Spatial dynamics of a Sirex noctilio woodwasp population within a pine plantation in Patagonia, Argentina

The woodwasp Sirex noctilio F. (Hymenoptera: Siricidae) is probably the most important pest of pine tree plantations of the southern hemisphere. We studied the spatial arrangement of an endemic population of the woodwasp S. noctilio within pine plantations located in northwest Patagonia, Argentina, during three successive years since colonization. By censusing healthy and attacked trees, which provided data on current and past yearly woodwasp attacks, we studied: (i) the spatial pattern of attacked trees during the endemic phase of a woodwasp population, and (ii) the changes in the spatial arrangement through time and with an increasing (i.e., no intervention) pest population. Among a total of 53 649 counted trees, attack rates were low during the study period (accumulated attack below 0.5%). Results of spatial statistical analysis showed that woodwasp attack is highly clumped, and that spatial aggregation increases with time, even with increasing numbers of attacked trees. The observed spatial arrangement, a consequence of a demographic process, can have important implications for the management of woodwasp populations and contributes to our understanding of the nature of outbreak population behaviour in this pestiferous forest insect.     

Biotic resistance and the spatiotemporal distribution of an invading woodwasp, <Emphasis Type="Italic">Sirex noctilio</Emphasis>

Quantifying the strength of interactions among introduced and native species across space and time is critical in understanding biological invasions as they can attenuate or amplify the magnitude of impact. The European woodwasp, Sirex noctilio F., a global threat to pines, is a recent invader to North America. It attacks and kills primarily Pinus resinosa and Pinus sylvestris, and encounters a diverse assemblage of potential competitors for this resource. We quantified spatial colonization patterns of this woodwasp and resident competitors including scolytine bark beetles, woodboring cerambycid and buprestid beetles, and the fungal root rot diseases Armillaria and Heterobasidion across an 80 year old pine plantation over 4 years. All xylophages were spatially aggregated, but only on a localized scale of 15–20 m. Colonizers occurred non-randomly within trees, with S. noctilio negatively or neutrally associated with all other colonizing agents, whereas all other insect and root rot colonizers were mostly positively co-associated. An autologistic regression with spatially-weighted variables indicated the probability of a dead tree exhibiting symptoms of S. noctilio attack was positively associated with tree density, host species (P. sylvestris), and density of S. noctilio-attacked trees from the current and previous year. Interspecific stand patterns were weaker; probability of attack was negatively associated only with root rot pathogens. Across spatial scales, there were mixed (woodborers) and neutral (bark beetles) associations between S. noctilio and other co-colonizing insects. Our results suggest that competitive interactions with resident species may be contributing to the limited success of S. noctilio in North America, but are unlikely to be driving it by themselves.     

Trapping for Sirex Woodwasp in Brazilian Pine Plantations: Lure,Trap Type and Height of Deployment

The Sirex woodwasp, Sirex noctilio (Hymenoptera: Siricidae) is considered a secondary pest of pine in its native range but has caused considerable economic losses in pine plantation forests in the southern hemisphere. In Brazil, trap trees are the primary tool used for early detection purposes but these are costly, labor-intensive to install and require stressing trees by herbicide application. Flight intercept traps baited with synthetic blends of host volatiles are an attractive alternative but have performed poorly in some settings. This study was carried out to look for alternatives to trap trees for use in Brazilian pine plantations for early detection of S. noctilio. Four field experiments were conducted in two consecutive flight seasons (2015–16 and 2016–17), in planted loblolly pine (Pinus taeda) stands, to compare captures among flight intercept traps baited with different lures, deployed at different heights and among different intercept trap designs. Two experiments compared different host volatile lures and a significant treatment effect was observed in one. No effect of trap design or height was observed.     

