Xeronemataceae, a New Family of Asparagoid Lilies from New Caledonia and New Zealand

Abstract

Summary. A new family of Asparagales, Xeronemataceae, is described. This small family of two species is native to New Zealand and was formerly included by several authors in Phormiaceae, to which they are grossly similar. However, they differ in a number of significant ways, and the results of DNA sequence analysis strongly support them as occupying an isolated position as sister to a clade composed of most of the higher Asparagales, thus making their description as a new family appropriate. Xeronema Brongn. & Gris is a poorly known genus of two species. It was initially thought to be monotypic with the only species being X. moorei Brongn. & Gris from New Caledonia. However, in 1924 another species, X. callistemon W. R. B. Oliv., was discovered on inaccessible inland cliff areas of the Poor Knights Islands, situated 15 miles off the northeastern coast of New Zealand (Oliver 1925, 1926). Xeronema callistemon was later found on the outlying New Zealand island Taranga (Cranwell 1933) but has never been recorded growing naturally in mainland New Zealand. The two species are rather similar in morphology, but in general X. callistemon is a larger plant than X. moorei, and there are differences in flower structure; for example, X. callistemon has a more persistent style and shorter, more tapering seeds (Moore 1957). Both species have leathery, unifacial equitant (ensiform) leaves and congested racemes bearing elongate, crimson flowers that all face upwards. The stamens are highly exserted and have persistent filaments. All parts of the flowers are red or orange, including the pollen; they could be bird or butterfly pollinated. The flowers have six free tepals, six free stamens with versatile anthers dehiscing by longitudinal introrse slits and a secretory tapetum. Pollen is monosulcate, with a finely reticulate exine, and normally boat-shaped with an elliptical sulcus (Fig. 1A), also reported by Cranwell (1953) and Schulze (1982). In material examined here (with standard SEM techniques), we found rare trichotomosulcate grains (Fig. iB), with a Y-shaped sulcus, among predominantly monosulcate grains (Fig. 1A). The ovary is superior, trilocular, with axile placentation and several crassinucellate ovules per locule. Prominent, branched, highly vascularised septal nectaries extend from the ovary base to openings around the style base (Rudall unpublished). Calcium oxalate raphides are present in idioblasts throughout all tissues, but styloid crystals are absent (Prychid & Rudall 1999). The fruit is purplish, with numerous black seeds with papillate surfaces (Oliver 1926).