Mesostigmatid Mites (Acari: Mesostigmata) on Rainforest Tree Trunks: Arboreal Specialists, but Substrate Generalists?

Predatory mites (Acari: Mesostigmata) on tree trunks without significant epiphytic growth in a subtropical rainforest in Eastern Australia were assessed for habitat specificity (i.e. whether they are tree trunk specialists or occupying other habitats) and the influence of host tree and bark structure on their abundance, species richness and species composition. The trunks of nine tree species from eight plant families representing smooth, intermediate and rough bark textures were sampled using a knockdown insecticide spray. In total, 12 species or morphospecies of Mesostigmata (excluding Uropodina sensu stricto) were collected, most of which are undescribed. Comparison with collections from other habitats indicates that epicorticolous Mesostigmata are mainly represented by suspended soil dwellers (six species), secondarily by generalists (four species) and a bark specialist (one species). A typical ground-dwelling species was also found but was represented only by a single individual. In terms of abundance, 50.5% of individuals were suspended soil dwellers, 40.7% bark specialists, and 8.3% generalists. Host species and bark roughness had no significant effect on abundance or species richness. Furthermore, there was no clear effect on species composition. The distribution of the most frequently encountered species suggests that most mesostigmatid mites living on bark use many or most rainforest tree species, independent of bark roughness. These findings support the hypothesis that some epicorticolous Mesostigmata use tree trunks as ‘highways’ for dispersing between habitat patches, while others use it as a permanent habitat.     

Fruiting patterns of macrofungi in tropical and temperate land use types in Yunnan Province,China

Despite the important contribution of fungi to forest health, biomass turnover and carbon cycling, little is known about the factors that influence fungal phenology. Therefore, in order to further our understanding on how macrofungal fruiting patterns change along a gradient from temperate to tropical climate zones, we investigated the phenological patterns of macrofungal fruiting at five sites along a combined altitudinal and latitudinal gradient in SW China and NW Laos, ranging from temperate to tropical climates. Observations were conducted in the dominant land use types at these study sites: mixed forest (all sites), coniferous forest (temperate sites) and grassland (temperate sites). In total, 2866 specimens were collected, belonging to 791 morpho species, 162 genera, and 71 families. At the site level, the fruiting of ectomycorrhizal (EcMF) and saprotrophic fungi (SapF) occurred at the same time among all land use types. The fruiting season of fungi in the tropical sites began earlier and ended later compared to that of fungi in the temperate sites, which we attribute mainly to the higher temperature and more abundant rainfall of the tropical areas. EcMF taxa richness in temperate forests (both coniferous and mixed forest) showed a distinct peak at the end of the rainy season in August and September, while no significant peak was observed for SapF taxa richness. Neither functional fungal groups showed significant seasonal fluctuations in tropical areas. The temporal turnover of fungal fruiting significantly increased with the shift from tropical to temperate forests along the elevation gradient. In the grasslands, macrofungal abundance was less than 22% of that of corresponding forest sites, and taxa richness was 42% of that of corresponding forest sites. Fungal fruiting showed no significant fluctuations across the rainy season. This work represents a case study carried out over one year, and further measurements will be needed to test if these results hold true in the longer term.     

Phylogeny of the hard ticks (Ixodidae) inferred from 18S rRNA indicates that the genus Aponomma is paraphyletic

We examined the phylogeny of ticks (Acari:Parasitiformes:Ixodida) and their closest known mite relatives (Acari:Parasitiformes:Mesostigmata and Holothyrida) using 18S rRNA sequences. In our analyses, we included sequences from 36 taxa. Sequences for 13 hard ticks (Family Ixodidae), 5 soft ticks (Family Argasidae), and 2 mesostigmatid mites were obtained from the GenBank database and we generated sequences for 15 hard ticks and 1 holothyrid mite. Ten of these tick species were endemic to Australia. Our analyses indicated that the suborder Holothyrida is more closely related to Ixodida than to Mesostigmata, the group used as outgroup in earlier molecular studies. This finding is consistent with Lehtinen's (1991) hypothesis that the Holothyrida rather than the Mesostigmata is the sister-group to the Ixodida. Within the hard ticks the genus Aponomma and thus the family Amblyomminae were paraphyletic. Taxonomic revision of these taxa is needed. The genus Amblyomma was paraphyletic without the inclusion of "typical" Aponomma species (Ap. latum and Ap. fimbriatum). There was a basal divergence between endemic Australian and other species in both the Metastriata and the Prostriata divisions of the hard ticks.     

