''Eucalyptus arborella'', commonly known as Twertup mallet,
is a
mallet
A mallet is a tool used for imparting force on another object, often made of rubber or sometimes wood, that is smaller than a maul or beetle, and usually has a relatively large head. The term is descriptive of the overall size and proport ...
or small tree that is
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to a small area in the
south-west
The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each se ...
of
Western Australia
Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
. It has smooth greyish bark, narrow lance-shaped adult leaves, flower buds in groups of thirteen to twenty fused together, yellowish green flowers, and fruits fused together in a woody mass.
Description
''Eucalyptus arborella'' is a mallet that typically grows to a height of and does not form a
lignotuber
A lignotuber is a woody swelling of the root crown possessed by some plants as a protection against destruction of the plant stem, such as by fire. Other woody plants may develop basal burls as a similar survival strategy, often as a response t ...
. The bark is a whitish-grey colour, sometimes becoming a coppery-pink and smooth over the length of the tree. The leaves on young plants and on
coppice
Coppicing is a traditional method of woodland management which exploits the capacity of many species of trees to put out new shoots from their stump or roots if cut down. In a coppiced wood, which is called a copse, young tree stems are repeated ...
regrowth are egg-shaped and up to long and wide. The adult leaves are elliptic to lance-shaped, the same glossy dark green on both sides, long and wide on a
petiole long. The flower buds are borne in groups of thirteen to twenty and are fused together in leaf
axil
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, st ...
s on a flattened
peduncle long. The cluster of buds is long at maturity with each bud is wide at the base of the
operculum. The operculum is long, between five and eight times as long as the
floral cup
In angiosperms, a hypanthium or floral cup is a structure where basal portions of the calyx, the corolla, and the stamens form a cup-shaped tube. It is sometimes called a floral tube, a term that is also used for corolla tube and calyx tube. It ...
, and curved. Flowering occurs from March to May and the flowers are greenish. The fruit are fused in a woody mass wide on a down-turned peduncle.
Taxonomy and naming
''Eucalyptus arborella'' was first formally described in 2002 by
Ian Brooker
Murray Ian Hill Brooker AM (2 June 1934 – 25 June 2016), better known as Ian Brooker, was an Australian botanist. He was widely recognised as the leading authority on the genus ''Eucalyptus''.
Ian Brooker was born in Adelaide, South Australi ...
and
Stephen Hopper
Stephen Donald Hopper AC FLS FTSE (born 18 June 1951) is a Western Australian botanist. He graduated in Biology, specialising in conservation biology and vascular plants. Hopper has written eight books, and has over 200 publications to his n ...
from a specimen collected near the Twertup field studies centre in the
Fitzgerald River National Park
Fitzgerald River National Park is a national park in the Shires of Ravensthorpe and the Jerramungup in Western Australia, southeast of Perth. The park is recognised on Australia's National Heritage List for its outstanding diversity of native ...
. The description was published in the journal ''
Nuytsia
''Nuytsia floribunda'' is a hemiparasitic tree found in Western Australia. The species is known locally as moodjar and, more recently, the Christmas tree or Western Australian Christmas tree. The display of intensely bright flowers during the ...
''.
The
specific epithet
In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
(''arborella'') is derived from the
Latin word ''arbor'' meaning "tree", with the
diminutive
A diminutive is a root word that has been modified to convey a slighter degree of its root meaning, either to convey the smallness of the object or quality named, or to convey a sense of intimacy or endearment. A (abbreviated ) is a word-formati ...
suffix
In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns, adjectives, and verb endings, which form the conjugation of verbs. Suffixes can carry ...
''-ellus'', hence "little tree".
''Eucalyptus arborella'' belongs in Eucalyptus subgenus ''Symphyomyrtus'' section ''Bisectae'' subsection ''Hadrotes'' because of its coarsely bisected cotyledons, erect stamens and larger, thick rimmed fruits. The subsection ''Hadrotes'' contains ten species of which eight do not have oil glands in the branchlet pith. Together these eight species form series ''Lehmannianae'', a group that have fruit with exserted valves that have fused tips even after the seeds are lost, a feature also shared with the distantly related ''
Eucalyptus cornuta
''Eucalyptus cornuta'', commonly known as yate, is a tree species, sometimes a mallee and is endemic to the southwest of Western Australia. It has rough, fibrous bark on all or most of its trunk, smooth bark above, mostly lance-shaped adult le ...
''.
Of the eight species in series ''Lehmannianae'' four species; ''
E. conferruminata'', ''
E. lehmannii'', ''
E. mcquoidii'' and ''E. arborella'' all have the buds in each an axillary cluster that is fused basally.
Distribution and habitat
The Twertup mallet grows in rocky places in the Fitzgerald River National Park and near Corackerup in the
Esperance Plains biogeographic region
An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of l ...
.
Conservation
This eucalypt is classified as "
Priority Three" by the Western Australian Government
Department of Parks and Wildlife
The Department of Parks and Wildlife (DPaW) was the department of the Government of Western Australia responsible for managing lands described in the ''Conservation and Land Management Act 1984'' and implementing the state's conservation and e ...
meaning that it is poorly known and known from only a few locations but is not under imminent threat.
See also
*
List of ''Eucalyptus'' species
References
{{Taxonbar, from=Q15400005
arborella
Endemic flora of Western Australia
Myrtales of Australia
Eucalypts of Western Australia
Plants described in 2002
Taxa named by Ian Brooker
Taxa named by Stephen Hopper