Platypus quercivorus

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Platypus quercivorus
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Curculionidae
Genus: Platypus
Species:
P. quercivorus
Binomial name
Platypus quercivorus
Murayama, 1925 [1]

Platypus quercivorus, the oak ambrosia beetle, is a species of weevil and pest of broad-leaved trees. [2] This species is most commonly known for vectoring the fungus responsible for excessive oak dieback in Japan since the 1980s. [3] It is found in Japan, India, Indonesia, New Guinea, and Taiwan.

Contents

Description

Since P. quercivorus belongs to the Platypodinae, it has distinct clubs on the end of its stout antennae with three solid segments. [4] Usually, the beetle is between 4 and 5 mm long, reddish-brown in colour, and is elongate and roughly cylindrical. [4] The prothorax is as wide as the head. [4]

Males have a shallow, unarmed plate on the underside of the thorax and a convex and downward slope of their elytra. [4] The elytra have a broad square end and spines at the top. [4]

Females have a mycangium on the pronotum for carrying symbiotic fungi spores. [5] [4] Although this trait may be in both females and males, it is always in females and rarely in males. [4]

Habitat

Although well known in Japan, this species also lives in India, Indonesia, New Guinea and Taiwan. [3] [6]

Trees to inhabit are often selected for based on olfactory and visual cues. [7] Infestation of these habitats occurs in stages beginning with males flying to and landing on a tree and then boring into the bark through the stems. [7] [6] Typically, this species aggregates in areas with clusters of similar, suitable trees to increase infestation efficiency. [7] This may be due to coevolutionary factors with tree species Quercus crispula as it is most suitable for gallery formation and is distributed in a clumped pattern. [8] This allows for an increased chance of more abundant, successful galleries. [8] Trees are also selected for more often with increasing diameter at breast height (DBH). [8]  This allows for more room for gallery formation, which are often located in lower trunks of oak trees. [7] [9]

Males of this species are attracted to soaked logs over dry logs. [10] The anaerobic conditions of the submerged logs increases the likelihood of a male choosing those logs to create a gallery. [10] This may occur because those conditions favour the growth of the beetle's fungi symbionts. [10]

There is a preference for edge habitats over deep forest interiors. [11] [12] Roadsides and other edges act as attractions for the beetle. [11] This attraction may be due to an increased light presence as the species is positively phototactic. [11] This beetle prefers habitats with the highest light intensity when offered varying intensities. [11]

It has been suggested that the 0.4˚C increase in average temperature compared to the last 100 years in Japan is responsible for the increased range of the beetle and oak dieback. [3] The warmer climate has allowed the beetle to move north, encountering its best suited host, Q. crispula. [3] It is proposed that as the climate increases, more overlap between the beetle and the best suited host will occur, resulting in an even stronger oak dieback epidemic. [3]

Reproduction

Mate choice

Due to the monogamous nature of the oak ambrosia beetle, mate selection is vital for both females and males. [6] It is in the male's best interest to select a mate capable of excavating the gallery, planting nourishing fungi for larvae, oviposition, and bringing frass to the male for removal. [6] For females, selecting a male that has bored into a tree with sufficient resources is important to increase fecundity. [6]

Mating is male-initiated. [2] Males will bore a cylindrical entrance tunnel during late spring to early summer, meet the female there, and mate at the entrance hole. [5] The male will enter the gallery first, followed by the female. [6] Then, both back out of the gallery, changing positions so that the female will enter first for the second entrance, and enter again. [6] They will then both back out until the female's abdomen is exposed and copulation will begin. [6] It is suggested that female mate choice occurs between the first and second entrance because she is then able to view the gallery whereas male mate choice occurs at the beginning of the process when he decides whether or not to let the female enter the tunnel he bored. [6] Once both the male and female have chosen to proceed with reproduction, males make signals to prevent other females from entering the gallery. [6]

Parental Care

Each pairing will create one gallery with vertical and lateral branches and die in it together. [11] [2] [12] The female will deposit eggs at the tunnel's ends two to three weeks following gallery completion. [13] This must be done in trees that have not been previously infested by other P. quercivorus. [11] [2] The male will then create a barricade at the gallery's entrance with his body. [2] Here, he waits for the female to bring frass and bored dust which the male will then discard outside. [2] This species has a high reproduction rate, which in addition to low brood mortality resulting from cooperative parental care, may contribute to the high reproductive success of this species. [2] [6]