Australian barnacles (cirripedia: thoracica), distributions and biogeographical affinities

Currently, 279 barnacle species are recognized in Australia waters. The barnacle fauna of tropical Australia exhibits high species diversity (221), with a high incidence of tropical species (87 Indo-west Pacific [IWP], 16 West Pacific and 65 Indo-Malayan), a low species endemicity (8), and 44 cosmopolitan and 1 Australasian species. Conversely, that of temperate Australia shows lower species diversity (129), with a lower incidence of tropical species (26 IWP, 10 West Pacific and 25 Indo-Malayan), higher species endemicity (23), 37 cosmopolitan, 6 Australasian species, and 3 Australasian/Antarctic species. Distributions corroborate the general patterns demonstrated by the shallow-water biota of northern tropical and southern temperate Australian biogeographic provinces. Tropical and temperate provinces grade into each other in a broad overlap zone along both the western and eastern Australian coasts. This overlap zone is essentially a transitional region, with the gradual replacement of a tropical barnacle fauna in the north by a predominantly temperate barnacle fauna in the south. Both western and eastern Australian coasts are bounded by major poleward-flowing warm currents that have considerable influence on the marine flora and fauna, distributing tropical species of many taxa much farther south than could be predicted by latitude. Currently, 16 barnacle species introduced into Australian waters are identified, although this number may increase in the future due to new port developments and increased shipping arrivals.     

Composition and vertical distribution patterns of the microarthropod fauna in a Negev desert soil

The faunal composition and changes in the vertical distribution patterns of soil mites and other microarthropods were described and monitored over an 18-h period at a site in the Negev desert of southern Israel. There was an overwhelming predominance of prostigmatid mites (55%) compared with Cryptostigmata (33%) in the collections. Specific determinations on the Cryptostigmata indicated that taxa, which could be identified as Mediterranean, made a sizeable contribution to this fauna. Microarthropod densities in general, and those of Prostigmata, Cryptostigmata and Mesostigmata in particular, compared favourably with those recorded from other arid desert sites in N. America and Australia. Prior to the sampling period which commenced at 6 p.m., the site was exposed to the drying effects of the Khamsin wind. Microarthropod populations were mainly located at depths below 6 cm during the following 18-h period, and this may be interpreted as an avoidance of the arid conditions obtaining at the surface, particularly during the hours from 6 p.m. to midnight. Soil temperatures remained low after midnight, but the relative humidity above the soil increased to 90% and there may have been some internal dew formation in the soil surface horizon at this time. There is some evidence of an upward movement of prostigmatid and cryptostigmatid mites as a response to increasing levels of humidity in the surface horizon during this period. We suggest that this study confirms the findings of Whitford et al. (1981) that soil microarthropods are sensitive to changes in soil moisture characteristics which operate on a diurnal scale.     

Distribution of Cryptostigmata and Mesostigmata (Acari) within the litter and soil layers of two subtropical forests

Differences in the litter and soil of northern temperate and tropical and subtropical forest soil and soil faunas are noted. Analyses of the distribution and abundance of Cryptostigmata and Mesostigmata mites in the litter and soil of two Australian subtropical forests are presented. The faunal associations in the litter and soil of these forests are different. It is suggested that the litter and soil habitats of subtropical and tropical forests should be regarded as separate but connected habitats in relation to their fauna. This contrasts with the assumption, for temperate forests, that litter and soil communities are portions of a single system.     

Rotifer communities of billabongs in northern and south-eastern Australia

Diversity and equitability of rotifer communities from billabongs (oxbows or cut-off meanders) in northern and southeastern Australia are compared. In both areas littoral taxa predominated in open water. Diversity values (Shannon-Wiener, H′) were higher than recorded for tropical assemblages elsewhere. Up to 80 rotifer species co-occurred in Northern Territory billabongs. Brachionids notably were absent; there was an apparent displacement of tropical assemblages into temperate Australia.     