Effect of temperature on woodwasp (Sirex noctilio F.) development and parasitism by the entomopathogenic nematode,Deladenus siricidicola

The woodwasp, Sirex noctilio, is a significant global pest of exotic pine plantations in the Southern Hemisphere and now threatens native pine forests in North America. Management in Australia relies on biocontrol using the nematode, Deladenus (= Beddingia) siricidicola (Bedding), which infects and sterilises females who then further disperse the nematode. This pest is spreading into warmer regions in Australia and South America and coupled with the threat of global climate change, there is uncertainty as to how increasing temperatures will affect the biocontrol program. S. noctilio within nematode-inoculated wood were reared at four temperatures (24, 25.3, 26.6 and 28 °C) to investigate the effects of elevated temperatures on wasp development (emergence time, sex ratio and size), development of eggs (number, size, and maturation) and infection by the nematode. At 24 °C, which reflects current field temperature, S. noctilio were bigger in size and all the eggs were normal and all were infected with nematodes. Modest rises in temperature reflecting climate change scenarios resulted in smaller sized S. noctilio, disrupted egg development and maturation, and lowered the nematode sterilisation rate in females. Reduced S. noctilio female body size and egg infection will likely compromise biocontrol by D. siricidicola in its current distribution, but disrupted egg development may act directly on the pest, limiting dispersal of S. noctilio into subtropical pine plantations and adaptation to climate change.     

Temperature explains variable spread rates of the invasive woodwasp Sirex noctilio in the Southern Hemisphere

The frequency of introductions of non-indigenous forest insects into new habitats is increasing worldwide, often with profoundly adverse consequences on natural and plantation forest ecosystems. Understanding rates and patterns of spread of invasive forest insects is important for predicting when and where these species will expand their geographical range, with the potential to improve mitigation strategies. The woodwasp Sirex noctilio is a damaging invasive forest insect that kills numerous species of Pinus. Despite encountering highly variable eco-climatic conditions, S. noctilio has arrived and established in exotic pine forest production areas throughout the Southern Hemisphere. In this study, we compiled historical records of S. noctilio invasion to compare spread rates among eight contrasting eco-climatic regions in the Southern Hemisphere and to explore how spread rate is predicted by landscape variation in climate, habitat characteristics and anthropogenic effects. Spread rates for S. noctilio varied considerably among the invaded regions, ranging from 12 to 82 km per year. Among regions, spread rates of S. noctilio increased with increasing mean annual temperature and isothermality. We hypothesize that temperature may directly or indirectly influence S. noctilio population growth and dispersal, thereby influencing spread rates.     

A dendroecological reconstruction of western spruce budworm outbreaks (Choristoneura occidentalis) in the Front Range,Colorado, from 1720 to 1986

Radial increment cores from Douglas-fir (Pseudotsuga menziesii) and blue spruce (Picea pungens), defoliated by western spruce budworm (Choristoneura occidentalis), were analyzed by means of dendrochronological methods and compared with cores from undefoliated ponderosa pine (Pinus ponderosa) and lodgepole pine (Pinus contorta) growing on the same sites in the Front Range, Colorado. Extensive deforestation during the gold and silver booms in the second part of the nineteenth century led to dense and almost pure stands of shadetolerant budworm host species. By using the skeleton plot method, the number of trees with clear growth reductions is obtained, thus representing an exact record of forest insect attacks. The analysis of abrupt growth reductions revealed at least nine outbreaks of western spruce budworm between 1720 and 1986, the majority occurring in the nineteenth century. The outbreaks were graphically compared with periods of attack in New Mexico and Colorado which were detected by other scientists employing tree-ring measurement techniques. No increase in the frequency of severe outbreaks during the twentieth century was observed, yet there is some evidence that the most recent outbreak might be the most severe ever recorded. Open Douglas-fir stands on higher sites were more susceptible to heavy budworm attack than dense stands on lower sites. Blue spruce was less frequently and less severely attacked than Douglas-fir. The spatial pattern of historical outbreaks generally was very patchy.     

Do Native Insects and Associated Fungi Limit Non-Native Woodwasp,Sirex noctilio,Survival in a Newly Invaded Environment?