Reproductive success is shown to be higher in logs than in living trees. [2] Galleries in living trees lowers reproductive success of the oak ambrosia beetle because the tree's defensive mechanism of sap secretion enters galleries and kills individuals. [2] Tree species Q. crispula is the most suitable host species for reproducing and rearing offspring. [3]

Growth and development

Eggs hatch in about a week. [5] The larvae then graze on the symbiotic fungi covering the gallery walls and pass through five instars. [5] Adults emerge from their mother galleries 2–4 hours following dawn due to their diurnal tendencies. [5] [3] Approximately 40% of broods reach adulthood by late summer to early fall. [2] After reaching adulthood, individuals usually leave their galleries but some remain in their maternal galleries. [2] The remaining 60% of broods will reach the fifth larval stage by mid fall and overwinter in pupal chambers. [2] These individuals emerge as adults in late spring to early summer. [2] This brooding technique is partially bivoltine because approximately 40% of each population takes one year to complete a life cycles whereas the other 60% may have two generations in a year. [2] Individuals that remain in maternal galleries are often shown to not reproduce but rather, clean the galleries, which presents the possibility that this species may have eusocial tendencies. [5] [2] It is assumed that parents die either before or during winter. [5]

Interspecific relationships

P. quercivorus has symbiotic relationships with fungi and oak trees. [13]

Symbiotic relationship with fungi

P. quercivorus acts as the primary vector for the parthenogenic fungus Raffaelea quercivora, which causes Japanese Oak Wilt disease. [2] The oak ambrosia beetle bores into sapwood and heartwood of host oaks commonly including Q. crispula and Quercus serrata. [2] Once infected, these trees wilt and die, paralleling the effects of Dutch elm disease. [2] [3] [5]

The oak ambrosia beetle carries not only the pathogen itself, but also dietary fungus symbionts in mycangia. [2] [4] [5] Once galleries are constructed by the beetle in the sapwood of a host tree, the released fungi disseminate in yeast-like microbes and grow on the gallery walls. [2] P. quercivorus larvae then hatch and feed on the growing fungi. [2]

In addition to R. quercivora, P. quercivorus has at least one other main symbiont, Candida kashinagacola, as these two fungi species are found in all tree host types selected for by the beetle. [2] The latter fungus species, however, has not been linked to any parasitic tree diseases. [12] [13] In both relationships, the beetle receives a food source and the fungus receives transport into its final host. [10] [9]

Predatory relationships with oak trees

By acting as a vector for R. quercivora, the oak ambrosia beetle has killed trees since the 1980s. [2] [7] This species attacks all trees and logs but prefers debilitated trees and fresh logs for rearing offspring. [8] Typically, infestation rates are high, possibly to efficiently utilize sparse resources. [8] Working together with the fungi they vector, the ambrosia beetle galleries disrupt the flow of water within trees, leading to necrosis within 2–3 months of the attack. [9] Mass attacks of the beetle are necessary to overcome defense mechanisms of trees. [3] Often, P. quercivorus attacks trees from the family Fagaceae but is known to attack 45 different woody plant species from 27 genera in 17 families. [5]

Infestation occurs in stages. [5] First, trees surrounding previously infested trees are infested early in the season. [5] Then, major infestation occurs from the epicentre formed at the upper forest margin or at a forest edge, which then spreads downward into the remaining forest. [5]

Dispersal

These individuals spread through long-distance dispersal and diffusion. [5] Endemic populations are limited to weakened, old, and highly stressed tree populations but will attack healthy trees once local P. quercivorus populations reach an overcrowded threshold. [5] Infestation happens quickly and parallels invasive species with no regulating factors. [3]

This species may grow in population size and numbers in sudden outbreaks. [5] These sudden outbreaks may be due to climatic and biological factors that cause host trees to reduce the amount of sap they secrete through parasite-induced necrosis, which is their main defense mechanism to control P. quercivorus populations. [5] [2] Additionally, habitats with an abundance of suitable host plants may encourage population outbreaks. [2] Populations form through the use of pheromones released by members of the species in order to attract more individuals to overcome the tree's defenses. [5]

From analyzing interception trap results, oak ambrosia beetles are known to move upwards along slopes. [11] Typically, adult movement is influenced by environmental factors such as light, wind, and gravity. [5] It is thought that upward movement of wind majorly influences P. quercivorus movement. [5] Additionally, oak ambrosia beetles have positive phototaxis and fly more near forest edges. [5] Adults tend to concentrate near upper edges of forests and have a gradient population along slopes. [11] This species is labelled as an edge species due to its preference for edge habitat. [11]

