1,720,974 research outputs found
Barbitistes vicetinus outbreaks in forest ecosystems (Orthoptera, Tettigoniidae)
Full text linkBarbitistes vicetinus (Galvagni & Fontana, 1993) (Orthoptera, Tettigoniidae) è un ortottero forestale endemico dell’Italia nord-orientale descritto nei primi anni ’90 e considerato specie rara per almeno 10 anni dopo il suo primo rinvenimento. Dal 2008, intense pullulazioni si sono ripetute nel suo areale collinare, causando gravi defogliazioni ai boschi e alle colture limitrofe. Al fine di approfondire le scarse conoscenze attualmente disponibili e fornire un primo approccio alla gestione delle esplosioni demografiche, il presente lavoro si focalizza principalmente su indagini biologiche ed ecologiche inerenti a questa specie.
In particolare, la riproduzione di B. vicetinus è stata studiata in 18 siti nel corso di 3 anni consecutivi (2013-2015), testando l’influenza della tipologia di vegetazione e della copertura del suolo sulla scelta dei siti di deposizione e sulla schiusa delle uova. Per la prima volta la densità di popolazione è stata indagata durante una pullulazione, facendo registrare valori medi superiori a 1 milione di individui/ha. I risultati ottenuti col presente lavoro indicano che, nonostante gli individui adulti di questa specie possano frequentemente alimentarsi sulle coltivazioni agrarie causando danni anche gravi, queste aree non costituiscono siti preferenziali per l’ovideposizione. Infatti, le più elevate densità di neanidi sono state rinvenute in aree boscate e con terreno coperto la lettiera di latifoglie, senza che, peraltro, venisse evidenziato un gradiente di densità progredendo dal margine del bosco verso il suo interno.
Negli stessi siti, in 4 anni consecutivi (2013-2016), il presente lavoro ha inoltre considerato la fenologia delle schiuse con l’obiettivo di incrementare le conoscenze sulla dinamica di popolazione delle neanidi e chiarire il ruolo di alcuni fattori ambientali nei riguardi di questi aspetti. Un effetto significativo della temperatura è stato riscontato sulle tempistiche di schiusa, evidenziando che la specie è in grado di schiudere anche a temperature basse (6°C). E’ stato inoltre dimostrato un ruolo fondamentale dell’altitudine e dell’esposizione sulle schiuse, ancora una volta in relazione al fattore temperatura.
Un’indagine specifica ha preso in considerazione l’ecologia spaziale della specie, studiando come diverse variabili, su differenti scale spaziali, influenzano la densità di popolazione. In due anni consecutivi (2014-2015) lo studio ha indagato 200 siti ricadenti entro l’area coinvolta dalle pullulazioni. Su una scala spaziale relativamente piccola (250-500 m) è stato riscontrato un effetto negativo della frammentazione forestale sulla densità di popolazione dell’insetto. Inoltre, sulla stessa scala spaziale, la presenza di specie
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forestali alloctone e sgradite all’insetto, in particolare la robinia, è corrisposta ad un’ulteriore riduzione della presenza di B. vicetinus, indipendentemente da quale fosse la composizione forestale su scala locale (10 m). Proprio su una scala locale, invece, si evince come l’insetto sia in grado di alimentarsi su un’ampia gamma di latifoglie forestali, causando intense defogliazioni, con danni medi fino al 40% nelle specie più colpite. Su una scala di paesaggio, la popolazione è globalmente diminuita tra il 2014 e il 2015, con un maggiore effetto dove la defogliazione dell’anno precedente era stata più intensa.
Il presente lavoro fornisce le prime conoscenze di base per questa specie riguardo la bio-ecologia di popolazioni in fase di pullulazione. Le informazioni acquisite riguardo la fenologia di schiusa e la scelta dei siti di ovideposizione rappresentano il primo passo per una gestione razionale delle esplosioni demografiche. Inoltre, l’analisi previsionale delle pullulazioni, basata sulla conoscenza della composizione del paesaggio nelle aree potenzialmente a rischio, potrà fornire un ulteriore contributo in tal senso. Infine, la comparazione di queste conoscenze con quelle relative ad altri ortotteri forestali potrà condurre a una maggiore e migliore comprensione del rapporto fitofago - pianta ospite anche in altri contesti modello
Forti presenze di Barbitistes vicetinus (Orthoptera, Ensifera) nei Colli Euganei. Note biologiche e possibilità di controllo.
No full textDefogliazioni di Barbitistes vicetinus (Orthoptera, Tettigoniidae) nei boschi dell’Italia nord orientale
No full textCan extensively managed perennial crops serve as surrogate habitat for orthopterans typical of dry calcareous grasslands?