Sirex noctilio F. (Hymenoptera: Siricidae) is an introduced pest of pines (Pinus spp.) in several countries in the Southern Hemisphere. Although S. noctilio is established in North America (first discovered in 2004), it has not been a destructive pest there so far, where forest communities more closely resemble those in its native Eurasian range—where it is not a pest. To investigate the influence of the existing community of associated insects (competitors + natural enemies) and fungi (vectored by insects) on S. noctilio survival in North America, we examined stage-specific mortality factors and their relative importance, generating life tables drawn from experimentally-manipulated and natural cohorts of Sirex spp. (mostly S. noctilio, but some native S. nigricornis F.). For both natural and experimentally-manipulated cohorts, factors which acted during the earliest Sirex life stages, most likely tree resistance and/or competition among fungal associates, were paramount in dictating woodwasp survival. Experimentally-manipulated life tables revealed that protection from the community of associates resulted in a significantly, and substantially larger (>15x) S. noctilio F1 generation than exposure to it. Seventy percent of generation mortality in the exposed cohort was due to tree resistance or unknown causes early in larval development, which could have included competition among other bark- or wood-inhabiting insects and/or their fungal associates. Only 46% of generation mortality in the protected cohort was due to tree resistance and/or unknown causes. Parasitoids, particularly endoparasitoids (Ibalia spp.), showed limited ability to control S. noctilio, and reduced the experimentally-established cohort by only 11%, and natural cohorts an average of 3.4%. The relative importance of tree resistance vs. competition with bark- and wood-borers in reducing S. noctilio survival remains unclear. Tree resistance and/or competition likely contribute more than natural enemies in maintaining the S. noctilio population in North America below damaging levels.     

Local antagonism and resource partitioning between two invasive pine plantation pests

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Influence of Nematode Parasitism,Body Size,Temperature, and Diel Period on the Flight Capacity of <Emphasis Type="Italic">Sirex noctilio</Emphasis> F. (Hymenoptera: Siricidae)

Sirex noctilio F. (Hymenoptera: Siricidae) is a woodwasp of pine trees that has recently invaded and established in North American forests. Although S. noctilio has had a limited impact in North America to date, there is some concern that it could have a significant impact on pine plantations, especially in the southeastern U.S.A. Moreover, there are few data on the flight capacity of male S. noctilio. We found no association between parasitism by D. siricidicola and whether or not S. noctilio initiated flight on the flight mill. Male wasps that were parasitized by nematodes were heavier than non-parasitized males, but there was no significant difference in mass between parasitized and non-parasitized females. We also examined the flight capacity of male and female S. noctilio in relation to nematode parasitism, body mass, temperature (for only males), and diel period. Body mass, temperature, and diel period affected flight in S. noctilio such that wasps were generally observed to fly faster, farther, and more frequently if they were heavier, flying at warmer temperatures, and flying during the photoperiod. The fact that nematode-parasitized male wasps were found to fly farther than the non-parasitized males is consistent with the hypothesis that nematode parasitism does not negatively affect the flight capacity of S. noctilio.     

Patterns and monitoring of Sesia apiformis infestations in poplar plantations at different spatial scales

Poplar plantations are expanding worldwide but little is known about the hornet clearwing moth, Sesia apiformis, one of their most severe pests. Thirty‐two poplar plantations of I‐214 clone were sampled in Spain, according to a factorial design combining stand age, site condition and understorey management to investigate the main drivers of S. apiformis habitat selection at both tree and stand level. In each plantation, one pheromone trap was activated during the flight season to test the correlation between captures and percentage of attacked trees. The proportion of other poplar forests in surrounding landscapes was calculated and used as a covariate in predictive models of trap catches. There were significantly more attacked trees in older stands. In young stands, the percentage of infested trees increased with the percentage cover of understorey vegetation. There was no significant effect of site quality on the rate of infestation and no difference in tree height, diameter or crown condition between attacked and un‐attacked trees within each stand, suggesting that S. apiformis could behave as primary pest. We hypothesized that the critical stage in the life cycle of the moth was the first instar larvae, which may benefit from protection of deep bark cracks in older stands and understorey vegetation in younger stands. We observed a positive correlation between trap capture and percentage of attacked trees in a radius of 100 m around the trap. The regression of trap catches against percentage of attacked trees was improved when the area of other poplar plantations within a distance of 600 m was incorporated in the model. This suggests that surrounding poplar stands may act as sources of immigrating moths in monitored stands. Our findings confirm that S. apiformis should be considered as a potential threat to poplar plantations and that pheromone trapping provides a suitable monitoring tool.     

Horizontal transmission of a parasitic nematode from a non-native to a native woodwasp?

