ANDROMONOECY AND FRUIT-SET IN LEPTOSPERMUM MYRSINOIDES AND L-CONTINENTALE (MYRTACEAE)

Leptospermum myrsinoides and L. continentale (Myrtaceae) are andromono ecious. All flowers of these species are potentially bisexual in funct ion and male flowers result when pistil development ceases after flora l initiation. All male flowers possess vestigial pistils. The proporti on of male flowers within three populations was recorded over three se asons. In both species, the proportion of male relative to bisexual fl owers increased as the flowering season progressed. A strong relations hip exists between flower sex and branch position, with bisexual flowe rs tending to occur on upper and outer positions on plants. Fruit set is not limited by pollination but by some other resource, possibly nut rients. Whilst andromonoecy sets the upper Limit of the number of frui t which may be formed, the number of fruit set on a plant is always le ss than the number of bisexual flowers. It is suggested that andromono ecy in L. myrsinoides and L. continentale is an evolutionary response to low resource availability allowing optimal resource allocation to r eproduction in these species.