No full textBoth agricultural intensification and abandonment are considered among the main drivers of biodiversity loss, especially for species typical of semi-natural grasslands. In the Mediterranean regions, semi-natural grasslands are often abandoned or replaced by perennial crops such as vineyards and olive groves with potential negative consequences on the associated diversity. However, when these crops are managed under low-intensity practices, their inter-row grass cover can potentially provide suitable habitats for grassland specialists. Here, we analysed the effects of land use on orthopterans by sampling 67 sites belonging to four different habitats (vineyards, olive groves, semi-natural grasslands and abandoned semi-natural grasslands) along a landscape composition gradient. Overall, species richness was highest in abandoned grasslands, while vineyards presented the lowest diversity. Semi-natural grasslands and olive orchards presented intermediate and similar species richness. However, this effect was significant only for Ensifera species, while species richness of Caelifera did not differ between the four habitats. Increasing forest cover within a scale radius of 500 m also increased Ensifera species richness probably providing undisturbed refugia at the margins. Orthopteran abundance was higher in semi-natural grasslands than in abandoned grasslands and vineyards. Despite the differences in species richness, we observed large overlap in species composition between olive groves and semi-natural grasslands suggesting that perennial crops managed under traditional, non-intensive practices can provide suitable habitats for orthopterans typical of semi-natural grasslands. In particular, olive groves appeared to be a better surrogate habitat than vineyards for the conservation of both Ensifera and Caelifera
Increasing temperatures affect multiyear life cycle of the outbreak bush-cricket Barbitistes vicetinus (Orthoptera, Tettigoniidae)
No full textAlthough outbreaks of rare species are unusual, several insect species have become emerging pests probably due to the ongoing environmental changes. Barbitistes vicetinus was first described in 1993 as an endemic bush-cricket of north-east Italy and was considered rare until 2008, when it became an established pest, causing severe damages to forests and crops. The possible role of temperature in changing its life cycle has still to be fully understood. Here, we explored the effect of summer temperature on egg diapause and the effect of winter temperature on egg survival. Field observations showed that the proportion of embryos that can complete development at the end of summer ranged from zero to nearly 90% depending on summer temperatures. A substantial shift in the rate of development from 20% to nearly 80% occurred in a thermal range of about 1 °C. On the contrary, overwinter egg survival was high and constant (90%) across a wide range of winter temperatures that go well beyond both the cold and warm thermal limits of the current species range. Overall, the results suggest a potential key role of summer temperature warming on the outbreak propensity of this species that is able to switch from a multiyear to an annual life cycle with just a 1–2 °C warming
Fungal communities associated with gallery systems of the European shot-hole borer (Anisandrus dispar) in declining oak trees
No full textTaxonomic identification and biological traits of Platystethynium triclavatum (Donev & Huber, 2002), comb. n. (Hymenoptera, Mymaridae), a newly recorded egg parasitoid of the Italian endemic pest Barbitistes vicetinus (Orthoptera, Tettigoniidae)
Full text linkThe little known fairyfly (Hymenoptera, Mymaridae), Platystethynium
(Platystethynium) triclavatum (Donev & Huber, 2002), comb. n. from
Pseudocleruchus Donev & Huber, 2002, is newly recorded as an egg parasitoid of
Barbitistes vicetinus Galvagni & Fontana, 1993 (Orthoptera, Tettigoniidae).
This bush-cricket is endemic to northeastern Italy (mainly Euganean Hills of
Veneto Region), where it has recently become an economically significant
agricultural and forest pest. Data on discovery, distribution, and some remarkable
biological traits of this gregarious egg parasitoid are presented. Its identification
and availability of many well-preserved fresh specimens have made possible
to re-define Pseudocleruchus Donev & Huber, 2002 syn. n., with type and the
only described species Pseudocleruchus triclavatus Donev & Huber, 2002,
as a synonym of Platystethynium Ogloblin, 1946 and its nominate subgenus,
P. (Platystethynium), and also to describe the brachypterous male of
P. (Platystethynium) triclavatum. It is the first known male for the entire genus.
Enlarged mandibles of the megacephalous males are used to chew holes in the hard
chorion of the host egg, allowing fully winged females, whose mandibles are
strongly reduced and do not cross over, to emerge after mating with the males
inside it. Up to 136 individual parasitoids (about 77 on average) can hatch from a
single egg of B. vicetinus, with their sex ratio being strongly female biased (80–97%
females per egg)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
High genetic diversity in the Culex pipiens complex from a West Nile Virus epidemic area in Southern Europe
Full text linkBackground
The Culex pipiens complex includes the most widespread mosquito species in the world. Cx. pipiens is the primary vector of the West Nile Virus (WNV) in Europe and North America. Cases of WNV have been recorded in Italy since 1998. In particular, wet areas along the Po River are considered some of the most WNV affected areas in Italy. Here, we analyzed the genetic structure of ten Cx. pipiens populations collected in the last part of the Po River including the Delta area.
Methods
We assessed the genetic variability of two mitochondrial markers, cytochrome oxidase 1 (COI) and 2 (COII), for a total of 1200 bp, and one nuclear marker, a fragment of acetylcholinesterase-2 (ace-2), 502 bp long. The effect of the landscape features was evaluated comparing haplotype and nucleotide diversity with the landscape composition.
Results
The analysis showed a high genetic diversity in both COI and COII gene fragments mainly shared by the populations in the Delta area. The COI-COII network showed that the set of haplotypes found was grouped into three main supported lineages with the higher genetic variability gathered in two of the three lineages. By contrast, ace-2 fragment did not show the same differentiation, displaying alleles grouped in a single clade. Finally, a positive correlation between mitochondrial diversity and natural wetland areas was found.
Conclusions
The high mitochondrial genetic diversity found in Cx. pipiens populations from the Po River Delta contrasts with the low variability of inland populations. The different patterns of genetic diversity found comparing mitochondrial and nuclear markers could be explained by factors such as differences in effective population size between markers, sex biased dispersal or lower fitness of dispersing females. Moreover, the correlation between genetic diversity and wetland areas is consistent with ecosystem stability and lack of insecticide pressure characteristic of this habitat. The mtDNA polymorphism found in the Po River Delta is even more interesting due to possible linkages between the mitochondrial lineages and different biting behaviors of the mosquitoes influencing their vector ability of arboviral infections
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