Control techniques

Although not yet implemented, researchers suggest that protecting frequently attacked trees is important. [7] One way to do this is by binding the trunks with vinyl sheets which will prevent the beetle from boring into trees and transmitting the fungus. [7] Researchers understand that not all trees should be protected but those with a high probability of being attacked should be. [7] Trees from the family Fagaceae that have a larger DBH, are in clumps, and are on edges near excess light should be included in the protection plan. [7]

Related Research Articles

Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae, which live in nutritional symbiosis with ambrosia fungi. The beetles excavate tunnels in dead, stressed, and healthy trees in which they cultivate fungal gardens, their sole source of nutrition. After landing on a suitable tree, an ambrosia beetle excavates a tunnel in which it releases spores of its fungal symbiont. The fungus penetrates the plant's xylem tissue, extracts nutrients from it, and concentrates the nutrients on and near the surface of the beetle gallery. Ambrosia fungi are typically poor wood degraders, and instead utilize less demanding nutrients. The majority of ambrosia beetles colonize xylem of recently dead trees, but some attack stressed trees that are still alive, and a few species attack healthy trees. Species differ in their preference for different parts of trees, different stages of deterioration, and in the shape of their tunnels ("galleries"). However, the majority of ambrosia beetles are not specialized to any taxonomic group of hosts, unlike most phytophagous organisms including the closely related bark beetles. One species of ambrosia beetle, Austroplatypus incompertus exhibits eusociality, one of the few organisms outside of Hymenoptera and Isoptera to do so.

Bark beetle Subfamily of beetles

A bark beetle is one of about 6,000 species in 247 genera of beetles in the subfamily Scolytinae. Previously, this was considered a distinct family (Scolytidae), but is now understood to be a specialized clade of the "true weevil" family (Curculionidae). Although the term "bark beetle" refers to the fact that many species feed in the inner bark (phloem) layer of trees, the subfamily also has many species with other lifestyles, including some that bore into wood, feed in fruit and seeds, or tunnel into herbaceous plants. Well-known species are members of the type genus Scolytus, namely the European elm bark beetle S. multistriatus and the large elm bark beetle S. scolytus, which like the American elm bark beetle Hylurgopinus rufipes, transmit Dutch elm disease fungi (Ophiostoma). The mountain pine beetle Dendroctonus ponderosae, southern pine beetle Dendroctonus frontalis, and their near relatives are major pests of conifer forests in North America. A similarly aggressive species in Europe is the spruce ips Ips typographus. A tiny bark beetle, the coffee berry borer, Hypothenemus hampei is a major pest on coffee plantations around the world.

Mycangium

The term mycangium is used in biology for special structures on the body of an animal that are adapted for the transport of symbiotic fungi. This is seen in many xylophagous insects, which apparently derive much of their nutrition from the digestion of various fungi that are growing amidst the wood fibers. In some cases, as in ambrosia beetles, the fungi are the sole food, and the excavations in the wood are simply to make a suitable microenvironment for the fungus to grow. In other cases, wood tissue is the main food, and fungi weaken the defense response from the host plant.

<i>Xyleborus glabratus</i> Species of beetle

Xyleborus glabratus, the redbay ambrosia beetle, is a type of ambrosia beetle invasive in the United States. It has been documented as the primary vector of Raffaelea lauricola, the fungus that causes laurel wilt, a disease that can kill several North American tree species in the family Lauraceae, including redbay, sassafras, and avocado.

Austroplatypus incompertus is a species of ambrosia beetle belonging to the true weevil family, native to Australia, with a verified distribution in New South Wales and Victoria. It forms colonies in the heartwood of Eucalyptus trees and is the first beetle to be recognized as a eusocial insect. Austroplatypus incompertus is considered eusocial because groups contain a single fertilized female that is protected and taken care of by a small number of unfertilized females that also do much of the work. The species likely passed on cultivated fungi to other weevils.

The Japanese temperate rainforest is located in the Japanese archipelago, in small batches over a wide range of islands, from Kyushu in the South to Hokkaido in the North. Due to its geographic features and climate, the Japanese temperate rainforest is very different from other temperate rainforests in the world. The islands in the Japanese archipelago comprise about 1/400 of the world’s land. The islands are located on a latitude that is normally dry; desert can be found elsewhere in the world at this latitude. However, the oceans surrounding Japan provide enough precipitation to maintain a temperate rainforest.

