Austroplatypus incompertus
Encyclopedia
Austroplatypus incompertus is a species of weevil
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.
s and their head grows from approximately 0.3 mm wide in the first instar to 0.9 mm wide in the fifth instar. They then pupa
te and hatch as adults that are approximately 6 mm long and 2 mm in diameter. Adults display sexual dimorphism
with males being the significantly smaller sex, an atypical arrangement among platypodine beetles.
ambrosia beetle
is applied to this and about 300 other weevils in the subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae
) that fill a similar ecological niche by living colonially (although not necessarily eusocially) inside trees and cultivating the same type of fungi.
with ambrosia fungi
. They excavate tunnels in dead trees in which they cultivate fungal gardens as their sole source of nutrition. New colonies are founded by fertilized females who use special hair-like structures called mycangia to transport fungi to a new host tree. The mycangia of A. incompertus and the specific manner in which the species acquires fungal spore
s for transport have been studied and compared with the mechanisms used by other ambrosia beetles. Fertilized females begin tunneling into trees in the autumn and take about seven months to penetrate 50 mm to 80 mm deep to lay their eggs.
on unprocessed logs and chips of eighteen woody plants species from Australia discovered A. incompertus in most of them including: Eucalyptus baxteri
, E. botryoides
, E. consideniana
, E. delegatensis
, E. eugenioides
, E. fastigata
, E. globoidea, E. macrorhyncha
, E. muelleriana
, E. obliqua
, E. pilularis
, E. radiata
, E. scabra
, E. sieberi
, and Corymbia gummifera
. Unlike most ambrosia beetles, it infests healthy, undamaged trees.
. Firstly, colonies contain individuals of overlapping generations. Secondly, they engage in cooperative broodcare. Thirdly, their population is divided into reproductive and unfertilized, non-reproductive castes. Their colonies are small; each contains a single fertilized female and approximately five non-breeding females who defend the breeding female against predators and do the work of digging more galleries in which to raise fungus.
Haplodiploidy, leading to the sharing of a high proportion (0.75) of genes between sisters, has been regarded by some as critical in explaining the evolution of eusociality in hymenopterans. Study has shown, however, that A. incompertus males and females are diploid, thus providing evidence against the notion that the haplodiploidy hypothesis might be similarly applied to the phylogenetically diverse non-hymenopteran taxa among which eusociality and other altruistic behaviors have evolved.
Weevil
A weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
native to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
with a verified distribution in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
and Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
. It forms colonies
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
in the heartwood of Eucalyptus
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
trees and is the first beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
to be recognized as a eusocial insect.
Life cycle
The eggs of A. incompertus are approximately 0.7 mm in length and 0.45 mm wide. They develop through five instarInstar
An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
s and their head grows from approximately 0.3 mm wide in the first instar to 0.9 mm wide in the fifth instar. They then pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...
te and hatch as adults that are approximately 6 mm long and 2 mm in diameter. Adults display sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
with males being the significantly smaller sex, an atypical arrangement among platypodine beetles.
Name
The common nameCommon name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
ambrosia beetle
Ambrosia beetle
Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae , which live in nutritional symbiosis with ambrosia fungi and probably with bacteria...
is applied to this and about 300 other weevils in the subfamilies Scolytinae and Platypodinae (Coleoptera, Curculionidae
Curculionidae
Curculionidae is the family of the "true" weevils . It was formerly recognized in 1998 as the largest of any animal family, with over 40,000 species described worldwide at that time...
) that fill a similar ecological niche by living colonially (although not necessarily eusocially) inside trees and cultivating the same type of fungi.
Habit
Like other ambrosia beetles, A. incompertus lives in nutritional symbiosisSymbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
with ambrosia fungi
Ambrosia fungi
Ambrosia fungi are fungal symbionts of ambrosia beetles.There are a few dozen described ambrosia fungi, currently placed in polyphyletic genera Ambrosiella, Rafaellea and Dryadomyces . Probably many more species remain to be discovered...
. They excavate tunnels in dead trees in which they cultivate fungal gardens as their sole source of nutrition. New colonies are founded by fertilized females who use special hair-like structures called mycangia to transport fungi to a new host tree. The mycangia of A. incompertus and the specific manner in which the species acquires fungal spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s for transport have been studied and compared with the mechanisms used by other ambrosia beetles. Fertilized females begin tunneling into trees in the autumn and take about seven months to penetrate 50 mm to 80 mm deep to lay their eggs.
Host trees
An assessment done by the United States Department of AgricultureUnited States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
on unprocessed logs and chips of eighteen woody plants species from Australia discovered A. incompertus in most of them including: Eucalyptus baxteri
Eucalyptus baxteri
The brown stringybark is a eucalypt which is native to Australia's southeast, occurring from southern New South Wales through Victoria and into the Fleurieu Peninsula and Kangaroo Island of eastern South Australia. It is a medium-sized tree which can reach 40 m in height. The rough stringy bark...
, E. botryoides
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. consideniana
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. delegatensis
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. eugenioides
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. fastigata
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. globoidea, E. macrorhyncha
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. muelleriana
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. obliqua
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. pilularis
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. radiata
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. scabra
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, E. sieberi
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, and Corymbia gummifera
Corymbia gummifera
Corymbia gummifera, commonly known as Red Bloodwood, is a hardwood tree native to eastern Australia.-Description:It usually grows as a tree, but may take the form of a mallee in very poor soils. As a tree it typically grows to a height of 20 to 34 metres and a trunk diameter of one metre dbh....
. Unlike most ambrosia beetles, it infests healthy, undamaged trees.
Eusociality
A. incompertus has been called "the Australian beetle that behaves like a bee" because it displays those "three phenomena which characterize eusociality" and are most associated with various species of HymenopteraHymenoptera
Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...
. Firstly, colonies contain individuals of overlapping generations. Secondly, they engage in cooperative broodcare. Thirdly, their population is divided into reproductive and unfertilized, non-reproductive castes. Their colonies are small; each contains a single fertilized female and approximately five non-breeding females who defend the breeding female against predators and do the work of digging more galleries in which to raise fungus.
Haplodiploidy, leading to the sharing of a high proportion (0.75) of genes between sisters, has been regarded by some as critical in explaining the evolution of eusociality in hymenopterans. Study has shown, however, that A. incompertus males and females are diploid, thus providing evidence against the notion that the haplodiploidy hypothesis might be similarly applied to the phylogenetically diverse non-hymenopteran taxa among which eusociality and other altruistic behaviors have evolved.