturbances

The ability to predict the responses of ecological communities and individual species to human-induced environmental change remains a key issue for ecologists and conservation managers alike. Responses are often variable among species within groups making general predictions difficult. One option is to include ecological trait information that might help to disentangle patterns of response and also provide greater understanding of how particular traits link whole clades to their environment. Although this “trait-guild” approach has been used for single disturbances, the importance of particular traits on general responses to multiple disturbances has not been explored. We used a mixed model analysis of 19 data sets from throughout the world to test the effect of ecological and life-history traits on the responses of bee species to different types of anthropogenic environmental change. These changes included habitat loss, fragmentation, agricultural intensification, pesticides and fire. Individual traits significantly affected bee species responses to different disturbances and several traits were broadly predictive among multiple disturbances. The location of nests - above vs. below ground - significantly affected response to habitat loss, agricultural intensification, tillage regime (within agriculture) and fire. Species that nested above ground were on average more negatively affected by isolation from natural habitat and intensive agricultural land use than were species nesting below ground. In contrast below-ground-nesting species were more negatively affected by tilling than were above-ground nesters. The response of different nesting guilds to fire depended on the time since the burn. Social bee species were more strongly affected by isolation from natural habitat and pesticides than were solitary bee species. Surprisingly, body size did not consistently affect species responses, despite its importance in determining many aspects of individuals’ interaction with their environment. Although synergistic interactions among traits remain to be explored, individual traits can be useful in predicting and understanding responses of related species to global change.     

Population trends of birds across the iron curtain: Brain matters

One approach to assess human impact on species’ population dynamics is to correlate ecological traits of species with their long-term population trends. Yet, few studies investigated population trends in multiple regions that differ in human impact to reveal which traits explain population trends over larger geographic areas and which only regionally. We examined the relationship between various species traits and long-term population trends of 57 common passerine bird species from 1991 to 2007 in three adjacent regions in central Europe that experienced differences in socioeconomic history: North-Western Germany, Eastern Germany and the Czech Republic. We tested effects of habitat, dietary and climatic niche, migratory strategy and cognitive ability, measured as relative brain size. We predicted that traits reflecting socioeconomic and land-use change had stronger effects in former communist countries than in North-Western Germany due to marked changes in these countries after 1990. We found that climatic niche and migratory strategy affected bird abundances similarly in all regions suggesting their influence is invariant across central Europe. In contrast, brain size showed regionally varying effects. The effects were negligible in North-Western Germany, slightly positive in Eastern Germany and strongly positive in the Czech Republic. Increases of species with large brains suggest that species with good cognitive abilities might have been better able to adapt to rapid socioeconomic change and make use of novel opportunities after the end of communism. Regional differences in population trends among species thus appear to be driven by an interaction between cognitive abilities and socioeconomic change.     

Population recovery patterns of Southeast Asian ungulates after poaching

Large ungulate populations in Southeast Asia have collapsed due to commercial poaching, but little is known about patterns of population recovery after poaching has been controlled. Using a sign-based index of abundance, we measured 6-year trends in abundance and habitat use of five ungulate species after poaching ceased at a site in Thailand. Regression slopes of annual indices against time indicated population growth rates (r) of 0.44 and 0.31 for muntjac (Muntiacus muntjak) and gaur (Bos gaurus), respectively—close to the intrinsic rates of natural increase for similarly-sized ungulates. Thus, muntjac and gaur can recover relatively rapidly from low population levels. In contrast, sambar (Cervus unicolor) remained consistently rare despite freedom from hunting, perhaps because prime males had been selectively targeted for trophies, disrupting the species mating system. Wild pigs (Sus scrofa) were already relatively abundant when monitoring started, illustrating their resilience to hunting and ability to quickly recolonize disturbed areas. Gaur herds (the key demographic unit of the population) and muntjac consistently selected deciduous over evergreen forest as their populations increased, revealing the importance of food-rich deciduous forest in driving recovery of these species. The unexpected failure of sambar to recover suggests that reproductive behavior may override seemingly positive interventions (i.e., stopping poaching) that reduce mortality. Small but well-protected recovery zones set within forested areas might help propel population recovery of ungulates and increase the prey base for endangered tigers.     

