Tag: weevils

12 new Oriental weevil species discovered using advanced imaging tools

Two of these new species occur in Japan, including one species found in Yanbaru National Park, Okinawa.

Jake Lewis, an entomologist in the Environmental Science and Informatics Section at the Okinawa Institute of Science and Technology (OIST), is fascinated by weevils, a diverse group of beetles that includes many species with elephant trunk-like mouthparts (called a rostrum). Weevils provide various ecosystem services such as pollination and decomposition, but some species are serious pests known to decimate crop fields and timber forests.

OIST entomologist and Insect Collection Manager, Jake Lewis, searches for weevils on Okinawa Island, Japan. He and his collaborators collected weevils from Japan, Taiwan, Vietnam, and Malaysia, and discovered 12 new species. Photo credit: Merle Naidoo, OIST

Using x-ray microtomography, a 3D imaging technique that uses x-rays to visualize cross sections of the internal structure of objects, Lewis and his collaborators digitally removed scales that cover the cuticle of the weevils. They found that the underlying cuticle differs significantly between species and can therefore be used for taxonomic and classification purposes. Using this technique in combination with traditional light microscopy and DNA barcoding, they discovered, described, and named 12 new weevil species from Japan, Malaysia, Vietnam, and Taiwan. These species range from 1.5 – 3.0 mm in length and are comparatively quite small weevils.

Two of these new species are present in Japan: Aphanerostethus magnus (Oo-daruma-kuchikakushi-zoumushi) and Aphanerostethus japonicus (Nippon-daruma-kuchikakushi-zoumushi). One of these, Aphanerostethus japonicus, is also found in Yanbaru National Park, Okinawa. This is the first time x-ray microtomography has been used to remove obscuring scales to examine underlying differences in morphology for taxonomic purposes. The findings from this study have been published in the open-access journal ZooKeys.

Researchers have discovered, described, and named 12 new weevil species in Japan, Malaysia, Vietnam, and Taiwan. Aphanerostethus magnus and Aphanerostethus japonicus are found in Japan, with the latter also found in Yanbaru National Park, Okinawa. Photo credit: Lewis et al., 2024

The researchers showed that removing scales using x-ray microtomography reveals significant morphological differences between species, which cannot be easily observed using other methods. Consequently, this technique may gain more popularity as a tool for identifying new insect species, especially those covered in scales or debris.

Lewis, OIST’s Insect Collection Manager and lead author of the paper, examined specimens from collections in Canada, Germany, Japan, Malaysia, Taiwan, and the Netherlands. One of the primary goals was to investigate the use of x-ray microtomography as a tool in weevil taxonomy. The genus Aphanerostethus was poorly studied in the past, but many undescribed species were discovered in museum collections around the world, including the two new species from Japan.

X-ray microtomography generated 3D models of weevil species from the genus Aphanerostethus with the right elytron (forewing) removed, revealing differences in the length, width, and pattern of veins in the hindwing. A lateral view of the full body is shown below each closeup for reference. The red, blue, and yellow arrows indicate the base, midpoint, and apex of the hindwing, respectively. A: Aphanerostethus bifidus; B: A. decoratus; C: A. japonicus; D: A. magnus. Image credit: Lewis et al., 2024

Multiple methods to find new species

The researchers used traditional methods such as light microscopy and dissections to observe differences between species, including the scales along the elytra (back), leg spines, and the shape of the rostral canal (a canal that protects the rostrum). They also used DNA barcoding to analyze their genes and create a phylogenetic tree of eight of the species. Some species were not as easy to separate based on morphology alone, but as the gene sequences differ between species, the phylogenetic tree was informative and provided additional evidence of new species.

: Phylogenetic tree of eight Aphanerostethus species constructed by comparing genetic information to see how closely related different species are.  This helped Lewis and his team verify their predictions about species classification by using DNA analysis instead of only physical traits. The colored, vertical bars represent different species and includes the two new species from Japan. Image credit: Lewis et al., 2024

Although the above methods are standard practice in taxonomy, the researchers’ use of X-ray microtomography was novel and was successfully used to examine the structure of not only the hidden cuticle, but also the hindwings. Aphanerostethus weevils have lost the ability to fly due to the gradual reduction of their hindwings, however the degree of reduction was shown to differ between species. Normally, specimens would have to be dissected to view the hindwings, but because x-ray microtomography allows for non-destructive examination of internal anatomy, it is invaluable when working with rare or precious specimens that cannot be dissected or altered.

