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Fig Pollinators At Palomar College 2 (More Images))
© W.P. Armstrong Updated 15 February 2025
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Banana Fig (Ficus pleurocarpa)

The banana fig (Ficus pleurocarpa) is endemic to wet tropical rainforests of northeastern Australia. It has distinctive, elongate, orange-red syconia different from other fig species. It starts out as an epiphytic strangler (hemiepiphyte) and later develops into a tree up to 25 meters tall in Australia. Seed germination of the banana fig in the campus greenhouse area has been perplexing. It was originally introduced without syconia, so it is doubtful that its documented native pollinator wasp species (Pleistodontes regalis, P. deuterus or P. nitens) were introduced. Its syconia appear to be packed with female flowers (drupelets), including very hard-shelled "seeds" that sink in water. If these "seeds" (technically drupelets) germinate, then how did they get pollinated? Were they pollinated by Pleistodontes imperialis from nearby rustyleaf fig (Ficus rubiginosa)? The answer to this question appears to be yes since the latter wasp species was discovered in a syconium in May 2025. I have dedicated this entire page to the banana fig because it is such a fascinating species.


Classification of 4 Palomar Species

    Subgenus Urostigma Section Conosycea

    1.   Indian Laurel Fig (Ficus microcarpa)

    Subgenus Urostigma Section Malvanthera

    2.   Rustyleaf Fig (Ficus rubiginosa)
    3.   Moreton Bay Fig (Ficus macrophylla)
    4.   Banana Fig (Ficus pleurocarpa)

Banana Fig (Ficus pleurocarpa)

Banana fig (Ficus pleurocarpa) on campus of Palomar College.

Receptive Australian Ficus Species At Palomar College
POLLEN
DONOR

F
I
G

W
A
S
P
Fig Wasps &
Fig Species
  F. microcarpa
Conosycea
  F. rubiginosa
Malvanthera
  F. macrophylla
Malvanthera
  F. pleurocarpa
Malvanthera
Eupristina
verticillata
(Conosycea)
Natural Host
Improbable
Improbable
Improbable
Pleistodontes
imperialis
(Malvanthera)
Improbable
Natural Host
Documented
Observed
Pleistodontes
froggatti
(Malvanthera)
Improbable
?
Natural Host
?
Table Showing Possible Fig Pollinations At Palomar College

Red: Improbable (Between Different Ficus Sections Conosycea & Malvanthera)
Yellow Squares Containing Question Mark ? (Unverified at Palomar College)
Blue Squares: Documented in the Literature or Observed at Palomar
Green Squares: Natural (Native) Host For This Wasp Species

Ficus pleurocarpa syconium. The center contains pollen-bearing anthers of male flowers. The outer drupelets are the fruits from old female flowers that have passed their receptive pollination stage. This is a good example of protogyny where the female flowers mature before male flowers, thus insuring cross pollination. The drupelets consist of a hard pericarp wall surrounding an endocarp layer. Most endocarps are hollow (seedless); however, some were pollinated and contain a minute seed.

Ficus pleurocarpa syconium. The center contains pollen-bearing anthers of male flowers that are almost ready to dehisce and shed pollen. The outer drupelets are the fruits of female flowers that have long since passed their receptive pollination stage (protogyny).

Magnified views of Ficus pleurocarpa syconium showing hair-lined wasp entrance (ostiole) and pollen-bearing anthers just inside ostiole.

The actual ripened ovary or fruit within the fig syconium is a tiny fruitlet technically called a drupelet. In Ficus pleurocarpa some of these contain a minute seed within the endocarp layer.

Magnified view of Ficus pleurocarpa syconium showing hollow (empty) drupelet, pollen from male flowers (anthers) and 2 minute seeds. 15x, Bausch & Lomb dissecting microscope.

Another magnified view of Ficus pleurocarpa syconium showing drupelets, some of which contain a minute seed. In my opinion, this is evidence that some female flowers were pollinated during their receptive stage.

How Small Are Banana Fig Seeds--See Next Image!

On 21 Feb. 2025 I examined syconia at early stage when they were smaller and presumedly receptive to pollen-bearing wasps; however, no fig wasps were observed. There may be other factors involved in seed formation of Ficus pleurocarpa. As of May 2025, the pollinator wasp Pleistodontes imperialis was discovered in a syconium of F. pleurocarpa. This widespread wasp species occurs in syconia of several fig species on campus and is a good example of pollinator-sharing.

Ficus pleurocarpa not only exhibits "pollinator-sharing" at Palomar with Pleistodontes imperialis, but 3 additional Pleistodontes species are listed in the literature for this Ficus species, including P. deuterus, P. regalis, & P. nitens, also qualifying it for the title of host-sharing.