Common names: Native Holly
This month I was really pleased to resolve the mystery of the great disparity in the percentages of male and female plants of this species. In my previous notes I have observed that the ratio of female to male plants exceeds 10 to 1. Until this month though I didn’t have a conclusive scientific explanation although what I had long hypothesized was in fact correct.
If you watched the ABC’s Gardening Australia program on Saturday 30 July you will recall that Jerry Coleby-Williams mentioned apomictic mandarin trees that produced seeds true to the parent plant because they were created without pollination and so were clones of the parent. When I researched apomixis in plants I was amazed to learn how this process was discovered. I quote from the reference I found:-
Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development. The initial discovery of apomixis in higher plants is attributed to the observation that a solitary female plant of Alchornea ilicifolia (syn. Caelebogyne ilicifolia) from Australia continued to form seeds when planted at Kew Gardens in England (Smith, 1841). Winkler (1908) introduced the term apomixis to mean “substitution of sexual reproduction by an asexual multiplication process without nucleus and cell fusion”.
I have only ever found one male plant in the reserve and only once did I see it in flower. However in the appropriate season almost all the female plants are covered in fruit containing fertile seeds. It is now clear that almost all of these seeds are produced without pollination and so are clones of the parent and therefore female. Hence the huge disparity in the ratio of male and female plants. (August 2011)
This is a fairly common understorey shrub in the bushland but does grow to about 5 metres high. The leaves are angled with a sharp spine on each angle. The plant resembles European holly, hence the common name and the specific epithet. These plants are extremely hardy and seem to have survived the drought quite well so far. Like so many of the plants in the reserve this species is dioecious with separate plants carrying the male and female flowers. As a casual and unscientific observation, I’d have to say that the ratio of female to male plants is very high, possibly as high as 10 to 1. It took about an hour of searching to find a male plant in bloom, while I passed dozens of female plants. Although I must say that a few plants were not in flower or carrying any fruit, so it is quite likely that these were male plants. (September 2007)