''Ranunculus acaulis'', in Australia and New Zealand called dune buttercup, sand buttercup or shore buttercup, is a yellow-flowered, small, fleshy herb, that grows in mats in damp places mostly near the sea. It occurs naturally in

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

and the

Falklands The Falkland Islands (; es, Islas Malvinas, link=no ) is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and about from Cape Dubouzet ...

. It flowers between August and April and sets seed from September till July.

Description

The dune buttercup is a small and hairless perennial herb that grows in matted patches, that are the result of numerous plants that develop at the nodes of long slender aerial shoots. The leaves form a rosette, are 12–45 mm long and have a stalk, are thick and shiny and have many very small light dots. The blades are three-lobed. The middle leaflet is entire or has three blunt teeth, and the lateral leaflets are entire with a blunt tip or have one blunt tooth at the basal margin. Flowers are 7–10 mm in diameter and are solitary on stems that are as long as the leaves. The three to five about 1½-2½ mm long

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined b ...

s are pale greenish or yellowish. The five to eight narrow yellow

petal Petals are modified Leaf, leaves that surround the reproductive parts of flowers. They are often advertising coloration, brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''c ...

s are about 5 mm long. At 1½-2 mm from the base is a single pocket-like

nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...

y. The ten to twenty yellow

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filame ...

s occupy about two circles around the raised green receptacle that carries six to twelve yellow

carpel Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more) ''pistils'' ...

s. The one-seeded dry fruits (or

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...

s) become beige when ripe, and are ovate, not flattened, with a somewhat curved, up to 1 mm long beak. ''R. acaulis'' has ninety six chromosomes (2n = 96).

Etymology

The generic name ''Ranunculus'' is the diminutive of the Latin ''rana'' frog (little frog) and probably refers to the wet location where some buttercup species live together with frogs. The species epithet ''acaulis'' is derived from the Greek "a"-, without and "kaulos", stalk or stem, because the flower is on such a short stem that it seems absent.

Distribution

The dune buttercup is an indigenous species in New Zealand, where it occurs on both main islands, Stewart Island, Chatham and Auckland Islands, in Australia on the West- and South-coast of Tasmania, in Chile in the provinces of Los Rios, Los Lagos, Aisen, and Magallanes, and on the Falkland Islands.

Taxonomy

According to genetic analysis, ''R. acaulis'' may be

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, with a specimen from Steward Island being most related to '' R. papulentus'', while a specimen from Chile is in a group with '' R. crassipes'' and '' R. biternatus''. The specimen from Chili is considerably larger and its leaves are thinner and more dentate. The type specimen was from New Zealand and would retain its name.

References

{{Taxonbar, from=Q15375946 acaulis Flora of New Zealand