In eastern North America, the exotic invasive woodwasp, Sirex noctilio, attacks pines (Pinus spp.) and often shares larval habitat with the native woodwasp, Sirex nigricornis. The parasitic nematode, Deladenus siricidicola, has been used widely in the southern hemisphere as a biological control agent because it sterilizes female S. noctilio. This nematode was introduced accidentally to North America along with S. noctilio. Historical reports indicate nematode-woodwasp fidelity: the parasitic nematode, D. siricidicola, exclusively infects S. noctilio, and the native nematode, Deladenus proximus, exclusively infects S. nigricornis. From two sites in southern Ontario, separated by 225 km, we collected woodwasps from three Pinus sylvestris, and identified the nematode species present in the abdomens of infected wasps. Both wasp species co-occurred in all three trees. D. siricidicola was present in the haemocoel, but not inside the eggs, of infected S. noctilio and S. nigricornis. This evidence suggests horizontal transmission of D. siricidicola likely occurred from S. noctilio to S. nigricornis.     

Stand‐replacing fires reduce susceptibility of lodgepole pine to mountain pine beetle outbreaks in Colorado

Aim As climate change is increasing the frequency, severity and extent of wildfire and bark beetle outbreaks, it is important to understand how these disturbances interact to affect ecological patterns and processes, including susceptibility to subsequent disturbances. Stand‐replacing fires and outbreaks of mountain pine beetle (MPB), Dendroctonus ponderosae, are both important disturbances in the lodgepole pine, Pinus contorta, forests of the Rocky Mountains. In the current study we investigated how time since the last stand‐replacing fire affects the susceptibility of the stand to MPB outbreaks in these forests. We hypothesized that at a stand‐scale, young post‐fire stands (< c. 100–150 years old) are less susceptible to past and current MPB outbreaks than are older stands. Location Colorado, USA. Methods We used dendroecological methods to reconstruct stand‐origin dates and the history of outbreaks in 23 lodgepole pine stands. Results The relatively narrow range of establishment dates among the oldest trees in most sampled stands suggested that these stands originated after stand‐replacing or partially stand‐replacing fires over the past three centuries. Stands were affected by MPB outbreaks in the 1940s/1950s, 1980s and 2000s/2010s. Susceptibility to outbreaks generally increased with stand age (i.e. time since the last stand‐replacing fire). However, this reduced susceptibility of younger post‐fire stands was most pronounced for the 1940s/1950s outbreak, less so for the 1980s outbreak, and did not hold true for the 2000s/2010s outbreak. Main conclusions Younger stands may not have been less susceptible to the most recent outbreak because: (1) after stands reach a threshold age of > 100–150 years, stand age does not affect susceptibility to outbreaks, or (2) the high intensity of the most recent outbreak reduces the importance of pre‐disturbance conditions for susceptibility to disturbance. If the warm and dry conditions that contribute to MPB outbreaks concurrently increase the frequency and/or extent of severe fires, they may thereby mitigate the otherwise increased landscape‐scale susceptibility to outbreaks. Potential increases in severe fires driven by warm and dry climatic trends may lead to a negative feedback by making lodgepole pine stands less susceptible to future MPB outbreaks.     

Sirex noctilio in North America: the effect of stem‐injection timing on the attractiveness and suitability of trap trees

• 1 Sirex noctilio Fabricius, an invasive woodwasp responsible for severe economic damage to pine industries in the southern hemisphere, is now established in the northeastern U.S.A. and portions of eastern Canada.
• 2 Parts of North America are considered to be high risk for S. noctilio invasion. Effective detection tools, including trap trees, are needed to monitor and survey S. noctilio populations.
• 3 The present study was conducted to determine the optimal time to chemically stress a tree when aiming to attract the most S. noctilio to the host substrate, as well as to determine which timing produced the most adult progeny. Both of these measures (host attraction and host suitability for development) support the main objectives of the study by offering improved methods for monitoring and management of S. noctilio.
• 4 Red pine (Pinus resinosa) and Scots pine (Pinus sylvestris) were treated with Dicamba at three time intervals. Multiple funnel lindgren traps were placed on these trees and, at the end of the flight season, the treatment trees were felled and brought into the laboratory. The number of S. noctilio caught in the traps (host attraction) and the number of S. noctilio emerged from the treated trees (host suitability) were determined.
• 5 Optimal timing of the chemical girdle was dependent on host species. Significantly more female S. noctilio were captured on trap trees prepared 1 month before flight (red pine and Scots pine) or prepared at flight (Scots pine) compared with other treatments. There were also significantly more females reared from Scots pine trap trees prepared at flight and red pine trap trees prepared 1 month before and/or at flight.
• 6 By the beginning of August, most (79%) of the S. noctilio for the flight season were caught in the traps at the trap trees. The sex ratio (males : females) was closer to 1 : 1 than previously reported in studies from other countries.
• 7 The results obtained in the present study demonstrate that timing is important when creating a trap tree with herbicide in North America, whether for the purpose of detection or as part of a biological control effort.