The impact of invasive cane toads on native wildlife in southern Australia

Commonly, invaders have different impacts in different places. The spread of cane toads (Rhinella marina: Bufonidae) has been devastating for native fauna in tropical Australia, but the toads' impact remains unstudied in temperate‐zone Australia. We surveyed habitat characteristics and fauna in campgrounds along the central eastern coast of Australia, in eight sites that have been colonized by cane toads and another eight that have not. The presence of cane toads was associated with lower faunal abundance and species richness, and a difference in species composition. Populations of three species of large lizards (land mullets Bellatorias major, eastern water dragons Intellagama lesueurii, and lace monitors Varanus varius) and a snake (red‐bellied blacksnake Pseudechis porphyriacus) were lower (by 84 to 100%) in areas with toads. The scarcity of scavenging lace monitors in toad‐invaded areas translated into a 52% decrease in rates of carrion removal (based on camera traps at bait stations) and an increase (by 61%) in numbers of brush turkeys (Alectura lathami). The invasion of cane toads through temperate‐zone Australia appears to have reduced populations of at least four anurophagous predators, facilitated other taxa, and decreased rates of scavenging. Our data identify a paradox: The impacts of cane toads are at least as devastating in southern Australia as in the tropics, yet we know far more about toad invasion in the sparsely populated wilderness areas of tropical Australia than in the densely populated southeastern seaboard.     

Life history strategies of cladocerans: comparisons of tropical and temperate taxa

We review recent works on different life history variables of cladoceran taxa in tropical and temperate freshwater bodies, comparing the strategies that cladocerans have evolved to adapt to contrasting environmental conditions in the two geographical regions. These life-history parameters relate to age and size at maturity, survival, fecundity, life-expectancy at birth, lifespan, gross, and net reproductive rates, generation time, the rate of population increase, peak population density and day of peak abundance. We also discuss the role of photoperiod and temperature on some of these life history parameters. We found a general paucity of experimental work and field data in tropics on cladocerans. There is very limited information on the few Daphnia species found in the tropics. The misconception of low species diversity of cladocerans in the tropics arose due to several reasons including lack of extensive and intensive field collections. Higher water temperatures apparently promote permanent infestation of tropical waters with toxic cyanobacteria, which reduce the zooplankton diversity. In addition to higher temperatures in the tropics, the year-round high predation pressure of planktivorous fish probably causes the tropical species, particularly in pelagic habitats, to reach maturity earlier (< 3 days) than in temperate regions. Species of Daphnia in temperate regions are particularly adapted to living at food concentrations that are much lower and seasonably more variable than those for tropical genera such as Diaphanosoma. This is further corroborated by the more than an order of magnitude higher threshold food concentration (TFC) for tropical Cladocera than for their temperate counterparts. Fecundity patterns differ between tropical and temperate cladoceran taxa: cultured under optimal temperature regimes, tropical taxa have fewer eggs than temperate species of a comparable body size. Predation pressure may act differently depending on the size of the cladoceran neonates and thus on their population size structure. Global warming and climate changes seem to affect the behaviour (migration), distribution, and abundance of cladocerans. Apparently, in direct response to these changes, the possibility of encountering the tropical cladocerans in the northern, temperate hemisphere (bioinvasions) is on the rise.     

Effects of a mulch layer on the assemblage and abundance of mesostigmatan mites and other arthropods in the soil of a sugarcane agro-ecosystem in Australia

Sugarcane farmers can utilise a soil conservation technique called green cane trash blanketing, a form of mulching that can increase plant productivity through a number of channels, e.g., via altering soil physical, chemical and biological characteristics, and influence soil arthropod assemblages. Predatory mites (Mesostigmata) are important components of soil communities because they can control populations of other soil-dwelling pest species. Our aim was to characterise mulch-influenced predatory Mesostigmata community assemblages in sugarcane soils in Queensland, Australia. We found that application of a mulch layer significantly increased the abundance of Mesostigmata, and oribatid mites and collembolans, in soils. Furthermore, we observed that the assemblages of Mesostigmata in soil covered by mulch were significantly different to those in bare soil; and the assemblages of Mesostigmata changed over time. The assemblages of Mesostigmata, but not Oribatida or collembolans, were significantly different in soil under mulch depending on whether the mulch was freshly laid, or decomposing. Our results show that the use of mulch, specifically the green cane trash blanket, can increase overall microarthropod abundance including Mesostigmata. This is likely due to increased habitat complexity and changing resource availability.     

