Geographical variation in Eucalyptus baxteri s.l. and the recognition of a new species, E. arenacea

Abstract

Morphological variation in Eucalyptus baxteri (Benth.) Maiden & Blakely ex Black is described throughout its range. There are two geographical forms, the principal differences between which are seedling morphology and the time of transition from juvenile to intermediate growth phase.

The forms are hereby recognised as two species. E. baxteri s.str. has adult leaves broad near the apex, warty flower buds, often large fruits, and an early transition to intermediate foliage. It occurs in South Australia on Kangaroo Island, Fleurieu Peninsula, Barossa Range and near Wandilo, and in Victoria on the Grampian Ranges, Great Dividing Range and coastal areas, E. arenacea sp. nov. has tapering adult leaves, generally more slender, non-warty flower buds with longer, narrower pedicels and peduncles. Fruits are generally smaller with the disc less raised. Seedlings typically show a later transition to the intermediate foliage. It occurs on Mt Stapylton in the Grampian Ranges and the desert sand country of north-western Victoria and south-eastern South Australia. It is parapatric with E. baxteri on Kangaroo Island and Fleurieu Peninsula, and is restricted to sand deposits.

A previous cladistic analysis suggested that E. baxteri s.l. is paraphyletic, E. arenacea sp. nov. being the sister taxon to E. baxteri s.str. and E. akina (an endemic of the Grampian Ranges). A sequence of evolutionary events is hypothesised by using the cladogram, the distribution of the taxa on different soils, and the geological history of the region.