Ficus show lots of natural variations when grown from seed. Leaf shape, leaf size, bark color, vigor etc. can vary greatly from one seedling to the next. This can even occur with seed harvested from the same mother tree.
Ficus virens with a rounder leaf form
Some of the leaves are quite round
The same tree to show its branch structure after defoliation
Here is one of many Ficus virens that I have grown from seed. This individual has a rounder leaf than the normal virens. Its other characteristics are pretty typical for Ficus virens but if one were to just use the leaf shape as a major factor in the identification it might just lead you astray. This is one of the most frustrating features of Ficus, their variability. While making our lives miserable by confusing our identification it is a useful trait for the species as it enables them to modify themselves and perhaps find an environmental niche to exploit.
Fig leaves are very variable from species to species. This is helpful in trying to identify a fig as belonging to a certain species. The problem is that the leaves on even a single plant can show great variation depending upon cultural conditions of light, moisture, growth in a container, wind, etc.
As an example the shot below shows several leaves removed from a single Ficus plant. The variability would make an attemp at a scientific identification very difficult. Many factors must be used to help in correctly identifying a fig. These include the leaf, bark, syconia, stipules etc.
Figs are wonderful plants to use for bonsai but they can infuriating to correctly identify without figs/syconia.
Ficus leaves removed from one plant showing the highly variable shape and character of the leaves