Assessing the relationship between patch type and soil mites: A molecular approach

An urgent need exists for indicators of soil health and patch functionality in extensive rangelands that can be measured efficiently and at low cost. Soil mites are candidate indicators, but their identification and handling is so specialised and time-consuming that their inclusion in routine monitoring is unlikely. The aim of this study was to measure the relationship between patch type and mite assemblages using a conventional approach. An additional aim was to determine if a molecular approach traditionally used for soil microbes could be adapted for soil mites to overcome some of the bottlenecks associated with soil fauna diversity assessment. Soil mite species abundance and diversity were measured using conventional ecological methods in soil from patches with perennial grass and litter cover (PGL), and compared to soil from bare patches with annual grasses and/or litter cover (BAL). Soil mite assemblages were also assessed using a molecular method called terminal-restriction fragment length polymorphism (T-RFLP) analysis. The conventional data showed a relationship between patch type and mite assemblage. The Prostigmata and Oribatida were well represented in the PGL sites, particularly the Aphelacaridae (Oribatida). For T-RFLP analysis, the mite community was represented by a series of DNA fragment lengths that reflected mite sequence diversity. The T-RFLP data showed a distinct difference in the mite assemblage between the patch types. Where possible, T-RFLP peaks were matched to mite families using a reference 18S rDNA database, and the Aphelacaridae prevalent in the conventional samples at PGL sites were identified, as were prostigmatids and oribatids. We identified limits to the T-RFLP approach and this included an inability to distinguish some species whose DNA sequences were similar. Despite these limitations, the data still showed a clear difference between sites, and the molecular taxonomic inferences also compared well with the conventional ecological data. The results from this study indicated that the T-RFLP approach was effective in measuring mite assemblages in this system. The power of this technique lies in the fact that species diversity and abundance data can be obtained quickly because of the time taken to process hundreds of samples, from soil DNA extraction to data output on the gene analyser, can be as little as 4 days.     

Habitat use of ponies and cattle foraging together in a coastal dune area

Grazing by large ungulates has been chosen as a management tool in scrub-dominated dune reserves at the Belgian coast. Due to morphological and physiological differences between cattle and ponies, differences in foraging behaviour and habitat use are expected, and these may result in a different impact on the spatially heterogeneous and nutrient-limited ecosystem. Grazing behaviour and habitat use of Shetland ponies and Highland cattle, grazing together in a coastal dune area (60 ha) were investigated at various levels of the foraging hierarchy (habitat, vegetation type, sward height and diet). Habitat use overlap was high in all seasons; both cattle and pony spent most of their grazing time in the grass-dominated habitat. However, Shetland ponies concentrated their grazing activity more on the grass-dominated habitat than did cattle. Cattle spent a greater proportion of their grazing activity in woodland and scrub, compared to the ponies. Foraging activity in woodland and scrub is strongly influenced by season. Within the grass-dominated habitat both species preferred foraging in the grasslands and avoided open vegetation and moss dunes. Within the grasslands, cattle grazed less on the short swards than did ponies. Both cattle and ponies predominantly foraged on graminoids, though there are minor differences between both species and among seasons. Browsing of woody plants occurred only by cattle. Where grazing management has been implemented to maintain dune grasslands and to avoid further invasion by scrub, a combination of cattle and ponies appears to be adequate. Ponies are suitable for maintaining grasslands, but they have no impact on invading scrub. Cattle have an impact on scrub development, both by direct consumption of various shrub species and by opening initially closed scrub.     

