Host tissue identification for cryptic hymenopteran parasitoids associated with Sirex noctilio

相似文献   

Emergence of adult female Sirex nigricornis F. and Sirex noctilio F. (Hymenoptera: Siricidae) coincides with a decrease in daily minimum and maximum temperature

相似文献   

Symbionts mediate oviposition behaviour in invasive and native woodwasps

相似文献   

Local antagonism and resource partitioning between two invasive pine plantation pests

相似文献   

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.     

Beneath the bark: associations among Sirex noctilio development,bluestain fungi,and pine host species in North America

1. Invasive species with global distributions encounter unique environmental and biotic variables that can greatly affect the magnitude of their impact. The European woodwasp, Sirex noctilio Fabricius, is a prime example that has invaded climatically and ecologically distinct ecosystems across the Southern Hemisphere and, more recently, North America. 2. Northeastern North America presents a unique set of conditions, including pine host species, native parasitoids, a diverse assemblage of native co‐colonising insects, and fungal associates of these co‐colonisers. In North America, S. noctilio attacks both a naturalised ancestral host (Pinus sylvestris L.) from Europe and a naïve native host (P. resinosa). A large assemblage of insects and their associated bluestaining ophiostomatoid fungi colonise these pines. Competition between S. noctilio and this group is a hypothesised mechanism of biotic resistance in the invaded region of North America, possibly via superior resource capture abilities or alteration of host tissue by bluestain fungi. 3. Investigating these ecological interactions is challenging because they manifest deep in the xylem tissue. To overcome this, 30 experimentally stressed trees were systematically dissected with an electric log splitter to investigate the effects of bluestain fungi and tree factors on S. noctilio development and parasitism by native hymenopterans. 4. Body size and colonisation density were affected by pine species, with S. noctilio being 25% larger and densities three‐fold greater in P. sylvestris than P. resinosa. Survivorship was slightly negatively correlated with the proportional volume of bluestain infection. Interestingly, rhyssine (Rhyssa and Megarhyssa spp.) parasitism responded positively to greater S. noctilio density, but there was no density relationship with Ibalia leucospoides ensiger parasitism. Pine host species appears to play a strong role in S. noctilio development, which is important considering uninvaded regions of North America have a diversity of pine species that likely vary in their susceptibility to this woodborer.     

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.     

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.     

Putative source of the invasive Sirex noctilio fungal symbiont, Amylostereum areolatum, in the eastern United States and its association with native siricid woodwasps

Two genotypes of the fungal symbiont Amylostereum areolatum are associated with the invasive woodwasp Sirex noctilio first found in North America in 2004. S. noctilio is native to Europe but has been introduced to Australasia, South America and Africa where it has caused enormous losses in pine plantations. Based on nucleotide sequence data from the intergenic spacer region (IGS) of the nuclear ribosomal DNA, the A. areolatum genotypes found in North America are most similar to genotypes found in Europe, and not to genotypes from the southern hemisphere. Although two IGS strains of A. areolatum were found in North America it cannot be stated whether A. areolatum was introduced to North America from Europe once or twice based on our study. Genetic groupings formed by sequencing data were in most cases supported by vegetative compatibility groups (VCGs). Other siricid woodwasp species in the genus Sirex are native to North America. The North American native Sirex edwardsii emerging from the same tree as S. noctilio carried the same strain of A. areolatum as S. noctilio. The North American native Sirex sp. ‘nitidus’ collected outside the geographical range of S. noctilio carried a unique strain within A. areolatum. Our findings of A. areolatum in the native North American species, S. sp. ‘nitidus’, contrast with the previous view that A. areolatum was not present in North America before the accidental invasion of S. noctilio.     

Fidelity Among Sirex Woodwasps and Their Fungal Symbionts

We report that associations between mutualistic fungi and their economically and ecologically important woodwasp hosts are not always specific as was previously assumed. Woodwasps in the genus Sirex engage in obligate nutritional ectosymbioses with two species of Amylostereum, a homobasid\iomycete genus of white rot fungi. In the present study, the Amylostereum species and genotypes associated with three species of Sirex native to eastern North America and one relatively recent invasive Sirex from Europe were investigated by comparing intergenic spacer regions (IGS). Sirex spp. were sampled over 6 years from 23 sites in six US states, ranging from Maine in the northeast to Louisiana in the southeast, to obtain samples of Amylostereum from mycangia of adult females. Two of the native Sirex species (Sirex nigricornis and Sirex nitidus) were associated with either Amylostereum chailletii or Amylostereum areolatum, refuting the hypothesis of strict species-specific relationships. However, the invasive Sirex noctilio and the native Sirex cyaneus were each collected with only A. areolatum or A. chailletii, respectively, although S. noctilio was associated with two different IGS genotypes of A. areolatum and S. cyaneus occurs sympatrically with the other native Sirex. In Pinus, the preferred host tree of S. nigricornis and S. noctilio, these species co-occurred in 25.9 % of trees sampled, and horizontal transmission of fungal strains from S. noctilio to S. nigricornis was documented, although only in one tree. The extent that further spread and establishment of S. noctilio will alter the composition of symbionts carried by native Sirex is unknown but will depend in part on the degree of flexibility in these host–symbiont associations.     

