''Abrotanella'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

in the family

Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

, of 23 species, native to

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

and southern South America. They are usually small plants, sometimes not reaching more than a few millimetres above the ground, although some form cushions in

bolster heath {{Short description, Type of vegetation community Bolster heath or cushion moorland is a type of vegetation community that features a patchwork of very low growing, tightly packed plants found at the limits of some alpine environments. The cushion ...

s reaching up to a metre in diameter.

Taxonomy

Genus ''Abrotanella'' is placed in the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Senecioneae and is the sole genus in the subtribe Abrotanellinae. The genus was formerly placed in the subtribe Blennospermatinae, but

molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...

and morphological studies have shown it to be distinct from other genera in that group.

Phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

studies have shown that Abrotanella forms a well-supported

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group. It is

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

formed by three other genera: '' Crocidium'', '' Blennosperma'', and '' Ischnea''. Within ''Abrotanella'', '' A. forsteroides'' from Tasmania is sister to all other species in the genus.

Evolutionary history

The evolutionary history of ''Abrotanella'' has been investigated using molecular dating techniques, providing insights into the timing of its diversification. According to these studies, the stem age of ''Abrotanella'' is estimated to be approximately 19.4 million years ago, placing its origin in the early

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

. However, the radiation of extant species began much later, around 4.2 million years ago during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58divergence In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the rate that the vector field alters the volume in an infinitesimal neighborhood of each point. (In 2D this "volume" refers to ...

event about 3.1 million years ago, which led to the formation of the two main lineages observed within the genus.

Biogeographic Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...

analyses suggest that South America was likely part of the ancestral area for ''Abrotanella''. The genus is thought to have reached New Zealand and other Pacific areas through

long-distance dispersal Biological dispersal refers to both the movement of individuals (animals, plants, fungi, bacteria, etc.) from their birth site to their breeding site ('natal dispersal') and the movement from one breeding site to another ('breeding dispersal' ...

, as the timing of its evolution postdates the separation of these landmasses. This finding challenges earlier hypotheses that might have attributed the distribution of ''Abrotanella'' to ancient

vicariance Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

events related to the break-up of

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

. The distribution of ''Abrotanella'' species reflects a complex history involving both vicariance and dispersal events. Researchers have proposed that this distribution pattern may have resulted from a combination of factors, including potential migration via

land bridge In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea le ...

s or stepping stones along the Antarctic coast, as well as long-distance dispersal across ocean barriers.

Description

''Abrotanella'' comprises small

alpine Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine National P ...

or subalpine plants, often forming cushions. They are typically found growing in moist habitats, herbfields, among rocks, or on bare soils. Most species of ''Abrotanella'' lack obvious adaptations for long-distance dispersal. However, some species, such as ''A. submarginata'' and ''A. muscosa'', have fruits with twin hairs and an apical

crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, parti ...

, which could potentially aid in dispersal. ; Species ; Synonyms * ''Abrotanella crassipes'' Skottsb. is synonym of '' Abrotanella linearifolia'' A.Gray * ''Abrotanella filiformis'' Petrie is synonym of '' Abrotanella linearis'' Bergg. * '' Rhamphogyne rhynchocarpa'' was formerly placed here with the name '' Abrotanella rhynchocarpa''

References

Bibliography

* * * Swenson U. 1995. Systematics of Abrotanella, an amphi-Pacific genus of Asteraceae (Senecioneae). ''Pl. Syst. Evol.'' 197. (1-4): 149–193. * Wagstaff, Steven J.; Breitwieser, Ilse & Swenson, Ulf 2006. Origin and relationships of the austral genus Abrotanella (Asteraceae) inferred from DNA sequences. ''Taxon'' 55(1):95-106.

External links

* {{Taxonbar, from=Q2560930 Asteraceae genera Taxa named by Henri Cassini