Impacts of drought at different time scales on forest growth across a wide climatic gradient in north-eastern Spain

We analyzed the impact of drought measured on different time-scales on radial growth of eight tree species during the period 1950-2005 growing across a wide climatic gradient encompassing semiarid Mediterranean woodlands and wet mountain forests in north-eastern Spain. A drought index (standardized precipitation index, SPI) at different time scales (1-48 months) was correlated with chronologies of ring width to determine the significant time scale at which drought affected most tree growth. The findings indicated that the impact of drought on growth varied noticeably among species and sites. Two distinct patterns were clearly observed considering spatial and temporal differences in the response of species to drought. Species growing in xeric sites (Pinus and Quercus species and Juniperus thurifera) showed the highest responses to SPI time-scales of 9-11 months while those located in mesic sites (Abies alba, Pinus sylvestris) did respond more to SPI time scales shorter than 5 months. The SPI-growth correlations were significant, although weak, up to 30 months in xeric sites while no consistent association was observed at higher time scales. Important seasonal differences were noticed in the SPI-growth associations. Species growing in xeric areas responded to spring-summer SPI while those distributed in mesic sites responded more to summer SPI. Our findings should be useful to understand forest responses to climate change, including an increasing frequency of severe droughts, and to adapt appropriate management strategies to mitigate the impact of drought on tree growth.     

Distance to edges, edge contrast and landscape fragmentation: Interactions affecting farmland birds around forest plantations

Afforestation often causes direct habitat losses for farmland birds of conservation concern, but it is uncertain whether negative effects also extend significantly into adjacent open land. Information is thus required on how these species react to wooded edges, and how their responses are affected by edge and landscape characteristics. These issues were examined in Mediterranean arable farmland, using bird counts at 0, 100, 200, 300 and >300 m from oak, pine and eucalyptus edges, embedded in landscapes with variable amounts and spatial configurations of forest plantations. Bird diversity declined away from edges, including that of woodland, farmland and ground-nesting birds. Positive edge responses were also found for overall and woodland bird abundances, and for five of the nine most widespread and abundant species (Galerida larks, stonechat, linnet, goldfinch and corn bunting). Strong negative edge effects were only recorded for steppe birds, with reduced abundances near edges of calandra larks and short-toed larks, but not of little bustards and tawny pipits. Edge contrast affected the magnitude of edge effects, with a tendency for stronger responses to old and tall eucalyptus plantations (hard edges) than to young and short oak plantations (soft edges). There were also species-specific interactions between edge and fragmentation effects, with positive edge responses tending to be strongest in less fragmented landscapes, whereas steppe birds tended to increase faster away from edges and to reach the highest species richness and abundances in large arable patches. Results suggest that forest plantations may increase overall bird diversity and abundance in adjacent farmland, at the expenses of steppe birds of conservation concern. Clustering forest plantations in a few large patches and thus reducing the density of wooded edges at the landscape-scale might reduce such negative impacts.     

Ecophysiological Differentiation of Two Mosla Species in Response to Nitrogen and Water Levels

Terrestrial ecosystems are experiencing increased inputs of nitrogen (N) and temporal fluctuations in precipitation, causing flooding or drought, and this could strongly affect the fate of terrestrial plant species, as they might have different abilities to adapt to the changing environment. We grew Mosla dianthera (a widespread species) and M. hangchowensis (an endangered species) under three water treatments (drought, sufficient water, and waterlogging) in combination with three levels of N supply (low, intermediate, and sufficient N) to study the ecophysiological responses of the congeneric species to those simulated environmental changes. The two species showed different responses to waterlogging and drought treatments, particularly when there was abundant N supply in the system. For example, under sufficient N but drought or waterlogging conditions, M. dianthera increased root mass ratio (RMR) and decreased leaf mass ratio (LMR), total leaf area (LA), and leaf area ratio (LAR); such changes can enhance water acquisition and reduce water loss under both drought and waterlogging conditions, in contrast to the general lack of change in those parameters with M. hangchowensis. These differentiations in traits suggest that increased N availability might worsen drought and waterlogging injury to M. hangchowensis and thus accelerate the decline of this population. However, M. dianthera maybe better adapted to high N availability and both drought and waterlogging conditions. We hypothesize that the different adaptive abilities to high N availability and drought and waterlogging conditions are partly responsible for the ecological differentiation observed between these two species in the field and may determine their fate in their native habitat. Further research should test this hypothesis in field experiments.     

