00/13 Progress Report: April02

Why is Hakea pulvinifera at the brink of extinction?
Jennifer Smith, A. Taji, N. Prakash and Dr. C. L. Gross, Agronomy and Soil Science, University of New England         Grant details

Hakea pulvinifera exists in one small population at Keepit Dam in NSW. Plants produce flowers, but do not set seed. The main objective of the study has been to attempt to recover this species from the brink of extinction through use of in vitro and ex situ breeding techniques.

To date, in situ hand pollination using pollen from donors greater than 30 m from recipient plants has resulted in no fruit set. Furthermore, we have found that H. pulvinifera produces very little pollen and that the pollen becomes trapped in the flaccid outer layer of the anther and can only be extracted manually. Pollen viability is also very low although early pollen tube development was observed under in vitro conditions. We have established that the species is diploid (2n = 20) and at present anatomical, developmental and reproductive studies are underway to ascertain the cause(s) of reproductive failure in H. pulvinifera. Since H. pulvinifera exists in only one population of 170 stems, we believe that the population is clonal with fecundity retarded as a result of inbreeding depression. Genetic studies to be conducted soon will determine if the population consists of one or more individuals (clones).

A comparison species within the same phylogenetic group, the Lorea or 'corkwood' group is included in the study. Hakea ednieana, a fertile (seed producing) desert species common in South Australia, extends into the extreme northwest of NSW. The NSW populations are considered to be intermediate with H. eyreana. The leaf shape of both study species is very similar but H. ednieana produces more inflorescences per plant and flowers per inflorescence than H. pulvinifera. Whilst fertile, fruit to flower ratios are very low, a common phenomenon in the Proteaceae family.

Understanding the developmental and ecological mechanisms of reproductive failure in H. pulvinifiera may assist in devising appropriate recovery strategies for the population. Identification of individual genets using molecular methods will enable each genotype to be represented in ex situ populations produced using in vitro and ex situ breeding techniques, thus minimising the possibility of species extinction.