Spider assemblages in bird burrows

The arachnofauna of bird burrows, which are excavated in the soil, is incompletely understood. The bird burrows have a potential to serve as refugia for cavity-adopting spider species particularly in anthropogenic habitats formed by sand mining, which otherwise suffer from a limited availability of other types of cavities. We hypothesized that the presence of abundant food resources and safe shelter in bird burrows excavated in the soil allow the existence of specialized assemblage of spiders, similarly to those known from cavities and nests made by other birds and mammals. Here we examined 353 burrows that had been previously occupied by Riparia riparia, Merops apiaster or Passer montanus. The burrows were examined in early May and early September in 24 Czech sand pits and construction sites. The burrows hosted a species-rich assemblage of spiders that, however, occurred at low abundances. The spiders were represented prevalently by species known to have distributions centered in anthropogenic and urban habitats, including species that were never observed outside of heated buildings in the study area and species that only were previously known from mammalian burrows and loess and karstic soil crevices. Spider assemblages strongly differed between bird burrows and cavities and nests made by other birds and mammals. The species composition and overall low abundance of spiders in bird burrows was unexpected and was in strong contrast to previous observations of spider assemblages in cavities and nests made by other birds and mammals. Concluded, we rejected the initial hypothesis and, instead, we have shown that bird burrows are rarely occupied by spiders and if occupied, the spider species that adopt old bird burrows and the nests inside of them predominantly consist of species known to have their distribution centered to anthropogenic and urban habitats.     

The species composition and ecological features of pea crabs of the genus <Emphasis Type="Italic">Pinnixa</Emphasis> White, 1846 (Brachyura: Pinnotheridae) in Peter the Great Bay,the Sea of Japan

This paper provides an overview of pea crabs of the genus Pinnixa White, 1846 (Brachyura: Pinnotheridae) that occur along the Russian coast of the Sea of Japan. Three species of the genus have been recorded for this area: P. tumida Stimpson, 1858, P. rathbuni Sakai, 1934, as well as P. banzu Komai, Nishi & Taru, 2014, which is the first record for the fauna of Russia. All species clearly differ ecologically: P. tumida was found in Posyet Bay in the intestine of the burrowing holothurian Paracaudina chilensis (Müller, 1850); P. rathbuni, in burrows of the echiuroid Urechis unicinctus (von Drasche, 1881); and P. banzu, in tubes of the polychaete Chaetopterus cautus Marenzeller, 1879. The paper also provides a definitive key to Pinnixa species and data on the size, behavior, symbionts, and parasites of P. rathbuni and P. banzu.     

Steeplebushes conquer the countryside: influence of invasive plant species on spider communities (Araneae) in former wet meadows

Central European wet meadows are diminished by abandonment of cultivation measures, drainage, pollution, intensive agriculture and climate change during the last decades. In addition, original wet meadow communities can be threatened by immigrating neophytes. Typical invasive species in wet meadows are the steeplebushes Spiraea tomentosa and Spiraea douglasii, but their impact on the indigenous arthropod fauna is unknown. The present study therefore investigates Spiraea-induced changes in ground- and herb dwelling spiders in Spiraea sites, uncultivated meadows with interspersed Spiraea sp. and mowed meadows without Spiraea sp. using pitfall traps and sweep netting. Light intensity, vegetation height and coverage differed significantly between the Spiraea sites and the mowed meadows. In consequence, the activity density of ground-dwelling spiders was much lower in the Spiraea sites and their habitat preferences differed significantly from the two meadow types. Species preferring forests and forest edges were more abundant in invaded sites whereas specimens preferring open habitats decreased. Although the vegetation height and coverage of mowed meadows and cultivated meadows did not differ remarkably, uncultivated meadows contained less spiders of open dry habitats whereas forest species increased. In contrast, differences between herb dwelling spider assemblages of the three habitat types were not significant. Based on the results of the project, the risk of steeple bush invasion and management methods of wet meadows are discussed.     

Fire frequency effects on soil and pollinators: what shapes sexual plant reproduction?