Differential seed germination responses to the ratio of red to far-red light in temperate and tropical species

Variation in vegetation density creates a range of red to far-red ratios of irradiance (R:FR) potentially permitting fine-scale discrimination of light conditions for seed germination. However, remarkably few studies have explored whether R:FR responses of germination vary among species that differ in distribution and life-history traits. In this study, we explored the relationships between R:FR requirements and four species characteristics: seed mass, latitudinal distribution (tropical vs. temperate), seed dormancy (dormant vs. nondormant), and plant growth form (woody vs. nonwoody). We obtained data on germination response to R:FR of 62 species from published literature and added new data for ten species from aseasonal tropical forests in Borneo. First, we analyzed whether species characteristics influenced overall light dependency of germination using phylogenetic logistic regression. We found that seed mass had a strong negative effect on light dependency, but that the seed mass at which tropical taxa had a 50 % probability of light dependency was 40 times that of temperate taxa. For light-dependent species, we found that the threshold R:FR that stimulates 50 % of maximum germination (R:FR₅₀) was also related to seed mass and latitudinal distribution. In agreement with an earlier study, we found that for temperate taxa, the R:FR₅₀ was significantly negatively correlated with seed mass. In contrast, for 22 tropical taxa, we found a significant positive correlation. These opposing relationships suggest contrasting selection pressures on germination responses of tropical taxa (mostly trees) and temperate herbaceous plants, and which are likely related to differences in seed longevity, seed burial rates, and reproductive output.     

Larger seeds in tropical floras: consistent patterns independent of growth form and dispersal mode

Many species of tropical moist forests have large seeds compared to those found in temperate floras. This could be attributed to a prevalence of woody growth forms, or adaptation to dispersal by vertebrates, or the dense shade of a closed canopy, rather than to an intrinsic tropical v. temperate difference. We compared tropical v. temperate seed mass data at two geographic scales; firstly within Australia between tropical, subtropical and temperate open woodlands, then between six tropical and temperate datasets from five continents. Within Australia we found that seed mass increased with decreasing latitude in ten out of eleven growth form-dispersal mode combinations: only wind-dispersed graminoids showed no significant effect. While the pattern of generally larger seeds in the tropical flora was associated with tropical families tending to have larger seeds than temperate families, we also found that tropical species had larger seeds than temperate cofamilials. As a preliminary test of the generality of these findings we included a further four tropical and temperate data sets in a second analysis. Average tropical seed masses were larger than temperate seed masses in all testable growth form-dispersal mode combinations, and statistically larger in five out of seven cases: unassisted, vertebrate- and wind-dispersed woody species, and unassisted and vertebrate-dispersed forbs. No difference was found for wind-dispersed forbs or for graminoids lacking dispersal structures. That an effect was found in these combinations rules out explanations based solely on characteristics of tropical v. temperate dispersers, although this may be a contributing factor. Instead we suggest that some aspect of tropical systems, for example higher metabolic costs of seedling production, has selected for a general increase in seed mass among tropical taxa.     

Taxonomic distribution of defensive alkaloids in Nearctic oribatid mites (Acari,Oribatida)

The opisthonotal (oil) glands of oribatid mites are the source of a wide diversity of taxon-specific defensive chemicals, and are likely the location for the more than 90 alkaloids recently identified in oribatids. Although originally recognized in temperate oribatid species, alkaloids have also been detected in related lineages of tropical oribatids. Many of these alkaloids are also present in a worldwide radiation of poison frogs, which are known to sequester these defensive chemicals from dietary arthropods, including oribatid mites. To date, most alkaloid records involve members of the superfamily Oripodoidea (Brachypylina), although few species have been examined and sampling of other taxonomic groups has been highly limited. Herein, we examined adults of more than 60 species of Nearctic oribatid mites, representing 46 genera and 33 families, for the presence of alkaloids. GC–MS analyses of whole body extracts led to the detection of 15 alkaloids, but collectively they occur only in members of the genera Scheloribates (Scheloribatidae) and Protokalumma (Parakalummidae). Most of these alkaloids have also been detected previously in the skin of poison frogs. All examined members of the oripodoid families Haplozetidae and Oribatulidae were alkaloid-free, and no mites outside the Oripodoidea contained alkaloids. Including previous studies, all sampled species of the cosmopolitan oripodoid families Scheloribatidae and Parakalummidae, and the related, mostly tropical families Mochlozetidae and Drymobatidae contain alkaloids. Our findings are consistent with a generalization that alkaloid presence is widespread, but not universal in Oripodoidea. Alkaloid presence in tropical, but not temperate members of some non-oripodoid taxa (in particular Galumnidae) deserves further study.     

