Ficus is a genus of plant familiar to most people. From the delightful edible fruit of Ficus carica to the Ficus species found in homes and offices worldwide, Ficus is a relatively regular player in our day to day lives. There is an estimated 750 Ficus species with native ranges throughout the tropics and subtropics. Perhaps, some of the most charismatic of these are the strangler figs (also known as banyan trees). These trees begin growing in the branches of a different species as an epiphyte and send roots down from their host's crown, slowly over taking their host tree.
Prior to moving to Hawaiʻi, the only Ficus species I was familiar with were the ones that produced edible figs (though I had never seen the tree), and the house plant in our living room growing up. Since moving though, I have gotten to experience their impressive characteristics first hand and have realized just why they have captivated so many.
First, their flowers are enclosed in what look like unripe fruits and pollinated solely by specialized fig wasps. These fig-wasp relationships represent one of the most fantastic cases of coevolution in our natural world. Second, and maybe even more impressive, figs survived what the dinosaurs could not and there is fossil evidence supporting that figs were important for mammals who also survived and flourished after the dinosaurs. Third, these trees have played important supporting roles to humans throughout history, both has sustenance and cultural icons.
While Ficus species are diverse and found throughout the tropics and subtropics, these plants were unable establish in the Hawaiian islands on their own. Either they did not successfully disperse to the islands, dispersed and didn't establish, or were unable to reproduce and persist without their unique pollinators. Historically, it was their reputation as hardy species that brought Ficus trees to Hawaiʻi by humans. Their quick growth and larger than life size were thought to be useful for watershed management by the Sugar Planters' Association during the early 1900s. Ficus trees would have been relatively harmless too, had their specific wasp pollinators not been introduced (no wasp, no seeds). However, reforestation efforts were deemed too slow without the natural seed production of Ficus and pollinators were introduced for at at least two Ficus species, with many other Ficus associating wasps and insects being recorded as introduced in the last thirty years.
Today, Ficus species can be found in arboretums and parks throughout Hawaiʻi. More worrisome though is that some species have made their homes in Hawaiian forests and, with their pollinators, are more than just a nonnative addition. With small bird-dispersed fruits filled with thousands of seeds, these trees are now considered to be invasive. While the Sugar Planter's Association may have had good intentions for trying to better the watershed, introduced Ficus trees and their pollinators have been an additional battle in the war against invasive species in the Hawaiʻi.
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