Increased fire frequency can significantly erode both soil properties and plant–pollinator interactions affecting plant reproductive success but they have seldom been assessed simultaneously. Here, we evaluate soil properties, pollinator assemblage and the reproductive success of two native Fabaceae herbs, Desmodium uncinatum and Rhynchosia edulis, growing in unburned, low and high fire frequency sites of Chaco Serrano across two consecutive years. Desmodium uncinatum is outcrossing with a high dependence on pollinators, whereas R. edulis is autogamous and completely independent of pollinators. We found that soil water content, nitrates and electrical conductivity significantly decreased in low and high fire frequency sites. Pollinator richness and composition visiting each plant species was similar across all fire frequency scenarios. However, fruit set of the exogamous D. uncinatum was strongly reduced in frequently burned sites, whereas fruit set of the autogamous R. edulis showed no significant changes. In both species, the probability of setting fruits was positively related to soil quality across fire frequency scenarios, implying that decreased reproduction was mainly driven by limitation of abiotic resources shaped by increased fire frequency. Because the pollinator-dependent D. uncinatum has a higher reproductive cost, reduced soil quality induced by fire frequency had stronger effects on its reproduction. Chronic reduction of sexual reproduction in frequently burned sites with depleted soils will limit population recruitment with negative consequences on long-term plant population persistence.     

Vegetation heterogeneity caused by an ecosystem engineer drives oviposition-site selection of a threatened grassland insect

Soil-disturbing ecosystem engineers play an important role in plant-species diversity in grasslands as they increase vegetation heterogeneity by creating gaps due to burrowing or mound-building activities. However, knowledge of the ecological importance of these microsites for arthropods is still rare. In this study, we analyse the role of ant-nest mounds of the yellow meadow ant (Lasius flavus) for oviposition-site selection of the silver-spotted skipper (Hesperia comma). Ant mounds were searched for H. comma eggs. Microclimatic and vegetation parameters were ascertained at occupied sites and control sites within the matrix vegetation. Furthermore, we analysed the habitat requirements of L. flavus by means of nest counting and the sampling of environmental parameters within different sites. L. flavus occurred most frequently in abandoned and less steep sites with deeper soils. Mean egg occupancy rates of H. comma on ant hills were 32 %, nearly twice as high as at control sites (18 %). In contrast to the surrounding vegetation, nest mounds were characterized by a lower vegetation cover and litter and a higher proportion of bare ground. Furthermore, they had a higher cover of host plants compared with control samples. These microhabitats offered the following essential key factors for the larval development of H. comma: (1) a suitable microclimate due to open vegetation and (2) a high amount of host plants. This study highlights the importance of L. flavus as an ecosystem engineer within central European grasslands because this species increases vegetation heterogeneity.     

Predation of <Emphasis Type="Italic">Halyomorpha halys</Emphasis> (Hemiptera: Pentatomidae) from Web-Building Spiders Associated with Anthropogenic Dwellings

The brown marmorated stink bug, or Halyomorpha halys, is an invasive pest in North America and Europe that causes severe agricultural damage and nuisance problems for homeowners; and it is originally from China, Taiwan, and the Republic of Korea. While the natural enemy community of H. halys has been evaluated in several agroecosystems, it has not been examined where H. halys overwinters in anthropogenic structures. The aims of the current study were to evaluate 1) whether spider webs commonly found in the home and yard can successfully ensnare H. halys, 2) whether entanglement resulted in consumption by spiders inhabiting the webs, and 3) how frequently H. halys becomes entangled in webs under ambient conditions. To accomplish this, adult H. halys were introduced into webs in and near anthropogenic structures in West Virginia and Maryland, United States, and the behavior of spiders was observed for 5-min intervals at 0, 1, 2, and 24 h after introduction. In addition, a survey of webs was performed to determine the frequency with which spiders naturally capture H. halys inside buildings and in the landscape. Overall, the study found seven spider families in anthropogenic structures. Adult H. halys that were introduced into the webs of Theridiidae, Pholcidae, or Agelenidae had a greater than 50% chance of being ensnared and consumed. Adult H. halys were found naturally most often in webs of Theridiidae. Webs with a funnel or cob web architecture had the greatest probability of ensnaring H. halys, while those with orb structures resulted in the fewest caught. In the wild, 13–20% of spider webs contained dead H. halys. Our results suggest that spiders may be an important contributing factor for mortality of H. halys at overwintering sites, and spiders in or outside homes may help reduce nuisance problems caused by H. halys.     

