Posts Tagged ‘tallow plum’

Tallow Plum (Ximenia americana) and Pre-historic Rafting Events

June 3, 2018

I posted the below photo on the Florida Flora and Systematics Facebook page, and the 2 plants in the picture were identified within about 5 minutes.  I saw this shrub and flower growing at Manatee State Park in Florida, while I was in the sunshine state visiting my sister and mother who recently moved there.  I joined that Facebook group because I am not as familiar with plants found in Florida as I am with Georgia’s flora.  I’ve read about tallow plum, but it was a big help for someone to help me identify it.

The flower in the foreground is Chapman’s pea (Chapmannia floridanus); the scrub bush in the background is tallow plum.

Tallow plum is in the Olalaceae family which includes olive, ash, and privet.  It produces an edible, waxy, sour fruit; and the tree reaches an height of 18 feet.  The tough plant thrives on sandy soils and can even grow on beaches, perhaps explaining its wide geographical distribution.  This species is found throughout most of Florida as well as the Caribbean, Central and South America, Africa, and Australia.  I wondered how it attained such a vast geographic distribution, but when I researched the species on google, I found no scientific studies delving into this mystery, and I learned no genomic wide studies of the Olalaceae family have been conducted yet.  I couldn’t even find any speculative discussions of its range, so the ancient history of this species has been overlooked.

I hypothesize tropical storms disbursed this species on rafts of vegetation to different continents near the equator.  Hurricanes can wash plant material far out to sea, and when it lands on a different continent, surviving flora and fauna can then colonize new territory.  (Animals often cling to these rafts of vegetation.) This hypothesis has also been proposed to explain how monkeys and rodents originating from Africa colonized South America, and it is the commonly accepted explanation for how anole lizards conquered Caribbean Islands and southeastern North America.  The ability of tallow plum to grow on sandy soils helped them set roots on beaches when they made landfall, following severe storms and currents that carried them halfway around the world.  Uprooted plants must have been able to survive for weeks while floating on the ocean before reaching land where perhaps waves or river currents reburied the roots in soil.  Some soil likely clung to the floating uprooted plants, and timely rains helped keep the plants alive.

The only fossil site with specimens of tallow plant is of Pliocene-age, and it is found in Africa.  The site is estimated to be between 4.3 million years BP-3.8 million years BP.  The only other species of tallow plum (X. caffra) is also found in Africa.  It seems likely Africa is the continent of origin for tallow plums.  Geneticists could shed light on the evolutionary history and distribution of tallow plum, if they ever look at its genome.