A habitat-based population viability analysis for ocelots (Leopardus pardalis) in the United States

Strategies are needed to recover the ocelot Leopardus pardalis from the endangered species list. Recently, a population viability analysis (PVA) was developed which concluded that combinations of different recovery strategies were needed to effectively reduce ocelot extinction probability in the United States (US), with habitat protection and restoration identified as the most effective recovery scenario. We expanded this PVA model by incorporating landscape data to develop a more realistic habitat-based PVA for ocelots in southern Texas. We used RAMAS/gis software to conduct a habitat-based PVA by linking landscape data with a demographic metapopulation model. The primary goal of this study was to provide a model for evaluating ocelot recovery strategies in the US. Each model scenario was simulated 1000 times over 50 years and we defined extinction as one individual remaining. Using the RAMAS/gis program we identified 11 possible ocelot habitat patches (i.e., subpopulations) occurring in southern Texas. In addition, based on the habitat-based PVA model we found that combinations of different recovery strategies were needed to effectively reduce ocelot extinction probability in the US, with reducing road mortality the single most effective strategy. Short-term recovery strategies should include reducing ocelot road mortality, and translocation of ocelots into the US from northern Mexico. Long-term recovery strategies should include the restoration of habitat between and around existing ocelot habitat patches and the establishment of a dispersal corridor between ocelot breeding populations.     

Soil microarthropods are only weakly impacted after 13 years of repeated drought treatment in wet and dry heathland soils

Studies of biological responses in the terrestrial environment to rapid changes in climate have mostly been concerned with aboveground biota, whereas less is known of belowground organisms. The present study focuses on mites and springtails of heathland ecosystems and how the microarthropod community has responded to simulated climate change in a long-term field experiment. Increased temperature and repeated drought was applied for 13 years to field plots located in Wales, The Netherlands and Denmark representing sites of contrasting climatic conditions with respect to precipitation and temperature. This approach provided an opportunity to study biological responses on a local (within sites) and regional scale. Warming treatments increasing night time temperature (0.3–1 °C higher than ambient at 5 cm soil depth) had no detectable effects on the microarthropod communities. Increased intensity and frequency of drought had only weak persistent effects on springtail species composition, but practically no effect on major mite groups (Oribatida, Prostigmata or Mesostigmata) suggesting that ecosystem functions of microarthropods may only be transiently impacted by repeated spring or summer drought.     

苯磺隆除草剂对农田土壤动物影响的研究

通过苯磺隆除草剂的模拟实验,研究了除草剂对土壤动物的影响。本实验共获得土壤动物1031个,隶属3门、5纲、9目。其中弹尾目和甲螨亚目为优势类群,其余为常见类群。本实验结果表明,随着苯磺隆除草剂处理浓度的提高,土壤动物种类和数量呈递减趋势。弹尾目和甲螨亚目可作为农药污染的重要指示生物。     