Trichomycete gut fungi from tropical regions of the world

Fifty-nine species of gut fungi in the orders Harpellales and Asellariales, Class Trichomycetes, have been collected in eight tropical regions of the world, some species occurring in more than one geographic region. Regarding the Harpellales, the rather low number of taxa, compared to reports in more temperate localities, is due primarily to relatively few collections in the tropics, as well as the usually warmer waters found in tropical regions that often have a lower species richness of potential immature insect hosts. Asellariales in freshwater, marine, and terrestrial habitats, likewise, have been seldom inventoried in the tropics. Nonetheless, it is clear that the tropics are fertile grounds for discovering new genera and species, and future investigations will undoubtedly reveal many new taxa that will lead to a better understanding of the evolution and biogeography of Trichomycetes.     

Of mites and bees: A review of mite–bee associations in Australia and a revision of Raymentia Womersley (Acari: Mesostigmata: Laelapidae), with the description of two new species of mites from Lasioglossum (Parasphecodes) spp. (Hymenoptera: Halictidae)

Social bees have a diverse fauna of symbiotic mesostigmatic mites, including highly pathogenic parasites of the honeybee, but there are few reports of Mesostigmata phoretic on or inhabiting the nests of solitary or communal, ground-nesting bees. In south-eastern Australia, however, native bees in the family Halictidae carry what appears to be a substantial radiation of host-specific mesostigmatans in the family Laelapidae. Herein, we redescribe the obscure genus Raymentia , associated with Lasioglossum ( Parasphecodes ) spp. bees (Halictidae) and describe two new species, R. eickwortiana from L. lacthium (Smith) and R. walkeriana from L. atronitens (Cockerell). The type species, R. anomala Womersley, is associated with L. altichum (Smith). In addition, we review the mites known to be associated with Australian bees, provide a key to differentiate them, and describe and illustrate acarinaria of the Halictinae. We also report on the first occurrences in Australia of the genera Trochometridium Cross (Heterostigmata: Trochometridiidae), from L. eremaean Walker (Halictidae), and Cheletophyes Oudemans (Prostigmata: Cheyletidae) from Xylocopa Latreille (Xylocopinae), and on the previously unknown association between a Neocypholaelaps Vitzthum (Mesostigmata: Ameroseiidae) and Lipotriches tomentifera (Friese) (Halictidae).     

Leaf domatia and foliar mite abundance in broadleaf deciduous forest of north Asia

Plant morphology may be shaped, in part, by the third trophic level. Leaf domatia, minute enclosures usually in vein axils on the leaf underside, may provide the basis for protective mutualism between plants and mites. Domatia are particularly frequent among species of trees, shrubs, and vines in the temperate broadleaf deciduous forests in north Asia where they may be important in determining the distribution and abundance of mites in the forest canopy. In lowland and montane broadleaf deciduous forests at Kwangn;akung and Chumbongsan in Korea, we found that approximately half of all woody species in all forest strata, including many dominant trees, have leaf domatia. Pooling across 24 plant species at the two sites, mites occupied a mode of 60% (range 20-100%) of domatia and used them for shelter, egg-laying, and development. On average, 70% of all active mites and 85% of mite eggs on leaves were found in domatia; over three-quarters of these were potentially beneficial to their hosts. Further, mite abundance and reproduction (expressed as the proportion of mites at the egg stage) were significantly greater on leaves of species with domatia than those without domatia in both forests. Effects of domatia on mite abundance were significant only for predaceous and fungivorous mite taxa; herbivore numbers did not differ significantly between leaves of species with and without domatia. Comparable patterns in broadleaf deciduous forest in North America and other biogeographic regions suggest that the effect of leaf domatia on foliar mite abundance is general. These results are consistent with several predictions of mutualism between plants and mites, and indicate that protective mutualisms may be frequent in the temperate zone.     

