Variation in Croton capitis-york (Euphorbiaceae)

Abstract

When Croton capitis-york was originally described (Airy Shaw 1980), two varieties were recognised, var. capitis-york and var. pilosus Airy Shaw. The latter variety was distinguished by the more pilose indumentum on the petioles, lamina nerves and inflorescences. Airy Shaw (1981) subsequently provided some additional brief notes (incorrectly citing the type of C. capitis-york var. pilosus as the type of C. capitis-york) stating that the species was known only from immature fertile material. While undertaking general field collecting in/rainforest communities on Cape York Peninsula, Queensland, Australia, I encountered several populations of Croton capitis-york Airy Shaw in the vicinity of the type locality of C. capitis-york var. pilosus. Some years earlier, John Clarkson had collected fertile male material in the vicinity of the type locality of C. capitis-york (distributed as C. insularis Baill.) and a fruiting collection had also been made further north by Ann Morton. With the availability of this fertile material it is now possible to provide both an amplified description and to examine the status of the two varieties. The character of indumentum used by Airy Shaw to distinguish his varieties in C. capitis-york is very slight and subject to environmental modification. As with other Australian taxa of Croton with white indumentum, e.g. C. phebalioides F. Muell. ex Muell. Arg., C. insularis Baill. and C. stigmatosus F. Muell., there can be considerable variation in leaf size and indumentum development on a single branch, let alone on different trees growing in varying situations. Examination of the much wider range of material now available for C. capitisyork revealed that the distinction of indumentum development could not be used reliably to sort material into the two varieties.