Banksia epica

Appearance

"Banksia epica" grows as a spreading bushy shrub with many branches to 3 metres tall. It has grey, fissured bark, and dark green, wedge-shaped leaves, 1+1⁄2 to 5 centimetres long and 6 to 15 millimetres wide, with serrated margins.

Flowers occur in "Banksia"'s characteristic "flower spike", an inflorescence made up of hundreds of pairs of flowers densely packed in a spiral round a woody axis. "B. epica"'s flower spike is yellow or cream-yellow in colour, cylindrical, 9 to 17 centimetres tall and around 6 centimetres in diameter. In bud, it may have green-grey or brownish pollen presenters, not unlike "B. robur". Each flower consists of a tubular perianth made up of four fused tepals, and one long wiry style. Characteristic of its taxonomic section, the styles of "B. epica" are straight rather than hooked. The style ends are initially trapped inside the upper perianth parts, but break free at anthesis. The fruiting structure is a stout woody "cone" embedded with up to 50 follicles; old withered flower parts persist on the "cones", giving them a hairy appearance. The follicles have an attractive purple hue.

"Banksia epica" is similar in appearance to its close relative "B. media", from which it differs in having slightly shorter leaves and larger flowers. In addition, the persistent flower parts on "B. epica"'s fruiting structures are curled and point upwards, whereas they are straight and point downwards on "B. media".

Distribution

"Banksia epica" is known only from two populations in eastern parts of the Esperance Plains region of the South West Botanical Province, near the western edge of the Great Australian Bight. The main population occurs about 30 kilometres west of Point Culver; there were over 2000 plants there when surveyed in June 1989. A smaller population occurs about 70 kilometres further east at Toolinna Cove; when surveyed in August 1991, this locality had around 350 plants. This latter population represents the easternmost limit of the western "Banksia" species; east of Toolinna Cove no "Banksia" species occurs for over 900 kilometres.

In both localities, "B. epica" occurs among heath on cliff-top dunes of deep, white siliceous sand over limestone. It co-occurs with "B. media" in both localities, and "B. praemorsa" is also present at Point Culver. Toolinna Cove sand is somewhat alkaline, making "B. epica" and "B. media" the only "Banksia" species that grow in alkaline soil.

These two localities are unusual in having cliff-top dunes of siliceous sand: cliff-top dunes are an unusual topographic formation, and nearly all soil in the area is calcareous. As "Banksia" species are intolerant of calcareous soils, and are not adapted to long range seed dispersal, the two populations of "B. epica" appear to be reproductively isolated. Nelson has suggested that there was once a continuous strip of siliceous sand along the coast, providing an extensive and unfragmented habitat for "B. epica"; rises in the sea level had submerged this strip, leaving only the cliff-top dunes as suitable habitat. The fact that the resultant isolated populations have not perceptibly speciated since then suggests that the species has been fragmented for only a short time, perhaps only since the Last Glacial Maximum.