Taxonomy, ecology, and conservation of Atriplex billardierei and A. hollowayi sp. nov. (Chenopodiaceae) in Australasia

Abstract

A new, endemic species Atriplex hollowayi (Chenopodiaceae) is described from the North Island, New Zealand. It is distinguished from the Australasian A. billardierei by its smaller stature; sturdy, erect, heavily branched shrub habit; distinctly irregular sinuate-dentate leaves; weakly fused chartaceous bracteoles; and smaller seeds. A detailed description of A. billardierei is provided to distinguish both species and a lectotype selected. The status of A. chrystallina, treated as a synonym of A. billardierei, is discussed and the name typified. A. billardierei and A. hollowayi are similar ecologically. Both are strand plants and show marked year-to-year variation in numbers. Germination is significantly better in seed that has been first soaked in salt water. Both species are considered to be at risk from competition with naturalised strand plants, browsing animals, sand mining, and, in the case of A. hollowayi, over-collecting. Atriplex hollowayi is rated as Critically Endangered and A. billardierei as Declining.