Ficus opposita is a sandpaper fig that grows across Northern Queensland, from Cape York to South Eastern Queensland and inland towards Northern Territory where it is replaced by Ficus aculeata.
Even though it is currently thought that opposita and aculeata are distinct and sexually isolated, I believe they are variations of the same plant and are freely hybridising in areas where they co habit.
I also wonder if there are such ‘hybrid’ zones where these two species meet in the wild, it seems more likely that the populations would slowly blend between one form to the next. Traveling from the East coast of Queensland inland, I feel that Ficus opposita would gradually change to become more and more like aculeata. I’d love to get my hands on all the collections of sandpaper fig from Queensland and check if my theory is right.
What I do know from my travels is that Ficus opposita is incredible variable. In Cape York the average opposita I observed was 3 or 4 m tall and about the same wide. They tend to have large round leaves, around 15cm long, with a stiff course texture. The bark is course and deeply fissured, grey or brown in colour.
Further south the average leaf is more narrow, some plants grow as small shrubs others as trees to 8 or so meters. Some have leaves with short stiff spines while others are covered in soft grey hair. Even within one region there doesn’t seem to be any consistency to the populations. This large variation of form is one reason I refuse to believe that the different sandpaper fig species are sexually isolated. My understanding is that plants with in a sexually isolated species would assimilate and take on a common appearance between individuals, as time went on variation would be reduced, this is far from the case when you observe opposita in the wild.
I have about 15 Ficus opposita, from various locations around Queensland. Though they all look similar, they are also quite different to each other. One plant looks like Ficus coronata, with leaves of similar shape and colour to it’s southern relative. Another has extremely long thin trifoliate leaves that are not uncommon on young or damaged Ficus opposita but rarely seen – as this plant – on adults. I’d suggest that you if you looked hard enough you would probably find a Ficus opposita that displays similarities to each of the other species of sandpaper fig around Australia, making me wonder if Ficus opposita is the original Australian sandpaper fig?
My current feeling is that Ficus opposita may have spread south from Indonesia into North East Queensland. Ficus melinocarpa, copiosa and congesta are thought to have done the same.
It may then have spread from Northeast Queensland west to become Ficus aculeata, coronulata, scobina and podocarpifolia, south west to become leptoclada, possibly mixing with congesta to form the east coast forms of fraseri and coronata.
If this is the case, it would be easy to believe that nearly all the native sandpaper figs are able to interbred, after all they may be nothing more than localised variations of the same species! One of my opposita forms ripe fruit every year without fail. I would assume that most of the pollen is provide by Ficus coronata because they are the next plants on the shelf. Because there is so much ripe fruit from Ficus opposita I won’t bother growing the seed but I will sometimes squash a fruit and leave it at the base of the plant to let the seed germinate. One example of this produced a surprising cross!
On the other side of the shelf are a row of leptoclada, and it seemed that one of these leptoclada had pollinated an opposita. The seedling that popped up had large leaves similar in size to opposita and oppositely arranged on the stem, again like opposita. Yet the foliage was thin, smooth and dark green like leptoclada. After a couple of years the plant formed it’s first fruit and it looked just like the fruit of a leptoclada.