Feeding behaviour and phylogeny: observations on early derivative Acari

Based on laboratory observations of three species of Allothyrus (Parasitiformes: Holothyrida: Allothyridae) from south east Queensland and gut content analysis of 62 individuals representing 11 species of Allothyrus from eastern Australia, we determined that Australian Allothyridae are scavengers that ingest fluids only. Living arthropods, nematodes, snails and annelids were ignored, but dead arthropods were readily fed upon and were sufficient to maintain adults and nymphs for many months. The adults were sluggish, timid animals that relied on armour, thanatosis and probably on noxious chemicals for protection: the juveniles produced secretions from idiosomal glands. In contrast, most early derivative Mesostigmata that we tested (Sejina, species of Sejus and Uropodella; Uropodina, Polyaspis sp. and Cercomegistina, an undescribed Asternoseiidae) were aggressive predators of small invertebrates and ingested fluids only; however, two species of Asternolaelaps (Sejina) had solid fungal and animal material in their guts. Similarly, the early derivative acariform (Palaeosomata, species of Stomacarus and Loftacarus) and opilioacariform mites (an undescribed Opilioacarida from Australia) that we examined all ingested particulate foods, including fungal and animal material. These observations are consistent with the hypothesis that the earliest mites were scavengers and opportunistic predators that ingested solid foods and that fluid feeding is a derived condition linking the three orders of Parasitiformes (Holothyrida, Ixodida and Mesostigmata).     

<Emphasis Type="Italic">In vitro</Emphasis> collecting (IVC). I. The effect of collecting method and antimicrobial agents on contamination in temperate and tropical collections

Summary In vitro collecting is the process of initiating tissue cultures in the field. In order for in vitro collecting to be broadly available as a technique for collecting plant germplasm, the levels of contamination in such cultures must be controlled. Two techniques for in vitro collecting were compared: leaf punch and needle collecting. The effectiveness of these methods for collecting leaf and stem tissues from plants at tropical and temperature sites was compared. Stem tissue collected by the needle collecting method gave cultures with an average contamination percentage of 31% and 16%, from the tropical and temperate sites, respectively, while with the leaf punch method, average contamination percentages were 90% and 69%. The effectiveness of antimicrobial agents in reducing contamination in leaf punch cultures was evaluated. Addition of the fungicide benlate and the antibiotics cefotaxime and vancomycin, to the leaf punch collections reduced contamination to an average of 30% in the tropical collections and 35% in the temperate collections. Over 90% of both tropical and temperature species collected in multiple samples of 10 or more had at least one clean sample using this medium. The use of either the leaf punch method in combination with a fungicide and antibiotics or the needle collecting technique yielded a high percentage of clean tissues for study and growth.     

Invertebrate zooplankton predator composition and diversity in tropical lentic waters

Invertebrate zooplankton predators are generally less diverse in average species numbers in tropical than in temperate lakes and reservoirs. Predatory Copepoda which comprise the majority of limnetic predators are particularly low in species numbers in the tropics. Predatory Cladocera are confined to the North Temperate zone. Chaoborus appears to be cosmopolitan. Among Rotifera, only the cosmopolitan predator Asplanchna occurs in tropical waters while the other common limnetic carnivorous genus Ploesoma is restricted to higher latitudes. Hydracarina, and insects besides Chaoborus, are generally restricted to the littoral and appear to be more diverse in the tropics. Lakes Awasa and Zwai, Ethiopia, are almost devoid of predators in the limnetic, which is invaded by a littoral chydorid Alona diaphana. Low diversity of lake types and low production of tropical zooplankton could restrict predator diversity too. Very low diversity of invertebrate predators in the limnetic and higher diversity in the littoral may characterize tropical lakes in contrast to temperate lakes, which have more invertebrate predators in the limnetic and perhaps relatively less in the littoral. Tropical zooplankton in freshwaters, appears to be a very immature community. Hence opportunistic species can readily invade the limnetic and even dominate in isolated situations as has been shown for Alona davidi, Hydracarina and some other unconventional forms.