     

Density related plasticity in stand-level spatial distribution of the ambrosia beetle, Platypus koryoensis (Coleoptera: Curculionidae)

We tested the hypothesis that the population density of ambrosia beetles at the stand level influences the spatial distribution of infested trees. We evaluated the spatial distribution of the ambrosia beetle, Platypus koryoensis (Murayama) in three oak forest stands that varied in beetle population density using a multi-year trapping survey. We used these data to inform a clustering analysis based on aggregation indices using the SADIE software. Four important findings emerged: (1) the spatial distribution pattern of P. koryoensis at the stand level changed as the population density of the beetle varied; (2) at low population densities, beetle distribution was contagious at the stand level; (3) as beetle population densities increased, the spatial distribution of infested trees became random, potentially due to beetle avoidance of mass attacked trees; and (4) at high beetle population densities, the spatial distribution of infested trees became contagious, possibly due to temporal changes in location of the attack epicenter within the stand. Our results support the hypothesis that beetle population density has consequences for the spatial distribution of infested trees at the within-stand scale. We conclude that the spatial distribution of infested trees is flexible in response to beetle population density, suggesting that beetle attack behaviors are mediated by one or more density-dependent effects.     

Tree response and mountain pine beetle attack preference,reproduction and emergence timing in mixed whitebark and lodgepole pine stands

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The effects of patch richness on con-specific interference in the parasitoid Ibalia leucospoides (Hymenoptera: Ibaliidae)

Abstract We experimentally studied con-specific interference in Ibalia leucospoides, a parasitoid of the woodwasp Sirex noctilio, on pine logs containing variable numbers of woodwasp larvae. Competiton occurred when two different-sized female parasitoids foraged on a host patch, and consequently the small female always abandoned the patch. Regardless of host density, con-specific presence did not affect the attack rate, the number of hosts attacked, nor patch residence time by the winner, when compared to a control female that foraged alone. In contrast, con-specific presence reduced patch time and the number of hosts attacked by the loser. Finally patch time (by both) as well as number of hosts attacked (by the winner only) increased with host density per patch. Our results suggest that con-specific presence has different consequences for different-sized females during patch exploitation.     

Changes in diversity and storage function of ectomycorrhiza and soil organoprofile dynamics after introduction of beech into Scots pine forests

Diversity and storage function of mycorrhiza as well as soil organoprofile formation were investigated in a chronosequence of a pure Scots pine (Pinus sylvestris L.) stand, of Scots pine stands that were underplanted with beech (Fagus sylvatica L.) and in three pure beech stands of different age. Mycorrhiza diversity was higher in the pure beech stands compared to the pure pine stand. Beech and pine trees in the mixed stands had similar dominant mycorrhiza morphotypes. However, trees in two of the three pure beech stands were mycorrhized with other types. Mycorrhizal abundance and nutrient amounts of mycorrhizae associated with beech trees were higher in the mixed and in the pure beech stands compared to pine mycorrhizae indicating that nutrient uptake was higher in older beech than in older pine trees. Humus quality varied from pine to beech stands. Plant litter storage in the humus layer was highest in the youngest mixed stand and lowest in the oldest beech stand. Humus forms changed from moder grass-type in the pure Scots pine stand to mor-like moder and moder rich in fine humus with increasing age of beeches in the mixed stands. The older beech stands were characterised by oligomull and mull-like moder as the dominating humus forms. The ecologically favourable humus forms, i.e., nutrient rich humus forms in the older beech stands correlate well with the higher mycorrhizal diversity and abundance as well as the higher nutrient storage of their mycorrhizae in these stands. The results are also discussed with regard to the 'base-pump effect' of beech trees.     

