Sex-Ratios and Related Characteristics in Spinifex sericeus (Poaceae)

Abstract

Spinifex sericeus R.Br. is a dioecious, stoloniferous grass which occurs on sand dunes around much of the south-eastern coastline of Australia, New Zealand and New Caledonia.

Sex ratios of ramets of S. sericeus and some associated characteristics were studied on the mid-north coast of New South Wales. Generally there was a male bias in the observed ramet sex ratio, although the extent of this bias varied with the beach investigated, the position in the dunes and the time of sampling. Male inflorescences matured and died more rapidly than females, and hence the observed male bias was greatest at the beginning of the flowering period. Male ramets were found to have more sexual tillers per clump than female ramets.

The genet sex ratio was estimated from plants grown from seed and separated from each other throughout the experimental period. Males and females were found to be equal in number, although this equality may not be a true reflection of the genet sex ratio in the field.