Influence of the community of associates on Sirex noctilio brood production is contextual

1. Competition and predation are important components of biotic resistance, which helps define the invasibility of an ecosystem. 2. To search for evidence of biotic resistance to the European woodwasp, Sirex noctilio Fabricius, in North America, cages were used to experimentally exclude the community of associates (natural enemies and competitors) from infested logs. Specifically, the study assessed S. noctilio brood production in pine forests in Ontario and New York, where there was a rich existing community of associates (other wood borers, bark beetles and associated fungi, and parasitoids), and in South Africa, where siricid wasps and pines are not native and a similar associate community is not present. In addition, in Ontario, associates were excluded by size, and for different periods of time to identify important associates and their temporal dynamics. 3. Evidence was found that biotic factors limit S. noctilio in North America, whereby exclusion of natural enemies and competitors had a positive influence on the abundance or presence of S. noctilio brood in Ontario and New York. This influence was absent in South Africa. 4. It is unclear which member(s) of the associated insect community in North America were most important in limiting S. noctilio brood production, although they probably acted quickly (< 2 weeks) following S. noctilio oviposition. 5. Further study is needed to determine whether associates have limited S. noctilio populations in pine forests throughout northeastern North America, and which specific natural enemies and/or competitors are important.     

Multiple introductions of <Emphasis Type="Italic">Sirex noctilio</Emphasis> (Hymenoptera: Siricidae) in northeastern North America based on microsatellite genotypes,and implications for biological control

The invasive woodwasp Sirex noctilio (Hymenoptera: Siricidae) has been moved from Eurasia into regions in the Southern Hemisphere, where extensive tree mortality has occurred in pines (Pinus spp.) introduced for forestry. More recently this woodwasp was found in northeastern North America, where pines are native, and it is a species of concern due to the economic importance of pines. Understanding the genetic diversity of North American S. noctilio points to new areas of inquiry, particularly regarding the ability of parasitic nematodes to sterilize woodwasps, which could provide control methods in the US and/or Canada. We investigated the genetic diversity of 924 S. noctilio from nine populations from New York and Pennsylvania (US), Ontario (CA), and Queensland (AU) using nine microsatellite loci. To avoid inflating the number of populations estimated by Bayesian inference, we measured the full-sibling relationships of woodwasps within 13 trees and removed all but one member of each full-sib family from the genetic analysis, resulting in a final sample size of 741 S. noctilio. Within a tree, on average 39% of woodwasps did not have a full sibling, and there were 5.6 families with at least two full-sibling members per tree. The mean family size across trees was 1.9 when single offspring (i.e., no full siblings) were included. Given the short time span since invasion, variation within North American S. noctilio is likely due to differences among founding genotypes. Genetic analyses support the hypothesis that at least two separate introductions occurred. Within North America, genetic distance measures were greatest between a site in southwestern Ontario and all other sites, suggesting that this population could represent a separate introduction event. Two methods of Bayesian clustering also support this idea; they detected 4 or 5 distinct genetic clusters with little admixture between the southwestern Ontario site and other North American populations. The wasps from Australia, where biological control with nematodes has been successful, showed low genetic diversity and clustered with the southwestern Ontario population in one out of two Bayesian analyses. Within the Ontario subset of samples, high woodwasp activity level (i.e., attack and mortality of trees) was associated with one genetic cluster more strongly than another. Population variation should be taken into account in studies of S. noctilio spread and management within North America.     

Predicting Sirex noctilio and S. nigricornis emergence using degree days

The study of temporal interactions between native insects and alien invaders can be facilitated by the ability to forecast adult emergence. We used field‐collected adult emergence data of Sirex noctilio Fabricius (Hymenoptera: Siricidae), a woodwasp native of Eurasia that has recently invaded northeastern North America, and Sirex nigricornis Fabricius, a woodwasp native to North America, to develop and test cumulative degree‐day (CDD) models. Five data sets were collected each in Ontario, Canada (S. noctilio) and Louisiana, USA (S. nigricornis) over 4 years; three data sets were used to develop models and two were used to test them. Males and females of each species were modelled separately. After testing several potential temperatures, chosen thresholds for CDD were 0 °C lower threshold and 25 °C upper threshold for both Sirex spp. We used a three‐parameter Gompertz growth function to model Sirex spp. emergence against CDD. Models predicted 10% emergence of S. noctilio in Ontario after 1 239 and 1 280 CDD, for males (start date = 1 April; R² = 0.91) and females (start date = 1 April; R² = 0.86), respectively. Models predicted 10% emergence of S. nigricornis in Louisiana after 3 980 and 5 016 CDD, for males (start date = 1 May; R² = 0.83) and females (start date = 1 March; R² = 0.73), respectively. Cumulative degree‐day models predicted 10 and 90% emergence of woodwasp populations with less error (1–13%) than they did 50% emergence (5–27%). For both Sirex spp., male emergence began a few days before and concluded at about the same time as that of females. In southern Ontario, models predict that S. noctilio adults will be in flight between 1 015 and 2 430 CDD (1 April start date for CDD; from early‐July until mid‐September). In Louisiana, models predict that S. nigricornis adults will be in flight between 3 854 and 4 700 CDD (1 May start date for CDD; from early‐October until late‐November).     