Biotic and abiotic effects on density,body size,sex ratio,and survival in immature stages of the European woodwasp,Sirex noctilio

Resource quality can have direct or indirect effects on female oviposition choice, offspring growth and survival, and ultimately on body size and sex ratio. We examined these patterns in Sirex noctilio Fabricus, the globally invasive European pine woodwasp, in South African Pinus patula plantations. We studied how tree position as well as natural variation in biotic and abiotic factors influenced sex‐specific density, larval size, tunnel length, male proportion, and survival across development. Twenty infested trees divided into top, middle, and bottom sections were sampled at three time points during larval development. We measured moisture content, bluestain fungal colonization, and co‐occurring insect density and counted, measured, and sexed all immature wasps. A subset of larval tunnels was measured to assess tunnel length and resource use efficiency (tunnel length as a function of immature wasp size). Wasp density increased from the bottoms to the tops of trees for both males and females. However, the largest individuals and the longest tunnels were found in bottom sections. Male bias was strong (~10:1) and likewise differed among sections, with the highest proportion in the middle and top sections. Sex ratios became more strongly male biased due to high female mortality, especially in top and middle sections. Biotic and abiotic factors such as colonization by Diplodia sapinea, weevil (Pissodes sp.) density, and wood moisture explained modest residual variation in our primary mixed effects models (0%–22%). These findings contribute to a more comprehensive understanding of sex‐specific resource quality for S. noctilio and of how variation in key biotic and abiotic factors can influence body size, sex ratio, and survival in this economically important woodwasp.     

Niche‐based relationship between sympatric bark living insect pests and tree vigor decline of Pinus yunnanensis

Forest stands of Pinus yunnanensis Franch in southwestern China are seriously damaged by several bark living insect pests. These pests commonly exist in the same host tree and exploit limited phloem resources. In this study, we hypothesized that sympatric pests would occupy different ecological niches to reduce interspecific competition, and their coordinated attack would aggravate the tree vigor decline of P. yunnanensis. To quantify the ecological niches, we used a sampling method involving three dimensional divisions of tree resource states: (a) sample plot dimension (to evaluate the extent of pest colonization at plot scale), (b) trunk height dimension, and (c) tree vigor dimension. Those attacked pine canopies and colonized trunks were analysed in the field study. The results showed that Tomicus minor and Tomicus yunnanensis both widely and uniformly distributed in lightly, moderately and heavily damaged canopies while they aggregated on particular trunks of dying and withered trees. Lower and middle trunk sections (1–4 m) were mainly occupied by Monochamus alternatus and T. minor, yet T. yunnanensis dominated the upper parts (5–6 m). There was an overlap of the pine shoot beetles in the middle sections (2–4 m), whereas all three species were ecologically segregated in other trunk sections. During the shoot feeding phase, tree vigor declined with pine shoot beetles' increasing shoot feeding density. They coexisted in the same host tree, while M. alternatus only attacked dying and withered tree trunks, causing a greater infestation. Colonization of pine shoot beetle then followed by M. alternatus could be the major causes of tree mortality. This study highlights the resource utilization pattern of sympatric bark living insect pests corresponding with tree vitality. Those findings would help to understand the mechanisms of pest outbreak in P. yunnanensis ecosystem and provide potential guidance for developing an early monitoring pest warning system.     

Evidence of interaction between Sirex noctilio and other species inhabiting the bole of Pinus

• 1 Sirex noctilio is a woodwasp native to Eurasia and Northern Africa and has recently been found infesting pines in eastern North America. Its pest status in this new range is not yet known, although it is an important pest in other areas where it has been introduced. Pinus spp. in North America are hosts to several native and alien species of subcortical insects. Interactions between the woodwasp and these species may influence its distribution or the characteristics of its life history, thus affecting its population dynamics over time.
• 2 Sixty S. noctilio‐infested Pinus spp. were felled in Ontario, Canada, and all phloem‐feeding and woodboring insects were collected and identified from each 1‐m section of the tree.
• 3 Sirex noctilio was in a tree alone 10% of the time but commonly shared the tree with subcortical beetles, such as Tomicus piniperda, Pissodes nemorensis, Ips grandicollis, Gnathotrichus materiarius and Monochamus carolinensis. The woodwasp was distributed throughout the tree stem and this distribution overlapped with that of the beetles.
• 4 Fewer but larger S. noctilio males emerged from trees with beetles compared with those without, although there was no statistical difference in females.
• 5 These findings suggest that co‐habiting beetles could negatively affect S. noctilio population dynamics over time. The potential mechanisms for this interaction are discussed.