Monoecious Ficus Hybrids?
The paper “Genetic Evidence for Natural Hybridization between Species of Dioecious Ficus on Island Populations” from 2006 is one of a few papers that discusses Ficus hybridisation. You might notice from it’s name that it focuses on dioecious figs – these are species that have ‘male’ and ‘female’ trees or at least plants that take on the role of being male and female. Sandpaper figs are dioecious, rock figs and stranglers are monoecious, so you might be wondering if monoecious figs hybridise as well?
Well I’m certain they do and here’s some things I’ve observed to date that make me think this.
Several of my monoeoius figs have grown ripe fruit out of their natural habitat. This to me is a good sign they are being pollinated by a different species. These monoecious figs include brachypoda from Central Australia, triradiata from Far North Queensland and a platypoda like plant from around Katherine. I’ve successfully grown hundreds of seedlings from these plants, most of which I’ve culled because I don’t have the room to look after them all.
The brachypoda offspring look like they’ve been pollinated by obliqua, I’m not sure what I would identify them as if I didn’t know their parentage.
The platypoda like plant (which isn’t a true platypoda because the bracts that cover the synconia grow from the base of the peduncle and fall off before the fruit matures. My understand is that ‘true’ platypoda have large bracts that cover the fruit for most of it’s development). There’s also a batch of triradiata seedlings that are too young to see morphologic signs of cross parentage.
In the field, especially around Kakadu, Katherine and Kunanarra there are figs that in my opinion don’t conform to any of the current species. In Nitmiluk National Park there are plants that have the leaf of a platypoda with the blue grey colouring and texture of subpuberula.
It would be easy to say these ‘non conforming’ plants are new species,
or ignore the obvious variation and in this case classify them as either platypoda or subpuberula, or you could suggest they are hybrids.
Another example would be a plant growing near Kununarra. At first appearance it was a lilliputiana yet it’s leaves were bigger, more elongated, the branches were longer and slightly pendulous. The leaves also had the blue grey colouring of subpuberula. There were plants near by that took on the typical form of both of these species and in this case I’d describe this plant as a lilliputiana x subpuberula.
In Macksville NSW not far from a rainforest population of watkinsiana is a small rubiginosa like tree that had large fruit resembled the fruit of a watkinsiana. A watkinsiana x rubigionosa? I’ve grown watkinsiana from seed collected in Sydney and if I didn’t know the provenience of these plants I wouldn’t identify them as watkinsiana. Since watkinsiana is rarely grown in Sydney there’s a good chance this tree was pollinated by one the many rubiginosa that grew with in eye sight.
Along the foot path of Parramatta Road in Victoria Park Sydney is a line of Ficus macrophylla. There’s the odd large Ficus rubiginosa mixed in with them. One or two of these rubiginosa have similar characteristics to macrophylla.
When comparing the trunk of one of these rubigionsa with it’s neighbouring macrophylla, you would think it too was a macrophylla. It’s branches start high up the trunk like the neighbouring macrophylla and it’s leaves and fruit are large, again like the macrophylla. My guess is that all these macrophylla were grown from seed and some of the seedlings are macrohpylla x rubiginosa.
I’m in the process of trying to prove macrophylla and rubigionsa can cross. My theory is that if you find a park and all the figs are rugbinosa except for one lonely macrophylla, that this macrophylla should be receiving pollen from the surrounding rubiginosa. If I grow enough seed from this lonely macrophylla at least some of the seedlings should resemble rubiginosa.
My current thought is that all the endemic monoecious Australian species of Ficus are able to interbreed with each other. There maybe smaller sexually isolated groups, for example I have a feeling that lilliputiana and subpuberula are able to interbreed but I’m not sure that lilliputiana can cross with any other species? But on the whole I think there is a lot of gene flow between the different species.