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Ambrosia beetles are beetles of the weevil
Weevil

A weevil is any beetle from the Curculionidae superfamily. They are usually small, less than 6 mm , and Herbivore. Due to the shape of their heads, weevils are commonly known as snout beetles....
 subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae
Curculionidae

Curculionidae is the family of the "true" weevils . With over 60,000 species described worldwide, it is the largest of the beetle families.They are recognized by their distinctive long snout and geniculate antennae with small clubs; beyond that curculionids have considerable diversity of form and size, with adult lengths ranging from 1&nbs...
), which live in nutritional symbiosis
Symbiosis

The term symbiosis commonly describes close and often long-term interactions between different biological species. The term was first used in 1879 by the Germany mycology Heinrich Anton de Bary, who defined it as "the living together of unlike organisms"....
 with ambrosia fungi
Ambrosia fungi

Ambrosia fungi are Fungus symbionts of ambrosia beetles.There are a few dozen described ambrosia fungi, currently placed in polyphyletic genera Ambrosiella, Rafaella and Dryadomyces ....
 and probably with bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
. The beetles excavate tunnels in dead trees in which they cultivate fungal gardens, their sole source of nutrition. An ambrosia beetle excavates a tunnel in which it releases spore
Spore

In biology, a spore is a reproduction structure that is adapted for biological dispersal and surviving for extended periods of time in unfavorable conditions....
s of its fungal symbiont. The fungus penetrates the plant's xylem
Xylem

In vascular plants, xylem is one of the two types of transport tissue, phloem being the other. The word "xylem" is derived from classical Greek language ????? , "wood", and indeed the best known xylem tissue is wood, though it is found throughout the plant....
 tissues, digests it, and then concentrates the nutrients.






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Ambrosia beetles are beetles of the weevil
Weevil

A weevil is any beetle from the Curculionidae superfamily. They are usually small, less than 6 mm , and Herbivore. Due to the shape of their heads, weevils are commonly known as snout beetles....
 subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae
Curculionidae

Curculionidae is the family of the "true" weevils . With over 60,000 species described worldwide, it is the largest of the beetle families.They are recognized by their distinctive long snout and geniculate antennae with small clubs; beyond that curculionids have considerable diversity of form and size, with adult lengths ranging from 1&nbs...
), which live in nutritional symbiosis
Symbiosis

The term symbiosis commonly describes close and often long-term interactions between different biological species. The term was first used in 1879 by the Germany mycology Heinrich Anton de Bary, who defined it as "the living together of unlike organisms"....
 with ambrosia fungi
Ambrosia fungi

Ambrosia fungi are Fungus symbionts of ambrosia beetles.There are a few dozen described ambrosia fungi, currently placed in polyphyletic genera Ambrosiella, Rafaella and Dryadomyces ....
 and probably with bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
. The beetles excavate tunnels in dead trees in which they cultivate fungal gardens, their sole source of nutrition. An ambrosia beetle excavates a tunnel in which it releases spore
Spore

In biology, a spore is a reproduction structure that is adapted for biological dispersal and surviving for extended periods of time in unfavorable conditions....
s of its fungal symbiont. The fungus penetrates the plant's xylem
Xylem

In vascular plants, xylem is one of the two types of transport tissue, phloem being the other. The word "xylem" is derived from classical Greek language ????? , "wood", and indeed the best known xylem tissue is wood, though it is found throughout the plant....
 tissues, digests it, and then concentrates the nutrients. The majority of ambrosia beetles colonize xylem (sapwood and/or heartwood) of dying or recently dead trees. Species differ in the preferred part of tree, in the shape of their tunnels (“galleries”) or in the preferred physical features of their host, but the majority of ambrosia beetles are not specialized to any taxonomic group of hosts, unlike majority of phytophagous organisms.

Taxonomy


Until recently ambrosia beetles have been placed in independent families Scolytidae and Platypodidae, however, they are in fact some of the most highly derived weevils.Marvaldi, A. E., A. S. Sequeira, et al. (2002): Molecular and Morphological Phylogenetics of Weevils (Coleoptera, Curculionoidea): Do Niche Shifts Accompany Diversifcation? Systematic Biology 51(5): 761-785. There are currently about 3,000 species of beetles employing the ambrosia strategy, most of them from the subfamily Platypodinae and the subtribe Xyleborina of subfamily Scolytinae, and numerous smaller groups within Scolytinae.

Note that the term ambrosia beetle does not denote a taxonomic group, and the ambrosia habit is an example of convergent evolution
Convergent evolution

Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action....
, in that several groups evolved the same symbiotic relationship independently. The highest diversity of ambrosia beetles is in the tropics. In the Paleotropical region, hundreds of species of Xyleborini
Xyleborini

Xyleborini are a tribe of bark beetles, highly specialized weevils of the subfamily Xyleborini. Much of the ambrosia beetle fauna in Eurasia and the Americas consists of Xyleborini species....
 and Platypodinae are the main agent initiating dead wood decomposition. In the Neotropic
Neotropic

In biogeography, Neotropic or Neotropical refers to one of the world's eight terrestrial ecozones.This ecozone includes South and Central America, the Mexico lowlands, the Caribbean islands, and southern Florida, because these regions share a large number of plant and animal groups....
s, Platypodinae and Xyleborini
Xyleborini