X-ray microtomography generated 3D models of Aphanerostethus pronota with scales removed, revealing otherwise hidden differences in underlying puncture morphology A–C Aphanerostethus magnus D–F Aphanerostethus morimotoi. Image credit: Lewis et al., 2024

The presence of partially reduced wings in some species offers a fascinating glimpse into the ongoing process of evolutionary change: “Some species have almost completely lost their hindwings, while others still have non-functional half-wings with remaining vein patterns. The differing degrees in hindwing loss is not only useful for taxonomy and systematics, but also shows how different species within the same group can be at different stages of losing a historically highly important organ that played a crucial role in insect evolution,” Lewis explained.

Investing in Japan’s natural heritage

The discovery of new weevil species can be challenging for two main reasons. Firstly, weevils are incredibly diverse, making complete cataloging time consuming and tedious. Secondly, many weevil species are highly host-specific, may only inhabit very particular microhabitats, and may only be active for a short period of time as adults. For example, some species feed on a single tree species and may only occupy a certain part of a tree, such as the canopy. Furthermore, some species of weevils are strictly nocturnal and rarely observed during the daytime.

Episomus mori weevils. Photo credit: Jake H. Lewis

This extreme specialization and variation in natural history means that unless researchers investigate at night and day, across seasons, and focus on specific parts of many different plant species, they will inevitably overlook certain species.  

Dr. Dan Warren, a research fellow at the Gulbali Institute for Applied Ecology and former leader of the Environmental Science and Informatics Section, emphasized the importance of investing in specimen collections: “These specimen collections are crucial for discovering new species and documenting biodiversity changes, both from human activities and natural cycles. They are essential tools for scientific research and conservation biology,” he stated. “Without proper support for them and the people who maintain them, we risk losing irreplaceable information on species and ecosystems, potentially before we even discover them.”

Euthycus weevils. Photo credit: Jake H. Lewis

“These new weevil species are part of Japan’s natural heritage, and although still poorly known ecologically, discovering and naming them is the first step towards an understanding of their biology,” Lewis added. Protected areas like Yanbaru National Park, home to the newly discovered A. japonicus, are essential to the protection of the island’s rich and endemic biodiversity.

Research article:

Citation: Lewis JH, Kojima H, Suenaga M, Petsopoulos D, Fujisawa Y, Truong XL, Warren DL (2024) The era of cybertaxonomy: X-ray microtomography reveals cryptic diversity and concealed cuticular sculpture in Aphanerostethus Voss, 1957 (Coleoptera, Curculionidae). ZooKeys 1217: 1–45. https://doi.org/10.3897/zookeys.1217.126626

Star Wars and Asterix characters amongst 103 beetles new to science from Sulawesi, Indonesia

From left to right: Trigonopterus asterix, T. obelix and T. idefix, three newly described species from Sulawesi (Indonesia). Image by Alexander Riedel.

The Indonesian island of Sulawesi has been long known for its enigmatic fauna, including the deer-pig (babirusa) and the midget buffalo. However, small insects inhabiting the tropical forests have remained largely unexplored.

Such is the case for the tiny weevils of the genus Trigonopterus of which only a single species had been known from the island since 1885. Nevertheless, a recent study conducted by a team of German and Indonesian scientists resulted in the discovery of a total of 103 new to science species, all identified as Trigonopterus. The beetles are described in the open-access journal ZooKeys.

“We had found hundreds of species on the neighboring islands of New Guinea, Borneo and Java – why should Sulawesi with its lush habitats remain an empty space?” asked entomologist and lead author of the study Dr Alexander Riedel, Natural History Museum Karlsruhe (Germany).

In fact, Riedel knew better. Back in 1990, during a survey of the fauna living on rainforest foliage in Central Sulawesi, he encountered the first specimens that would become the subject of the present study. Over the next years, a series of additional fieldwork, carried out in collaboration with the Indonesian Institute of Sciences (LIPI), managed to successfully complete the picture.