High abundance of non-mycorrhizal plant species in severely phosphorus-impoverished Brazilian <Emphasis Type="Italic">campos rupestres</Emphasis>

Background and aims

We sought to describe the species and functional composition of Brazilian campos rupestres plant communities on severely nutrient-impoverished white sands, to test hypotheses relating plant communities and physiological adaptations to infertile soils. Based on recently-published information on a south-western Australian dune chronosequence, we hypothesised that campos rupestres plant communities would similarly contain a relatively large proportion of non-mycorrhizal species, because of the phosphorus-(P) impoverished nature of the soils. We also sought to test the hypothesis that many of these non-mycorrhizal species have high leaf manganese (Mn) concentrations as a consequence of carboxylate exudation to mobilise soil P.

Methods

We conducted flora surveys and quantified mycorrhizal status and foliar Mn concentrations in field sites with strongly-weathered sandy soils. Rhizosphere carboxylates were collected from glasshouse-grown plants to assess a potential correlation of carboxylates and leaf Mn concentrations.

Results

Soils were depleted of all major plant nutrients. Non-mycorrhizal plants were abundant in most field sites (mean relative cover = 48%). Vellozia species were dominant aboveground; belowground, roots were colonised more by dark septate endophytic fungi than by mycorrhizal fungi. From the field sites, foliar Mn concentrations in non-mycorrhizal species increased with decreasing soil P concentrations, but only when soil Mn concentrations were above a minimum threshold (exchangeable [Mn] above detection limit). Across all species, however, there was no relationship of foliar Mn concentrations with soil P concentrations.

Conclusions

Our hypothesis that white-sand campos rupestres communities contain a relatively large proportion of non-mycorrhizal plants was supported. Comparison with similar ecosystems in south-western Australia suggests that plant communities on severely P-impoverished sandy soils, despite differing evolutionary histories and little overlap in plant families, follow convergent evolutionary paths towards increasing abundance of non-mycorrhizal species.

     

Miocene Trace Fossils from Borneo

In the Miocene Belait formation of northern Sarawak, Brunei and Sabah burrows ofOphiomorpha Lundgren were found, described here asOphiomorpha borneensis n. ichnosp. A few associated spiral tunnels of theXenohelix-type were also found. Two species ofHäntzschelinia Vialov occurred on Labuan Island. A third type of structure was found in Brunei and it probably represents castings of an unknown lamellibranch. The burrows and castings were made in a brackish water environment, probably in the littoral zone of an embayment or delta.     

Ants Do Not Traverse the Silk of Adult Female <Emphasis Type="Italic">Nephila clavipes</Emphasis> (Linnaeus) Webs

Many organisms use chemicals to deter enemies. Some spiders can modify the composition of their silk to deter predators from climbing onto their webs. The Malaysian golden orb-weaver Nephila antipodiana (Walckenaer) produces silk containing an alkaloid (2-pyrrolidinone) that functions as a defense against ant invasion—ants avoid silk containing this chemical. In the present study, we test the generality of ants’ silk avoidance behavior in the field. We introduced three ant species to the orb webs of Nephila clavipes (Linnaeus) in the tropical rainforest of La Selva, Costa Rica. We found that predatory army ants (Eciton burchellii Westwood) as well as non-predatory leaf-cutting ants (Atta cephalotes Linnaeus and Acromyrmex volcanus Wheeler) avoided adult N. clavipes silk, suggesting that an additional species within genus Nephila may possess ant-deterring silk. Our field assay also suggests that silk avoidance behavior is found in multiple ant species.     

