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The Asian seed beetle Megabruchidius dorsalis, which develops inside the seeds of native Gleditsia species, was first recorded in Europe in Italy in 1989. In Slovenia, it was first recorded in Maribor in 2017. Its presence was confirmed in 15 other European countries. In the new range, the seed beetle switched to two new hosts from North America, the honey locust (Gleditsia triacanthos) and the Kentucky coffeetree (Gymnocladus dioicus) both related to the Asian Gleditsia species. Mature G. triacanthos and Gy. dioicus seed pods were collected from the ground at locations in the central and the northeastern parts of Slovenia to investigate the presence of M. dorsalis outside the first described locations in Maribor. Seed pods were kept in bags under constant conditions in laboratory. Exit holes of seed pods and seeds typical of M. dorsalis were found at 36 locations (97%), while alive or dead M. dorsalis beetles were recorded at 26 locations (70%). Azijski hrošč semenar Megabruchidius dorsalis, ki se razvija v semenih azijskih vrst gledičevk (Gleditsia), je bil v Evropi prvič zabeležen v Italiji leta 1989, v Sloveniji pa prvič v Mariboru leta 2017. Pojavlja se še v 15 drugih evropskih državah. V novem okolju je vrsta preskočila na dva nova gostitelja iz Severne Amerike, trnato gledičevko (Gleditsia triacanthos) in rogovilarja (Gymnoladus dioicus), sicer oba sorodna azijskim vrstam gledičevke. Med našo raziskavo smo nabrali zrele stroke trnate gledičevke in rogovilarja na različnih lokacijah po osrednji in severovzhodni Sloveniji z namenom raziskati razširjenost M. dorsalis zunaj prvih opisanih lokacij v Mariboru. Stroke smo gojili v gojitvenih vrečah pod stalnimi razmerami v laboratoriju. Vrsto M. dorsalis smo potrdili v šestih krajih po Sloveniji. Na 36 lokacijah (97 %) smo našli izhodne luknje na strokih in semenih, značilne za M. dorsalis, žive ali mrtve hrošče pa smo našli na 26 lokacijah (70 %).

Novel interactions between introduced and native species commonly occur and can even be predicted from existing native interactions in a certain area. However, novel interactions between two species both alien to a region are less common and can result in intriguing relationships. In this study, we investigate how the North American honey locust Gleditsia triacanthos might benefit from a novel interaction with an Asian monophagous seed beetle Megabruchidius dorsalis, which recently switched its host, in the introduced range of Europe. The honey locust tree is a popular ornamental in Europe and has been reported to escape cultivated areas. We observed spontaneous occurrence of seedlings, saplings, and young trees in the wider urban area of Maribor, Slovenia. We collected mature honey locust pods at several locations and investigated the possible reasons for dormancy break in physically dormant seeds and their successful germination in an urban environment by performing imbibition and germination experiments with variously treated seeds. Our results show that the success of honey locust imbibition and germination can be related to M. dorsalis larva acting as a scarifying agent and thus breaking the seed dormancy, delaying germination, and enabling asynchronous germination. However, the beneficial effect of larvae on germination is possible only if the larva drills the entrance hole, but dies before the seed germinates. Here we show that novel interaction established can occasionally act as mutual facilitation in which each species aids the other to exist and even to increase their invasion success.

Megabruchidius dorsalis and Bruchidius coreanus are sympatric bean weevil species that bore into Gleditsia sinensis seeds, seriously affecting the commercial development of this plant. Here, we aimed to understand potential changes in the distribution of these two sympatric pests under current and future climate conditions to provide a reference for the prediction of their occurrence and facilitate their prevention and control. Based on empirical field data, we predicted the potential distribution of M. dorsalis and B. coreanus in suitable habitat areas using the MaxEnt model and explored the relationships among different spatiotemporal distributions using change analysis. Our findings showed that compared with the current situation, the suitable areas for M. dorsalis and B. coreanus were predicted to increase by 4.8141% and 3.1009%, respectively, in the future. Isothermality (BIO3), min temperature of coldest month (BIO6), and variance in precipitation (BIO15) in the coldest month were determined to be the main factors restricting the current distribution of M. dorsalis and B. coreanus. Areas currently suitable for the two species are mainly in the central region of Guizhou and are predicted to move eastward in the future. Significant area under the receiver operating characteristics curve values for M. dorsalis (0.878) and B. coreanus (0.833) indicated that MaxEnt could be used to predict the potential habitats of these weevils, providing valuable information to inform their control in Guizhou Province.

Megabruchidius dorsalis (Fåhraeus, 1839) (Coleoptera: Bruchinae) is an important pest that damages the seeds of Gleditsia L. (Fabaceae: Caesalpinioideae). This beetle searches for host plants with its sensory system. To further explore the mechanisms of host location and to understand the ultrastructure of M. dorsalis, we examined the morphology and distribution of its sensilla on the antennae and mouthparts of male and female adults, using scanning electron microscopy (SEM). Both male and female antennae are serrated and can be divided into scape, pedicel, and flagellum. There were seven types and eight subtypes of antennal sensilla, including Bőhm bristles (BB), two subtypes of sensilla trichoid (ST1, ST2), two subtypes of sensilla chaetica (SC1, SC2), four subtypes of sensilla basiconic (SB1, SB2, SB3, SB4), sensilla cavity (SCa), sensilla auricillica (SA), and sensilla gemmiformium (SG). Five types of maxillary and labial palp sensilla in the mouthparts were observed: sensilla chaetica (SC), sensilla trichoidea (ST), sensilla styloconica (SSt), sensilla coeloconica (SCo), and sensilla digitiform (SD). No sexual dimorphism in sensilla type was observed, but there were variations between males and females in the numbers and distribution along the antennae. There were more SA in males than in females, while the number of ST sensilla in the maxillary palps were lower in males than in females. ST1 were most abundant in both sexes. We discussed potential function related to structure via comparisons with previous investigations of bruchids and other insects. Our results provide a theoretical basis for further studies on sensory physiological function, using semiochemicals as effective biological controls of M. dorsalis.

На юго-востоке Казахстана (город Алматы и окрестности) вид зерновки Megabruchidius dorsalis Fahreus, 1839 известен с 2016 года, и в настоящее время отмечен повсюду, где произрастают его кормовые растения. В Туркестанской области ранее обнаруживался нами только в г. Шымкент, и высказывалось предположение о возможности его дальнейшеего расселения в окрестностях города и в области. Мы обнаружили этот вид в городе Кентау и окрестностях в Туркестанской области на юге Казахстана. Найденные особи относились к разным полам. Семена Gleditsia triacanthos, собранные и просмотренные нами, были повреждены всего на 10 %. Это позволяет сделать вывод, что вид уже интродуцировался в Кентауской городской агломерации, но еще не достиг максимальной численности и продолжает постепенно расселяться в её пределах. Это указывает на расширение ареала вредителя в пределах юга страны. Инвазия вида произошла из города Шымкент (южный Казахстан), куда в свою очередь вид попал из г. Алматы (юго-восточный Казахстан), откуда он был известен с 2016 года.