<i>Ips</i> (beetle) Genus of beetles

Ips is a genus of beetles in the family Curculionidae, the true weevils. They are bark beetles, members of the subfamily Scolytinae. Species are distributed throughout the Northern Hemisphere. Some are known as introduced species in Australia and Africa. Many species are pests of forest trees, especially pines and spruces. They are known commonly as engraver beetles, ips engraver beetles, and pine engravers.

Raffaelea quercivora is a species of fungus in the family Ophiostomataceae. It causes Japanese oak wilt disease, and is spread by the ambrosia beetle. It has small obovoid to pyriform sympodioconidia and slender, long conidiophores. The fungus has been isolated from the body surfaces and mycangia of the beetle.

<i>Platypus</i> (beetle) Genus of beetles

Platypus is a weevil genus in the subfamily Platypodinae.

The foamy bark canker is a disease affecting oak trees in California caused by the fungus Geosmithia pallida and spread by the Western oak bark beetle. This disease is only seen through the symbiosis of the bark beetles and the fungal pathogen. The bark beetles target oak trees and bore holes through the peridermal tissues, making tunnels within the phloem. The fungal spores are brought into these tunnels by the beetles and begin to colonize the damaged cells inside the tunnels. Symptoms of the developing fungus include wet discoloration seeping from the beetle entry holes as the fungus begins to consume phloem and likely other tissues. If bark is removed, necrosis of the phloem can be observed surrounding the entry hole(s). As the disease progresses, a reddish sap and foamy liquid oozes from entry holes, thus giving the disease the name Foamy bark canker. Eventually after the disease has progressed, the tree dies. This disease is important because of its detrimental effects on oak trees and its ability to spread to several new Californian counties in just a couple years.

Japanese oak wilt is a fungal disease caused by Raffaelea quercivora fungus affecting by oak trees. In 1998, Japanese plant pathologists group was isolation, inoculation and reisolation the dead tree. It's the first disease known that Raffaela fungus cause plant disease.

<i>Platypus apicalis</i> Wood boring beetle endemic to New Zealand

Platypus apicalis, known by its common name the New Zealand pinhole boring beetle, is a wood-boring beetle endemic to New Zealand and found throughout the North and South Island in a range of environments.

<i>Xylosandrus compactus</i> Species of beetle

Xylosandrus compactus is a species of ambrosia beetle. Common names for this beetle include black twig borer, black coffee borer, black coffee twig borer and tea stem borer. The adult beetle is dark brown or black and inconspicuous; it bores into a twig of a host plant and lays its eggs, and the larvae create further tunnels through the plant tissues. These beetles are agricultural pests that damage the shoots of such crops as coffee, tea, cocoa and avocado.

<i>Platypus cylindrus</i> Species of beetle

Platypus cylindrus, commonly known as the oak pinhole borer, is a species of ambrosia beetle in the weevil family Scolytinae. The adults and larvae burrow under the bark of mature oak trees. It is native to Europe.

<i>Xylosandrus crassiusculus</i> Species of beetle

Xylosandrus crassiusculus, known generally as the Asian ambrosia beetle or granulate ambrosia beetle, is a species of tropical bark beetle in the family Curculionidae. It is native to Asia and has spread to Africa, Europe, Australasia and the Americas. The adult beetle is reddish-brown and some 2 to 3 mm long.

Xyloterinus is a genus of typical bark beetles in the family Curculionidae. This is a monotypic genus and the one described species is Xyloterinus politus. It is native to North America where it infests both hardwood and softwood trees, as well as stacks of logs.

Euplatypus parallelus, previously known as Platypus parallelus, is a species of ambrosia beetle in the weevil family Curculionidae. The adults and larvae form galleries in various species of tree and logs. It is native to Central and South America but has spread globally, is present in Africa and is well established in tropical Asia.

<i>Arrenodes minutus</i> Species of beetle

Arrenodes minutus, commonly known as the oak timberworm, is a species of primitive weevil in the family Brentidae. These beetles are pests of hardwoods in North America. Adult oak timberworms are shiny, elongate, and range 7 to 25 mm in length. They are reddish-brown to brownish-black in coloration, with yellow spots on their elytra. Adults display strong sexual dimorphism; females have long, slender, straight mouthparts, while males possess flattened, broadened mouthparts with large mandibles. Males are known to be aggressive and use these large mandibles for combat. These mandibles are also used in courtship. Larvae are elongate, cylindrical, white, and curved. They have 3 pairs of jointed legs on the thorax and 1 pair of prolegs near the end of the abdomen.