Survival possibilities of the dragonfly <Emphasis Type="Italic">Aeshna viridis</Emphasis> (Insecta,Odonata) in southern Sweden predicted from dispersal possibilities

We use public records from 1980 to 2014 to analyse survival of the EU Annex IV species Aeshna viridis in Sweden, a dragonfly strongly associated with the plant Stratiotes aloides. We clustered localities with S. aloides based on assumed dispersal abilities of A. viridis, using a dispersing radius of 2–100 km, calculating the proportion of sites with S. aloides that A. viridis is able to reach. If mean dispersal capability is high (40 km or above) 92.6 % or more of the localities are connected. For a good disperser, the probability of long-time survival is good. We further analysed the species richness of other Odonata and aquatic plants at 98 localities from the dataset. A. viridis co-occurred with more Odonata in the presence of S. aloides and running water but not in lakes. S. aloides sites had a higher number of other aquatic plants. Area had no impact on the occurrence of the species. For the present situation we surveyed 32 localities with known occurrence of the species. Only half of the sites for S. aloides contained any specimens while A. viridis occurred in the same number of sites. The species co-occurred in only 8 of 32 sites. In four sites A. viridis larvae appeared among Menyanthes trifoliata, Phragmites australis, Potamogeton natans and Sphagnum spp., indicating that at high latitudes A. viridis breeds among other species. Indirect monitoring based only on S. aloides would underestimate the number of populations of the dragonfly.     

Location of low copy genes in chromosomes of <Emphasis Type="Italic">Brachiaria</Emphasis> spp.

Repetitive DNA sequences have been widely used in cytogenetic analyses. The use of gene sequences with a low-copy-number, however, is little explored especially in plants. To date, the karyotype details in Brachiaria spp. are limited to the location of rDNA sites. The challenge lies in developing new probes based on incomplete sequencing data for the genus or complete sequencing of related species, since there are no model species with a sequenced genome in Brachiaria spp. The present study aimed at the physical location of conserved genes in chromosomes of Brachiaria ruziziensis, Brachiaria brizantha, and Brachiaria decumbens using RNAseq data, as well as sequences of Setaria italica and Sorghum bicolor through the fluorescent in situ hybridization technique. Five out of approximately 90 selected sequences generated clusters in the chromosomes of the species of Brachiaria studied. We identified genes in synteny with 5S and 45S rDNA sites, which contributed to the identification of chromosome pairs carrying these genes. In some cases, the species of Brachiaria evaluated had syntenic segments conserved across the chromosomes. The use of genomic sequencing data is essential for the enhancement of cytogenetic analyses.     

The changing nature of plant–microbe interactions during a biological invasion

Invasive plant species can alter belowground microbial communities. Simultaneously, the composition of soil microbial communities and the abundance of key microbes can influence invasive plant success. Such reciprocal effects may cause plant–microbe interactions to change rapidly during the course of biological invasions in ways that either inhibit or promote invasive species growth. Here we use a space-for-time substitution to illustrate how effects of soil microbial communities on the exotic legume Vicia villosa vary across uninvaded sites, recently invaded sites, and sites invaded by V. villosa for over a decade. We find that soil microorganisms from invaded areas increase V. villosa growth compared to sterilized soil or live soils collected from uninvaded sites, likely because mutualistic nitrogen-fixing rhizobia are not abundant in uninvaded areas. Notably, the benefits resulting from inoculation with live soils were higher for soils from recently invaded sites compared to older invasions, potentially indicating that over longer time scales, soil microbial communities change in ways that may reduce the success of exotic species. These findings suggest that short-term changes to soil microbial communities following invasion may facilitate exotic legume growth likely because of increases in the abundance of mutualistic rhizobia, but also indicate that longer term changes to soil microbial communities may reduce the growth benefits belowground microbial communities provide to exotic species. Our results highlight the changing nature of plant–microbe interactions during biological invasions and illustrate how altered biotic interactions could contribute to both the initial success and subsequent naturalization of invasive legume species.     