“Our survey is not yet complete and possibly we have just scratched the surface. Sulawesi is geologically complex and many areas have never been searched for these small beetles,” said Raden Pramesa Narakusumo, curator of beetles at the Museum Zoologicum Bogoriense (MZB), Indonesian Research Center for Biology.

Dense mountain forest of Central Sulawesi, where some of the new species have been found. Image by Alexander Riedel.

 

Why have all these beetles remained overlooked for so long?

Unlike the all-time favourite stag beetles or jewel beetles, tiny beetles that measure no more than 2-3 millimeters seem to have been attracting little interest from entomologists. Their superficial resemblance does not help identification either.

In fact, the modern taxonomic approach of DNA sequencing seems to be the only efficient method to diagnose these beetles. However, the capacity for this kind of work in Indonesia is very limited. While substantial evidence points to thousands of undescribed species roaming the forests in the region, there is only one full-time position for a beetle researcher at the only Indonesian Zoological Museum near Jakarta. Therefore, international collaboration is crucial.

103 newly discovered species of the genus Trigonopterus from Sulawesi. Image by Alexander Riedel.

103 beetle names

Coming up with as many as 103 novel names for the newly described species was not a particularly easy task for the researchers either. While some of the weevils were best associated with their localities or characteristic morphology, others received quite curious names.

A small greenish and forest-dwelling species was aptly named after the Star Wars character Yoda, while a group of three species were named after Asterix, Obelix and Idefix – the main characters in the French comics series The Adventures of Asterix. Naturally, Trigonopterus obelix is larger and more roundish than his two ‘friends’.

Other curious names include T. artemis and T. satyrus, named after two Greek mythological characters: Artemis, the goddess of hunting and nature and Satyr, a male nature spirit inhabiting remote localities.

Additionally, the names of four of the newly described beetles pay tribute to renowned biologists, including Charles Darwin (father of the Theory of Evolution), Paul D. N. Hebert (implementer of DNA barcoding as a tool in species identification) and Francis H. C. Crick and James D. Watson (discoverers of the structure of DNA).

 

Six-legged déjà vu

Back in 2016, in another weevil discovery, Dr Alexander Riedel and colleagues described four new species from New Britain (Papua New Guinea), which were also placed in the genus Trigonopterus. Similarly, no weevils of the group had been known from the island prior to that study. Interestingly, one of the novel species was given the name of Star Wars’ Chewbacca in reference to the insect’s characteristically dense scales reminiscent of Chewie’s hairiness. Again, T. chewbacca and its three relatives were described in ZooKeys.

The flightless beetle species Trigonopterus chewbacca, described as new to science in 2016. Image by Alexander Riedel.

 

On the origin of Trigonopterus weevils

Sulawesi is at the heart of Wallacea, a biogeographic transition zone between the Australian and Asian regions. The researchers assume that Trigonopterus weevils originated in Australia and New Guinea and later reached Sulawesi. In fact, it was found that only a few populations would one day diversify into more than a hundred species. A more detailed study on the rapid evolution of Sulawesi Trigonopterus is currently in preparation.

 

Future research

To help future taxonomists in their work, in addition to their monograph paper in ZooKeys, the authors have uploaded high-resolution photographs of each species along with a short scientific description to the website Species ID.

“This provides a face to the species name, and this is an important prerequisite for future studies on their evolution,” explained the researchers.

“Studies investigating such evolutionary processes depend on names and clear diagnoses of the species. These are now available, at least for the fauna of Sulawesi.”

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Original Source:

Riedel A, Narakusumo RP (2019) One hundred and three new species of Trigonopterus weevils from Sulawesi. ZooKeys 828: 1-153. https://doi.org/10.3897/zookeys.828.32200

New species of parasitic wasp discovered in the eggs of leaf-rolling weevils in Africa

A new species of parasitic wasp has been obtained from the eggs of weevils, associated with bushwillows, collected and identified by Dr. Silvano Biondi. Given the tiny insect from northeastern Gabon is the first record of its genus for West-Central Africa, the researchers Dr. Stefania Laudonia and Dr. Gennaro Viggiani, both affiliated with Italy’s University of Naples Federico II, decided to celebrate it by assigning the species a name that refers to the continent. Their team has published the findings in the open access journal ZooKeys.