Sueus niisimai, is a species of weevil found in India, Sri Lanka, China, Japan, Taiwan, Korea, Malaysia and Indonesia. It is also found in Australia and Fiji, presumably introduced.

<i>Xyleborus monographus</i> Species of beetle

Xyleborus monographus, the Mediterranean oak borer, is a species of ambrosia beetle in the family Curculionidae. It is native to oaks in the regions around the Mediterranean Sea, but since 2019 has been found in California, where the oak trees it infests may be more vulnerable.

References

  1. ↑ Sone, K., Mori, T., Ide, M. (1998). Life history of the oak borer, Platypus quercivorus (Murayama) (Coleoptera : Platypodidae). Applied Entomology and Zoology 33: 67-75.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Sone, K., Mori, T., Ide, M. (1998). Life history of the oak borer, Platypus quercivorus (Murayama) (Coleoptera : Platypodidae). Applied Entomology and Zoology 33: 67-75.
  3. 1 2 3 4 5 6 7 8 9 10 Kamata, N., Esaki, K., Kato, K., Igeta, Y., Wada, K. (2002). Potential impact of global warming on deciduous oak dieback caused by ambrosia fungus Raffaelea sp carried by ambrosia beetle Platypus quercivorus (Coleoptera : Platypodidae) in Japan. Bulletin of Entomological Research 92: 119-126.
  4. 1 2 3 4 5 6 7 8 Benzel, J. (2015). Screening aid: Ambrosia beetles, Platypus quercivorus (Murayama), Megaplatypus mutatus (Chapuis). Identification Technology Program (ITP), USDA-APHIS-PPQ-S&T, Fort Collins, CO. 7 pp.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Esaki, K., Kato, K., Kamata, N. (2004). Stand-level distribution and movement of Platypus quercivorus adults and patterns of incidence of new infestation. Agricultural and Forest Entomology 6: 71-82.
  6. 1 2 3 4 5 6 7 8 9 10 11 Kobayashi, M., Ueda, A. (2002). Preliminary study of mate choice in Platypus quercivorus (Murayama) (Coleoptera : Platypodidae). Applied Entomology and Zoology 37: 451-457.
  7. 1 2 3 4 5 6 7 8 9 Yamasaki, M., Futai, K. (2012). Discrimination among host tree species by the ambrosia beetle Platypus quercivorus. Journal of Forest Research 17: 149-155.
  8. 1 2 3 4 5 Yamasaki, M., Sakimoto, M. (2009). Predicting oak tree mortality caused by the ambrosia beetle Platypus quercivorus in a cool-temperate forest. Journal of Applied Entomology 133: 673-681.
  9. 1 2 3 Kuroda, K. (2001). Responses of Quercus sapwood to infection with the pathogenic fungus of new wilt disease vectored by the ambrosia beetle Platypus quercivorus. Journal of Wood Science 47: 425-429.
  10. 1 2 3 4 Kitajima, H., Goto, H. (2004). Rearing technique for the oak platypodid beetle, Platypus quercivorus (Murayama) (Coleoptera : Platypodidae), on soaked logs of deciduous oak tree, Quercus serrata Thunb. Ex Murray. Applied Entomology and Zoology 39: 7-13.
  11. 1 2 3 4 5 6 7 8 9 Igeta, Y., Esaki, K., Kato, K., Kamata, K. (2003). Influence of light condition on the stand-level distribution and movement of the ambrosia beetle Platypus quercivorus (Coleoptera : Platypodidae). Applied entomology and Zoology 38: 167-175.
  12. 1 2 3 Kinuura, H., Kobayashi, M. (2006). Death of Quercus crispula by inoculation with adult Platypus quercivorus (Coleoptera : Platypodidae). Applied Entomology and Zoology 41: 123-12.
  13. 1 2 3 Endoh, R., Suzuki, M., Okada, G., Takeuchi, Y., Futai, K. (2011). Fungus Symbionts Colonizing the Galleries of the Ambrosia Beetle Platypus quercivorus. Microbial Ecology 62: 106-120.
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