Narrow endemics in Mediterranean scrublands: high gene flow buffers genetic impoverishment in the annual monospecific <Emphasis Type="Italic">Castrilanthemum</Emphasis> (Asteraceae)

Castrilanthemum debeauxii is a critically endangered annual plant narrowly distributed in mountains of SE Iberia. It occurs in spiny scrublands on limestone soils dominated by Erinacea anthyllis at medium altitudes. Phylogenetic results indicate that the monotypic Castrilanthemum constitutes a paleoendemic lineage that diverged from its closest extant relatives in the Miocene. To achieve a better understanding of its recent evolution and conservation status, we performed an analysis of genetic variation and structure of four subpopulations using plastid haplotypes and AFLPs. We also investigated additional characteristics (ecological requirements, reproductive biology, pre-dispersal seed predation) that are relevant to evaluate the conservation status of the species. Castrilanthemum was found to be a facultative selfer with no major germination limitations. We detected moderate levels of genetic diversity based on AFLPs and plastid DNA sequences. The low genetic structure found for both nuclear and plastid markers, together with species distribution modeling results, pointed to high gene flow, which might counteract processes of genetic erosion caused by the low number of individuals. We found significant levels of pre-dispersal seed predation by the burrowing larvae of a tephritid fly, which may have contributed to the decline of the populations. Based on our results, we suggest directions for the management of Castrilanthemum. In particular, we recommend seeding and collection of seeds for banks, and discuss the possibilities of population reinforcement and reintroduction in localities where the species is currently extinct.     

Detection of Cryptic <Emphasis Type="Italic">Candida</Emphasis> Species Recognized as Human Pathogens Through Molecular Biology Techniques

Purpose of Review

The aim of this review is to evaluate these molecular-based methods able to identify pathogenic cryptic Candida spp. focusing on those that demonstrated to be useful in clinical laboratory settings.

Recent Findings

It is long known that some Candida spp. are genetically heterogeneous. Firstly, individual species were divided into groups based on differences on the sequence of some genes. Later, those groups were designated as cryptic species and defined as phenotypically indistinguishable species that are only identified by their DNA sequences. Many common Candida spp. are now considered complexes formed by several cryptic species. Some of them have been recognized as human pathogens. The identification of these species is problematic but necessary since they have different host range, infection sites, infection severity, and antifungal susceptibility. Several independent DNA markers were proposed as tools for the differentiation of highly related species. We will concentrate on the three species complexes most frequently associated with human infections including Candida albicans, C. glabrata, and C. parapsilosis complexes and a fourth group of less common but multiresistant species including C. haeumulonii complex and C. auris.

Summary

We review the clinically useful molecular tools able to differentiate the cryptic species of C. albicans, C. glabrata, and C. parapsilosis complexes and designated to uncover emerging multiresistant species.

     

Direct and indirect effects of termites on savanna tree-seedling growth

Termites are considered to be ecosystem engineers because they modify their biophysical environments. We tested the effects of soil-nutrient alteration in termite-enriched soils compared with termite-free open savannas. We also tested whether non-nutrient alterations (soil disturbance) induced by termites led to changes in tree-seedling growth. Soil samples taken from termite-enriched soils and adjacent open savanna sites in KwaZulu-Natal, South Africa were analyzed for nitrogen, pH, organic carbon and water-holding capacity. Seeds from three dominant tree species, Acacia sieberiana, Celtis africana and Ziziphus mucronata, were grown in soils taken from termite-enriched soils and adjacent savannas. Overall, organic carbon and nitrogen content were higher in termite-enriched soils than in adjacent savannas. We found that these differences in nutrients did not directly affect seedling growth rates or final height. However, C. africana had increased growth rates in compacted termite-enriched soils, while A. sieberiana seedlings were taller in non-compacted soils. We conclude that the indirect effects of disturbance by termites may be as important as the direct effects of increased nutrients for growth of savanna trees.     