Evidence that the availability of suitable pine limits non‐native Sirex noctilio in Ontario

相似文献   

Lack of fidelity revealed in an insect–fungal mutualism after invasion

Symbiont fidelity is an important mechanism in the evolution and stability of mutualisms. Strict fidelity has been assumed for the obligate mutualism between Sirex woodwasps and their mutualistic Amylostereum fungi. This assumption has been challenged in North America where the European woodwasp, Sirex noctilio, and its fungal mutualist, Amylostereum areolatum, have recently been introduced. We investigate the specificity of the mutualism between Sirex and Amylostereum species in Canada, where S. noctilio co-infests Pinus with native Sirex nigricornis and its mutualist, Amylostereum chailletii. Using phylogenetic and culture methods, we show that extensive, reciprocal exchange of fungal species and strains is occurring, with 75.3 per cent of S. nigricornis carrying A. areolatum and 3.5 per cent of S. noctilio carrying A. chailletii. These findings show that the apparent specificity of the mutualism between Sirex spp. and their associated Amylostereum spp. is not the result of specific biological mechanisms that maintain symbiont fidelity. Rather, partner switching may be common when shifting geographical distributions driven by ecological or anthropogenic forces bring host and mutualist pairs into sympatry. Such novel associations have potentially profound consequences for fitness and virulence. Symbiont sharing, if it occurs commonly, may represent an important but overlooked mechanism of community change linked to biological invasions.     

Retracing the routes of introduction of invasive species: the case of the Sirex noctilio woodwasp

Understanding the evolutionary histories of invasive species is critical to adopt appropriate management strategies, but this process can be exceedingly complex to unravel. As illustrated in this study of the worldwide invasion of the woodwasp Sirex noctilio, population genetic analyses using coalescent‐based scenario testing together with Bayesian clustering and historical records provide opportunities to address this problem. The pest spread from its native Eurasian range to the Southern Hemisphere in the 1900s and recently to Northern America, where it poses economic and potentially ecological threats to planted and native Pinus spp. To investigate the origins and pathways of invasion, samples from five continents were analysed using microsatellite and sequence data. The results of clustering analysis and scenario testing suggest that the invasion history is much more complex than previously believed, with most of the populations being admixtures resulting from independent introductions from Europe and subsequent spread among the invaded areas. Clustering analyses revealed two major source gene pools, one of which the scenario testing suggests is an as yet unsampled source. Results also shed light on the microevolutionary processes occurring during introductions, and showed that only few specimens gave rise to some of the populations. Analyses of microsatellites using clustering and scenario testing considered against historical data drastically altered our understanding of the invasion history of S. noctilio and will have important implications for the strategies employed to fight its spread. This study illustrates the value of combining clustering and ABC methods in a comprehensive framework to dissect the complex patterns of spread of global invaders.     

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.

     

Perception and knowledge of the Sirex woodwasp and other forest pests in South Africa

• 1 Sirex noctilio F. (Siricidae: Hymenoptera) is one of the most serious invasive pests of pine. In South Africa, there has been a national effort to control S. noctilio, including a campaign to increase awareness of the pest amongst the local forestry community.
• 2 We considered the impacts that the arrival of the pest and the awareness campaign have had on perceptions and knowledge of S. noctilio, as well as other forestry pests, amongst members of the forestry community.
• 3 For data collection, a survey questionnaire was developed and used in telephone interviews.
• 4 The results obtained in the present study showed that the Sirex awareness campaign had increased knowledge of forestry pests in general but basic knowledge regarding the identification and symptoms of specific pests, such as S. noctilio, was poor. This will negatively influence monitoring efficacy.
• 5 Traditional paper‐based media and personal contact contributed most to enhanced awareness. Electronic media were less effective and improvement would require a more focused effort. It was of concern that private farmers and contractors, as well as non‐European first language speakers, were less well informed about forestry pests.
• 6 Clearly, a fragmented landscape in terms of ownership and language, presents challenges for effective communication of forestry pest threats.

     

Variables associated with the occurrence of Ips beetles,red turpentine beetle and wood borers in live and dead ponderosa pines with post‐fire injury

相似文献   

Assessing trap and lure effectiveness for the monitoring of Sirex noctilio

相似文献