Named Poropoea africana, the new species belongs to a large worldwide group of wasps well-known as egg parasitoids of leaf-rolling weevils. Using characteristically long ovipositors, they lay their own eggs in the eggs of the hosts, found in cigar-like rolls.

The new wasp measures less than 2 mm. It can be distinguished from related species by a number of characters, including the structure of the antennae, and the front and hind legs, which are more robust than the middle ones. The latter, which is a unique trait for the genus, seems to be an adaptation to host parasitisation, where the modified legs likely support the body and improve the propulsive efficiency of the ovipositor.

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Original source:

Laudonia S, Viggiani G, Biondi S (2017) A new species of Poropoea Foerster from Africa (Hymenoptera, Chalcidoidea, Trichogrammatidae). ZooKeys 658: 81-87. https://doi.org/10.3897/zookeys.658.11501

Champions of biodiversity: A weevil genus beats records of explosive evolutive radiation

With as many as 120 recently discovered weevils placed in the genus Laparocerus, it now hosts a total of 237 known species and subspecies. They are all flightless beetles and most of them endemic (living exclusively in one geographic location) to a single island of the archipelagos of Madeira, Selvagens and the Canary Islands (17 islands in total). Only two species inhabit Morocco, the nearest continental land.

Independent Canarian entomologist Dr. Antonio Machado, who has been collecting and studying this genus of weevils for the last sixteen years and researched 46,500 specimens so far, was helped by geneticist Dr. Mariano Hernández, from the University of La Laguna, Tenerife, Canary Islands, Spain, to undertake a phylogenetic study using three mitochondrial genes and one nuclear gene. The resulting phylogenetic tree also allowed for estimating the whole evolutionary process along a timeframe of about 11.2 million years. Their study is published in the open access journal ZooKeys.

The molecular analysis confirms that all Laparocerus weevils have a common evolutionary ancestor (monophyly), but could not clarify whether that ancient founding species arrived from southern Europe or northwestern Africa. The two extant Moroccan species were found to be the result of a back-colonisation from the Canary Islands to Africa, and not the ancestral source lineage, which unfortunately is still unknown.

weevils PR 2Colonisation of Macaronesia started in Porto Santo, Madeiran archipelago, which is the oldest island, and from there it ‘jumped’ to Madeira and the Desertas. The colonisation of the Canary Islands started shortly after, and it basically moved stepwise from the east to the west in line with the decreasing age of the volcanic islands. Yet, there have been several back-colonisations, as well (see map). Large islands, such as Tenerife (2034 km2), ended up with 65 species and subspecies. Globally, there is an outstanding ratio of one endemic Laparocerus for each 35.7 km2; a record not beaten by any other genus of plant or animal in Macaronesia.

The evolutionary process responsible for such richness comprises sequential radiation events in these archipelagoes, each generating several monophyletic groups. These groups, 20 in total, have been recognised as subgenera of Laparocerus, and five of them — Aridotrox, Belicarius, Bencomius, Canariotrox, and Purpuranius — are described as new to science in this study. Colonisation routes, habitat shifts, disruption of populations by volcanism, dispersal by massive landslides, and other relevant aspects for adaptive and non-adaptive radiation, are largely discussed and confronted with previously published data referring to other groups of beetles or to other biological organisms (spiders, bush crickets, plants, etc.).

“If oceanic islands have been traditionally considered as laboratories of evolution and species-producing machines, Laparocerus will become the ideal guinea-pig for broadening studies in dispersal and speciation processes of all kinds,” say the authors. “Working with such a group is like getting a picture of Nature with more pixels. Several intriguing cases highlighted in this contribution may turn into the inspiration for further phylogeographic research.”

The scientists hope that, in near future Laparocerus will merit sharing the podium with Darwin´s finches or Drosophila in the studies of island evolution”.

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Original source:

Machado A, Rodríguez-Expósito E, López M, Hernández M (2017) Phylogenetic analysis of the genus Laparocerus, with comments on colonisation and diversification in Macaronesia (Coleoptera, Curculionidae, Entiminae). Zookeys 651: 1-77 (02 Feb 2017) https://doi.org/10.3897/zookeys.651.10097