The Pollination Ecology of 'Grevillia beadleana' McGillivray, an Endangered Shrub from Northern New South Wales, Australia

Abstract

'Grevillea beadleana' (Proteaceae) is an endangered species known from five populations in northern New South Wales, Australia. The reproductive ecology of 'G. beadleana' was compared in two populations with a ten-fold difference in the number of plants. 'Grevillea beadleana' was found to be self-compatible in both populations and an examination of pollen viability and stigma maturation revealed that the species is protandrous. Flowering within inflorescences is acropetallous. In the first season plants in the largest population produced approx. ten-fold more inflorescences than those in the smaller population and, although the number of flowers per inflorescence did not vary significantly between populations the first season, the larger population produced more fruit per inflorescence than the smaller population. However, fruit to flower ratios were less than 0·2 in both seasons and populations. In both populations the number of fruit was significantly greater at the proximal end of the inflorescence, where flowers open first, compared with medial and distal positions. Several bird species were observed visiting flowers, although few birds were recorded foraging at plants in the smaller population. Within both populations, birds tended to make more within- than between-plant visits. Self-compatibility, acropetally and proximal fruit-set, combined with the predominantly within-plant movement of honeyeaters, suggests inbreeding may be common within both populations of 'G. beadleana'. Pollination and fruiting success are discussed for 'G. beadleana' and breeding systems among rare and common taxa in Grevillea are reviewed.