Responses of <Emphasis Type="Italic">Venerupis philippinarum</Emphasis> (Mollusca: Bivalvia) to Predators and Changes in Hydrodynamics

The rate of burrowing into sand by the bivalve mollusk Venerupis philippinarum was studied under laboratory conditions. It is found that an increase in the intensity of water flow to an average of 1000 ml/min stimulates the burrowing of the mollusk, while higher values suppress burrowing; the threshold values are somewhat different for the young and adult specimens. It is shown that the presence of the starfish Asterias amurensis in the experimental environment decreases the rate of burrowing of V. philippinarum by 10–20% depending upon the sizes of the predator and the potential victim, but the depth of penetration of the mollusks into the sediment increases. It is supposed that in V. philippinarum and other species of bivalve mollusks related to the same life form and characterized by a moderate capability to burrow into the ground, the adaptive strategy of threat avoiding (great wave activity, an approach of a predator) is expressed as burrowing into a depth uncommon for usual situations and waiting. This behavior, to a significant degree, provides the capability of some species to inhabit shallow water areas with poor hydrodynamics inhabited by numerous predators.     

Synergy between two invasive species,redback spiders and rabbits,threaten the endangered Cromwell chafer beetle

Interactions between invasive species can be difficult to predict and can result in unanticipated impacts of significance for native fauna. Here we show that introduced European rabbits (Oryctolagus cuniculus) create habitat that enables invasive redback spiders (Latrodectus hasselti Thorell, 1870) to establish and prey upon the nationally endangered, endemic Cromwell chafer beetle (Prodontria lewisii Broun, 1904). We examined the spatial relationship between rabbit holes and redback spider occurrence, recorded all prey caught in redback spider webs over a 4-month period, and tested the role rabbit holes play in providing habitat for redback spiders experimentally, by filling in rabbit holes in areas used by spiders and monitoring subsequent occupation of the areas over four months. Redback spiders predominately resided in old rabbit holes, with the highest densities of spiders coinciding with high densities of rabbit holes. Cromwell chafer beetles were commonly caught in webs. Filling in rabbit holes eliminated the presence of redback spiders at all treated sites and reduced prey capture in those areas. Conservation management to protect Cromwell chafer beetles should focus on eliminating rabbits and their holes from beetle habitat.     

Effect of <Emphasis Type="Italic">Pinus ponderosa</Emphasis> afforestation on soilborne <Emphasis Type="Italic">Frankia</Emphasis> and saprophytic Actinobacteria in Northwest Patagonia,Argentina

Large areas in the extra-Andean region in the forest - steppe ecotone in “Northwestern Argentinean Patagonia” have been replaced by plantations of the exotic conifer Pinus ponderosa which modify soils physical and chemical factors and alter the biodiversity. Considering that in the region occur saprophytic soilborne actinobacteria that play important role as the fixation of atmospheric nitrogen (N₂) in symbiosis with native plant species and the production of bioactive molecules in plants rhizosphere, we aimed to study the effect of the plantation on the abundance of the N₂ fixer Frankia and on the genus diversity of cultivable rhizospheric actinobacteria. The study was performed with soils of six paired sites with pine plantations and natural neighbor areas (including steppes or shrublands). Abundance of infective Frankia was estimated by evaluating the nodulation capacity of soils, through a plant bioassay using Ochetophila trinervis as trap plant. Isolation trials for saprophytic actinobacteria were performed by applying chemotactic and successive soils dilutions methods. We concluded that P. ponderosa afforestation affect soil actinobacteria. This was mainly evidenced by a decrease in the Frankia nodulation capacity in O. trinervis, which was related to plantation age, to lower soil carbon and nitrogen content, higher available phosphorus, and to a slight decrease in soils pH. Pine plantation influence on the cultivable saprophytic actinobacteria was less clear. The study highlights the importance of soils as source of Frankia and rhizospheric actinobacteria in relation to disturbance caused by pine plantation in natural environments with native actinorhizal plant species.