管理措施及土壤因子对5种农田生境地表蜘蛛群落多样性的影响

以往的研究表明有机管理有利于生物多样性保护,但在不同农业生境类型中是否都存在这个结论呢?基于此问题,本研究在一个多生境的有机管理农场与一个相邻的多生境常规集约化管理农区,采用陷阱法进行蜘蛛取样,对比有机和常规管理措施下大棚菜地、果园、稻田田埂、露天田块及农田边界等5种生境类型的农田蜘蛛多样性的差异,并分析土壤因子对蜘蛛多样性的影响。研究发现:1)有机管理与常规管理的蜘蛛物种数没有显著差异,但有机管理的果园中蜘蛛个体数比常规管理的果园中多139%,且差异显著。同一管理措施下,仅常规管理农田区的农田边界蜘蛛个体数和物种数分别显著高于其他生境均值104%和59%。2)有机管理农场比常规管理农田的蜘蛛物种组成差异略大,且在有机管理下不同生境间的蜘蛛群落组成差异更明显。3)土壤因子中有机质、全氮、全磷含量等对蜘蛛群落结构有显著影响,但对蜘蛛个体数和物种数没有显著影响,仅土壤Cu含量和蜘蛛个体数呈显著负相关。在本研究中虽然有机管理和土壤因子对蜘蛛多样性有一定影响,但不同生境间管理强度、植被结构等差异对蜘蛛多样性的影响更大。因此,发展多种农业生境类型的有机农业可提升物种β多样性。同时,在常规集约化管理农区,保留农田边界等半自然生境、适当减少化肥和农药等投入、降低农田内部的管理强度、防止土壤重金属污染等措施均有助于保护蜘蛛多样性。     

Assessing critical habitat: Evaluating the relative contribution of habitats to population persistence

A principal challenge of species conservation is to identify the specific habitats that are essential for long-term persistence or recovery of imperiled species. However, many commonly used approaches to identify important habitats do not provide direct insight into the contribution of those habitats to population persistence. To assess how habitats contribute to overall population viability and characterize their relative importance, a spatially-explicit population viability model was used to integrate a species occurrence model with habitat quality and demographic information to simulate the population dynamics of the Ord’s kangaroo rat (Dipodomys ordii) in Alberta, Canada. Long-term productivity (births-deaths) in each patch was simulated and iterative patch removal experiments were conducted to generate estimates of the relative contribution of habitat types to overall population viability. Our results indicated that natural dune habitats are crucial for population viability, while disturbed/human-created habitats make a minor contribution to population persistence. The results also suggest that the habitats currently available to Ord’s kangaroo rats in Alberta are unlikely to support long-term persistence. Our approach was useful for identifying habitats that did not contribute to population viability. A large proportion of habitat (39%) represented sinks and their removal increased estimated population viability. The integration of population dynamics with habitat quality and occurrence data can be invaluable when assessing critical habitat, particularly in regions with variable habitat quality. Approaches that do not incorporate population dynamics may undermine conservation efforts by under- or over-estimating the value of habitats, erroneously protecting sink habitats, or failing to prioritize key source habitats.     

Morphological modifications among oribatid mites (Acari: Oribatida) in relation to habitat differentiation in mangrove forests

We examined morphological modifications among oribatid species in five microhabitats in mangrove forests in the Ryukyu Islands of Japan. A total of 89 oribatid species were recorded from canopy (leaves and branches), bark of flooded trunks (trunks of 0–50 cm high and knee roots), bark of other trunks higher than 50 cm, and littoral algae in mangrove forests, and the forest-floor soil in an adjacent bank forest. There were no significant differences in the body length, body width, and notogastral length among oribatid species from the five microhabitats. The mean sensillus length of the oribatid species from the forest-floor soil was about twice as long as that from the other microhabitats. Claw morphology was characterized by two attributes: number (monodactyly and tridactyly) and length. In the canopy and trunks, the proportion of tridactyl species was higher than that of monodactyl species. On the other hand, the proportion of tridactyl species in the forest-floor soil accounted for only about 20%, and that in the flooded trunks and littoral algae approximated to zero. The mean claw length was larger in the oribatid species from the flooded trunks and littoral algae than in both monodactyl and tridactyl species from every other microhabitat. Trydactyl species with short claws in the arboreal environments might have been selected by a compromise between grip and mobility for unpredictable environmental changes such as wind and rain. The dominance of monodactyl species with a longer claw in the littoral environments implies a consequence of selection for regular tidal flooding, which requires oribatids to grip tighter on the substrate. The modifications in claw morphology of oribatid mites in mangrove forest might be interpreted as adaptations to a difference in the predictability of the environmental conditions of microhabitats.