Xyleborini are a tribe of bark beetles, highly specialized weevils of the subfamily Xyleborini. Much of the ambrosia beetle fauna in Eurasia and the Americas consists of Xyleborini species....
 are joined by the scolytine tribe Cortylini. Ambrosial beetle fauna in the Nearctic
Nearctic

The Nearctic is one of the eight Terrestrial ecoregion ecozones dividing the Earth's land surface.The Nearctic ecozone covers most of North America, including Greenland and the highlands of Mexico....
 is rather limited, dominated by a few species from Cortylini, Xyleborini and Xyloterini. In the Palearctic
Palearctic

The Palearctic or Palaearctic is one of the eight ecozones dividing the Earth surface.Physically, the Palearctic is the largest ecozone....
 ecozone
Ecozone

An ecozone or biogeographic realm is the largest scale biogeography division of the earth's surface based on the historic and evolutionary distribution patterns of plants and animals....
, significant groups are Platypodinae and Xyleborini and Scolytoplatypodini.

The symbiotic relationship

Beetles and their larvae
Larvae

In Roman mythology, the larvae or lemures were the spectres or spirits of the dead; they were the malignant version of the lares. Some Roman writers describe lemures as the common name for all the spirits of the dead, and divide them into two classes: the lares, or the benevolent souls of the family, which haunted and guard...
 graze on mycelium
Mycelium

Mycelium is the Vegetative reproduction part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the Fairy rings fungi....
 exposed on the gallery walls and on bodies called sporodochia, clusters of the fungus’ spores. Most ambrosia beetle species don’t ingest the wood tissue; instead the sawdust resulting from the excavation (called frass) is pushed out of the gallery. Following the larval and pupal stage, adult ambrosia beetles collect masses of spores of their symbionts into their mycangia
Mycangium

The term mycangium is used in biology for special structures on the body of an animal that are adapted for the transport of symbiose fungi . This is seen in many xylophagy insects , which apparently derive much of their nutrition from the digestion of various fungi that are growing amidst the wood fibers....
 and leave the gallery to find their own tree.

Recent discovery of bacterial acsociates in the similar bark beetle
Bark beetle

A bark beetle is one of approximately 220 genera with 6,000 species of beetles in the subfamily Scolytinae. Traditionally this was considered a distinct family Scolytidae, but nowadays it is understood that bark beetles are in fact very specialized members of the "true weevil" family ....
-fungus mutualism provides a hint to the mechanisms of resilience of this symbiotic complex. Actinomycete bacteria inhabiting galleries of a Dendroctonus
Dendroctonus

Dendroctonus is a genus of bark beetles. It includes several species notorious for destroying trees in the forests of North America.Species include:...
 bark beetle produce antifungal antibiotics which are protecting the gallery from opportunistic wood-decomposing fungi or from insect pathogens.

A few dozen species of ambrosia fungi have been described, currently in the polyphyletic genera Ambrosiella, Raffaelea and Dryadomyces (all from Ophiostomatales, Ascomycetes). Many more species remain to be discovered. Little is known about the bionomy or specificity of ambrosia fungi. Ambrosia fungi are thought to be dependent on transport and inoculation provided by their beetle symbionts, as they have not been found in any other habitat
Habitat

The term habitat has a number of meanings:* Habitat , a place where a species lives and grows** Human habitat, a place where humans live, work or play...
. All ambrosia fungi are probably asexual
Asexual reproduction

Asexual reproduction is reproduction which does not involve meiosis, ploidy reduction, or fertilization. Only one parent is involved in asexual reproduction....
 and clonal.

During the evolution of this symbiotic lifestyle, most scolytid and all platypodid groups became progressively more dependent on fungi regularly cohabiting dead trees. This evolution had various outcomes in different groups:
  • Some phloem
    Phloem

    In vascular plants, phloem is the living Biological tissue that carries organic nutrients , particularly sucrose, a sugar, to all parts of the plant where needed....
    -eating bark beetles (phloeophages) are able to attack and kill live trees since their fungal symbiont is an aggressive phytopathogen.
  • Many of phloem-feeding bark beetles use phloem-infesting fungi as an addition to their diet; some phloeophages became more or less dependent on such a mixed diet and evolved mycangia
    Mycangium

    The term mycangium is used in biology for special structures on the body of an animal that are adapted for the transport of symbiose fungi . This is seen in many xylophagy insects , which apparently derive much of their nutrition from the digestion of various fungi that are growing amidst the wood fibers....
     to transport their symbionts from maternal trees to newly infested trees. These beetles are called mycophloeophages.
  • The closest association evolved between ambrosia beetles and ambrosia fungi, where both the beetle and the fungus are completely dependent on each other in multiple stages of life.


See also

  • Laurel wilt disease


External links

  • The contains and worldwide species list from the Catalog of Scolytidae and Platypodidae of S.L. Wood and D.E. Bright (1992)]
  • More information on ambrosia beetle social behaviour and fungiculture on


on the UF
University of Florida

The University of Florida is a Public university land-grant university, sea grant colleges, Space grant colleges major research university located on a campus in Gainesville, Florida, in the United States....
 / IFAS
Institute of Food and Agricultural Sciences

The University of Florida?s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information accessible....
 Featured Creatures Web site


site